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Polymers, Volume 11, Issue 1 (January 2019) – 186 articles

Cover Story (view full-size image): The need for antimicrobial smart packaging solutions is dictated by consumers’ demands for improved quality and shelf life of perishable goods. Among numerous available antimicrobial agents, essential oils stand out for their renowned efficiency and sustainability. Herein, we report on the fabrication of antimicrobial packaging films coated with thyme oil-loaded light-responsive nanocapsules. The light-induced release of volatile thyme oil was monitored over time, demonstrating that a 15 min UV exposure of the coated films led to an eight-fold increase of thyme oil concentration in the headspace after 24 h. These films are proposed as smart devices for on-demand release of antimicrobials in non-contact active packaging. View this paper
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14 pages, 3104 KiB  
Article
Design and Compressive Behavior of a Photosensitive Resin-Based 2-D Lattice Structure with Variable Cross-Section Core
by Shuai Li, Jiankun Qin, Bing Wang, Tengteng Zheng and Yingcheng Hu
Polymers 2019, 11(1), 186; https://doi.org/10.3390/polym11010186 - 21 Jan 2019
Cited by 29 | Viewed by 4843
Abstract
This paper designed and manufactured photosensitive resin-based 2-D lattice structures with different types of variable cross-section cores by stereolithography 3D printing technology (SLA 3DP). An analytical model was employed to predict the structural compressive response and failure types. A theoretical calculation was performed [...] Read more.
This paper designed and manufactured photosensitive resin-based 2-D lattice structures with different types of variable cross-section cores by stereolithography 3D printing technology (SLA 3DP). An analytical model was employed to predict the structural compressive response and failure types. A theoretical calculation was performed to obtain the most efficient material utilization of the 2-D lattice core. A flatwise compressive experiment was performed to verify the theoretical conclusions. A comparison of theoretical and experimental results showed good agreement for structural compressive response. Results from the analytical model and experiments showed that when the 2-D lattice core was designed so that R/r = 1.167 (R and r represent the core radius at the ends and in the middle), the material utilization of the 2-D lattice core improved by 13.227%, 19.068%, and 22.143% when n = 1, n = 2, and n = 3 (n represents the highest power of the core cross-section function). Full article
(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)
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Figure 1

Figure 1
<p>Variable cross-section core schematic illustration.</p> Full article ">Figure 2
<p>2-D lattice structure with the variable cross-section core unit cell schematic illustration.</p> Full article ">Figure 3
<p>2-D lattice structure with variable cross-section core shaping technology.</p> Full article ">Figure 4
<p>Manufactured 2-D lattice structures with variable cross-section cores.</p> Full article ">Figure 5
<p>The force method of (<b>a</b>) the basic structure and (<b>b</b>) the basic system.</p> Full article ">Figure 6
<p>Failure mode maps of the 2-D lattice structures with variable cross-section cores.</p> Full article ">Figure 7
<p>(<b>a</b>) 2-D lattice structures with the variable cross-section core failure types and (<b>b</b>) compressive stress–strain curves for the 3 failure types.</p> Full article ">Figure 8
<p>Flatwise compressive load capacity of (<b>a</b>) n = 1, (<b>b</b>) n = 2, and (<b>c</b>) n = 3.</p> Full article ">Figure 9
<p>Equivalent compressive elastic modulus of (<b>a</b>) n = 1, (<b>b</b>) n = 2, and (<b>c</b>) n = 3.</p> Full article ">Figure 10
<p>The specific strength of the 2-D lattice structure with the variable cross-section core.</p> Full article ">
11 pages, 2726 KiB  
Article
A Parallel Bicomponent TPU/PI Membrane with Mechanical Strength Enhanced Isotropic Interfaces Used as Polymer Electrolyte for Lithium-Ion Battery
by Ming Cai, Jianwei Zhu, Chaochao Yang, Ruoyang Gao, Chuan Shi and Jinbao Zhao
Polymers 2019, 11(1), 185; https://doi.org/10.3390/polym11010185 - 21 Jan 2019
Cited by 51 | Viewed by 8224
Abstract
In this work, a side-by-side bicomponent thermoplastic polyurethane/polyimide (TPU/PI) polymer electrolyte prepared with side-by-side electrospinning method is reported for the first time. Symmetrical TPU and PI co-occur on one fiber, and are connected by an interface transition layer formed by the interdiffusion of [...] Read more.
