[go: up one dir, main page]
Next Issue
Volume 10, August
Previous Issue
Volume 10, June
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
8.0
4.7
Journals
Polymers
Volume 10
Issue 7
polymers-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

Polymers, Volume 10, Issue 7 (July 2018) – 118 articles

Cover Story (view full-size image): Amphiphilic block copolymers consisting of hydrophobic regioregular chiral or achiral polythiophene chains and a hydrophilic poly(acrylic acid) chain were synthesized using a macromolecular click reaction, which formed micelles in water. The chiral polythiophene chain formed supramolecular π-stacked chiral aggregates in the micelle core that were stable in aqueous solution for long periods without precipitation. Micelles consisting of chiral and achiral copolymers showed negative nonlinear effects on supramolecular chiral aggregate formation in the core. Chiral polythiophene aggregates formed in the micelle cores were highly stabilized by the crosslinking of poly(acrylic acid) blocks with diamines in the shell. View the paper here.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
17 pages, 5436 KiB  
Article
3D-Printing of Microfibrous Porous Scaffolds Based on Hybrid Approaches for Bone Tissue Engineering
by Ranjith Kumar Kankala, Xiao-Ming Xu, Chen-Guang Liu, Ai-Zheng Chen and Shi-Bin Wang
Polymers 2018, 10(7), 807; https://doi.org/10.3390/polym10070807 - 23 Jul 2018
Cited by 62 | Viewed by 7398
Abstract
In recent times, tremendous progress has been evidenced by the advancements in various methods of generating three-dimensional (3D) porous scaffolds. However, the applicability of most of the traditional approaches intended for generating these biomimetic scaffolds is limited due to poor resolution and strict [...] Read more.
In recent times, tremendous progress has been evidenced by the advancements in various methods of generating three-dimensional (3D) porous scaffolds. However, the applicability of most of the traditional approaches intended for generating these biomimetic scaffolds is limited due to poor resolution and strict requirements in choosing materials. In this work, we fabricated 3D porous scaffolds based on the composite inks of gelatin (Gel), nano-hydroxyapatite (n-HA), and poly(lactide-co-glycolide) (PLGA) using an innovative hybrid strategy based on 3D printing and freeze-drying technologies for bone tissue engineering. Initially, the PLGA scaffolds were printed using the 3D printing method, and they were then coated with the Gel/n-HA complex, yielding the Gel/n-HA/PLGA scaffolds. These Gel/n-HA/PLGA scaffolds with exceptional biodegradation, mechanical properties, and biocompatibility have enabled osteoblasts (MC3T3-E1) for their convenient adhesion as a layer and have efficiently promoted their growth, as well as differentiation. We further demonstrated the bone growth by measuring the particular biomarkers that act as key players in the ossification process (i.e., alkaline phosphatase (ALP), osteocalcin (OC), and collagen type-I (COL-I)) and the total proteins of the MC3T3-E1 cells. We anticipate that the convenient generation of highly porous 3D scaffolds based on Gel/n-HA/PLGA fabricated through an innovative combinatorial approach of 3D printing technology and freeze-drying methods may undoubtedly find widespread applications in regenerative medicine. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic illustration representing the fabrication of the gelatin (Gel)/nano-hydroxyapatite (n-HA)/poly(lactide-<span class="html-italic">co</span>-glycolide) (PLGA) scaffolds. Initially, the PLGA microfibrous scaffolds were prepared by a three-dimensional (3D) printing method, and then, their humidified 3D scaffold architectures were dispersed in Gel and n-HA for the preparation of the Gel/n-HA/PLGA scaffolds.</p> Full article ">Figure 2
<p>Physical characterization of the 3D PLGA scaffolds, as well as of the humidified scaffolds, in comparison to the raw PLGA. (<b>A</b>) FTIR, (<b>B</b>) XRD, (<b>C</b>) differential scanning calorimetry (DSC), and (<b>D</b>) TGA, of the raw PLGA, the 3D PLGA scaffolds, and their humidified scaffolds.</p> Full article ">Figure 3
<p>Contact angle test for determining the extent of the wetting of the 3D PLGA scaffolds. (<b>A</b>) 3D PLGA scaffolds, and (<b>B</b>) Humidified scaffolds.</p> Full article ">Figure 4
<p>Optical images of various scaffolds and mechanical, as well as physical, properties of the Gel/n-HA/PLGA scaffolds. Optical Images showing the (<b>A</b>) printed 3D PLGA scaffolds and their successive Gel/n-HA/PLGA scaffolds at different (<b>B</b>) filling spaces and (<b>C</b>) thicknesses. (<b>D</b>) Graphical representation showing the changes in the mechanical and physical properties (<b>i</b>. compressive strength; <b>ii</b>. compressive modulus; <b>iii</b>. yield stress; and <b>iv</b>. porosity) of the Gel/n-HA/PLGA scaffolds at different (<b>D</b>) filling spaces and (<b>E</b>) thicknesses of the scaffold. *** represents <span class="html-italic">p</span> &lt; 0.005.</p> Full article ">Figure 5
<p>Physicochemical characterization of scaffolds after the deposition of Gel/n-HA. (<b>A</b>) Water absorption capacity of the 3D PLGA scaffolds at different exposure times (6, 9, and 12 h). (<b>B</b>) FTIR spectra of n-HA, and the Gel/n-HA composite. (<b>C</b>) SEM images of the Gel/n-HA/PLGA scaffolds at different amounts of Gel. (<b>i</b>: 2; <b>ii</b>: 3; <b>iii</b>: 4 g). * represents <span class="html-italic">p</span> &lt; 0.05. ** represents <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 6
<p>Biocompatibility measurement of the Gel/n-HA/PLGA scaffolds. The relative growth rate of the various cell lines (L929, BMSCs, and MC3T3-E1 cells) after exposure to the extract of the Gel/n-HA/PLGA scaffolds at different time intervals, (<b>A</b>) 24, (<b>B</b>) 48, and (<b>C</b>) 72 h.</p> Full article ">Figure 7
<p>Biodegradation behavior of various scaffolds in physiological fluids. SEM images representing the biodegradation behavior of various scaffolds (the 3D PLGA scaffolds and the Gel/n-HA/PLGA scaffolds) exposed at different time intervals (1, 5, 9 weeks).</p> Full article ">Figure 8
<p>Cell adhesion rate of various scaffolds. SEM images showing the adhesion of embryonic osteoblast precursor cells (MC3T3-E1 cells) onto the Gel/n-HA/PLGA scaffolds exposed to various time intervals (<b>A</b>) 4 h, (<b>B</b>) 12 h, and (<b>C</b>) the magnified view of the image captured after 24 h of exposure. (<b>D</b>) Graphical representation showing the adherence rate of various scaffolds at different exposure time points. * represents <span class="html-italic">P</span> &lt; 0.05. ** represents <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 9
<p>Cell viability analysis of various scaffolds. Confocal laser scanning microscope (CLSM) images of MC3T3-E1 cells showing that the cells were effectively deposited onto various Gel/n-HA/PLGA scaffolds after incubation for 4 and 8 h.</p> Full article ">Figure 10
<p>Effect of the degradation products on the osteoblast differentiation. Graphical representation showing the (<b>A</b>) proliferation rate of rat osteoblasts, (<b>B</b>) alkaline phosphatase (ALP) activity, as well as (<b>C</b>) Total protein synthesis, in the extract of the degradation solutions of the Gel/n-HA/PLGA scaffolds that have been incubated for predetermined time intervals. (<b>D</b>) osteocalcin (OC) and (<b>E</b>) collagen type 1 COL-I, levels were measured by exposing the cells to both extracts, as well as scaffolds, (a) blank group, and leaching solutions, as well as the stents of the samples of the 3D PLGA scaffolds (b, e), the humidified scaffold (c, f), the Gel/n-HA/PLGA scaffold (d, g), respectively. * represents <span class="html-italic">p</span> &lt; 0.05. ** represents <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">
22 pages, 6096 KiB  
Article
Rational Development of a Novel Hydrogel as a pH-Sensitive Controlled Release System for Nifedipine
by Fabián Avila-Salas, Yeray A. Rodriguez Nuñez, Adolfo Marican, Ricardo I. Castro, Jorge Villaseñor, Leonardo S. Santos, Sergio Wehinger and Esteban F. Durán-Lara
Polymers 2018, 10(7), 806; https://doi.org/10.3390/polym10070806 - 23 Jul 2018
Cited by 20 | Viewed by 4875
Abstract
This work depicts the rational development (in-silico design, synthesis, characterization and in-vitro evaluation) of polyvinyl alcohol hydrogels (PVAH) cross-linked with maleic acid (MA) and linked to γ-cyclodextrin molecules (γ-CDPVAHMA) as systems for the controlled and sustained release of nifedipine (NFD). Through computational studies, [...] Read more.
This work depicts the rational development (in-silico design, synthesis, characterization and in-vitro evaluation) of polyvinyl alcohol hydrogels (PVAH) cross-linked with maleic acid (MA) and linked to γ-cyclodextrin molecules (γ-CDPVAHMA) as systems for the controlled and sustained release of nifedipine (NFD). Through computational studies, the structural blocks (PVA chain + dicarboxylic acid + γ-CD) of 20 different hydrogels were evaluated to test their interaction energies (ΔE) with NFD. According to the ΔE obtained, the hydrogel cross-linked with maleic acid was selected. To characterize the intermolecular interactions between NFD and γ-CDPVAHMA, molecular dynamics simulation studies were carried out. Experimentally, three hydrogel formulations with different proportions of γ-CD (2.43%, 3.61% and 4.76%) were synthesized and characterized. Both loading and release of NFD from the hydrogels were evaluated at acid and basic pH. The computational and experimental results show that γ-CDs linked to the hydrogels were able to form 1:1 inclusion complexes with NFD molecules. Finally, γ-CDPVAHMA-3 demonstrated to be the best pH-sensitive release platform for nifedipine. Its effectiveness could significantly reduce the adverse effects caused by the anticipated release of NFD in the stomach of patients. Full article
(This article belongs to the Special Issue Polymers: Design, Function and Application)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic depiction of γ-CDPVAHMA (Polyvinyl alcohol hydrogel cross-linked with maleic acid and also linked with γ-cyclodextrin molecules). General syntheses were divided into two phases. First phase (pre-gel solution): Crosslinking reaction of PVA by esterification using MA as crosslinking agent. Second phase: Crosslinking reaction of PVA-MA (pre-gel solution) with γ-CD. Scheme was based on the process published by Marican et al. (2018) [<a href="#B17-polymers-10-00806" class="html-bibr">17</a>].</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) Spatial distribution of the 200 conformations with the best interaction energy for the complexes: PVAchain-MaleicAcid-γ-CD/NFD at acid and neutral-basic pH, respectively. (<b>c</b>,<b>d</b>) Representative description of the inclusion processes that led to the formation of the γ-CD/NFD complex at acid and neutral-basic pH, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>,<b>b</b>) Radius of Gyration (RGYR) and Solvent Accessible Surface Area (SASA) plots of the γ-CDPVAHMA at acid (0–50 ns) and neutral-basic pH (51–100 ns), respectively. (<b>c</b>) Number of NFD molecules retained by γ-CDPVAHMA during the three simulations: in methanol (0–50 ns), at acid pH (51–100 ns) and at neutral-basic pH (101–150 ns). (<b>d</b>) Schematic representing the possible interactions between carboxylic groups at acid pH (formation of hydrogen bonds) and hydrogen bonds between deprotonated carboxylic groups and water molecules at neutral-basic pH.</p> Full article ">Figure 4
<p>(<b>a</b>) Snapshots of the final results of each molecular dynamics simulation between γ-CDPVAHMA and NFD in methanol and in environment of acid and neutral-basic pH. Snapshots of the main intermolecular interactions generated between γ-CDPVAHMA and NFD: (<b>b</b>) in superficial nano-cavities of the hydrogel; (<b>c</b>) with the hydrophobic cavities of γ-CD added to the hydrogel; and (<b>d</b>,<b>e</b>) front and back face of the γ-CD/NFD inclusion complex.</p> Full article ">Figure 5
<p>Dependence of the %ESR of γ-CDPVAHMA hydrogels on the amount of γ-CD and pH: (<b>a</b>) %ESR of γ-CDPVAHMA1 at pH 3.0 and pH 7.4; (<b>b</b>) %ESR of γ-CDPVAHMA1 at pH 3.0 and pH 7.4; and (<b>c</b>) %ESR of γ-CDPVAHMA1 at pH 3.0 and pH 7.4.</p> Full article ">Figure 6
<p>%ESR of γ-CDPVAHMA1, γ-CDPVAHMA2, and γ-CDPVAHMA3 at pH 3.0 and 7.4 with respect to time.</p> Full article ">Figure 7
<p>Photographs: (<b>a</b>) a small fragment of xerogel γ-CDPVAHMA3 without NFD; and (<b>b</b>) of small fragment of xerogel γ-CDPVAHMA3 with NFD. The formulations were lyophilized after the swelling process.</p> Full article ">Figure 8
<p>NFD release profile from γ-CDPVAHMA formulations in two model solutions, pH 7.4 and pH 3.0: (<b>a</b>) cumulative release from γ-CDPVAHMA1, −2, and −3 at pH 3.0; and (<b>b</b>) cumulative release from γ-CDPVAHMA1, −2, and −3 at pH 7.4.</p> Full article ">Figure 9
<p>(<b>a</b>) Standardized Pareto chart for NFD release due to hydrogel treatment (A, time; B, pH; C, γ-CD proportion; AB, BC, and AC, interactions; and the line represents the critical <span class="html-italic">t</span>-value, 95% confidence); and (<b>b</b>) estimated response surface.</p> Full article ">Figure 10
<p>Thermograms of PVA, γ-CD, γ-CDPVAHMA1, γ-CDPVAHMA2, and γ-CDPVAHMA3.</p> Full article ">Figure 11
<p>(<b>a</b>) DTG curves of γ-CDPVAHMAs and DTG and deconvolution curves of γ-CDPVAHMAs between 230 °C and 500 °C; (<b>b</b>) γ-CDPVAHMA1; (<b>c</b>) γ-CDPVAHMA2; and (<b>d</b>) γ-CDPVAHMA3.</p> Full article ">Figure 12
<p>FT-IR spectra of typical γ-CDPVAHMA and starting material γ-CD and PVA.</p> Full article ">Figure 13
<p>(<b>a</b>) Ratio (%) of cell viability, acquired from the MTT assay of the L929 fibroblast cells with respect to a negative control (without formulations); and (<b>b</b>) photograph of fibroblast cells cocultured with 2500 μg mL<sup>−1</sup> of γ-CDPVAHMA3 (magnification 100×).</p> Full article ">
9 pages, 2561 KiB  
Article
Coupling of Defect Modes in Cholesteric Liquid Crystals Separated by Isotropic Polymeric Layers
by Shaohua Gao, Yanzi Zhai, Xinzheng Zhang, Xiao Song, Jiayi Wang, Irena Drevensek-Olenik, Romano A. Rupp and Jingjun Xu
Polymers 2018, 10(7), 805; https://doi.org/10.3390/polym10070805 - 23 Jul 2018
Cited by 14 | Viewed by 7312
Abstract
Cholesteric liquid crystal structures with multiple isotropic defect layers exhibit localized optical modes (defect modes). Coupling effects between these modes were simulated using the finite difference time domain method. Analogous to the well-known result of the tight-binding approximation in solid state physics, splitting [...] Read more.
Cholesteric liquid crystal structures with multiple isotropic defect layers exhibit localized optical modes (defect modes). Coupling effects between these modes were simulated using the finite difference time domain method. Analogous to the well-known result of the tight-binding approximation in solid state physics, splitting of the defect modes takes place, as soon as the structure contains more than one defect layer. The dispersion relation of the mini-bands forming within the photonic band gap of the structure is calculated numerically. The structures might have promising applications for multiwavelength filters and low-threshold lasers. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Sketch of the MDL-CLC structure.</p> Full article ">Figure 2
<p>Transmission spectra (for RCP light) of composite structures with varying number of structural units. The thicknesses of the CLC and polymer layer are 4 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m and 2 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) evolution of the transmission spectra of a MDL-CLC structure with two defect layers with increasing distance between the defect layers; (<b>b</b>) relation between coupling factor <math display="inline"><semantics> <mrow> <mo>|</mo> <mi>δ</mi> <mo>|</mo> </mrow> </semantics></math> and separation distance between defect layers. The whole thickness of the CLCs inside two boundary layers is 69<span class="html-italic">p/2</span>.</p> Full article ">Figure 4
<p>Electric field distributions for RCP light in composite structures with (<b>a</b>) one, (<b>b</b>) two, and (<b>c</b>) three isotropic layers; (<b>d</b>–<b>f</b>) electric field profiles of the defect modes at their resonant wavelengths, corresponding to (<b>a</b>–<b>c</b>), respectively.</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) dispersion diagrams of the CLC (black curve) and of the mini-bands formed in the MDL-CLC (blue and red curves) for RCP light in the first Brillouin zone; the quantity <math display="inline"><semantics> <msub> <mi>ω</mi> <mi>c</mi> </msub> </semantics></math> is the center frequency of the PBG; (<b>c</b>) group velocity corresponding to the mini-bands.</p> Full article ">Figure 6
<p>(<b>a</b>) calculated transmission spectra for RCP light (red) and LCP light (blue) for composite structures with 0, 1, 2, and 3 defect layers; (<b>b</b>) calculated relative DOS <math display="inline"><semantics> <mrow> <mi>ρ</mi> <mo>/</mo> <msub> <mi>ρ</mi> <mrow> <mi>i</mi> <mi>s</mi> <mi>o</mi> </mrow> </msub> </mrow> </semantics></math> for RCP and LCP light.</p> Full article ">
13 pages, 4776 KiB  
Article
In Vivo Investigation into Effectiveness of Fe3O4/PLLA Nanofibers for Bone Tissue Engineering Applications
by Wei-Yi Lai, Sheng-Wei Feng, Ya-Hui Chan, Wei-Jen Chang, Hsin-Ta Wang and Haw-Ming Huang
Polymers 2018, 10(7), 804; https://doi.org/10.3390/polym10070804 - 22 Jul 2018
Cited by 31 | Viewed by 4505
Abstract
Fe3O4 nanoparticles were loaded into poly-l-lactide (PLLA) with concentrations of 2% and 5%, respectively, using an electrospinning method. In vivo animal experiments were then performed to evaluate the potential of the Fe3O4/PLLA nanofibrous material [...] Read more.