In this work, a side-by-side bicomponent thermoplastic polyurethane/polyimide (TPU/PI) polymer electrolyte prepared with side-by-side electrospinning method is reported for the first time. Symmetrical TPU and PI co-occur on one fiber, and are connected by an interface transition layer formed by the interdiffusion of two solutions. This structure of the as-prepared TPU/PI polymer electrolyte can integrate the advantages of high thermal stable PI and good mechanical strength TPU, and mechanical strength is further increased by those isotropic interface transition layers. Moreover, benefiting from micro-nano pores and the high porosity of the structure, TPU/PI polymer electrolyte presents high electrolyte uptake (665%) and excellent ionic conductivity (5.06 mS·cm−1) at room temperature. Compared with PE separator, TPU/PI polymer electrolyte exhibited better electrochemical stability, and using it as the electrolyte and separator, the assembled Li/LiMn2O4 cell exhibits low inner resistance, stable cyclic and notably high rate performance. Our study indicates that the TPU/PI membrane is a promising polymer electrolyte for high safety lithium-ion batteries. Full article
(This article belongs to the Special Issue Electrospun Nanofibers: Theory and Its Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Apparatus schematic of side-by-side electrospinning.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) PE, (<b>b</b>) TPU, (<b>c</b>) PI, (<b>d</b>) TPU/PI and (<b>e</b>) TPU+PI membrane. (<b>f</b>) Fluorescence microscope images of TPU/PI.</p> Full article ">Figure 3
<p>(<b>a</b>) fiber stress-strain test curve: TPU, PI, TPU+PI and TPU/PI polymer electrolyte. (<b>b</b>) Structure diagram of the fiber membranes. (<b>c</b>) Formation diagram of the interface transition layers. (<b>d</b>) Schematic diagram of the “notch affect”.</p> Full article ">Figure 4
<p>The photograph and SEM of PE, TPU and TPU/PI before and after heat treatment at 170 °C and 230 °C for 30 min.</p> Full article ">Figure 5
<p>Contact angles of (<b>a</b>) PE, (<b>b</b>) TPU membrane, (<b>c</b>) TPU/PI membrane.</p> Full article ">Figure 6
<p>(<b>a</b>) EIS of PE and TPU/PI membranes, (<b>b</b>) EIS of batteries assembled with PE and TPU/PI membranes.</p> Full article ">Figure 7
<p>(<b>a</b>) LSV of the PE and TPU/PI after saturated with 1 mol·L<sup>−1</sup> LiPF<sub>6</sub> electrolyte. (<b>b</b>) 1, 50, 100 cycles discharge curves of the batteries with PE and TPU/PI. (<b>c</b>) Cyclic and (<b>d</b>) rate performance of batteries with PE and TPU/PI polymer electrolyte.</p> Full article ">
16 pages, 6428 KiB  
Article
High Response CO Sensor Based on a Polyaniline/SnO2 Nanocomposite
by Kai-Syuan Jian, Chi-Jung Chang, Jerry J. Wu, Yu-Cheng Chang, Chien-Yie Tsay, Jing-Heng Chen, Tzyy-Leng Horng, Gang-Juan Lee, Lakshmanan Karuppasamy, Sambandam Anandan and Chin-Yi Chen
Polymers 2019, 11(1), 184; https://doi.org/10.3390/polym11010184 - 21 Jan 2019
Cited by 55 | Viewed by 5948
Abstract
A polyaniline (PANI)/tin oxide (SnO2) composite for a CO sensor was fabricated using a composite film composed of SnO2 nanoparticles and PANI deposition in the present study. Tin oxide nanoparticles were synthesized by the sol-gel method. The SnO2 nanoparticles [...] Read more.
A polyaniline (PANI)/tin oxide (SnO2) composite for a CO sensor was fabricated using a composite film composed of SnO2 nanoparticles and PANI deposition in the present study. Tin oxide nanoparticles were synthesized by the sol-gel method. The SnO2 nanoparticles provided a high surface area to significantly enhance the response to the change in CO concentration at low operating temperature (<75 °C). The excellent sensor response was mainly attributed to the relatively good properties of PANI in the redox reaction during sensing, which produced a great resistance difference between the air and CO gas at low operating temperature. Therefore, the combination of n-type SnO2 nanoparticles with a high surface area and a thick film of conductive PANI is an effective strategy to design a high-performance CO gas sensor. Full article
(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)
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Figure 1

Figure 1
<p>XRD patterns of the (<b>a</b>) as-synthesized SnO<sub>2</sub> powder and screen-printed SnO<sub>2</sub> powder coatings (<b>b</b>) without and with (<b>c</b>) 45 and (<b>d</b>) 55 wt % PANI depositions.</p> Full article ">Figure 2
<p>(<b>a</b>) TEM image and (<b>b</b>) its corresponding SAED patterns of sol-gel SnO<sub>2</sub> nanoparticles.</p> Full article ">Figure 2 Cont.
<p>(<b>a</b>) TEM image and (<b>b</b>) its corresponding SAED patterns of sol-gel SnO<sub>2</sub> nanoparticles.</p> Full article ">Figure 3
<p>SEM micrographs of the screen-printed SnO<sub>2</sub> powder coatings (<b>a</b>) without, and with (<b>b</b>) 45 and (<b>c</b>) 55 wt % PANI deposition after heat treatment. The insets in the images (<b>b</b>,<b>c</b>) show the corresponding higher magnification SEM images.</p> Full article ">Figure 3 Cont.
<p>SEM micrographs of the screen-printed SnO<sub>2</sub> powder coatings (<b>a</b>) without, and with (<b>b</b>) 45 and (<b>c</b>) 55 wt % PANI deposition after heat treatment. The insets in the images (<b>b</b>,<b>c</b>) show the corresponding higher magnification SEM images.</p> Full article ">Figure 4
<p>EDS mappings of (<b>a</b>) C, (<b>b</b>) N, and (<b>c</b>) Sn obtained from a screen-printed SnO<sub>2</sub> powder coating with 45 wt % PANI deposition. (<b>d</b>) EDS spectrum and elemental analysis of the 45 wt % deposited SnO<sub>2</sub> coating.</p> Full article ">Figure 5
<p>FTIR spectra of the SnO<sub>2</sub> powder coatings (<b>a</b>) without and (<b>b</b>) with 55 wt % PANI deposition.</p> Full article ">Figure 6
<p>Electrical resistance of screen-printed SnO<sub>2</sub> powder coatings (<b>a</b>) without, and with (<b>b</b>) 45, and (<b>c</b>) 55 wt % PANI depositions under different CO concentrations as a function of sensing temperature.</p> Full article ">Figure 6 Cont.
<p>Electrical resistance of screen-printed SnO<sub>2</sub> powder coatings (<b>a</b>) without, and with (<b>b</b>) 45, and (<b>c</b>) 55 wt % PANI depositions under different CO concentrations as a function of sensing temperature.</p> Full article ">Figure 7
<p>Sensor response of the screen-printed SnO<sub>2</sub> powder coatings (<b>a</b>) without, and with (<b>b</b>) 45 and (<b>c</b>) 55 wt % PANI depositions under different CO concentrations as a function of sensing temperature.</p> Full article ">Figure 8
<p>Sensor response of the screen-printed SnO<sub>2</sub> powder coatings without and with PANI deposition as functions of (<b>a</b>) operating temperature and (<b>b</b>) CO concentration.</p> Full article ">Figure 8 Cont.
<p>Sensor response of the screen-printed SnO<sub>2</sub> powder coatings without and with PANI deposition as functions of (<b>a</b>) operating temperature and (<b>b</b>) CO concentration.</p> Full article ">Figure 9
<p>Resistance of the SnO<sub>2</sub> powder coatings without and with 45 wt % PANI deposition as a function of operating temperature under air and 25 ppm CO. The corresponding schematic diagrams based on the space-charge layer model of the sensors are also shown in this figure.</p> Full article ">Figure 10
<p>Dynamic sensor response of SnO<sub>2</sub> powder coatings (<b>a</b>) without and (<b>b</b>) with 45 wt % PANI deposition as a function of time toward a change in CO concentration in the range of air to 50 ppm at 100 °C.</p> Full article ">
19 pages, 2962 KiB  
Article
Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes
by Vikramjit S. Rathee, Hythem Sidky, Benjamin J. Sikora and Jonathan K. Whitmer
Polymers 2019, 11(1), 183; https://doi.org/10.3390/polym11010183 - 21 Jan 2019
Cited by 24 | Viewed by 6518
Abstract
The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in [...] Read more.
The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in the process. One must contend with the inherent structural and solvation properties of the polymer, the presence of counterions, and local chemical equilibria enforced by background salt concentration and solution acidity. Moreover, for these cases, the systems of interest have locally high concentrations of monomers, induced by polymer connectivity or confinement, and thus deviate from ideal titration behavior. This work furthers knowledge in this limit utilizing hybrid Monte Carlo–Molecular Dynamics simulations to investigate the influence of salt concentration, pK a , pH, and counterion valence in determining the coil-to-globule transition of poorly solvated weak polyelectrolytes. We characterize this transition at a range of experimentally relevant salt concentrations and explicitly examine the role multivalent salts play in determining polyelectrolyte ionization behavior and conformations. These simulations serve as an essential starting point in understanding the complexation between weak polyelectrolytes and ion rejection of self-assembled copolymer membranes. Full article
(This article belongs to the Special Issue Simulations of Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Typical simulation snapshots for linear and star polyelectrolytes on either side of the CGT. The red background denotes more acidic conditions (<math display="inline"><semantics> <mrow> <mi>pH</mi> <mo>−</mo> <msub> <mi>pK</mi> <mi mathvariant="normal">a</mi> </msub> <mo>=</mo> <mn>1.302</mn> </mrow> </semantics></math>) while the blue background denotes more basic conditions (<math display="inline"><semantics> <mrow> <mi>pH</mi> <mo>−</mo> <msub> <mi>pK</mi> <mi mathvariant="normal">a</mi> </msub> <mo>=</mo> <mn>3.040</mn> </mrow> </semantics></math>). Between these two states, a swelling transition exists whose sharpness is topology-dependent. States (<b>a</b>,<b>c</b>) correspond to collapsed globule configurations in the linear (<b>a</b>) and star (<b>c</b>) polyelectrolytes, with states (<b>b</b>,<b>d</b>) defining the corresponding swollen configurations. The salt concentration is regulated by chemical equilibrium with a solution of NaCl at 0.1 M concentration. Na<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> and Cl<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> are represented by pink and green beads, respectively. The titration steps (see methods for full description) require OH<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> ions, which are regulated by chemical equilibrium with a reservoir of KOH. The <math display="inline"><semantics> <mi>pOH</mi> </semantics></math> is fixed at ≈2.7 (<math display="inline"><semantics> <mrow> <mi>pH</mi> <mo>≈</mo> <mn>11.3</mn> </mrow> </semantics></math>), with K<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> ion being depicted in red and OH<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> ion depicted in purple.</p> Full article ">Figure 2
<p>Schematic of the Monte Carlo moves utilized in our simulations. The color scheme is as follows: light blue and dark blue beads represent uncharged and charged monomers; red and purple beads represent K<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> and OH<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math> ions; and pink and green beads represent Na<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> and Cl<math display="inline"><semantics> <msup> <mrow/> <mo>−</mo> </msup> </semantics></math>. The KOH and NaCl or MgSO<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math> reservoir are representative of bulk concentrations whereas the concentration within the simulation box is representative of the environment around the weak polyelectrolyte in the combined system. KOH concentration in the reservoir or bulk concentration is fixed at 0.002 M which corresponds to pOH ≈ 2.7 whereas the salt bulk concentration is considered here as a variable. The salt bulk concentration depicted in this schematic corresponds to ≈0.01 M. Titration moves charge the monomer bead, as defined in the governing reaction (Equation (<a href="#FD6-polymers-11-00183" class="html-disp-formula">6</a>)). Charge annealing moves simulate the equilibrium dissociation and recombination of the monomer bead in another location on the polymer, while grand canonical Monte Carlo (GCMC) moves govern the exchange of ions with the bulk.</p> Full article ">Figure 3