Fe3O4 nanoparticles were loaded into poly-l-lactide (PLLA) with concentrations of 2% and 5%, respectively, using an electrospinning method. In vivo animal experiments were then performed to evaluate the potential of the Fe3O4/PLLA nanofibrous material for bone tissue engineering applications. Bony defects with a diameter of 4 mm were prepared in rabbit tibias. Fe3O4/PLLA nanofibers were grafted into the drilled defects and histological examination and computed tomography (CT) image detection were performed after an eight-week healing period. The histological results showed that the artificial bony defects grafted with Fe3O4/PLLA nanofibers exhibited a visibly higher bone healing activity than those grafted with neat PLLA. In addition, the quantitative results from CT images revealed that the bony defects grafted with 2% and 5% Fe3O4/PLLA nanofibers, respectively, showed 1.9- and 2.3-fold increases in bone volume compared to the control blank sample. Overall, the results suggest that the Fe3O4/PLLA nanofibers fabricated in this study may serve as a useful biomaterial for future bone tissue engineering applications. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Procedure of animal experiment. (<b>a</b>) The tibia of the rabbit was scraped, (<b>b</b>) two implantation holes with a diameter of 4 mm were prepared at each tibia of the rabbit, (<b>c</b>) neat PLLA was grafted into one implantation site and Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers were grafted into the other.</p> Full article ">Figure 1 Cont.
<p>Procedure of animal experiment. (<b>a</b>) The tibia of the rabbit was scraped, (<b>b</b>) two implantation holes with a diameter of 4 mm were prepared at each tibia of the rabbit, (<b>c</b>) neat PLLA was grafted into one implantation site and Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers were grafted into the other.</p> Full article ">Figure 2
<p>SEM microstructures of electrospun PLLA nanofibers incorporating Fe<sub>3</sub>O<sub>4</sub> nanoparticles. (<b>a</b>) Neat PLLA nanofibers; and (<b>b</b>) Fe<sub>3</sub>O<sub>4</sub> nanoparticles (black arrows) integrated within PLLA nanofibers.</p> Full article ">Figure 3
<p>Energy dispersive X-ray spectroscopy results for surface compositions of: (<b>a</b>) neat PLLA nanofibers; (<b>b</b>) 2% Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers; and (<b>c</b>) 5% Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers. The <span class="html-italic">y</span>-axis shows the count number of X-rays received by the detector (with a unit of 1000 count, KCnt) and the <span class="html-italic">x</span>-axis shows the energy level of the peaks (with a unit of kiloelectron volts, KeV).</p> Full article ">Figure 4
<p>Histological images of samples grafted with 5% Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers after: (<b>a</b>) one; (<b>b</b>) two; (<b>c</b>) four; and (<b>d</b>) eight weeks. B: blood, CT: connective tissue. GM: grafted material, IC: inflammatory cell, MS: marrow space, NB: new bone, OB: old bone, OS: osteocyte, OSB: osteoblast, OSC: osteoclast, WB: woven bone. Scale bar: 250 μm.</p> Full article ">Figure 5
<p>Histological images of samples grafted with: (<b>a</b>) blank; (<b>b</b>) neat PLLA; (<b>c</b>) 2% Fe<sub>3</sub>O<sub>4</sub>/PLLA; and (<b>d</b>) 5% Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers after eight weeks. Scale bar: 2 mm.</p> Full article ">Figure 6
<p>Micro-CT images of artificial defects after four weeks (<b>a</b>,<b>b</b>) and eight weeks (<b>c</b>,<b>d</b>). (<b>a</b>,<b>c</b>) show blank control (upper defects) and 2% Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofiber-filled samples (lower defects), respectively; (<b>b</b>,<b>d</b>) show neat PLLA (upper defects) and 5% Fe<sub>3</sub>O<sub>4</sub>/PLLA (lower defects) nanofiber-filled samples, respectively.</p> Full article ">Figure 7
<p>BV/TV% values for artificial bony defects filled with blank, neat PLLA and Fe<sub>3</sub>O<sub>4</sub>/PLLA nanofibers after eight weeks (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
13 pages, 6335 KiB  
Article
Improve the Performance of Mechanoelectrical Transduction of Ionic Polymer-Metal Composites Based on Ordered Nafion Nanofibres by Electrospinning
by Yang Zhao, Jiazheng Sheng, Di Xu, Minzhong Gao, Qinglong Meng, Dezhi Wu, Lingyun Wang, Wenlong Lv, Qinnan Chen, Jingjing Xiao and Daoheng Sun
Polymers 2018, 10(7), 803; https://doi.org/10.3390/polym10070803 - 21 Jul 2018
Cited by 12 | Viewed by 4568
Abstract
An ionic polymer–metal composite (IPMC) is a kind of soft material. The applications of IPMC in actuators, environmental sensing, and energy harvesting are currently increasing rapidly. In this study, an ordered Nafion nanofibre mat prepared by electrospinning was used to investigate the characteristics [...] Read more.
An ionic polymer–metal composite (IPMC) is a kind of soft material. The applications of IPMC in actuators, environmental sensing, and energy harvesting are currently increasing rapidly. In this study, an ordered Nafion nanofibre mat prepared by electrospinning was used to investigate the characteristics of the mechanoelectrical transduction of IPMC. The morphologies of the Nafion nanofibre mat were characterized. The proton conductivity, ion exchange capacities, and water uptake potential of the Nafion nanofibre mat were compared to traditional IPMC, respectively. A novel mechanism of Nafion nanofibre IPMC was designed and the open circuit voltage and short circuit current were measured. The maximum voltage value reached 100 mv. The output power was 3.63 nw and the power density was up to 42.4 μW/Kg under the load resistance. The Nafion nanofibre mat demonstrates excellent mechanoelectrcical transduction behavior compared to traditional IPMC and could be used for the development of self-powered devices in the future. Full article
(This article belongs to the Special Issue Electrospinning of Nanofibres)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic diagram of IPMC (<b>a</b>) “Sandwich” Structure (<b>b</b>) Molecular Formula of Nafion.</p> Full article ">Figure 2
<p>Schematic diagram of the rotating roller electrospinning.</p> Full article ">Figure 3
<p>Schematic of the experimental mechanism of the ordered Nafion nanofibre mat.</p> Full article ">Figure 4
<p>Schematic of the mechanoelectrical transduction process.</p> Full article ">Figure 5
<p>(<b>a</b>) SEM image of the ordered nanofibre mat and (<b>b</b>) the diameter of Nafion nanofibres.</p> Full article ">Figure 6
<p>WUP of Nafion-117 and the nanofibre mat.</p> Full article ">Figure 7
<p>IEC of Nafion-117 and the nanofibre mat.</p> Full article ">Figure 8
<p>The test sample of Nafion nanofibre IPMC.</p> Full article ">Figure 9
<p>Electrical output of Nafion nanofibre IPMC (Nafion nanofibre mat 203 μm).</p> Full article ">Figure 10
<p>Electrical output of Nafion nanofibre IPMC (Nafion nanofibre mat 310 μm).</p> Full article ">Figure 11
<p>The open circuit voltage and short circuit current of Nafion nanofibre IPMC in a dry state.</p> Full article ">Figure 12
<p>The open circuit voltage and short circuit current under different external loads.</p> Full article ">Figure 13
<p>The peak output voltage under different external loads.</p> Full article ">Figure 14
<p>Comparison of the output voltage under different load resistances.</p> Full article ">Figure 15
<p>The output power under different load resistances.</p> Full article ">
10 pages, 578 KiB  
Article
GC-MS Screening Analysis for the Identification of Potential Migrants in Plastic and Paper-Based Candy Wrappers
by Soraya Galmán Graíño, Raquel Sendón, Julia López Hernández and Ana Rodríguez-Bernaldo de Quirós
Polymers 2018, 10(7), 802; https://doi.org/10.3390/polym10070802 - 21 Jul 2018
Cited by 36 | Viewed by 9422
Abstract
Food packaging materials may be a potential source of contamination through the migration of components from the material into foodstuffs. Potential migrants can be known substances such as additives (e.g., plasticizers, stabilizers, antioxidants, etc.), monomers, and so on. However, they can also be [...] Read more.
Food packaging materials may be a potential source of contamination through the migration of components from the material into foodstuffs. Potential migrants can be known substances such as additives (e.g., plasticizers, stabilizers, antioxidants, etc.), monomers, and so on. However, they can also be unknown substances, which could be non-intentionally added substances (NIAS). In the present study, non-targeted analysis using mass spectrometry coupled to gas chromatography (GC-MS) for the identification of migrants in plastic and paper-based candy wrappers was performed. Samples were analyzed after extraction with acetonitrile. Numerous compounds including N-alkanes, phthalates, acetyl tributyl citrate, tributyl aconitate, bis(2-ethylhexyl) adipate, butylated hydroxytoluene, etc. were identified. Many of the compounds detected in plastic samples are not included in the positive list of the authorized substances. One non-intentionally added substance, 7,9-Di-tert-butyl-1-oxaspiro(4,5)deca-6-9-diene-2,8-dione, which has been reported as a degradation product of the antioxidant Irganox 1010, was found in several samples of both plastic and paper packaging. The proposed method was shown to be a useful approach for the identification of potential migrants in packaging samples. The toxicity of the compounds identified was estimated according to Cramer rules. Then, a second targeted analysis was also conducted in order to identify photoinitiators; among the analyzed compounds, only 2-hydroxybenzophenone was found in five samples. Full article
(This article belongs to the Special Issue Polymers for Packaging Applications)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Mass spectrometry coupled to gas chromatography (GC-MS) chromatograms of samples M1.1, M3, P4, and P3.1.</p> Full article ">
16 pages, 4109 KiB  
Article
Micro-Structure and Thermomechanical Properties of Crosslinked Epoxy Composite Modified by Nano-SiO2: A Molecular Dynamics Simulation
by Qing Xie, Kexin Fu, Shaodong Liang, Bowen Liu, Lu Lu, Xueming Yang, Zhengyong Huang and Fangcheng Lü
Polymers 2018, 10(7), 801; https://doi.org/10.3390/polym10070801 - 20 Jul 2018
Cited by 51 | Viewed by 5406
Abstract
Establishing the relationship among the composition, structure and property of the associated materials at the molecular level is of great significance to the rational design of high-performance electrical insulating Epoxy Resin (EP) and its composites. In this paper, the molecular models of pure [...] Read more.
Establishing the relationship among the composition, structure and property of the associated materials at the molecular level is of great significance to the rational design of high-performance electrical insulating Epoxy Resin (EP) and its composites. In this paper, the molecular models of pure Diglycidyl Ether of Bisphenol A resin/Methyltetrahydrophthalic Anhydride (DGEBA/MTHPA) and their nanocomposites containing nano-SiO2 with different particle sizes were constructed. The effects of nano-SiO2 dopants and the crosslinked structure on the micro-structure and thermomechanical properties were investigated using molecular dynamics simulations. The results show that the increase of crosslinking density enhances the thermal and mechanical properties of pure EP and EP nanocomposites. In addition, doping nano-SiO2 particles into EP can effectively improve the properties, as well, and the effectiveness is closely related to the particle size of nano-SiO2. Moreover, the results indicate that the glass transition temperature (Tg) value increases with the decreasing particle size. Compared with pure EP, the Tg value of the 6.5 Å composite model increases by 6.68%. On the contrary, the variation of the Coefficient of Thermal Expansion (CTE) in the glassy state demonstrates the opposite trend compared with Tg. The CTE of the 10 Å composite model is the lowest, which is 7.70% less than that of pure EP. The mechanical properties first increase and then decrease with the decreasing particle size. Both the Young’s modulus and shear modulus reach the maximum value at 7.6 Å, with noticeable increases by 12.60% and 8.72%, respectively compared to the pure EP. In addition, the thermal and mechanical properties are closely related to the Fraction of Free Volume (FFV) and Mean Squared Displacement (MSD). The crosslinking process and the nano-SiO2 doping reduce the FFV and MSD value in the model, resulting in better thermal and mechanical properties. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Mechanism of crosslinking reaction between the epoxy, acid anhydride curing agent and nano-SiO<sub>2</sub>. (<b>a</b>) Under the effect of trace moisture existing in the system, part of the epoxy groups open and anhydrides hydrolyze to further react with each other and produce monoester containing carboxyl; (<b>b</b>) carboxyl reacts with the epoxy groups and generates hydroxyl groups; (<b>c</b>) the hydroxyl groups on the surface of SiO<sub>2</sub> and the generated hydroxyl react with the epoxy groups to generate hydroxyl groups; (<b>d</b>) the hydroxyl groups on the surface of SiO<sub>2</sub> and the generated hydroxyl react with anhydrides to generate carboxylic acids.</p> Full article ">Figure 2
<p>Molecular models. (<b>a</b>) Diglycidyl Ether of Bisphenol A resin (DGEBA); (<b>b</b>) Methyltetrahydrophthalic Anhydride (MTHPA); (<b>c</b>) DGEBA-MTHPA; (<b>d</b>) SiO<sub>2</sub>.</p> Full article ">Figure 3
<p>The crosslinked network in Epoxy Resin (EP) nanocomposite models. (<b>a</b>) For 6.5 Å; (<b>b</b>) for 7.6 Å; (<b>c</b>) for 8.8 Å; (<b>d</b>) for 10 Å.</p> Full article ">Figure 4
<p>The Fraction of Free Volume (<span class="html-italic">FFV</span>) of each system with different crosslinking densities.</p> Full article ">Figure 5
<p>The variation of Mean Squared Displacement (<span class="html-italic">MSD</span>) values with time. (<b>a</b>) <span class="html-italic">MSD</span> values of the 6.5 Å system at 300 K with different crosslinking densities; (<b>b</b>) <span class="html-italic">MSD</span> values of the 67% crosslinking density system with 6.5 Å particle sizes at different temperatures; (<b>c</b>) <span class="html-italic">MSD</span> values of the 67% crosslinking density system at 300 K with different particle sizes.</p> Full article ">Figure 5 Cont.
<p>The variation of Mean Squared Displacement (<span class="html-italic">MSD</span>) values with time. (<b>a</b>) <span class="html-italic">MSD</span> values of the 6.5 Å system at 300 K with different crosslinking densities; (<b>b</b>) <span class="html-italic">MSD</span> values of the 67% crosslinking density system with 6.5 Å particle sizes at different temperatures; (<b>c</b>) <span class="html-italic">MSD</span> values of the 67% crosslinking density system at 300 K with different particle sizes.</p> Full article ">Figure 6
<p>Linear fitting of the density-temperature curve in each system.</p> Full article ">Figure 7
<p>The <span class="html-italic">T<sub>g</sub></span> value of EP and its composites. (<b>a</b>) The <span class="html-italic">T<sub>g</sub></span> value of pure EP and EP composite with 6.5 Å nano-SiO<sub>2</sub> at different crosslinking densities; (<b>b</b>) the <span class="html-italic">T<sub>g</sub></span> value of pure EP and EP composite with different particle sizes at 67% crosslinking density.</p> Full article ">Figure 8
<p>The Coefficient of Thermal Expansion (CTE) in the glassy state and rubbery state. (<b>a</b>) Glassy state; (<b>b</b>) rubbery state.</p> Full article ">Figure 9
<p>The CTE with different particle sizes under 67% crosslinking density.</p> Full article ">Figure 10
<p>The static mechanical properties of the pure EP and 6.5 Å composites with different crosslinking densities. (<b>a</b>) Young’s modulus; (<b>b</b>) shear modulus.</p> Full article ">Figure 11
<p>The static mechanical properties of the pure EP and composites with different particle sizes at a crosslinking density of 67%. (<b>a</b>) Young’s modulus; (<b>b</b>) shear modulus.</p> Full article ">
7 pages, 765 KiB  
Article
Influence of SiO2/TiO2 Nanocomposite on the Optoelectronic Properties of PFO/MEH-PPV-Based OLED Devices
by Bandar Ali Al-Asbahi
Polymers 2018, 10(7), 800; https://doi.org/10.3390/polym10070800 - 20 Jul 2018
Cited by 32 | Viewed by 4896
Abstract
The influence of SiO2/TiO2 nanocomposites on the performance of organic light-emitting diodes (OLEDs) based on poly(9,9′-di-n-octylfluorenyl-2,7-diyl) (PFO) and various amounts of poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) was investigated. Prior to the fabrication of the OLEDs on indium-tin oxide (ITO) substrates, the hybrids of [...] Read more.