<p>A comparison of the swelling behavior for weak polyelectrolyte chains (<b>a</b>,<b>c</b>) and stars (<b>b</b>,<b>d</b>). Panels (<b>a</b>,<b>b</b>) depict the charge fraction as a function of <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math> at a fixed <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics></math>, while (<b>c</b>,<b>d</b>) plot the corresponding radius of gyration, demonstrating the swelling of the polymers. The plotted <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math> for explicit-ion systems represents the Debye length calculated from the reservoir ion concentration (see <a href="#sec2-polymers-11-00183" class="html-sec">Section 2</a> for more details). Note that in the case of a linear polyelectrolyte, the charging and swelling effects as <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math> is decreased are much less pronounced in the explicit salt limit, as screening of the strong charged interactions between adhering monomers is necessary to charge the polymer, which requires ions to enter the collapsed core, energetically favorable, but entropically unfavorable enough to strongly limit swelling. The topological restraints of the star polyelectrolyte (<b>b</b>,<b>d</b>) cut down the amount of entropy that can be realized in swelling of the polyelectrolyte, thus suppressing charging and swelling significantly in both cases. Further, it should be noted that the charging curves for the explicit-ion systems are remarkably similar in both cases, due to both states remaining largely collapsed until <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math> is on the order of a monomer diameter. Snapshots in panels (<b>c</b>,<b>d</b>) correspond to typical configurations, with nearby counterions in the explicit salt case, at the state denoted by the arrow.</p> Full article ">Figure 4
<p>Effects of charging chemical potential <math display="inline"><semantics> <mi>μ</mi> </semantics></math> on the state of weak polyelectrolyte. As in <a href="#polymers-11-00183-f003" class="html-fig">Figure 3</a>, panels (<b>a</b>,<b>c</b>) plot results for the linear polymer, while panels (<b>b</b>,<b>d</b>) show the behavior for 10-arm stars. The dependence of charge fraction <span class="html-italic">f</span> on <math display="inline"><semantics> <mi>μ</mi> </semantics></math> is given in (<b>a</b>,<b>b</b>), and each demonstrates clear divergence from the Henderson–Hasselbalch behavior expected of isolated monomers. Adhesive interactions suppress charging of the polyelectrolytes until a salt-concentration-dependent threshold value of <math display="inline"><semantics> <mi>μ</mi> </semantics></math> is reached. Increasing the salt concentration favors charging. Notably, there appears to be a discontinuous jump in the charge fraction <span class="html-italic">f</span>, indicative of a first-order phase transition, in the linear polyelectrolyte that is not present for the star. Panels (<b>c</b>,<b>d</b>) demonstrate the swelling that accompanies the increased charge in each polymer. Swelling is more prominent when the polyelectrolyte is more charged in both cases, though the effect is more pronounced in the linear rather than the star polymer. This can be understood by appealing to relative compactness of each polymer, which disfavors swelling and charging relative to compact conformations which maximize adhesive monomer interactions, and the larger entropy that the linear chain gains in transitioning to a coil relative to that available in the star. Larger salt concentrations permit more ions to occupy the cloud around the polyelectrolyte, increasing both enthalpically favorable binding of counterions, and screening between sites on swollen polymers.</p> Full article ">Figure 5
<p>Effect of polymer topology on the CGT behavior of the weak polyelectrolytes. Molecular weight for all topology is identical. (<b>a</b>,<b>c</b>) represents the low NaCl conditions (∼0.01 M) whereas as (<b>b</b>,<b>d</b>) represents the high NaCl conditions (∼0.1 M). The figure depicts that the charging and swelling behavior of 5-arm stars is in between that for the linear and 10-arm polymer, indicating <span class="html-italic">smoothing</span> of the CGT as we go from linear to 5-arm to 10-arm star polymers, due to increased topological restrictions as the structure of the polymer becomes more branched. Overall, this figure suggests the suppression of charging (deprotonation here) induced continuous CGT with the increase in the number of arms of the polymer.</p> Full article ">Figure 6