The influence of SiO2/TiO2 nanocomposites on the performance of organic light-emitting diodes (OLEDs) based on poly(9,9′-di-n-octylfluorenyl-2,7-diyl) (PFO) and various amounts of poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) was investigated. Prior to the fabrication of the OLEDs on indium-tin oxide (ITO) substrates, the hybrids of PFO/MEH-PPV, in the presence and absence of the SiO2/TiO2 nanocomposites, were prepared via the solution blending technique. Improvement of the performances of the devices in the presence of the SiO2/TiO2 nanocomposites was detected. The existence of the SiO2/TiO2 nanocomposites led to better charge carrier injection and, thus, a significant reduction in the turn-on voltage of the devices. The enhancement of MEH-PPV electroluminescence peaks in the hybrids in the presence of SiO2/TiO2 nanocomposites is not only a result of the Förster resonance energy transfer, but also of hole-electron recombination, which is of greater significance. Moreover, the existence of the SiO2/TiO2 nanocomposites led to a shift of the CIE chromaticity coordinates of the devices. Full article
(This article belongs to the Special Issue Nanoparticle-Reinforced Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Current-voltage (I-V) measurements of the OLEDs based on hybrids of PFO/MEH-PPV. (<b>a</b>) In the absence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites; (<b>b</b>) in the presence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites. The inset shows the I-V curve of the OLEDs based on pristine MEH-PPV.</p> Full article ">Figure 2
<p>Electroluminescence (EL) spectra of the OLEDs based on PFO/MEH-PPV hybrids at applied voltages corresponding to maximum luminance. (<b>a</b>) In the absence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites; (<b>b</b>) in the presence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites. The inset shows the EL spectra of the OLEDs based on pristine MEH-PPV.</p> Full article ">Figure 3
<p>CIE coordinates of the OLEDs based on PFO/MEH-PPV hybrids when the applied voltage was increased from 26–34 V. (<b>a</b>) In the absence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites, (<b>b</b>) in the presence of SiO<sub>2</sub>/TiO<sub>2</sub> nanocomposites.</p> Full article ">
12 pages, 3850 KiB  
Article
Ball-Milled Recycled Lead-Graphite Pencils as Highly Stretchable and Low-Cost Thermal-Interface Materials
by Chun-An Liao, Yee-Kwan Kwan, Tien-Chan Chang and Yiin-Kuen Fuh
Polymers 2018, 10(7), 799; https://doi.org/10.3390/polym10070799 - 20 Jul 2018
Cited by 7 | Viewed by 4489
Abstract
A simple and sustainable production of nanoplatelet graphite at low cost is presented using carbon-based materials, including the recycled lead-graphite pencils. In this work, exfoliated graphite nanoplatelets (EGNs), ball-milled exfoliated graphite nanoplatelets (BMEGNs) and recycled lead-graphite pencils (recycled 2B), as well as thermally [...] Read more.
A simple and sustainable production of nanoplatelet graphite at low cost is presented using carbon-based materials, including the recycled lead-graphite pencils. In this work, exfoliated graphite nanoplatelets (EGNs), ball-milled exfoliated graphite nanoplatelets (BMEGNs) and recycled lead-graphite pencils (recycled 2B), as well as thermally cured polydimethylsiloxane (PDMS), are used to fabricate highly stretchable thermal-interface materials (TIMs) with good thermally conductive and mechanically robust properties. Several characterization techniques including scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) showed that recycled nanoplatelet graphite with lateral size of tens of micrometers can be reliably produced. Experimentally, the thermal conductivity was measured for EGNs, BMEGNs and recycled 2B fillers with/without the effect of ball milling. The in-plane thermal conductivities of 12.97 W/mK (EGN), 13.53 W/mK (recycled 2B) and 14.56 W/mK (BMEGN) and through-plane thermal conductivities of 0.76 W/mK (EGN), 0.84 W/mK (recycled 2B) and 0.95 W/mK (BMEGN) were experimentally measured. Anisotropies were calculated as 15.31, 15.98 and 16.95 for EGN, recycled 2B and BMEGN, respectively. In addition, the mechanical robustness of the developed TIMs is such that they are capable of repeatedly bending at 180 degrees with outstanding flexibility, including the low-cost renewable material of recycled lead-graphite pencils. For heat dissipating application in high-power electronics, the TIMs of recycled 2B are capable of effectively reducing temperatures to approximately 6.2 °C as favorably compared with thermal grease alone. Full article
(This article belongs to the Special Issue Polymers for Packaging Applications)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>A schematic representation of (<b>a</b>) recycled 2B; (<b>b</b>) optical photo showing the mechanical setup to produce nanoplatelet graphite from recycled pencil lead by ball milling where (1) is the ball-mill machine; (2) suspension of the recycled nanoplatelet graphite in the ethanol medium; (3) 25 mL ball-mill jar; and (<b>c</b>) recycled nanoplatelet graphite.</p> Full article ">Figure 2
<p>(<b>a</b>) Digital optical photo of recycled 2B as prepared; (<b>b</b>–<b>g</b>) schematic of sample preparation route for the recycled 2B; (<b>h</b>) shows the excellent flexibility of fabricated TIMs.</p> Full article ">Figure 3
<p>Optical photos of (<b>a</b>) recycled 2B composite, compared with (<b>b</b>) a commercial TIM. The recycled 2B composite is experimentally shown to be mechanically flexible and structurally robust after bending 180 degrees by tweezer. (Samples’ dimensions: 20 mm × 20 mm × 1 mm)</p> Full article ">Figure 4
<p>SEM images of EGN, recycled 2B and BMEGN. (<b>A</b>) Digital photos of (<b>A</b>-<b>a</b>) EGN, (<b>A</b>-<b>b</b>) recycled 2B, (<b>A</b>-<b>c</b>) BMEGN; (<b>B</b>–<b>D</b>) SEM images of (<b>B</b>) EGN, (<b>C</b>) ball-milled for 4 h recycled lead-graphite pencils (recycled 2B), and (<b>D</b>) ball-milled for 4 h exfoliated graphite nanoplatelets (BMEGNs).</p> Full article ">Figure 5
<p>Comparison of Raman spectra (laser excitation 569 nm) for all three types of graphite sample.</p> Full article ">Figure 6
<p>TGA curves of pure EGN, recycled 2B, BMEGN and graphite composites.</p> Full article ">Figure 7
<p>(<b>a</b>) Measurement setups of thermal conductivity in the through-plane (<span class="html-italic">K</span><sub>┴</sub>) and (<b>b</b>) in-plane (<span class="html-italic">K</span><sub>//</sub>); (<b>c</b>) measurement results of EGN, recycled 2B and BMEGN composites; (<b>d</b>) calculated anisotropy values (<span class="html-italic">K</span><sub>//</sub>/<span class="html-italic">K</span><sub>┴</sub>).</p> Full article ">Figure 8
<p>Inverter experiment operating at a frequency of 20 kHz pulse frequency. (<b>a</b>) <span class="html-italic">V</span><sub>GE</sub> voltage flow over an IGBT inverter for upper and lower arms; (<b>b</b>) measurement result of AC waveforms <span class="html-italic">V</span><sub>AC</sub>, <span class="html-italic">I</span><sub>AC</sub>; (<b>c</b>) TIMs (red dotted square) in measurements on the IGBT heat sources. Red rectangles show the 3 IGBTs in the normal operation position.</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic setup of the heat dissipation test, showing three TIMs sandwiched between the IGBT chips and aluminum heat sink; (<b>b</b>) thermal resistance network; (<b>c</b>) temperature measurements of heat dissipation tests of EGN, recycled 2B and BMEGN composites.</p> Full article ">
12 pages, 2376 KiB  
Article
Immobilizing Laccase on Modified Cellulose/CF Beads to Degrade Chlorinated Biphenyl in Wastewater
by Na Li, Quiyang Xia, Yuan Li, Xiaobang Hou, Meihong Niu, Qingwei Ping and Huining Xiao
Polymers 2018, 10(7), 798; https://doi.org/10.3390/polym10070798 - 19 Jul 2018
Cited by 25 | Viewed by 5002
Abstract
Novel modified cellulose/cellulose fibril (CF) beads (MCCBs) loaded with laccase were prepared to degrade polychlorinated biphenyls (PCBs) in wastewater. The proper porous structure in MCCBs was achieved by introducing nano CaCO3 (as a pore forming agent) in cellulose/CF (CCBs) beads during the [...] Read more.
Novel modified cellulose/cellulose fibril (CF) beads (MCCBs) loaded with laccase were prepared to degrade polychlorinated biphenyls (PCBs) in wastewater. The proper porous structure in MCCBs was achieved by introducing nano CaCO3 (as a pore forming agent) in cellulose/CF (CCBs) beads during the preparation process. Cellulose/CF composite beads were modified by maleic anhydride to introduce carboxyl groups. Laccase was immobilized on the MCCBs through electrostatic adsorption and covalent bonding. The effects of pH, laccase concentration and contact time on immobilization yields and recovered activity were investigated. The best conditions were pH 4, concentration 16 g/L and contact time 3 h. The immobilized laccase under these conditions showed a good performance in thermal and operational stability. The laccase immobilized on MCCB beads can remove 85% of 20 mg/L 4-hydroxy-3,5-dichlorobiphenyl (HO-DiCB) in wastewater. The results demonstrated that MCCBs, as a new type of green-based support, are very promising in material immobilizing laccase. This technology may be of potential advantage for the removal of polychlorinated biphenyls in wastewater from an environmental point of view. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>FT-IR of CCBs and MCCBs.</p> Full article ">Figure 2
<p>Scanning electron micrographs of cross-section MCCBs. A, B and C are cellulose; D and E are CF.</p> Full article ">Figure 3
<p>Effect of pH on immobilized laccase recovered activity and laccase immobilization yield by adsorption on MCCBs.</p> Full article ">Figure 4
<p>Effect of initial enzyme concentration on immobilized laccase recovered activity and laccase immobilization yield by absorption on MCCBs.</p> Full article ">Figure 5
<p>Effect of contact time on immobilized laccase recovered activity and laccase immobilization yield by absorption on MCCBs.</p> Full article ">Figure 6
<p>EDS spectra of the MCCBs (<b>A</b>) and immobilized laccase MCCBs (<b>B</b>).</p> Full article ">Figure 7
<p>Thermal and operational stability of laccase immobilized on MCCBs by absorption at pH 4.0, 16 g/L initial lacasse concentration and 3 h contact time.</p> Full article ">Figure 8
<p>Removal rate of HO-DiCB by immobilized laccase and control (CCBs without laccase) at pH 4.0 room temperature; inlet: ln(1 − <span class="html-italic">r</span>) vs. <span class="html-italic">t</span> plot of curve for immobilized laccase.</p> Full article ">
12 pages, 2066 KiB  
Article
Fabrication of Porous Polyvinylidene Fluoride/Multi-Walled Carbon Nanotube Nanocomposites and Their Enhanced Thermoelectric Performance
by Fei-Peng Du, Xuan Qiao, Yan-Guang Wu, Ping Fu, Sheng-Peng Liu, Yun-Fei Zhang and Qiu-Yu Wang
Polymers 2018, 10(7), 797; https://doi.org/10.3390/polym10070797 - 19 Jul 2018
Cited by 26 | Viewed by 4206
Abstract
In this paper, a solvent vapor-induced phase separation (SVIPS) technique was used to create a porous structure in polyvinylidene fluoride/Multi-walled carbon nanotube (PVDF/MWNTs) composites with the aim of increasing the electrical conductivity through the incorporation of MWNTs while retaining a low thermal conductivity. [...] Read more.
In this paper, a solvent vapor-induced phase separation (SVIPS) technique was used to create a porous structure in polyvinylidene fluoride/Multi-walled carbon nanotube (PVDF/MWNTs) composites with the aim of increasing the electrical conductivity through the incorporation of MWNTs while retaining a low thermal conductivity. By using the dimethylformamide/acetone mixture, porous networks could be generated in the PVDF/MWNTs composites upon the rapid volatilization of acetone. The electrical conductivity was gradually enhanced by the addition of MWNTs. At the same time, the thermal conductivity of the PVDF film could be retained at 0.1546 W·m−1·K−1 due to the porous structure being even by loaded with a high content of MWNTs (i.e., 15 wt.%). Thus, the Seebeck coefficient, power factor and figure of merit (ZT) were subsequently improved with maximum values of 324.45 μV/K, 1.679 μW·m−1·K−2, and 3.3 × 10−3, respectively. The microstructures, thermal properties, and thermoelectric properties of the porous PVDF/MWNTs composites were studied. It was found that the enhancement of thermoelectric properties would be attributed to the oxidation of MWNTs and the porous structure of the composites. The decrease of thermal conductivity and the increase of Seebeck coefficient were induced by the phonon scattering and energy-filtering effect. The proposed method was found to be facile and effective in creating a positive effect on the thermoelectric properties of composites. Full article
(This article belongs to the Special Issue Polymers for Thermoelectric Application)
►▼ Show Figures

Figure 1

Figure 1
<p>The cross-section microstructure of PVDF/MWNTs composites with (<b>a</b>) 7 wt.% MWNTs; (<b>b</b>) 15 wt.% MWNTs; (<b>c</b>) 25 wt.% MWNTs and (<b>d</b>) 35 wt.% MWNTs.</p> Full article ">Figure 2
<p>DSC thermograms of PVDF/MWNTs composites with (<b>a</b>) pure PVDF; (<b>b</b>) 7 wt.% MWNTs, (<b>c</b>) 15 wt.% MWNTs; (<b>d</b>) 25 wt.% MWNTs and (<b>e</b>) 35 wt.% MWNTs.</p> Full article ">Figure 3
<p>The thermal conductivity of PVDF/MWNTs composites with different content of MWNTs at room temperature.</p> Full article ">Figure 4
<p>Seebeck coefficient of PVDF/MWNTs composites with different content of MWNTs at room temperature.</p> Full article ">Figure 5
<p>Electrical conductivity of PVDF composites with different content of MWNTs at room temperature.</p> Full article ">Figure 6
<p>Power factor of PVDF composites with different content of MWNTs at room temperature.</p> Full article ">Figure 7
<p>ZT values of PVDF composites with different content of MWNTs at room temperature.</p> Full article ">
19 pages, 4051 KiB  
Article
Star Shaped Long Chain Branched Poly (lactic acid) Prepared by Melt Transesterification with Trimethylolpropane Triacrylate and Nano-ZnO
by Le Yang, Zaijun Yang, Feng Zhang, Lijin Xie, Zhu Luo and Qiang Zheng
Polymers 2018, 10(7), 796; https://doi.org/10.3390/polym10070796 - 19 Jul 2018
Cited by 23 | Viewed by 5426
Abstract
Long chain branched poly (lactic acid) (LCBPLA) was prepared via transesterification between high molecular weight poly (lactic acid) (PLA) and low molar mass monomer trimethylolpropane triacrylate (TMPTA) during melt blending in the presence of zinc oxide nanoparticles (nano-ZnO) as a transesterification accelerant in [...] Read more.
Long chain branched poly (lactic acid) (LCBPLA) was prepared via transesterification between high molecular weight poly (lactic acid) (PLA) and low molar mass monomer trimethylolpropane triacrylate (TMPTA) during melt blending in the presence of zinc oxide nanoparticles (nano-ZnO) as a transesterification accelerant in a torque rheometer. Compared with the traditional processing methods, this novel way is high-efficiency, environmentally friendly, and gel-free. The results revealed that chain restructuring reactions occurred and TMPTA was grafted onto the PLA backbone. The topological structures of LCBPLA were verified and investigated in detail. It was found that the concentration of the accelerants and the sampling occasion had very important roles in the occurrence of branching structures. When the nano-ZnO dosage was 0.4 phr and PLA was sampled at the time corresponding to the reaction peak in the torque curve, PLA exhibited a star-shaped topological structure with a high branching degree which could obviously affect the melt strength, extrusion foaming performances, and crystallization behaviors. Compared with pristine PLA, LCBPLA showed a higher melt strength, smaller cell diameter, and slower crystallization speed owing to the synergistic effects of nano-ZnO and the long chain branches introduced by the transesterification reaction in the system. However, severe degradation of the LCBPLAs would take place under a mixing time that was too long and lots of short linear chains generated due to the excessive transesterification reaction, with a sharp decline in melt strength. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Torque curves of PLA samples at 190 °C.</p> Full article ">Figure 2
<p><sup>1</sup>H-NMR spectra of PLA samples.</p> Full article ">Figure 3
<p>Zn 2p<sub>3/2</sub>, C 1s, and O 1s high-resolution XPS spectra recorded at a 90° takeoff angle for ZnO at room temperature.</p> Full article ">Figure 4
<p>(<b>a</b>) 3D image of in situ FTIR of PLA/TMPTA/nano-ZnO blend; (<b>b</b>) in situ FTIR bands in the range of 1300–700 cm<sup>−1</sup> at different temperatures before melting; and (<b>c</b>) ATR FTIR curves of purified Sample B2 and pristine PLA.</p> Full article ">Figure 5
<p>Schematic diagram of the coordination effect of nano-ZnO with PLA chains and the monomer TMPTA.</p> Full article ">Figure 6
<p>The proposed reaction mechanism for the exchange reaction of PLA with TMPTA accelerated by nano-ZnO.</p> Full article ">Figure 7
<p>Molecular weight distributions of pristine PLA and modified samples.</p> Full article ">Figure 8
<p>Rheological plots of PLA samples at 170 °C obtained from frequency sweeps: (<b>a</b>) storage modulus <span class="html-italic">G</span>′ and (<b>b</b>) loss modulus <span class="html-italic">G</span>″ as a function of angular frequency.</p> Full article ">Figure 9
<p>Reduced vGP plots for pristine PLA and modified samples at 170 °C.</p> Full article ">Figure 10
<p>The relationship of structure constant (<span class="html-italic">υ</span>) with branching frequency (<span class="html-italic">X</span>).</p> Full article ">Figure 11
<p>Tensile stress growth coefficients η<sup>+</sup> of PLA samples at a strain rate of 1.0 s<sup>−1</sup>.</p> Full article ">Figure 12
<p>Haul-off force vs. Haul-off speed of PLA samples at 170 °C.</p> Full article ">Figure 13
<p>(<b>a</b>) SEM images and cell diameter distribution of extrusion foaming PLA; (<b>b</b>) Extrusion foaming behavior of linear PLA and LCBPLA melts.</p> Full article ">Figure 14
<p>(<b>a</b>) DSC second heating curves and (<b>b</b>) relative cold crystallinity versus time of PLA samples at a heating rate of 10 °C·min<sup>−1</sup>.</p> Full article ">
15 pages, 3756 KiB  
Article
Functionalized Graphene Oxide Modified Polyethersulfone Membranes for Low-Pressure Anionic Dye/Salt Fractionation
by Lifen Liu, Xin Xie, Rahul S. Zambare, Antony Prince James Selvaraj, Bhuvana NIL Sowrirajalu, Xiaoxiao Song, Chuyang Y. Tang and Congjie Gao
Polymers 2018, 10(7), 795; https://doi.org/10.3390/polym10070795 - 19 Jul 2018
Cited by 20 | Viewed by 4280
Abstract
In this study, polyelectrolyte assembled functionalized graphene oxide (PE-GO) membranes were fabricated through a one-step charge facilitated deposition method for high performance dye/salt separation. According to the intercalation of polydopamine (PDA) and (ionic liquid) IL functional moieties into the GO membranes, the pore [...] Read more.
In this study, polyelectrolyte assembled functionalized graphene oxide (PE-GO) membranes were fabricated through a one-step charge facilitated deposition method for high performance dye/salt separation. According to the intercalation of polydopamine (PDA) and (ionic liquid) IL functional moieties into the GO membranes, the pore size of the resulted PE-pGO and PE-iGO membrane increased from 2.69 nm to 4.13 nm and 6.54 nm, respectively. Correspondingly, a pure water flux of 13.8 ± 2.2, 36.7 ± 3.4, and 52.1 ± 6.7 L m−1 h−1 bar−1 was achieved for PE-GO, PE-pGO and PE-iGO membrane, respectively. PE-iGO membrane with the largest pore size could be operated with significant water permeability (28.3 to 38.3 L m−1 h−1 bar−1) at a low operating pressure range of 0.5–2 bar (dye concentration = 100 ppm, salt concentration = 5 g/L). More importantly, functionalities introduced to the GO nanosheets are found to impact the dye adsorption to the membrane surface. The IL intercalation promotes the elution of dye molecules from the IL moieties at elevated pH, therefore enhancing the efficiency of alkaline washing of the membrane. By contrast, the intercalation of PDA weakens such efficiency due to its strong adhesion force to the dye molecules even at the alkaline condition. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The molecular structure, molecular weight, and estimated molecular size of DR80 and CR. Molecular size was estimated according to a previous study [<a href="#B17-polymers-10-00795" class="html-bibr">17</a>].</p> Full article ">Figure 2
<p>The TEM images of nanosheets: as-synthesized (<b>a</b>); GO (<b>b</b>) iGO; and (<b>c</b>) pGO. The FTIR spectrum of the nanosheets (<b>d</b>).</p> Full article ">Figure 3
<p>(<b>a1</b>–<b>a4</b>) The FESEM surface images of the UF30, PE-GO, PE-pGO, and PE-iGO membranes. The length of scale bar (white) is 1 µm; (<b>b1</b>–<b>b4</b>) The cross-section images of the same membranes. The rejective layer is highlighted with shallow orange color. The length of scale bar (white) is 100 nm; (<b>c1</b>–<b>c4</b>) AFM scans on the surface of the same membranes.</p> Full article ">Figure 4
<p>(<b>a</b>) The Surface Zeta potential of PE-GO, PE-pGO, PE-iGO, and the substrate membrane as a function of pH value; and (<b>b</b>) the contact angle of the said membranes; insert pictures shows water droplets on top of the same membranes.</p> Full article ">Figure 5
<p>(<b>a</b>) The log-normal plot of solute rejection rate versus solute radius for PE-GO, PE-pGO, and PE-iGO membranes; (<b>b</b>) the probability density function curve of pore radius for the membranes; and (<b>c</b>) the cumulative pore distribution curve of pore radius for the membranes.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) The impact of operation pressure on the DR80 and CR rejection and flux evaluated using dead-end flow configuration. Stirring speed = 600 rpm. Dye concentration = 100 ppm; (<b>c</b>,<b>d</b>) The impact of DR80 and CR concentration on the flux and rejection evaluated using dead-end flow configuration. Operation pressure = 2 bar, stirring speed = 600 rpm.</p> Full article ">Figure 7
<p>The (<b>a</b>) normalized water flux, (<b>b</b>) dye rejection, and (<b>c</b>) salt rejection for IL-GO membrane under different pressure and salt concentrations, DR80 concentration = 100 ppm. Pressure = 2 bar. The test was carried out in cross-flow configuration.</p> Full article ">Figure 8
<p>(<b>a</b>) The long-term fouling recovery test for PE-GO membranes. DR80 concentration = 100 ppm. Pressure = 2 bar. The test was carried out in cross-flow configuration. (<b>b</b>) The digital photos show a comparison of virgin membranes versus the fouled membranes (after alkaline cleaning).</p> Full article ">Figure 9
<p>An illustration shows the deposition of DR80 molecules on PE-iGO membrane during dye filtration process (<b>left</b>) and the elution of dye molecules during alkaline wash due to weakened absorption force (<b>right</b>) (pH = 11).</p> Full article ">
37 pages, 8129 KiB  
Review
Polysiloxane-Based Side Chain Liquid Crystal Polymers: From Synthesis to Structure–Phase Transition Behavior Relationships
by Lanying Zhang, Wenhuan Yao, Yanzi Gao, Cuihong Zhang and Huai Yang
Polymers 2018, 10(7), 794; https://doi.org/10.3390/polym10070794 - 19 Jul 2018
Cited by 25 | Viewed by 7908
Abstract
Organosilicon polymer materials play an important role in certain applications due to characteristics of much lower glass transition temperatures (Tg), viscosities, surface energy, as well as good mechanical, thermal stabilities, and insulation performance stemming from the higher bond energy and [...] Read more.
Organosilicon polymer materials play an important role in certain applications due to characteristics of much lower glass transition temperatures (Tg), viscosities, surface energy, as well as good mechanical, thermal stabilities, and insulation performance stemming from the higher bond energy and the larger bond angles of the adjacent silicon-oxygen bond. This critical review highlights developments in the synthesis, structure, and phase transition behaviors of polysiloxane-based side chain liquid crystal polymers (PSCLCPs) of linear and cyclic polysiloxanes containing homopolymers and copolymers. Detailed synthetic strategies are elaborated, and the relationship between molecular structures and liquid crystalline phase transition behaviors is systematically discussed, providing theoretical guidance on the molecular design of the materials. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical structures of the polysiloxane and polyacrylate polymers [<a href="#B97-polymers-10-00794" class="html-bibr">97</a>].</p> Full article ">Figure 2
<p>Chemical structures of the Polymethacrylates (4′-n-PMA), Polyacrylates (4′-n-PAC), and Polysiloxanes (4′-n-PS) containing 4-hydroxy-4′-methoxya-methylstilbene based mesogens [<a href="#B99-polymers-10-00794" class="html-bibr">99</a>].</p> Full article ">Figure 3
<p>The chemical structures of PSC-11 and PMC-11 [<a href="#B100-polymers-10-00794" class="html-bibr">100</a>].</p> Full article ">Figure 4
<p>Chemical structures of the polysiloxanes and polymethacrylates [<a href="#B104-polymers-10-00794" class="html-bibr">104</a>].</p> Full article ">Figure 5
<p>Chemical structures of the polymers based on polysiloxane, polyacrylate and polymethacrylate backbones [<a href="#B105-polymers-10-00794" class="html-bibr">105</a>].</p> Full article ">Figure 6
<p>Chemical structures of the polysixanes with fluorene unit [<a href="#B112-polymers-10-00794" class="html-bibr">112</a>,<a href="#B113-polymers-10-00794" class="html-bibr">113</a>].</p> Full article ">Figure 7
<p>Chemical structures of the polysiloxanes and copolysiloxanes containing mesogenic unit [<a href="#B102-polymers-10-00794" class="html-bibr">102</a>].</p> Full article ">Figure 8
<p>The chemical structures of the liquid crystalline homopolysiloxanes and copolysiloxanes with dimesogenic side groups [<a href="#B118-polymers-10-00794" class="html-bibr">118</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic representation of the DSC and X-ray investigation of the homopolysiloxanes and copolysiloxanes (S<sub>A</sub>: smectic A phase, N: nematic phase, I: isotropic phase); (<b>b</b>) The layer spacings; (d) as a function of number of the inserted dimethylsioxane unites (<span class="html-italic">y</span>) [<a href="#B118-polymers-10-00794" class="html-bibr">118</a>].</p> Full article ">Figure 10
<p>The chemical structures of the poly[6-(4-cyanobiphenyl-4′-oxy)-hexylmetylsiloxanes] (PCS-n) [<a href="#B120-polymers-10-00794" class="html-bibr">120</a>].</p> Full article ">Figure 11
<p>(<b>a</b>) Changes in phase transition temperature (<span class="html-italic">T</span><sub>g</sub> and <span class="html-italic">T</span><sub>i</sub>) and enthalpy change of PCS-n as a function of the degree of substitution (DS); (<b>b</b>) Changes in layer-spacing and intermolecular spacing of the PCS-n as a function of the degree of substitution (DS) [<a href="#B120-polymers-10-00794" class="html-bibr">120</a>].</p> Full article ">Figure 12
<p>Chemical structures of the copolymers based on PMMS backbone and linear siloxane tetramer backbone [<a href="#B121-polymers-10-00794" class="html-bibr">121</a>,<a href="#B122-polymers-10-00794" class="html-bibr">122</a>].</p> Full article ">Figure 13
<p>Chemical structures of the liquid crystalline oligo[methyl(hydrogen)cyclosiloxanes] [<a href="#B123-polymers-10-00794" class="html-bibr">123</a>].</p> Full article ">Figure 14
<p>The chemical structures of the cyclic siloxane LCPs [<a href="#B125-polymers-10-00794" class="html-bibr">125</a>].</p> Full article ">Figure 15
<p>The chemical structures of the cyclic and linear polysiloxanes [<a href="#B124-polymers-10-00794" class="html-bibr">124</a>].</p> Full article ">Figure 16
<p>(<b>a</b>) Mesophase-isotropic transition temperatures for cyclic (•) and linear (▪) polysiloxanes containing the cyanoester mesogenic groups; (<b>b</b>) Mesophase-isotropic transition temperatures for cyclic (•) and linear (▪) polysiloxanes containing the cyanobiphenyl mesogenic groups [<a href="#B124-polymers-10-00794" class="html-bibr">124</a>].</p> Full article ">Figure 17
<p>Chemical structures of the cyclic and linear polysiloxane tetramers [<a href="#B122-polymers-10-00794" class="html-bibr">122</a>,<a href="#B132-polymers-10-00794" class="html-bibr">132</a>].</p> Full article ">Figure 18
<p>Chemical structures of the side chain LC homo-polysiloxanes and co-polysiloxanes containing end-on fixed mesogens and oligooxyethylenic spaces [<a href="#B150-polymers-10-00794" class="html-bibr">150</a>].</p> Full article ">Figure 19
<p>Schematic representation of the mechanism of salt complexation and its effect on the arrangement of the mesogenic side groups of polysiloxanes containing oligooxyethylenic spacers [<a href="#B150-polymers-10-00794" class="html-bibr">150</a>].</p> Full article ">Figure 20
<p>Chemical structures of the side chain LC homo-polysiloxanes containing side-on fixed mesogens and oligooxyethylenic spaces [<a href="#B151-polymers-10-00794" class="html-bibr">151</a>].</p> Full article ">Figure 21
<p>Schematic representation of the mechanism of salt complexation and its effect on the arrangement of the mesogenic groups of a side chain LC homo-polysiloxanes based on oligooxyethylenic spacers and side-on fixed mesogenic groups [<a href="#B151-polymers-10-00794" class="html-bibr">151</a>].</p> Full article ">Figure 22
<p>Chemical structures of the cyanobiphenyl-based polysiloxanes containing long thioether spacers [<a href="#B154-polymers-10-00794" class="html-bibr">154</a>].</p> Full article ">Figure 23
<p>Example of an “interdigitated” structure observed by X-ray analysis: P8, 2 [<a href="#B154-polymers-10-00794" class="html-bibr">154</a>].</p> Full article ">Figure 24
<p>Chemical structures of the polysiloxane-based LCPs with thioether spacer via thiol−ene click chemistry [<a href="#B39-polymers-10-00794" class="html-bibr">39</a>].</p> Full article ">Figure 25
<p>Chemical structures of PMMS-CN-based polymers [<a href="#B90-polymers-10-00794" class="html-bibr">90</a>].</p> Full article ">Scheme 1
<p>Typical synthetic route of PSCLCPs by hydrosilylation reaction.</p> Full article ">Scheme 2
<p>Typical synthetic route of PSCLCPs by chlorination reaction.</p> Full article ">Scheme 3
<p>Typical synthetic route and mechanism of PSCLCPs by thiol–ene click chemistry.</p> Full article ">Scheme 4
<p>Typical synthetic route of PSCLCPs by atom transfer radical polymerization [<a href="#B60-polymers-10-00794" class="html-bibr">60</a>].</p> Full article ">Scheme 5
<p>Typical synthetic route of PSCLCPs by Steglich esterification reaction [<a href="#B63-polymers-10-00794" class="html-bibr">63</a>].</p> Full article ">Scheme 6
<p>Typical synthetic route of PSCLCPs by acyl chloresterification.</p> Full article ">Scheme 7
<p>Typical synthetic route of PSCLCPs by Wiliamson nucleophilic substitution.</p> Full article ">Scheme 8
<p>Structure of self-assembled hydrogen-bonded supramolecular PSCLCPs [<a href="#B69-polymers-10-00794" class="html-bibr">69</a>,<a href="#B70-polymers-10-00794" class="html-bibr">70</a>,<a href="#B71-polymers-10-00794" class="html-bibr">71</a>].</p> Full article ">
25 pages, 10129 KiB  
Article
Synthesis of Low Melting Temperature Aliphatic-Aromatic Copolyamides Derived from Novel Bio-Based Semi Aromatic Monomer
by Syang-Peng Rwei, Palraj Ranganathan, Whe-Yi Chiang and Yi-Huan Lee
Polymers 2018, 10(7), 793; https://doi.org/10.3390/polym10070793 - 19 Jul 2018
Cited by 23 | Viewed by 7707
Abstract
This work investigated the synthesis of a novel low melting temperature polyamide 6 (PA6) copolyamide (PA6-BABT/SA) with different aliphatic/aromatic units weight content using a melt poly-condensation process. The bio-based aromatic N1,N4-bis(4-aminobutyl) terephthalamide diamine (BABT) and long-chain aromatic polyamide [...] Read more.