<p>Influence of NaCl concentration on the titration of the linear and star polyelectrolytes for varying <math display="inline"><semantics> <mi>μ</mi> </semantics></math> conditions spanning the CGT. Panels (<b>a</b>,<b>c</b>) plot the charge fraction <span class="html-italic">f</span> and radius of gyration <math display="inline"><semantics> <msub> <mi>R</mi> <mi mathvariant="normal">g</mi> </msub> </semantics></math> for linear weak polyelectrolytes, while panels (<b>b</b>,<b>d</b>) depict the same quantities for 10-arm star polymers. As intuition would suggest, an increase in <math display="inline"><semantics> <mi>μ</mi> </semantics></math> leads to a higher charge for both linear and star polymer. For linear polymers, the CGT is seen to shift toward lower values of <math display="inline"><semantics> <mi>μ</mi> </semantics></math> as the salt concentration is increased, as evidenced by the gap between higher-charge and more swollen states shifting from between <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>6</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>7</mn> </mrow> </semantics></math> at low salt concentrations (high <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math>) to between <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>4</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics></math> at high salt concentrations (low <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math>). Note that increasing the strength of screening results in higher <span class="html-italic">f</span> and reduced <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>g</mi> </msub> <mo>/</mo> <mi>σ</mi> </mrow> </semantics></math> uniformly across <math display="inline"><semantics> <mi>μ</mi> </semantics></math>. For the star polymers in panels (<b>b</b>,<b>d</b>), a continuous transition in each measured quantity is seen for all <math display="inline"><semantics> <mi>μ</mi> </semantics></math> and <math display="inline"><semantics> <msub> <mi>λ</mi> <mi mathvariant="normal">D</mi> </msub> </semantics></math> values.</p> Full article ">Figure 7
<p>Effect of salt valence on the charging of the weak polyelectrolyte. Panels (<b>a</b>,<b>b</b>) show the charging behavior of the linear and star polyelectrolyte, respectively, in the presence of monovalent salt (NaCl) and divalent salt (MgSO<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>) at <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>4</mn> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics></math>. Panels (<b>c</b>,<b>d</b>) depict the <math display="inline"><semantics> <mrow> <msub> <mi>R</mi> <mi>g</mi> </msub> <mo>/</mo> <mi>σ</mi> </mrow> </semantics></math> for linear and star polyelectrolyte respectively corresponding to conditions of (<b>a</b>,<b>b</b>). An increase in the concentration of MgSO<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math> leads to higher charge fractions <span class="html-italic">f</span> compared to NaCl but retains the collapsed configuration. In order to elucidate the different charging and swelling behavior seen in (<b>a</b>–<b>d</b>), panel (<b>e</b>) depicts the distribution of Mg<math display="inline"><semantics> <msup> <mrow/> <mrow> <mn>2</mn> <mo>+</mo> </mrow> </msup> </semantics></math> and Na<math display="inline"><semantics> <msup> <mrow/> <mo>+</mo> </msup> </semantics></math> ions, denoted as <math display="inline"><semantics> <msub> <mi>N</mi> <mi mathvariant="normal">s</mi> </msub> </semantics></math>, in the concentric spherical shells around the center of mass (CM) of the linear polymer, for the states corresponding to point ’X’ and ’O’ in (<b>c</b>).</p> Full article ">
14 pages, 2389 KiB  
Article
Photocatalytic Dye and Cr(VI) Degradation Using a Metal-Free Polymeric g-C3N4 Synthesized from Solvent-Treated Urea
by Chechia Hu, Yi-Ching Chu, Yan-Ru Lin, Hung-Chun Yang and Ke-Hsuan Wang
Polymers 2019, 11(1), 182; https://doi.org/10.3390/polym11010182 - 21 Jan 2019
Cited by 37 | Viewed by 7155
Abstract
The development of visible-light-driven polymeric g-C3N4 is in response to an emerging demand for the photocatalytic dye degradation and reduction of hexavalent chromium ions. We report the synthesis of g-C3N4 from urea treated with various solvents such [...] Read more.
The development of visible-light-driven polymeric g-C3N4 is in response to an emerging demand for the photocatalytic dye degradation and reduction of hexavalent chromium ions. We report the synthesis of g-C3N4 from urea treated with various solvents such as methanol, ethanol, and ethylene glycol. The samples were characterized and the Williamson–Hall method was applied to investigate the lattice strain of the samples. The activity of the samples was evaluated by observing the degradation of methyl orange and K2Cr2O7 solution under light irradiation. Photocatalytic reaction kinetics were determined as pseudo-first-order and zero-order for the degradation of methyl orange and reduction of hexavalent chromium, respectively. Due to the inhibited charge separation resulting from the small lattice strain, reduced crystal imperfection, and sheet-like structure, g-C3N4 obtained from ethanol-treated urea exhibited the highest activity among the evaluated samples. Full article
(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>XRD patterns of mCN, uCN, MeCN, EtCN, and EgCN samples.</p> Full article ">Figure 2
<p>FTIR spectra of mCN, uCN, MeCN, EtCN, and EgCN samples. Inset shows the proposed molecular structure of g-C<sub>3</sub>N<sub>4</sub>.</p> Full article ">Figure 3
<p>UV-vis spectra of mCN, uCN, MeCN, EtCN, and EgCN samples. Inset shows the Tauc plot of these samples.</p> Full article ">Figure 4
<p>SEM images of (<b>a</b>) uCN, (<b>b</b>) MeCN, (<b>c</b>) EtCN, and (<b>d</b>) EgCN samples. Inset of (<b>a</b>) shows an image of mCN.</p> Full article ">Figure 5