This work investigated the synthesis of a novel low melting temperature polyamide 6 (PA6) copolyamide (PA6-BABT/SA) with different aliphatic/aromatic units weight content using a melt poly-condensation process. The bio-based aromatic N1,N4-bis(4-aminobutyl) terephthalamide diamine (BABT) and long-chain aromatic polyamide salt (BABT/SA, salt of BABT, and sebacic acid), components used for the synthesis of copolyamides, were obtained from bio-based monomers. For the first time, the pertinent BABT/SA aromatic polyamide salt was isolated as a white solid and completely characterized. By varying the weight ratio of BABT/SA salt, a series of copolyamides with different molecular weights and physical properties were prepared. The aromatic BABT/SA salt disrupted crystallization of the final copolyamides and lowered the onset of melting. The Fourier transform infrared spectroscopy and X-ray diffraction results indicated a steady decrease in the degrees of crystallinity with increasing BABT/SA salt segment ratio. Furthermore, compared to neat PA6, the obtained PA6-BABT/SA copolymers possessed a similar thermal stability and high transparency, but lower glass transition temperature around human body temperature. The PA6-BABT/SA copolymers with number-average molecular weight ≥30,000 Da presented good mechanical properties, specifically showing excellent tensile strength and elongation at break up to 105.2 MPa and 218.3%, respectively. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Hydrogen nuclear magnetic resonance (<sup>1</sup>H NMR) spectra of <span class="html-italic">N</span><sup>1</sup>,<span class="html-italic">N</span><sup>4</sup>-bis(4-aminobutyl) terephthalamide diamine (BABT) diamine.</p> Full article ">Figure 2
<p>Fourier transform infrared (FT-IR) spectra of BABT diamine and BABT/sebacic acid (SA) salt.</p> Full article ">Figure 3
<p><sup>1</sup>H NMR spectra of BABT/SA salt.</p> Full article ">Figure 4
<p><sup>1</sup>H NMR spectra of PA6 and PA6-BABT/SA copolyamides.</p> Full article ">Figure 5
<p>FT-IR spectra of PA 6 and PA6-BABT/SA copolyamides.</p> Full article ">Figure 6
<p><sup>13</sup>C NMR spectrum of neat PA6 recorded in trifluoroacetic acid-d (TFAA) solvent.</p> Full article ">Figure 7
<p><sup>13</sup>C NMR spectrum of PA6-BABT/SA<sub>30</sub> copolyamide recorded in TFAA solvent.</p> Full article ">Figure 8
<p>(<b>A</b>) <sup>13</sup>C NMR Expanded spectra of BABT-SA, PA6, and PA6-BABT/SA<sub>30</sub> recorded in TFAA solvent. (<b>B</b>) Assignment of the carbonyl resonances (marked with an asterisk) in the PA6-BABT/SA copolyamides for possible dyad sequences.</p> Full article ">Figure 9
<p>Gel permeation chromatography (GPC) chromatographs of (<b>A</b>) neat PA6, (<b>B</b>) PA6-BABT/SA<sub>10</sub>, (<b>C</b>) PA6-BABT/SA<sub>20</sub>, and (<b>D</b>) PA6-BABT/SA<sub>30</sub>.</p> Full article ">Figure 10
<p>Differential scanning calorimetry (DSC) traces of (<b>A</b>) BABT and (<b>C</b>) BABT/SA salt; thermogravimetric analysis (TGA) of (<b>B</b>) BABT and (<b>D</b>) BABT/SA salt.</p> Full article ">Figure 11
<p>DSC analysis of (<b>A</b>) PA6, (<b>B</b>) PA6-PABT/SA10, (<b>C</b>) PA6-BABT/SA20, and (<b>D</b>) PA6-BABT/SA30 copolyamides.</p> Full article ">Figure 12
<p>(<b>A</b>) TGA of PA6 and PA6-BABT/SA copolyamides. (<b>B</b>) DTG (differential thermogravimetric) curves of PA6 and PA6-BABT/SA copolyamides.</p> Full article ">Figure 13
<p>X-ray diffraction (SRD) of PA6 and PA6-BABT/SA copolyamides with different weight contents of BABT/SA salt.</p> Full article ">Figure 14
<p>Dynamic mechanical analysis (DMA) curves (Tan δ and storage modulus E’) of (<b>A</b>) PA6 and (<b>B</b>–<b>D</b>) PA6-BABT/SA copolyamides.</p> Full article ">Figure 15
<p>(<b>A</b>) DMA curves (loss modulus E”) of PA6 and PA6-BABA/SA copolyamides. (<b>B</b>) Tensile strength curves of PA6 and PA6-BABA/SA copolyamides.</p> Full article ">Figure 16
<p>(<b>A</b>) The ultraviolet (UV) spectra of polyamide samples with different BABT/SA contents. (<b>B</b>) UV-visible transmittance spectra of neat PA6 and PA6-BABT/SA copolaymides. (<b>C</b>) Transmittance values of the polyamides films with different content of BABT/SA.</p> Full article ">Figure 17
<p>Transparency images of representative PA6 and PA6-BABT/SA copolyamides films: (<b>A</b>) original picture, (<b>B</b>) pure PA6, (<b>C</b>) PA6-BABT/SA<sub>10</sub>, (<b>D</b>) PA6-BABT/SA<sub>20</sub>, and (<b>E</b>) PA6-BABT/SA<sub>30</sub>.</p> Full article ">Scheme 1
<p>Synthesis of <span class="html-italic">N</span><sup>1</sup>,<span class="html-italic">N</span><sup>4</sup>-bis (4-aminobutyl) terephthalamide (BABT) monomer.</p> Full article ">Scheme 2
<p>Synthesis of polyamide salt, a BABT/sebacic acid (SA) salt.</p> Full article ">Scheme 3
<p>Steps 1–3 of the synthesis of polyamide 6 (PA6)-BABT/SA copolyamide based on ε-caprolactam with long chain aromatic BABT/SA salt.</p> Full article ">Scheme 4
<p>Poly-addition initiated by amino group at one side of BABT and the subsequent poly-condensation with SA.</p> Full article ">Scheme 5
<p>Poly-addition initiated by amino group at both sides of BABT and following the poly-condensation with SA.</p> Full article ">
14 pages, 2158 KiB  
Article
Dynamic and Static Mechanical Properties of Crosslinked Polymer Matrices: Multiscale Simulations and Experiments
by Daria V. Guseva, Vladimir Yu. Rudyak, Pavel V. Komarov, Boris A. Bulgakov, Alexander V. Babkin and Alexander V. Chertovich
Polymers 2018, 10(7), 792; https://doi.org/10.3390/polym10070792 - 19 Jul 2018
Cited by 18 | Viewed by 5017
Abstract
We studied the static and dynamic mechanical properties of crosslinked polymer matrices using multiscale simulations and experiments. We continued to develop the multiscale methodology for generating atomistic polymer networks, and applied it to the case of phthalonitrile resin. The mechanical properties of the [...] Read more.
We studied the static and dynamic mechanical properties of crosslinked polymer matrices using multiscale simulations and experiments. We continued to develop the multiscale methodology for generating atomistic polymer networks, and applied it to the case of phthalonitrile resin. The mechanical properties of the resulting networks were analyzed using atomistic molecular dynamics (MD) and dissipative particle dynamics (DPD). The Young’s and storage moduli increased with conversion, due both to the appearance of a network of covalent bonds, and to freezing of degrees of freedom and lowering of the glass transition temperature during crosslinking. The simulations’ data showed good quantitative agreement with experimental dynamic mechanical analysis measurements at temperatures below the glass transition. The data obtained in MD and DPD simulations at elevated temperatures were conformable. This makes it possible to use the suggested approach for the prediction of mechanical properties of a broad range of polymer matrices, including ones with high structural heterogeneity. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Chemical structures of the phthalonitrile monomer, bis(3-(3,4-dicyanophenoxy) phenyl) phenyl phosphate (DPPPP), and the initiator (diamine curing agent 1,3-bis(4-aminophenoxy)benzene, APB) with their coarse-grained mapping schemes. Red and blue beads have valences of two and one, respectively.</p> Full article ">Figure 2
<p>Schematic representation of coarse-grained reactions of initiation (<b>a</b>,<b>b</b>) and polymerization (<b>b</b>–<b>d</b>). Terminal beads of each monomer (red) and initiator (blue) have a nonzero valence; asterisk indicates an active bead. Red arrows show the reaction pathways.</p> Full article ">Figure 3
<p>Determination of the storage and loss moduli for systems at <span class="html-italic">T</span> = 450 K: (<b>a</b>) The case of a viscous medium, when E″ &gt; E′ for the system at the conversion degree, 0.1, (E′ = 0.14 GPa, E″ = 0.22 GPa, tan <span class="html-italic">δ</span> = 1.56182), and (<b>b</b>) the case of elastic medium, when E′ &gt; E″ for the system at the conversion degree 0.9 (E′ = 2.55 GPa, E″ = 0.31 GPa, tan <span class="html-italic">δ</span> = 0.12104). The oscillation frequency varied in the range of 5.3·10<sup>8</sup>–5.4·10<sup>8</sup> Hz.</p> Full article ">Figure 4
<p>The Young’s modulus of systems at temperatures <span class="html-italic">T</span> = 300 K, 450 K, and 600 K, deformed with a rate of 5·10<sup>−5</sup> nm/ps along the Z direction, as a function of the conversion degree.</p> Full article ">Figure 5
<p>The dynamic mechanical moduli, E′, E″, and mechanical loss coefficient, tan δ, for systems at <span class="html-italic">T</span> = 450 K as a function of the conversion degree. The oscillation frequency varied in the range of 5.3·10<sup>8</sup>–5.4·10<sup>8</sup> Hz.</p> Full article ">Figure 6
<p>Comparison of the moduli of elasticity in dissipative particle dynamics (DPD) and molecular dynamics (MD) simulations (at <span class="html-italic">T</span> = 600 K). The relation between the two scales (DPD and MD) was chosen by fitting these two datasets with a fixed zero level.</p> Full article ">Figure 7
<p>Comparison of the mechanical properties in MD simulations and in experiments: (<b>a</b>) The Young’s modulus in MD simulations (at <span class="html-italic">T</span> = 300 K) and the storage modulus in experiments (at <span class="html-italic">T</span> = 323 K) as a function of the glass transition temperature; (<b>b</b>) the dynamic moduli, E′, in MD simulations (for the sample of the conversion degree of 0.9) and in experiments (for the sample post-cured at 300 °C for 6 h) as a function of the oscillating frequency. Both simulations and experimental measurements were performed at 450 K.</p> Full article ">
18 pages, 2307 KiB  
Article
Surface Functionalization by Stimuli-Sensitive Microgels for Effective Enzyme Uptake and Rational Design of Biosensor Setups
by Larisa V. Sigolaeva, Dmitry V. Pergushov, Marina Oelmann, Simona Schwarz, Monia Brugnoni, Ilya N. Kurochkin, Felix A. Plamper, Andreas Fery and Walter Richtering
Polymers 2018, 10(7), 791; https://doi.org/10.3390/polym10070791 - 19 Jul 2018
Cited by 36 | Viewed by 7136
Abstract
We highlight microgel/enzyme thin films that were deposited onto solid interfaces via two sequential steps, the adsorption of temperature- and pH-sensitive microgels, followed by their complexation with the enzyme choline oxidase, ChO. Two kinds of functional (ionic) microgels were compared in this work [...] Read more.
We highlight microgel/enzyme thin films that were deposited onto solid interfaces via two sequential steps, the adsorption of temperature- and pH-sensitive microgels, followed by their complexation with the enzyme choline oxidase, ChO. Two kinds of functional (ionic) microgels were compared in this work in regard to their adsorptive behavior and interaction with ChO, that is, poly(N-isopropylacrylamide-co-N-(3-aminopropyl)methacrylamide), P(NIPAM-co-APMA), bearing primary amino groups, and poly(N-isopropylacrylamide-co-N-[3-(dimethylamino) propyl]methacrylamide), P(NIPAM-co-DMAPMA), bearing tertiary amino groups. The stimuli-sensitive properties of the microgels in the solution were characterized by potentiometric titration, dynamic light scattering (DLS), and laser microelectrophoresis. The peculiarities of the adsorptive behavior of both the microgels and the specific character of their interaction with ChO were revealed by a combination of surface characterization techniques. The surface charge was characterized by electrokinetic analysis (EKA) for the initial graphite surface and the same one after the subsequent deposition of the microgels and the enzyme under different adsorption regimes. The masses of wet microgel and microgel/enzyme films were determined by quartz crystal microbalance with dissipation monitoring (QCM-D) upon the subsequent deposition of the components under the same adsorption conditions, on a surface of gold-coated quartz crystals. Finally, the enzymatic responses of the microgel/enzyme films deposited on graphite electrodes to choline were tested amperometrically. The presence of functional primary amino groups in the P(NIPAM-co-APMA) microgel enables a covalent enzyme-to-microgel coupling via glutar aldehyde cross-linking, thereby resulting in a considerable improvement of the biosensor operational stability. Full article
(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) The temperature dependence of the hydrodynamic radius of the P(NIPAM-<span class="html-italic">co</span>-APMA) microgel particles, where P(NIPAM-<span class="html-italic">co</span>-APMA) stands for poly(<span class="html-italic">N</span>-isopropylacrylamide-<span class="html-italic">co</span>-<span class="html-italic">N</span>-(3-aminopropyl)methacrylamide), at pH 5.5 (α ≅ 1.0) and pH 9.5 (α ≅ 0.45). (<b>b</b>) The pH-dependence of the protonation degree α of the P(NIPAM-<span class="html-italic">co</span>-APMA) microgel obtained from the potentiometric titration data (blue circles) and the electrophoretic mobility (EPM) values of the microgel particles at different pH-values obtained at 25 °C by laser microelectrophoresis (red circles).</p> Full article ">Figure 2
<p>(<b>a</b>) <span class="html-italic">ζ</span>-potential as a function of the pH for the bare graphite surface and the graphite surface modified with MnO<sub>2</sub>; (<b>b</b>) <span class="html-italic">ζ</span>-potential as a function of the pH for the film of the P(NIPAM-<span class="html-italic">co</span>-APMA) microgel adsorbed at different pH-values and temperatures onto graphite surface premodified with MnO<sub>2</sub>, and further interacted with choline oxidase (ChO) at pH 7 and room temperature. (<b>c</b>) <span class="html-italic">ζ</span>-potential as a function of the pH for the film of the P(NIPAM-<span class="html-italic">co</span>-DMAPMA) microgel, where P(NIPAM-<span class="html-italic">co</span>-DMAPMA) stands for poly(<span class="html-italic">N</span>-isopropylacrylamide-<span class="html-italic">co</span>-<span class="html-italic">N</span>-[3-(dimethylamino)propyl] methacrylamide), adsorbed at pH 9.3 and different temperatures onto graphite surface premodified with MnO<sub>2</sub> and further interacted with ChO at pH 7 and room temperature. The support is a poly(vinyl chloride) (PVC) film. MG is the abbreviation used for a microgel.</p> Full article ">Figure 3
<p>Normalized frequency, <span class="html-italic">F/n</span>, (blue lines) and dissipation, <span class="html-italic">D</span>, (red lines) shifts for gold-coated quartz crystal upon the adsorption of the P(NIPAM-<span class="html-italic">co</span>-APMA) microgel (<b>a</b>,<b>c</b>) or the P(NIPAM-<span class="html-italic">co</span>-DMAPMA) microgel (<b>b</b>,<b>d</b>), followed by the adsorption of ChO. Conditions: (Step 1) microgel adsorption from 1 g/L at pH 9.3 at 25 °C (<b>a</b>,<b>b</b>) or 50 °C (<b>c</b>,<b>d</b>); (Step 1′) temperature-induced swelling of the microgel film at pH 9.3 upon a temperature decrease from 50 to 25 °C; (Step 1″) temperature-induced deswelling of the microgel film at pH 9.3 upon a temperature increase from 25 to 50 °C; (Step 2) ChO uptake from the solution with the enzyme concentration of 0.4 g/L at pH 7.0 by the microgel film at 25 °C, in the case of the microgel film deposited at 50 °C, the enzyme uptake takes place simultaneously with microgel swelling upon a temperature jump from 50 to 25 °C (‘spongelike’ adsorption).</p> Full article ">Figure 4
<p>Sensor responses to choline (10<sup>−5</sup> M) measured in 50 mM HEPES/30 mM KCl buffer (pH 7.5) at room temperature for the P(NIPAM-<span class="html-italic">co</span>-APMA)/ChO or P(NIPAM-<span class="html-italic">co</span>-DMAPMA)/ChO films vs. the enzyme adsorption time used for the biosensor preparation. Conditions of the fabrication of the microgel/enzyme films: (1) Adsorption of the microgels onto the SPE/MnO<sub>2</sub>-surface from 1 g/L solution at pH 9.3 at 50 °C for 1 h, followed by washing. (2) Uptake of ChO from 4 g/L solution at pH 7.0 at room temperature for a specified time, followed by washing. Lines through the experimentally obtained datapoints are drawn only as a guide to the eye. SPE stands for a screen-printed electrode.</p> Full article ">Scheme 1
<p>Bottom-up construction of microgel-based biosensor setups.</p> Full article ">Scheme 2
<p>(<b>a</b>) Principle of electrochemical detection of choline and (<b>b</b>) a typical biosensor response to the addition of choline.</p> Full article ">
11 pages, 6211 KiB  
Article
Synthesis and Characterization of Fully Conjugated Ladder Naphthalene Bisimide Copolymers
by Feng Liu, Yonggang Wu, Chao Wang, Junshu Ma, Fan Wu, Ye Zhang and Xinwu Ba
Polymers 2018, 10(7), 790; https://doi.org/10.3390/polym10070790 - 18 Jul 2018
Cited by 9 | Viewed by 4730
Abstract
Fully conjugated ladder copolymers have attracted considerable attention due to their unique fused-ring structure and optoelectronic properties. In this study, two fully conjugated ladder naphthalene diimide (NDI) copolymers, P(NDI-CZL) and P(NDI-TTL) with imine-bridged structures are presented in high yields. Both of the two [...] Read more.
Fully conjugated ladder copolymers have attracted considerable attention due to their unique fused-ring structure and optoelectronic properties. In this study, two fully conjugated ladder naphthalene diimide (NDI) copolymers, P(NDI-CZL) and P(NDI-TTL) with imine-bridged structures are presented in high yields. Both of the two copolymers have good solubility and high thermal stability. The corresponding compounds with the same structure as the copolymers were synthesized as model system. The yields for each step of the synthesis of the model compounds are higher than 95%. These results suggest that P(NDI-CZL) and P(NDI-TTL) can be synthesized successfully with fewer structural defects. The structures and optoelectronic properties of compounds and copolymers are investigated by NMR, fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and cyclic voltammetry (CV). Both in solution and as a thin film, the two copolymers show two UV-vis absorption bands (around 300–400 nm and 400–750 nm) and a very weak fluorescence. The collective results suggest that the two fully conjugated ladder copolymers can be used as potential acceptor materials. Full article
(This article belongs to the Special Issue Synthesis and Application of Conjugated Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The SEC chromatograms of polymers.</p> Full article ">Figure 2
<p>The thermogravimetric analysis (TGA) traces of the polymers. (<b>a</b>) for P(NDI-CZ), P(NDI-CZL) and (<b>b</b>) for P(NDI-TT), P(NDI-TTL).</p> Full article ">Figure 3
<p>The differential scanning calorimetry (DSC) thermograms of the polymers. (<b>a</b>) for P(NDI-CZ), P(NDI-CZL) and (<b>b</b>) for P(NDI-TT), P(NDI-TTL).</p> Full article ">Figure 4
<p>FTIR Spectra of compounds and copolymers before and after ladderization. (<b>a</b>,<b>b</b>) for compounds; (<b>c</b>,<b>d</b>) for copolymers.</p> Full article ">Figure 5
<p>(<b>a</b>,<b>c</b>) Solution UV-vis absorption spectra; (<b>b</b>,<b>d</b>) thin-film UV-vis absorption spectra.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>c</b>) Solution UV-vis absorption spectra; (<b>b</b>,<b>d</b>) thin-film UV-vis absorption spectra.</p> Full article ">Figure 7
<p>The cyclic voltammograms of polymers (0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) in CH<sub>2</sub>Cl<sub>2</sub> solution, the scan rate was 30 mV·s<sup>−1</sup>).</p> Full article ">Scheme 1
<p>The synthetic routes to compound NDI-CZL and polymer P(NDI-CZL).</p> Full article ">Scheme 2
<p>The synthetic routes to compound NDI-TTL and polymer P(NDI-TTL).</p> Full article ">
7 pages, 1757 KiB  
Communication
Controlling the Internal Structures of Polymeric Microspheres via the Introduction of a Water-Soluble Organic Solvent
by Yanping He, Xin Li, Tianci Zhu, Mengxing Shan, Linhua Zhu, Tian Si, Hong Wang and Yanlin Sun
Polymers 2018, 10(7), 789; https://doi.org/10.3390/polym10070789 - 18 Jul 2018
Cited by 12 | Viewed by 4367
Abstract
Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in [...] Read more.
Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale. Full article
(This article belongs to the Special Issue Microporous Organic Polymers: Synthesis, Characterization and Applications)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Optical microscope images and SEM images of PS microspheres prepared under varying experimental conditions: concentrations of EtOH at (<b>a</b>) 0, (<b>b</b>) 5.0 wt %, (<b>c</b>) 7.0 wt %, (<b>d</b>) 10.0 wt %, (<b>e</b>) 14.0 wt %, (<b>f</b>) 20.0 wt %.</p> Full article ">Figure 2
<p>The diameter of PS microspheres as a function of the EtOH concentration.</p> Full article ">Figure 3
<p>(<b>a</b>) Schematic diagrams of the process to prepare polymeric microspheres; (<b>b</b>) the mechanism to control the inner structures of polymeric microspheres by introducing a water-soluble organic solvent.</p> Full article ">Figure 4
<p>SEM images of PS microspheres prepared under varying experimental conditions: (<b>a</b>–<b>d</b>) water is used as a continuous phase and PS/DCM is 5 wt %, 10 wt %, 16.7 wt %, 25 wt %, respectively; (<b>e</b>–<b>h</b>) 10.0 wt % EtOH solution is used as a continuous phase and PS/DCM is 5 wt %, 10 wt %, 16.7 wt %, 25 wt %, respectively.</p> Full article ">Figure 4 Cont.
<p>SEM images of PS microspheres prepared under varying experimental conditions: (<b>a</b>–<b>d</b>) water is used as a continuous phase and PS/DCM is 5 wt %, 10 wt %, 16.7 wt %, 25 wt %, respectively; (<b>e</b>–<b>h</b>) 10.0 wt % EtOH solution is used as a continuous phase and PS/DCM is 5 wt %, 10 wt %, 16.7 wt %, 25 wt %, respectively.</p> Full article ">
13 pages, 1095 KiB  
Article
Multi-Objective Optimization of Acoustic Performances of Polyurethane Foam Composites
by Shuming Chen, Wenbo Zhu and Yabing Cheng
Polymers 2018, 10(7), 788; https://doi.org/10.3390/polym10070788 - 18 Jul 2018
Cited by 31 | Viewed by 4707
Abstract
Polyurethane (PU) foams are widely used as acoustic package materials to eliminate vehicle interior noise. Therefore, it is important to improve the acoustic performances of PU foams. In this paper, the grey relational analysis (GRA) method and multi-objective particle swarm optimization (MOPSO) algorithm [...] Read more.
Polyurethane (PU) foams are widely used as acoustic package materials to eliminate vehicle interior noise. Therefore, it is important to improve the acoustic performances of PU foams. In this paper, the grey relational analysis (GRA) method and multi-objective particle swarm optimization (MOPSO) algorithm are applied to improve the acoustic performances of PU foam composites. The average sound absorption coefficient and average transmission loss are set as optimization objectives. The hardness and content of Ethylene Propylene Diene Monomer (EPDM) and the content of deionized water and modified isocyanate (MDI) are selected as design variables. The optimization process of GRA method is based on the orthogonal arrays L9(34), and the MOPSO algorithm is based on the Response Surface (RS) surrogate model. The results show that the acoustic performances of PU foam composites can be improved by optimizing the synthetic formula. Meanwhile, the results that were obtained by GRA method show the degree of influence of the four design variables on the optimization objectives, and the results obtained by MOPSO algorithm show the specific effects of the four design variables on the optimization objectives. Moreover, according to the confirmation experiment, the optimal synthetic formula is obtained by MOPSO algorithm when the weight coefficient of the two objectives set as 0.5. Full article
(This article belongs to the Special Issue Polymeric Foams)
►▼ Show Figures

Figure 1

Figure 1
<p>Pareto solutions of Response Surface (RS) model.</p> Full article ">Figure 2
<p>(<b>a</b>) Effect of chemical compositions on sound absorption ability; (<b>b</b>) Effect of functional particle on sound absorption ability; (<b>c</b>) Effect of chemical compositions on sound insulation ability; and (<b>d</b>) Effect of functional particle on sound insulation ability.</p> Full article ">Figure 3
<p>Acoustic performances curve of the PU foam composites (<b>a</b>) Sound absorption coefficient curves; and, (<b>b</b>) Transmission loss curves.</p> Full article ">
25 pages, 572 KiB  
Article
Dynamics of a Polymer Network Modeled by a Fractal Cactus
by Aurel Jurjiu and Mircea Galiceanu
Polymers 2018, 10(7), 787; https://doi.org/10.3390/polym10070787 - 18 Jul 2018
Cited by 12 | Viewed by 4137
Abstract
In this paper, we focus on the relaxation dynamics of a polymer network modeled by a fractal cactus. We perform our study in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. By performing real-space renormalization transformations, we [...] Read more.
In this paper, we focus on the relaxation dynamics of a polymer network modeled by a fractal cactus. We perform our study in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. By performing real-space renormalization transformations, we determine analytically the whole eigenvalue spectrum of the connectivity matrix, thereby rendering possible the analysis of the Rouse-dynamics at very large generations of the structure. The evaluation of the structural and dynamical properties of the fractal network in the Rouse type-approach reveals that they obey scaling and the dynamics is governed by the value of spectral dimension. In the Zimm-type approach, the relaxation quantities show a strong dependence on the strength of the hydrodynamic interaction. For low and medium hydrodynamic interactions, the relaxation quantities do not obey power law behavior, while for slightly larger interactions they do. Under strong hydrodynamic interactions, the storage modulus does not follow power law behavior and the average displacement of the monomer is very low. Remarkably, the theoretical findings with respect to scaling in the intermediate domain of the relaxation quantities are well supported by experimental results from the literature. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The fractal cactus polymer network at generations 1, 2, and 3.</p> Full article ">Figure 2
<p>Histogram of the eigenvalues of the connectivity matrix <math display="inline"><semantics> <mi mathvariant="bold">A</mi> </semantics></math> for the fractal cactus network of size <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>12</mn> </msup> </mrow> </semantics></math>. The width of the bins is 0.001.</p> Full article ">Figure 3
<p>The mean-squared radius of gyration of the fractal cactus network calculated in the Rouse model.</p> Full article ">Figure 4
<p>The averaged monomer displacement under the action of an external force in the Rouse model. Displayed in dimensionless units is the <math display="inline"><semantics> <mrow> <mo>&lt;</mo> <mo>&lt;</mo> <mi>Y</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> <mo>&gt;</mo> <mo>&gt;</mo> </mrow> </semantics></math> for the fractal cactus networks with <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>6</mn> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>9</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>12</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>15</mn> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>3</mn> <mn>18</mn> </msup> </semantics></math> from above. For guidance, the black dashed lines indicate that the slope equals 1.</p> Full article ">Figure 5
<p>Storage modulus <math display="inline"><semantics> <mrow> <msup> <mi>G</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>, displayed in dimensionless units for the fractal cactus networks with <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>6</mn> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>9</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>12</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>15</mn> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>3</mn> <mn>18</mn> </msup> </semantics></math> from below. For guidance, the dashed black line indicates the slope 2 and the red dashed line indicates the slope 0, Rouse model.</p> Full article ">Figure 6
<p>Loss modulus <math display="inline"><semantics> <mrow> <msup> <mi>G</mi> <mrow> <mo>″</mo> </mrow> </msup> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>, displayed in dimensionless units for the fractal cactus networks with <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>6</mn> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>9</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>12</mn> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>3</mn> <mn>15</mn> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>3</mn> <mn>18</mn> </msup> </semantics></math> from below. For guidance, the dashed black line indicates the slope 1 and the red dashed line indicates the slope <math display="inline"><semantics> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </semantics></math>, Rouse model.</p> Full article ">Figure 7
<p>Averaged monomer displacement <math display="inline"><semantics> <mrow> <mo>&lt;</mo> <mo>&lt;</mo> <mi>Y</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> <mo>&gt;</mo> <mo>&gt;</mo> </mrow> </semantics></math> of the fractal cactus network under the action of external forces in the Zimm model. Displayed in dimensionless units are the results for the network size <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>8</mn> </msup> </mrow> </semantics></math> and hydrodynamic interaction strength <math display="inline"><semantics> <mrow> <msub> <mi>ζ</mi> <mi>r</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>25</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>3</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>33</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>4</mn> </mrow> </semantics></math>. For guidance, the black dashed lines indicate that the slope equals 1.</p> Full article ">Figure 8
<p>Local slopes <math display="inline"><semantics> <mi>γ</mi> </semantics></math> of the curves of <a href="#polymers-10-00787-f007" class="html-fig">Figure 7</a>. The inset gives the considered values of the hydrodynamic interaction strength. Zimm model.</p> Full article ">Figure 9
<p>Storage modulus <math display="inline"><semantics> <mrow> <msup> <mi>G</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>, displayed in dimensionless units for the fractal cactus network of size <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>8</mn> </msup> </mrow> </semantics></math> and hydrodynamic interaction strength <math display="inline"><semantics> <mrow> <msub> <mi>ζ</mi> <mi>r</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>25</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>3</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>33</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>4</mn> </mrow> </semantics></math>. For guidance, the dashed black line indicates slope 2 and the red dashed line indicates slope 0. Zimm model.</p> Full article ">Figure 10
<p>Local slopes <math display="inline"><semantics> <mi>α</mi> </semantics></math> of the curves of <a href="#polymers-10-00787-f009" class="html-fig">Figure 9</a>. The inset gives the considered values of the hydrodynamic interaction strength. Zimm model.</p> Full article ">Figure 11
<p>Left-hand side panel: Storage modulus <math display="inline"><semantics> <mrow> <msup> <mi>G</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>, displayed in dimensionless units for the dual Sierpinski gasket with size <math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <msup> <mn>3</mn> <mn>8</mn> </msup> </mrow> </semantics></math>, and the hydrodynamic interaction strength <math display="inline"><semantics> <mrow> <msub> <mi>ζ</mi> <mi>r</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>25</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>3</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>36</mn> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>38</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mn>0</mn> <mo>.</mo> <mn>45</mn> </mrow> </semantics></math>. For guidance, the dashed black line indicates slope 2 and the red dashed line indicates slope 0. Right-hand side panel: Local slopes <math display="inline"><semantics> <mi>α</mi> </semantics></math> of the curves of the left-hand side panel. Zimm model.</p> Full article ">Figure A1
<p>First transformation.</p> Full article ">Figure A2
<p>Second transformation.</p> Full article ">
9 pages, 2029 KiB  
Article
Novel PSMA-Coated On-Off-On Fluorescent Chemosensor Based on Organic Dots with AIEgens for Detection of Copper (II), Iron (III) and Cysteine
by Rui Jiang, Na Liu, Fan Li, Wensheng Fu, Yun Zhou and Yan Zhang
Polymers 2018, 10(7), 786; https://doi.org/10.3390/polym10070786 - 17 Jul 2018
Cited by 15 | Viewed by 4370
Abstract
Herein, a novel on-off-on fluorescent chemosensor for copper (II) ion (Cu2+), iron (III) ion (Fe3+) and cysteine is developed simply by the nano-precipitation method. The prepared organic dots with AIEgens (AIE dots) are advantageous over other metal ions in [...] Read more.
Herein, a novel on-off-on fluorescent chemosensor for copper (II) ion (Cu2+), iron (III) ion (Fe3+) and cysteine is developed simply by the nano-precipitation method. The prepared organic dots with AIEgens (AIE dots) are advantageous over other metal ions in detecting Cu2+, Fe3+ with high selectivity and sensitivity by forming agglomerations (on-off). The agglomerations formed by AIE dots and Cu2+ redistributed and the fluorescence was obviously recovered in the presence of cysteine (off-on). This sensor has a wide linear range for Cu2+, Fe3+ and cysteine. The fluorescent detection limits of AIE dots are calculated to be 107 nM for Cu2+, 120 nM for Fe3+ and 78 nM for cysteine, respectively. These results indicate that the AIE dots can be used as a potential probe for Cu2+, Fe3+ and cysteine detection. Full article
(This article belongs to the Special Issue Polymer Based Bio-Sensors)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Absorption, excitation, and emission spectra of AIE dots; (<b>B</b>) the fluorescence quantum yield of AIE dots as a function of the mass ratio between PSMA and DSA (PSMA:DSA = 4:1, 2:1, 1:1, 1:2).</p> Full article ">Figure 2
<p>(<b>A</b>) Fluorescence spectra of AIE dots in the presence of different metal ions (20 μM). (<b>B</b>) Selective fluorescence responses of the Cu<sup>2+</sup> system in the presence of other metal ions. The black bars represent the emission in the presence of different ions with a concentration of 0.1 mM. The red bars represent the emission in the presence of 20 μM Cu<sup>2+</sup> and another metal ion with a concentration of 0.1 mM. <span class="html-italic">F</span><sub>0</sub> and <span class="html-italic">F</span> correspond to the fluorescence intensity at 524 nm in the absence and the presence of Cu<sup>2+</sup>, respectively. (<b>C</b>) TEM image of AIE dots. (<b>D</b>) TEM image of AIE dots with Cu<sup>2+</sup> (20 μM).</p> Full article ">Figure 3
<p>(<b>A</b>) Fluorescence spectra of AIE dots in the presence of different concentrations of Cu<sup>2+</sup> excited at 406 nm. (<b>B</b>) The plot of the fluorescence intensity ratio of AIE dots at 524 nm versus different concentrations of Cu<sup>2+</sup>; the inset shows the signal change in the Cu<sup>2+</sup> concentration range of 0–6 μM.</p> Full article ">Figure 4
<p>(<b>A</b>) Fluorescence changes of AIE dots/Cu<sup>2+</sup> in the presence of different amino acids with a concentration of 5 μM. (<b>B</b>) Fluorescence intensity as a function of the cycle number. The fluorescence intensity of AIE dots after quenching by Cu<sup>2+</sup> (5 μM) can be recovered by the addition of 2.5 μM cysteine.</p> Full article ">Scheme 1
<p>The detection mechanism of AIE dots in the presence of Cu<sup>2+</sup> and cysteine.</p> Full article ">
14 pages, 2051 KiB  
Article
Poly(propylene 2,5-thiophenedicarboxylate) vs. Poly(propylene 2,5-furandicarboxylate): Two Examples of High Gas Barrier Bio-Based Polyesters
by Giulia Guidotti, Michelina Soccio, Nadia Lotti, Massimo Gazzano, Valentina Siracusa and Andrea Munari
Polymers 2018, 10(7), 785; https://doi.org/10.3390/polym10070785 - 17 Jul 2018
Cited by 77 | Viewed by 5712
Abstract
Both academia and industry are currently devoting many efforts to develop high gas barrier bioplastics as substitutes of traditional fossil-based polymers. In this view, this contribution presents a new biobased aromatic polyester, i.e., poly(propylene 2,5-thiophenedicarboxylate) (PPTF), which has been compared with the furan-based [...] Read more.
Both academia and industry are currently devoting many efforts to develop high gas barrier bioplastics as substitutes of traditional fossil-based polymers. In this view, this contribution presents a new biobased aromatic polyester, i.e., poly(propylene 2,5-thiophenedicarboxylate) (PPTF), which has been compared with the furan-based counterpart (PPF). Both biopolyesters have been characterized from the molecular, thermo-mechanical and structural points of view. Gas permeability behavior has been evaluated with respect to 100% oxygen, carbon dioxide and nitrogen at 23 °C. In case of CO2 gas test, gas transmission rate has been also measured at different temperatures. The permeability behavior at different relative humidity has been investigated for both biopolyesters, the thiophen-containing sample demonstrating to be better than the furan-containing counterpart. PPF’s permeability behavior became worse than PPTF’s with increasing RH, due to the more polar nature of the furan ring. Both biopolyesters under study are characterized by superior gas barrier performances with respect to PEF and PET. With the simple synthetic strategy adopted, the exceptional barrier properties render these new biobased polyesters interesting alternatives in the world of green and sustainable packaging materials. The different polarity and stability of heterocyclic rings was revealed to be an efficient tool to tailor the ability of crystallization, which in turn affects mechanical and barrier performances. Full article
(This article belongs to the Special Issue Polymers for Packaging Applications)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Poly(propylene 2,5-furandicarboxylate) (PPF) and poly(propylene 2,5-thiophendicarboxylate) (PPTF) chemical structure.</p> Full article ">Figure 2
<p>Dipole moment vector of furan and thiophene rings.</p> Full article ">Figure 3
<p><sup>1</sup>H-NMR spectrum of: (<b>a</b>) PPF; (<b>b</b>) PPTF with resonance assignments.</p> Full article ">Figure 4
<p>Thermogravimetric curve (solid line) and corresponding derivative (dashed line) under nitrogen flow for PPF and PPTF.</p> Full article ">Figure 5
<p>Calorimetric traces of PPF and PPTF powder and film (20 °C/min): 1st scan and 2nd scan after melt quenching.</p> Full article ">Figure 6
<p>X-ray diffraction profiles of PPTF powder, PPTF film, PPF powder, PPF film and PPF film after annealing for 45 min. at 110 °C.</p> Full article ">Figure 7
<p>XRD patterns collected in situ at the indicated temperatures for PPTF powder (<b>A</b>) and PPTF film (<b>B</b>).</p> Full article ">Figure 8
<p>GTR at 23 °C and 38 °C 0% RH, at 23 °C and 85% RH, at 38 °C and 90% RH.</p> Full article ">
11 pages, 1949 KiB  
Article
Modeling of Laser Beam Absorption in a Polymer Powder Bed
by Fuad Osmanlic, Katrin Wudy, Tobias Laumer, Michael Schmidt, Dietmar Drummer and Carolin Körner
Polymers 2018, 10(7), 784; https://doi.org/10.3390/polym10070784 - 17 Jul 2018
Cited by 42 | Viewed by 6510
Abstract
In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the [...] Read more.
In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for polymer powders and, therefore, can increase the energy density at the powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine powder distributions and high powder bed densities are discussed. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The incoming ray <math display="inline"><semantics> <mover accent="true"> <mi>k</mi> <mo stretchy="false">→</mo> </mover> </semantics></math> is divided into a reflected <math display="inline"><semantics> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">→</mo> </mover> <mi>R</mi> </msub> </semantics></math> and refracted <math display="inline"><semantics> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">→</mo> </mover> <mi>T</mi> </msub> </semantics></math> part at the interface of media <span class="html-italic">A</span> and <span class="html-italic">B</span>. <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> are the reflection and refraction angle, respectively.</p> Full article ">Figure 2
<p>(<b>Left</b>) Arbitrary geometry <span class="html-italic">G</span>. (<b>Middle</b>) Volume of fluid (VOF) representation of <span class="html-italic">G</span> on a 5 × 5 grid. The exact surface is indicated by the dashed line. The grey scale shows the volume fraction of the geometry within one cell. (<b>Right</b>) Reconstruction of the surface in one cell.</p> Full article ">Figure 3
<p>Relative intensity distribution of a laser irradiating onto a flat surface with two incident angles <math display="inline"><semantics> <mi>γ</mi> </semantics></math> of <math display="inline"><semantics> <msup> <mn>0</mn> <mo>∘</mo> </msup> </semantics></math> (upper row) and <math display="inline"><semantics> <msup> <mn>45</mn> <mo>∘</mo> </msup> </semantics></math> (lower row) for three different spatial resolutions <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>x</mi> <mo>=</mo> <mfenced separators="" open="[" close="]"> <mn>40</mn> <mspace width="4pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> <mo>,</mo> <mspace width="0.277778em"/> <mn>20</mn> <mspace width="4pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> <mo>,</mo> <mspace width="0.277778em"/> <mn>5</mn> <mspace width="4pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mfenced> </mrow> </semantics></math> (left to right).</p> Full article ">Figure 4
<p>Comparison of the analytical (Equation (<a href="#FD15-polymers-10-00784" class="html-disp-formula">15</a>)) and numerical relative intensity distribution in the beam center along the normal direction for five resolutions and three incident angles.</p> Full article ">Figure 5
<p>Trace of a ray cast from the top of the simulation domain propagating towards a powder bed. From left to right, the number of rays is increased.</p> Full article ">Figure 6
<p>Sampling area for infrared spectroscopy mapping and positions for infrared spectra.</p> Full article ">Figure 7
<p>(<b>Left</b>) Relative transmission in a thin foil of PA12 with different film thicknesses. (<b>Right</b>) Comparison of the relative transmission and reflection in a PA12 powder bed between experimental data [<a href="#B15-polymers-10-00784" class="html-bibr">15</a>] and the simulation.</p> Full article ">Figure 8
<p>(<b>Right</b>) Three powder beds with their relative absorbed intensity distributions. (<b>Left</b>) The mean intensity <math display="inline"><semantics> <msub> <mi>I</mi> <mi>m</mi> </msub> </semantics></math> over the powder bed depth for the corresponding relative densities with <math display="inline"><semantics> <mrow> <msub> <mi>n</mi> <mrow> <mi>m</mi> <mi>e</mi> <mi>d</mi> </mrow> </msub> <mo>=</mo> <mn>1.7</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>100</mn> <mspace width="0.277778em"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m.</p> Full article ">Figure 9
<p>The correlation between <math display="inline"><semantics> <msub> <mi>λ</mi> <mrow> <mi>e</mi> <mi>f</mi> <mi>f</mi> </mrow> </msub> </semantics></math> and <math display="inline"><semantics> <msub> <mi>ρ</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>l</mi> </mrow> </msub> </semantics></math> for three different refractive indices. The dot-dashed line indicates penetration depth <math display="inline"><semantics> <mrow> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>100</mn> <mspace width="0.277778em"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m in bulk material.</p> Full article ">
22 pages, 22531 KiB  
Article
Enhancement of Colour Effects of Dyed-Yarn Mixed Fabrics Using Cramming Motion and Finer Polyester Yarns
by Lau Yiu Tang, Xiao Tian and Tao Hua
Polymers 2018, 10(7), 783; https://doi.org/10.3390/polym10070783 - 16 Jul 2018
Cited by 2 | Viewed by 4218
Abstract
This paper reports the study of the effects of cramming motion implemented during weaving and finer weft yarns used on dyed-yarn mixed woven fabrics produced by using raw white warps and multicolored-wefts. The cramming motion was used to increase the dyed-weft yarns cover [...] Read more.
This paper reports the study of the effects of cramming motion implemented during weaving and finer weft yarns used on dyed-yarn mixed woven fabrics produced by using raw white warps and multicolored-wefts. The cramming motion was used to increase the dyed-weft yarns cover factor of fabric, and thus, to reduce the negative effect of white warp floats at the fabric face on the color attributes of fabric. The surface structure of fabric was characterized by using several key geometrical parameters that determined the resultant fabric color attributes. The effects of fabric structure and density, weft yarn count, and the introduction of black yarn on the fabric face layer on the fabric surface geometrical parameters, physical properties, as well as color attributes were investigated under the implementation of cramming motion on the fabric. The color attributes of fabrics using cramming motion and finer yarns were also compared to the fabrics without cramming motion. The experimental results indicate that the weft yarn density and cover factor of fabric face layer are increased by applying cramming motion and finer yarns for fabricating the blue-red and/or black mixed fabrics. Consequently, the fabric lightness can be further reduced for achieving a better color effect on colorful and figured woven fabrics mainly using dyed-wefts for color mixing. Full article
(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Diagrams of structures of fabric face layer: (<b>a</b>) RE-BLU mixing; (<b>b</b>) RE-BLU-BLK mixing.</p> Full article ">Figure 2
<p>Application of characterization of geometry of fabric face layer: (<b>a</b>) RE-BLU mixing; (<b>b</b>) RE-BLU-BLK mixing.</p> Full article ">Figure 3
<p>Effect of fabric weave on the width of repeating unit.</p> Full article ">Figure 4
<p>Effect of fabric weave on the length of one weave repeat.</p> Full article ">Figure 5
<p>Effect of fabric weave on the length of one segment.</p> Full article ">Figure 6
<p>Effect of fabric weave on the distance between two adjacent face weft yarns.</p> Full article ">Figure 7
<p>Effect of fabric density on the geometrical parameters: (<b>a</b>) width of repeating unit; (<b>b</b>) length of repeating unit; (<b>c</b>) length of segment; (<b>d</b>) spacing between two adjacent face weft yarns in different segments.</p> Full article ">Figure 7 Cont.
<p>Effect of fabric density on the geometrical parameters: (<b>a</b>) width of repeating unit; (<b>b</b>) length of repeating unit; (<b>c</b>) length of segment; (<b>d</b>) spacing between two adjacent face weft yarns in different segments.</p> Full article ">Figure 8
<p>Effect of weft yarn count on the geometrical parameters: (<b>a</b>) width of repeating unit; (<b>b</b>) length of repeating unit; (<b>c</b>) length of one segment; (<b>d</b>) spacing between two adjacent face weft yarns in different segments.</p> Full article ">Figure 9
<p>Comparison of fabric thickness.</p> Full article ">Figure 10
<p>Comparison of fabric weight.</p> Full article ">Figure 11
<p>Comparison of fabric tensile property: (<b>a</b>) in warp-wise; (<b>b</b>) in weft-wise.</p> Full article ">Figure 12
<p>Comparison between fabrics in different fabric weave in terms of fabrics’ color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c</b>) b*.</p> Full article ">Figure 12 Cont.
<p>Comparison between fabrics in different fabric weave in terms of fabrics’ color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c</b>) b*.</p> Full article ">Figure 13
<p>Comparison between fabrics in different weft density in terms of fabrics color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c)</b> b*.</p> Full article ">Figure 14
<p>Comparison between fabrics in different weft linear density in terms of fabrics’ color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c</b>) b*.</p> Full article ">Figure 15
<p>Influence of adding black yarn floats on the fabric color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c</b>) b*.</p> Full article ">Figure 15 Cont.
<p>Influence of adding black yarn floats on the fabric color performance: (<b>a</b>) L*; (<b>b</b>) a*; (<b>c</b>) b*.</p> Full article ">Figure 16
<p>Comparison of the fabric lightness with blue-red fabric without cramming motion [<a href="#B20-polymers-10-00783" class="html-bibr">20</a>].</p> Full article ">Figure 17
<p>Comparison of the fabric lightness with blue-red-black fabric without cramming motion [<a href="#B20-polymers-10-00783" class="html-bibr">20</a>].</p> Full article ">
13 pages, 3911 KiB  
Article
Synthesis of Benzene Tetracarboxamide Polyamine and Its Effect on Epoxy Resin Properties
by Seoyoon Yu, Wonjoo Lee, Bongkuk Seo and Chung-Sun Lim
Polymers 2018, 10(7), 782; https://doi.org/10.3390/polym10070782 - 16 Jul 2018
Cited by 5 | Viewed by 5704
Abstract
Epoxy resins have found various industrial applications in high-performance thermosetting resins, high-performance composites, electronic-packaging materials, adhesives, protective coatings, etc., due to their outstanding performance, including high toughness, high-temperature performance, chemical and environmental resistance, versatile processability and adhesive properties. However, cured epoxy resins are [...] Read more.
Epoxy resins have found various industrial applications in high-performance thermosetting resins, high-performance composites, electronic-packaging materials, adhesives, protective coatings, etc., due to their outstanding performance, including high toughness, high-temperature performance, chemical and environmental resistance, versatile processability and adhesive properties. However, cured epoxy resins are very brittle, which limits their applications. In this work, we attempted to enhance the toughness of cured epoxy resins by introducing benzene tetracarboxamide polyamine (BTCP), synthesized from pyromellitic dianhydride (PMDA) and diamines in N-methyl-2-pyrrolidone (NMP) solvent. During this reaction, increased viscosity and formation of amic acid could be confirmed. The chemical reactions were monitored and evidenced using 1H-NMR spectroscopy, FT-IR spectroscopy, water gel-phase chromatography (GPC) analysis, amine value determination and acid value determination. We also studied the effect of additives on thermomechanical properties using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamical mechanical analysis (DMA), thermomechanical analysis (TMA) and by measuring mechanical properties. The BTCP-containing epoxy resin exhibited high mechanical strength and adhesion strength proportional to the amount of BTCP. Furthermore, field-emission scanning electron microscopy images were obtained for examining the cross-sectional morphology changes of the epoxy resin specimens with varying amounts of BTCP. Full article
(This article belongs to the Special Issue Hybrid Materials Based on Thermosets)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical structures of the epoxy resin (Bisphenol A), curing agent (DICY) and BTCP.</p> Full article ">Figure 2
<p>Reaction scheme for the synthesis of BTCP.</p> Full article ">Figure 3
<p>Schematic illustrations of (<b>a</b>) neat epoxy networks and (<b>b</b>) hydrogen bonds and free volume in BTCP-modified epoxy networks.</p> Full article ">Figure 4
<p><sup>1</sup>H-NMR spectra of (<b>a</b>) amic acid and (<b>b</b>) BTCP.</p> Full article ">Figure 5
<p>FT-IR spectra of (<b>a</b>) diamine, (<b>b</b>) amic acid and (<b>c</b>) BTCP.</p> Full article ">Figure 6
<p>TMA graphs of epoxy compositions.</p> Full article ">Figure 7
<p>DMA graphs of epoxy compositions (<b>a</b>) storage modulus and (<b>b</b>) tan <span class="html-italic">δ</span>.</p> Full article ">Figure 8
<p>Universal tensile testing: (<b>a</b>) tensile strength and (<b>b</b>) elongation at break of cured epoxy compositions.</p> Full article ">Figure 9
<p>Flexural strength of cured epoxy samples.</p> Full article ">Figure 10
<p>Impact strength of cured epoxy samples.</p> Full article ">Figure 11
<p>FE-SEM images of the fractured surface after impact testing with different BTCP contents: (<b>a</b>) 0 phr, (<b>b</b>) 5 phr, (<b>c</b>) 10 phr and (<b>d</b>) 20 phr.</p> Full article ">
16 pages, 4467 KiB  
Article
The Synthesis of Low-Viscosity Organotin-Free Moisture-Curable Silane-Terminated Poly(Urethane-Urea)s
by Chen Tan, Viivi Luona, Teija Tirri and Carl-Eric Wilen
Polymers 2018, 10(7), 781; https://doi.org/10.3390/polym10070781 - 16 Jul 2018
Cited by 15 | Viewed by 6704
Abstract
This work explores the possibility of synthesizing moisture-curable silane-terminated poly(urethane-urea)s (SPURs) of low viscosity. First, NCO-terminated urethane prepolymers were prepared, followed by silane end-capping. The impact of polyol molecular weight and the ratio of isocyanate to polyol (NCO/OH) on viscosity and the properties [...] Read more.
This work explores the possibility of synthesizing moisture-curable silane-terminated poly(urethane-urea)s (SPURs) of low viscosity. First, NCO-terminated urethane prepolymers were prepared, followed by silane end-capping. The impact of polyol molecular weight and the ratio of isocyanate to polyol (NCO/OH) on viscosity and the properties of SPUR were examined. As alternatives to the organotin catalysts traditionally used for the polyurethane synthesis and curing processes, bismuth carboxylate catalysts were evaluated. In addition, the effect of organofunctional groups in the aminosilane structure (R1–NH–R2–Si(OR3)3), i.e., R1 (alkyl, aryl or trimethoxysilyl-propyl), the spacer R2 (α or γ) and alkyl group R3 (methyl or ethyl), was examined. The chemical and physical structures of the SPUR were investigated by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and the mechanical properties were evaluated by tensile tests. The results reveal that silane-terminated, moisture-curable polyurethanes can be successfully synthesized and cured with bismuth carboxylate catalysts. SPUR exhibiting low viscosity, with adequate tensile strength and elongation can be prepared using environmentally benign bismuth carboxylate catalyst having a high metal content of 19%–21%, by utilizing secondary aminosilane end-cappers and an optimal combination of the polyol molecular weight and NCO/OH ratio. Full article
(This article belongs to the Collection Polymeric Adhesives)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Two general routes for SPUR synthesis.</p> Full article ">Figure 2
<p><sup>1</sup>H-NMR spectrum of SPUR 6.</p> Full article ">Figure 3
<p><sup>13</sup>C-NMR spectrum of SPUR 6.</p> Full article ">Figure 4
<p>The expanded <sup>13</sup>C-NMR spectra (155–157 ppm) for samples with different catalysts.</p> Full article ">Figure 5
<p>The comparison of ATR-FTIR spectra of SPUR 8 taken at different reaction stages.</p> Full article ">Figure 6
<p>The comparison of ATR-FTIR spectra of SPUR 8 before and after cure.</p> Full article ">Figure 7
<p>ATR-FTIR spectra in the isocyanate stretching region of samples taken at different reaction times during 1st stage reaction for different catalyst systems: (<b>a</b>) SPUR 2 (Bi2); (<b>b)</b> SPUR 7 (Bi1); (<b>c</b>) SPUR 8 (DOTL).</p> Full article ">Figure 7 Cont.
<p>ATR-FTIR spectra in the isocyanate stretching region of samples taken at different reaction times during 1st stage reaction for different catalyst systems: (<b>a</b>) SPUR 2 (Bi2); (<b>b)</b> SPUR 7 (Bi1); (<b>c</b>) SPUR 8 (DOTL).</p> Full article ">Figure 8
<p>The ATR-FTIR spectral comparison of relevant samples with different variables in N–H stretching region (3450–3200 cm<sup>−1</sup>) (left) and C=O stretching region (1760–1600 cm<sup>−1</sup>) (right). (<b>1a</b>,<b>b</b>): Impact of NCO/OH ratio; (<b>2a</b>,<b>b</b>): Impact of PPG chain length.</p> Full article ">Figure 8 Cont.