<p>(<b>a</b>) Photocatalytic degradation of MO aqueous solution (2.5 × 10<sup>−5</sup> M) using mCN, uCN, MeCN, EtCN, and EgCN samples under irradiation from a Xe lamp, and (<b>b</b>) the pseudo-first-order reaction kinetics plot for these samples. Insets of (<b>a</b>) and (<b>b</b>) show the photocatalytic reduction of Cr<sup>(VI)</sup> using the mCN and EtCN samples, and their pseudo-zero-order reaction kinetics, respectively.</p> Full article ">Figure 6
<p>Photoluminescence spectra of mCN, uCN, MeCN, EtCN, and EgCN samples excited at wavelength of 360 nm at room temperature.</p> Full article ">Figure 7
<p>Proposed mechanism for synthesis of g-C<sub>3</sub>N<sub>4</sub> using melamine or solvent-treated urea as raw materials.</p> Full article ">
11 pages, 6567 KiB  
Article
Functional Porous Carboxymethyl Cellulose/Cellulose Acetate Composite Microspheres: Preparation, Characterization, and Application in the Effective Removal of HCN from Cigarette Smoke
by Peijian Sun, Song Yang, Xuehui Sun, Yipeng Wang, Lining Pan, Hongbo Wang, Xiaoyu Wang, Jizhao Guo and Cong Nie
Polymers 2019, 11(1), 181; https://doi.org/10.3390/polym11010181 - 21 Jan 2019
Cited by 16 | Viewed by 5686
Abstract
To selectively reduce the yield of hydrogen cyanide (HCN) in the cigarette smoke, functional porous carboxymethyl cellulose/cellulose acetate (CMC/CA) composite microspheres were prepared via the double emulsion-solvent evaporation method. Cupric ions, which have a high complexing ability toward HCN, were introduced to the [...] Read more.
To selectively reduce the yield of hydrogen cyanide (HCN) in the cigarette smoke, functional porous carboxymethyl cellulose/cellulose acetate (CMC/CA) composite microspheres were prepared via the double emulsion-solvent evaporation method. Cupric ions, which have a high complexing ability toward HCN, were introduced to the CMC/CA composite microspheres during the fabrication process via an in situ ion cross-link method. The microspheres were characterized using nitrogen adsorption, mercury intrusion porosimetry, and scanning electron microscopy (SEM). The microspheres have a predominantly macroporous structure indicating weak physisorption properties, but sufficient functional cupric ion groups to selectively adsorb HCN. With these CMC/CA microspheres as filter additives, the smoke yield of HCN could be reduced up to 50%, indicating the great potential of these microspheres as absorbents for removing HCN from cigarette smoke. Full article
(This article belongs to the Collection Biopolymers and Biobased Polymers: Chemistry and Engineering)
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<p>Synthesis pathway of CMC/CA microspheres.</p> Full article ">Figure 2
<p>Device to simulate the addition of absorbents to the cigarette filter. (1) cigarette, (2) homemade device, (3) cigarette holder, (4) 120 mesh sieve, (5) sample, (6) Cambridge filter pad, and (7) smoking machine.</p> Full article ">Figure 3
<p>(<b>a</b>) FTIR of CMC (i), CA (ii), and CMC/CA microspheres (iii). (<b>b</b>) Typical nitrogen adsorption curves of CMC/CA microspheres.</p> Full article ">Figure 4
<p>(<b>a</b>,<b>b</b>) SEM images of CMC/CA microsphere. (<b>c</b>,<b>d</b>) The corresponding EDS spectra of CMC/CA microsphere. (<b>a</b>,<b>c</b>) denotes the surface structure while (<b>b</b>,<b>d</b>) were the cross-section structure of the microspheres.</p> Full article ">Figure 5
<p>The SEM images of CMC/CA microspheres fabricated with 2% (<b>a</b>,<b>d</b>), 3% (<b>b</b>,<b>e</b>), 4% (<b>c</b>,<b>f</b>) CMC concentrations. Images (<b>a</b>–<b>c</b>) were the surface images while (<b>d</b>–<b>f</b>) were the cross-section images of CMC/CA microspheres.</p> Full article ">Figure 6
<p>(<b>a</b>) Cumulative mercury intrusion traces and (<b>b</b>) pore size distribution of the CMC/CA microspheres fabricated with 2% (A1), 3% (A2), 4% (A3) CMC concentration.</p> Full article ">Figure 7
<p>The SEM images of CMC/CA microspheres fabricated with W1/O ratios of 10/100 (<b>a</b>,<b>f</b>), 30/100 (<b>b</b>,<b>g</b>), 50/100 (<b>c</b>,<b>h</b>), 70/100 (<b>d</b>,<b>i</b>), and 90/100 (<b>e</b>,<b>j</b>). Images (<b>a</b>–<b>e</b>) were the surface images while (<b>f</b>–<b>j</b>) were the cross-section images of the CMC/CA microspheres.</p> Full article ">Figure 8
<p>(<b>a</b>) Cumulative mercury intrusion traces and (<b>b</b>) pore size distribution of the CMC/CA microspheres fabricated with W1/O ratios of 10/100 (B1), 30/100 (B2), 50/100 (B3), 70/100 (B4), and 90/100 (B5).</p> Full article ">Figure 9
<p>The SEM images of CMC/CA microspheres fabricated with Cu(II) content of 25mM (<b>a</b>,<b>e</b>), 50mM (<b>b</b>,<b>f</b>), 100mM (<b>c</b>,<b>g</b>), 200mM (<b>d</b>,<b>h</b>) in the outer aqueous solution. Images (<b>a</b>–<b>d</b>) are the surface images while (<b>e</b>–<b>h</b>) are the cross-section images of the CMC/CA microspheres.</p> Full article ">Figure 10
<p>(<b>a</b>) Cumulative mercury intrusion traces and (<b>b</b>) pore size distribution of the CMC/CA microspheres fabricated with Cu(II) content of 25mM (C1), 50mM (C2), 100mM (C3), and 200mM (C4) in the outer aqueous solution.</p> Full article ">
18 pages, 6970 KiB  
Article
Valorization of Industrial Lignin as Biobased Carbon Source in Fire Retardant System for Polyamide 11 Blends
by Neeraj Mandlekar, Aurélie Cayla, François Rault, Stéphane Giraud, Fabien Salaün and Jinping Guan
Polymers 2019, 11(1), 180; https://doi.org/10.3390/polym11010180 - 21 Jan 2019
Cited by 19 | Viewed by 5223
Abstract
In this study, two different types of industrial lignin (i.e., lignosulphonate lignin (LL) and kraft lignin (DL)) were exploited as charring agents with phosphorus-based flame retardants for polyamide 11 (PA11). The effect of lignins on the thermal stability and fire behavior of PA11 [...] Read more.