<p>The ATR-FTIR spectral comparison of relevant samples with different variables in N–H stretching region (3450–3200 cm<sup>−1</sup>) (left) and C=O stretching region (1760–1600 cm<sup>−1</sup>) (right). (<b>1a</b>,<b>b</b>): Impact of NCO/OH ratio; (<b>2a</b>,<b>b</b>): Impact of PPG chain length.</p> Full article ">Figure 9
<p>Effect of catalysts on cure time of formulated SPUR samples.</p> Full article ">Figure 10
<p>Effect of silanes on cure time of formulated SPUR samples.</p> Full article ">
17 pages, 7035 KiB  
Article
Preparation of Molecularly Imprinted Microspheres as Biomimetic Recognition Material for In Situ Adsorption and Selective Chemiluminescence Determination of Bisphenol A
by Yan Xiong, Qing Wang, Ming Duan, Jing Xu, Jie Chen and Shenwen Fang
Polymers 2018, 10(7), 780; https://doi.org/10.3390/polym10070780 - 16 Jul 2018
Cited by 12 | Viewed by 4139
Abstract
Bisphenol A (BPA) is an endocrine disrupter in environments which can induce abnormal differentiation of reproductive organs by interfering with the action of endogenous gonadal steroid hormones. In this work, the bisphenol A (BPA) molecularly-imprinted microspheres (MIMS) were prepared and used as biomimetic [...] Read more.
Bisphenol A (BPA) is an endocrine disrupter in environments which can induce abnormal differentiation of reproductive organs by interfering with the action of endogenous gonadal steroid hormones. In this work, the bisphenol A (BPA) molecularly-imprinted microspheres (MIMS) were prepared and used as biomimetic recognition material for in situ adsorption and selective chemiluminescence (CL) determination of BPA. Through non-covalent interaction, the BPA-MIMS was successfully prepared by Pickering emulsion polymerization using a BPA template, 4-vinylpyridine (4-VP) monomer, ethylene glycol dimethacrylate (EGDMA) cross-linker, and a SiO2 dispersion agent. The characterization of scanning electron microscopy (SEM) and energy-disperse spectroscopy (EDS) showed that the obtained MIMS possessed a regular spherical shape and narrow diameter distribution (25–30 μm). The binding experiment indicated BPA could be adsorbed in situ on the MIMS-packing cell with an apparent maximum amount Qmax of 677.3 μg g−1. Then BPA could be selectively detected by its sensitive inhibition effect on the CL reaction between luminol and periodate (KIO4), and the inhibition mechanism was discussed to reveal the CL reaction process. The CL intensity was linear to BPA concentrations in two ranges, respectively from 0.5 to 1.5 μg mL−1 with a detection limit of 8.0 ng mL−1 (3σ), and from 1.5 to 15 μg mL−1 with a limit of detection (LOD) of 80 ng mL−1 (3σ). The BPA-MIPMS showed excellent selectivity for BPA adsorption and the proposed CL method has been successfully applied to BPA determination in environmental water samples. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>The typical fluorescence responses to different BPA concentrations.</p> Full article ">Figure 2
<p>(<b>a</b>) The Langmuir adsorption isotherm curve of MIMS with equilibration time of 2 h; (<b>b</b>) Scatchard plot to estimate the binding nature of MIMS with equilibration time of 2 h; (<b>c</b>) kinetic adsorption curve for dynamic analysis of 10 μg mL<sup>−1</sup>; and (<b>d</b>) adsorption rate of MIMS with time changing.</p> Full article ">Figure 3
<p>(<b>a</b>) Optical image of SiO<sub>2</sub> NPs; (<b>b</b>) DLS measurement for size distribution; and (<b>c</b>) an optical image of emulsion droplets after locating the silica NPs at the interface.</p> Full article ">Figure 4
<p>(<b>a</b>) The surface morphologies of the dried MIMS examined using FESEM; (<b>b</b>) the surface morphologies of the MIMS examined using LSCM; and (<b>c</b>) FTIR spectra of the synthesized MIMS.</p> Full article ">Figure 5
<p>The EDS results of the MIMS after SiO<sub>2</sub> removing.</p> Full article ">Figure 6
<p>Spectra comparison in the presence and absence of BPA. (<b>a</b>) CL spectra; and (<b>b</b>) fluorescence spectra.</p> Full article ">Figure 7
<p>The linear response for different BPA concentration.</p> Full article ">Scheme 1
<p>(<b>a</b>) Schematic illustration of the synthesis of molecularly imprinted microspheres with self-assembly at Oil/Water interfaces in a SiO<sub>2</sub> NP-stabilized Pickering emulsion; and (<b>b</b>) the overall scheme of the BPA-MIMS fabrication process.</p> Full article ">
20 pages, 1075 KiB  
Article
Structure-Properties Relations for Polyamide 6, Part 2: Influence of Processing Conditions during Injection Moulding on Deformation and Failure Kinetics
by Emanuele Parodi, Gerrit W. M. Peters and Leon E. Govaert
Polymers 2018, 10(7), 779; https://doi.org/10.3390/polym10070779 - 16 Jul 2018
Cited by 15 | Viewed by 5624
Abstract
The effect of processing conditions during injection on the structure formation and mechanical properties of injection molded polyamide 6 samples was investigated in detail. A large effect of the mold temperature on the crystallographic properties was observed. Also the the effect of pressure [...] Read more.
The effect of processing conditions during injection on the structure formation and mechanical properties of injection molded polyamide 6 samples was investigated in detail. A large effect of the mold temperature on the crystallographic properties was observed. Also the the effect of pressure and shear flow was taken in to consideration and analysed. The yield and failure kinetics, including time-to-failure, were studied by performing tensile and creep tests at several test temperatures and relative humidities. As far as mechanical properties are concerned, a strong influence of temperature and relative humidity on the yield stress and time-to-failure was found. A semi-empirical model, able to describe yield and failure kinetics, was applied to the experimental results and related to the crystalline phase present in the sample. In agreement with findings in the literature it is observed that for high mold temperatures the sample morphology is more stable with respect to humidity and temperature than in case of low mold temperatures and this effects could be successfully captured by the model. The samples molded at low temperatures showed, during mechanical testing, a strong evolution of the crystallographic properties when exposed to high testing temperature and high relative humidity, i.e., an increase of crystallinity or a crystal phase transition. This makes a full description of the mechanical behavior rather complicated. Full article
(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic representation of a sample obtained by injection molding (70 × 70 × 1 mm).</p> Full article ">Figure 2
<p>WAXD integrated patterns of samples molded at different temperatures; experiments performed at room temperature (23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C) and dry condition.</p> Full article ">Figure 3
<p>Deconvolution analysis of WAXD patterns. Crystallinity, <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>γ</mi> </semantics></math> fractions as functions of mold temperature. (<b>a</b>) Case: compression molding, (<b>b</b>) case: injection molding.</p> Full article ">Figure 4
<p>Dilatometry-PVT experiment, cooling at ≈1 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C/s and 200 bar with no shear flow. The circle indicates the crystallization onset temperature.</p> Full article ">Figure 5
<p>(<b>a</b>). Crystallization onset temperature obtained by cooling upon different pressures and cooling rates. Lines are just guides to the eye. (<b>b</b>) Crystallization onset temperature obtained by cooling upon different shear flow rates and 100 bar.</p> Full article ">Figure 6
<p>(<b>a</b>) SAXS integrated patterns of samples molded at different temperatures; experiments performed at room temperature (23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C) and dry condition. (<b>b</b>) Lamellar thickness as a function of mold temperature; experiments performed at room temperature (23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C) and dry condition.</p> Full article ">Figure 7
<p>Azimuthal integration over a range from 0° to 180° of samples at dry conditions and room temperature. The solid lines are guide to the eye.</p> Full article ">Figure 8
<p>(<b>a</b>) Tensile tests at strain rate from <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math> to <math display="inline"><semantics> <mrow> <mn>3</mn> <mspace width="4pt"/> <mo>×</mo> </mrow> </semantics></math> <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math> at 23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C; comparison between samples cut in parallel (solid lines) and perpendicular (dashed lines) direction compare to the flow. (<b>b</b>) Yield stress as a function of strain rate. Samples molded at 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 9
<p>(<b>a</b>) Tensile tests at strain rate from <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math> to <math display="inline"><semantics> <mrow> <mn>3</mn> <mspace width="4pt"/> <mo>×</mo> </mrow> </semantics></math> <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math> and 23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C; comparison between samples cut in parallel (solid lines) and perpendicular (dashed lines) direction compare to the flow. (<b>b</b>) Yield stress as a function of strain rate. Samples molded at 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 10
<p>Stress-strain response at different temperatures and strain rates of samples molded at (<b>a</b>) 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 11
<p>Stress-strain response at different temperatures and strain rates of samples molded at (<b>a</b>) 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 12
<p>Yield kinetics (yield stress as a function of strain rate) of samples in dry condition, molded at (<b>a</b>) 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C (<b>b</b>) 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C. Lines are the the results of the Ree-Eyring equation.</p> Full article ">Figure 13
<p>Yield kinetics (yield stress as a function of strain rate) of samples in dry condition, molded at (<b>a</b>) 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C (<b>b</b>) 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C. Lines are the the results of the Ree-Eyring equation.</p> Full article ">Figure 14
<p>(<b>a</b>) Comparison between the yield kinetics of samples molded at 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C. (<b>b</b>) Yield stress as a function of temperature. In the case of the samples molded at 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C, the transition from unfilled to filled markers, is due to the fact that after ≈45 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C the samples start to cold-crystallize. Thus, the filled markers are not really representative of the samples molded at 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C but an evolution of those. Strain rate <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math>.</p> Full article ">Figure 15
<p>DMTA experiments for samples conditioned at different relative humidities, tan(<math display="inline"><semantics> <mi>δ</mi> </semantics></math>) as a function temperature for samples molded at (<b>a</b>) 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C. Markers indicate the measured <math display="inline"><semantics> <msub> <mi>T</mi> <mi>g</mi> </msub> </semantics></math>’s.</p> Full article ">Figure 16
<p>DMTA experiments for samples conditioned at different relative humidities, tan(<math display="inline"><semantics> <mi>δ</mi> </semantics></math>) as a function temperature for samples molded at (<b>a</b>) 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C. Markers are the selected <math display="inline"><semantics> <msub> <mi>T</mi> <mi>g</mi> </msub> </semantics></math>.</p> Full article ">Figure 17
<p>Glass transition temperatures as functions of (<b>a</b>) relative humidities and (<b>b</b>) normalized absorbed water fraction. The line is a guide to the eye.</p> Full article ">Figure 18
<p>(<b>a</b>) Wide angle X-ray diffraction integrated patterns, samples molded at 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and conditioned at different humidities. (<b>b</b>) Deconvolution analysis of the integrated WAXD patterns, crystalline, <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>γ</mi> </semantics></math> fraction as a function of relative humidity.</p> Full article ">Figure 19
<p>(<b>a</b>) Wide angle X-ray diffraction integrated patterns, samples molded at 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and conditioned at different humidities. (<b>b</b>) Deconvolution analysis of the integrated WAXD patterns, crystalline, <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>γ</mi> </semantics></math> fraction as a function of relative humidity.</p> Full article ">Figure 20
<p>(<b>a</b>) Wide angle X-ray diffraction integrated patterns, samples molded at 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and conditioned at different humidities. (<b>b</b>) Deconvolution analysis of the integrated WAXD patterns, crystalline, <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>γ</mi> </semantics></math> fraction as a function of relative humidity.</p> Full article ">Figure 21
<p>(<b>a</b>) Wide angle X-ray diffraction integrated patterns, samples molded at 35 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and conditioned at different humidities. (<b>b</b>) Deconvolution analysis of the integrated WAXD patterns, crystalline, <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>γ</mi> </semantics></math> fraction as a function relative humidity.</p> Full article ">Figure 22
<p>(<b>a</b>) Stress-strain response of samples conditioned at different relative humidities and tested at strain rate in a range from <math display="inline"><semantics> <mrow> <mn>3</mn> <mspace width="4pt"/> <mo>×</mo> </mrow> </semantics></math> <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>5</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math> to <math display="inline"><semantics> <mrow> <mn>3</mn> <mspace width="4pt"/> <mo>×</mo> </mrow> </semantics></math> <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </semantics></math> s<math display="inline"><semantics> <msup> <mrow/> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </semantics></math>. (<b>b</b>) Yield stress kinetics of samples molded at 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 23
<p>Yield stress kinetics of samples conditioned at 23 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C different relative humidities and molded at (<b>a</b>) 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 24
<p>Creep tests, applied load as a function of time-to-failure for samples conditioned at different relative humidities and room temperature. The lines are the results of Equation (<a href="#FD3-polymers-10-00779" class="html-disp-formula">3</a>). (<b>a</b>) Mold temperature 160 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C and (<b>b</b>) 130 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 25
<p>Creep tests, applied load as a function of time-to-failure for samples conditioned at different relative humidities and room temperature. The lines are the results of Equation (<a href="#FD3-polymers-10-00779" class="html-disp-formula">3</a>). Mold temperature 85 <math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math>C.</p> Full article ">Figure 26
<p>(<b>a</b>) Rate factor I and (<b>b</b>) rate factor II as functions of lamellar thickness. Lines are guides to the eye.</p> Full article ">
22 pages, 4066 KiB  
Article
Identification and Characterization of Novel Fc-Binding Heptapeptides from Experiments and Simulations
by Xiaoquan Sun, Justin Weaver, Sumith Ranil Wickramasinghe and Xianghong Qian
Polymers 2018, 10(7), 778; https://doi.org/10.3390/polym10070778 - 16 Jul 2018
Cited by 5 | Viewed by 4406
Abstract
Purification of biologically-derived therapeutics is a major cost contributor to the production of this rapidly growing class of pharmaceuticals. Monoclonal antibodies comprise a large percentage of these products, therefore new antibody purification tools are needed. Small peptides, as opposed to traditional antibody affinity [...] Read more.
Purification of biologically-derived therapeutics is a major cost contributor to the production of this rapidly growing class of pharmaceuticals. Monoclonal antibodies comprise a large percentage of these products, therefore new antibody purification tools are needed. Small peptides, as opposed to traditional antibody affinity ligands such as Protein A, may have advantages in stability and production costs. Multiple heptapeptides that demonstrate Fc binding behavior that have been identified from a combinatorial peptide library using M13 phage display are presented herein. Seven unique peptide sequences of diverse hydrophobicity and charge were identified. All seven peptides showed strong binding to the four major human IgG isotypes, human IgM, as well as binding to canine, rat, and mouse IgG. These seven peptides were also shown to bind human IgG4 from DMEM cell culture media with 5% FCS and 5 g/L ovalbumin present. These peptides may be useful as surface ligands for antibody detection and purification purposes. Molecular docking and classical molecular dynamics (MD) simulations were conducted to elucidate the mechanisms and energetics for the binding of these peptides to the Fc region. The binding site was found to be located between the two glycan chains inside the Fc fragment. Both hydrogen bonding and hydrophobic interactions were found to be crucial for the binding interactions. Excellent agreement for the binding strength was obtained between experimental results and simulations. Full article
(This article belongs to the Special Issue Polymers for Bioseparations)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The structures of two glycan chains in the hIgG4 Fc fragment. Glycan chain 1 and 2 connect to the Fc fragment of hIgG4 by the <span class="html-italic">N</span>-glycan linkages on two ASN residues.</p> Full article ">Figure 2
<p>ELISA results showing hIgG4 binding by peptide-virus clones eluted with (second round) 5 µM Protein A followed by (third round) 0.2 M glycine pH 2.4.</p> Full article ">Figure 3
<p>ELISA results showing hIgG4 binding by peptide-virus clones eluted with (second round) 5 µM Protein A followed by (third round) Protein A.</p> Full article ">Figure 4
<p>ELISA results showing hIgG4 binding by peptide-virus clones eluted with (second round) 0.2 M glycine pH 2.4 followed by (third round) 0.2 M glycine pH 2.4.</p> Full article ">Figure 5
<p>ELISA results for peptide binding to hIgG4 in DMEM, 5% fetal calf serum, and 5 g/L BSA. Original phage library (Lib) binding to hIgG4 coated wells and original library binding to uncoated wells (Lib Neg) are presented as well.</p> Full article ">Figure 6
<p>Peptide binding to various human antibody isotypes, as well as canine IgG (cIgG), murine IgG (mIgG), and rat IgG (rIgG).</p> Full article ">Figure 7
<p>The binding locations of seven heptapeptide ligands in the Fc fragment from the molecular docking studies. Ligand 1–7 are colored blue, red, orange, green, black, yellow, and violet respectively. Glycan chains are shown in white.</p> Full article ">Figure 8
<p>Interaction between ligand 2 and the Fc fragment. Panel A shows the binding pocket. The surface of the Fc fragment shown: GLY and glycan chains (gray), hydrophobic residues (dark green), polar uncharged residues (cyan); positively charged residues (blue), negatively charged residues (red). Ligand 2 is shown by a mesh surface. Panel B is the enlarged view of the binding site. Panel C exhibits hydrogen bonding (dashed lines) interaction between glycan chains and ligand 2. Gray is the hydrophobic residues.</p> Full article ">Figure 9
<p>VdW and electrostatic interaction energies between ligand 2 and the Fc fragment during the 150 ns simulation period.</p> Full article ">Figure 10
<p>2D diagram of interactions between ligand 2 and the surrounding residues at the Fc fragment. Structure water molecules are also selected. Ligand 2 is presented by sticks and balls. Water molecule is cyan ball.</p> Full article ">Figure 11
<p>Average number of hydrogen bonds formed between ligand 2 and the Fc fragment in each 10 ns during the whole 150 ns simulation.</p> Full article ">
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-118
Previous Issue
Next Issue
Back to TopTop