In this study, two different types of industrial lignin (i.e., lignosulphonate lignin (LL) and kraft lignin (DL)) were exploited as charring agents with phosphorus-based flame retardants for polyamide 11 (PA11). The effect of lignins on the thermal stability and fire behavior of PA11 combined with phosphinate additives (namely, aluminum phosphinate (AlP) and zinc phosphinate (ZnP)) has been studied by thermogravimetric analysis (TGA), UL 94 vertical flame spread, and cone calorimetry tests. Various blends of flame retarded PA11 were prepared by melt process using a twin-screw extruder. Thermogravimetric analyses showed that the LL containing ternary blends are able to provide higher thermal stability, as well as a developed char residue. The decomposition of the phosphinates led to the formation of phosphate compounds in the condensed phase, which promotes the formation of a stable char. Flammability tests showed that LL/ZnP ternary blends were able to achieve self-extinction and V-1 classification; the other formulations showed a strong melt dripping and higher burning. In addition to this, cone calorimetry results showed that the most enhanced behavior was found when 10 wt % of LL and AlP were combined, which strongly reduced PHRR (−74%) and THR (−22%), due to the interaction between LL and AlP, which not only promotes char formation but also confers the stability to char in the condensed phase. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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<p>Scanning Electron Microscopy (SEM) micrograph of polyamide 11 (PA11) and its binary and ternary blends. (<b>a</b>) PA11; (<b>b</b>) PA<sub>80</sub>-LL<sub>20</sub>; (<b>c</b>) PA<sub>80</sub>-DL<sub>20</sub>; (<b>d</b>) PA<sub>80</sub>-ZnP<sub>20</sub>; (<b>e</b>) PA<sub>80</sub>-AlP<sub>20</sub>; (<b>f</b>) PA<sub>80</sub>-LL<sub>10</sub>-ZnP<sub>10</sub>; (<b>g</b>) PA<sub>80</sub>-DL<sub>10</sub>-ZnP<sub>10</sub>; (<b>h</b>) PA<sub>80</sub>-LL<sub>10</sub>-AlP<sub>10</sub>; (<b>i</b>) PA<sub>80</sub>-DL<sub>10</sub>-AlP<sub>10</sub> at 5000× magnification.</p> Full article ">Figure 2
<p>Scanning Electron Microscopy (SEM) micrographs of unfilled polyamide 11 (PA11) and the ternary blends. (<b>a</b>) PA11; (<b>b</b>) PA<sub>80</sub>-LL<sub>10</sub>-AlP<sub>10</sub>; (<b>c</b>) PA<sub>80</sub>-DL<sub>10</sub>-AlP<sub>10</sub>; (<b>d</b>) PA<sub>80</sub>-DL<sub>10</sub>-ZnP<sub>10</sub> and (<b>e</b>) PA<sub>80</sub>-LL<sub>10</sub>-ZnP<sub>10</sub> at 2500× magnification and corresponding energy dispersive X-rays (EDX) spectra and elemental maps.</p> Full article ">Figure 3
<p>Thermogravimetric (TG) curves of polyamide 11 (PA11) blends of lignosulphonate lignin (LL) in combination with zinc phosphinate (ZnP) and aluminum phosphinate (AlP) in N<sub>2</sub> ((<b>a</b>) and (<b>c</b>)) and air atmosphere ((<b>b</b>) and (<b>d</b>)).</p> Full article ">Figure 4
<p>Thermogravimetric (TG) curves of polyamide 11 (PA11) blends of kraft lignin (DL) in combination with zinc phosphinate (ZnP) and aluminum phosphinate (AlP) in N<sub>2</sub> ((<b>a</b>) and (<b>c</b>)) and air atmosphere ((<b>b</b>) and (<b>d</b>)).</p> Full article ">Figure 5
<p>Curves of residual mass loss difference for polyamide 11 (PA11) ternary blends with lignosulphate lignin (LL) (<b>a</b>) and with kraft lignin (DL) (<b>b</b>) in air.</p> Full article ">Figure 6
<p>Pictures of PA11 blends specimen left after UL 94 vertical flame test. (<b>a</b>) PA11; (<b>b</b>)PA<sub>80</sub>-ZnP<sub>20</sub>; (<b>c</b>) PA<sub>80</sub>-AlP<sub>20</sub>; (<b>d</b>) PA<sub>80</sub>-LL<sub>20</sub>; (<b>e</b>) PA<sub>80</sub>-DL<sub>20</sub>; (<b>f</b>) PA<sub>80</sub>-LL<sub>10</sub>-ZnP<sub>10</sub>; (<b>g</b>) PA<sub>80</sub>-DL<sub>10</sub>-ZnP<sub>10</sub>; (<b>h</b>) PA<sub>80</sub>-DL<sub>10</sub>-ZnP<sub>10</sub>; (<b>i</b>) PA<sub>80</sub>-DL<sub>10</sub>-AlP<sub>10</sub>.</p> Full article ">Figure 7
<p>Heat release rate (HRR) and total heat release (THR) curves of polyamide 11 (PA11) blends. (<b>a</b>) and (<b>b</b>) for PA–LL–ZnP blends; (<b>c</b>) and (<b>d</b>) for PA–LL–AlP blends.</p> Full article ">Figure 8
<p>Heat release rate (HRR) and total heat release (THR) curves of polyamide 11 (PA11) blends. (<b>a</b>) and (<b>b</b>) for PA–DL–ZnP blends; (<b>c</b>) and (<b>d</b>) for PA–DL–AlP blends.</p> Full article ">Figure 9
<p>CO and CO<sub>2</sub> evolution during combustion. (<b>a</b>) and (<b>b</b>) for PA–LL–ZnP blends; (<b>c</b>) and (<b>d</b>) for PA–LL–AlP blends.</p> Full article ">Figure 10
<p>Pictures of char residues collected at the end of cone calorimetry test: (<b>a</b>) unfilled polyamide 11 (PA11); (<b>b</b>) PA<sub>80</sub>–ZnP<sub>20</sub>; (<b>c</b>) PA<sub>80</sub>–AlP<sub>20</sub>; (<b>d</b>) PA<sub>80</sub>–LL<sub>20</sub>; (<b>e</b>) PA<sub>80</sub>–DL<sub>20</sub>; (<b>f</b>) PA<sub>80</sub>–LL<sub>10</sub>–AlP<sub>10</sub>; (<b>g</b>) PA<sub>80</sub>–LL<sub>10</sub>–ZnP<sub>10</sub>; (<b>h</b>) PA<sub>80</sub>–DL<sub>10</sub>–AlP<sub>10</sub> and (<b>i</b>) PA<sub>80</sub>–DL<sub>10</sub>–ZnP<sub>10</sub> blends.</p> Full article ">Figure 11
<p>Scanning Electron Microscopy (SEM) micrographs of char residue surface after forced combustion for (<b>a</b>) PA<sub>80</sub>–LL<sub>10</sub>–AlP<sub>10</sub>; (<b>b</b>) PA<sub>80</sub>–LL<sub>10</sub>–ZnP<sub>10</sub>; (<b>c</b>) PA<sub>80</sub>–DL<sub>10</sub>–AlP<sub>10</sub> and (<b>d</b>) PA<sub>80</sub>–DL<sub>10</sub>–ZnP<sub>10</sub> blends at 1000× and 5000× magnification.</p> Full article ">
12 pages, 5025 KiB  
Article
Color Tuning by Oxide Addition in PEDOT:PSS-Based Electrochromic Devices
by Delphin Levasseur, Issam Mjejri, Thomas Rolland and Aline Rougier
Polymers 2019, 11(1), 179; https://doi.org/10.3390/polym11010179 - 21 Jan 2019
Cited by 53 | Viewed by 9121
Abstract
Poly(3,4-ethylenedi-oxythiophene) (PEDOT) derivatives conducting polymers are known for their great electrochromic (EC) properties offering a reversible blue switch under an applied voltage. Characterizations of symmetrical EC devices, built on combinations of PEDOT thin films, deposited with a bar coater from commercial inks, and [...] Read more.
Poly(3,4-ethylenedi-oxythiophene) (PEDOT) derivatives conducting polymers are known for their great electrochromic (EC) properties offering a reversible blue switch under an applied voltage. Characterizations of symmetrical EC devices, built on combinations of PEDOT thin films, deposited with a bar coater from commercial inks, and separated by a lithium-based ionic membrane, show highest performance for 800 nm thickness. Tuning of the color is further achieved by mixing the PEDOT film with oxides. Taking, in particular, the example of optically inactive iron oxide Fe2O3, a dark blue to reddish switch, of which intensity depends on the oxide content, is reported. Careful evaluation of the chromaticity parameters L*, a*, and b*, with oxidizing/reducing potentials, evidences a possible monitoring of the bluish tint. Full article
(This article belongs to the Special Issue Electrochromic Polymers)
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<p>(<b>a</b>) Cyclic voltammograms of the electrochromic symmetrical displays built from PEDOT:PSS thin films with varying thickness from 109 nm to 1106 nm, (<b>b</b>) chronoamperograms (<span class="html-italic">CA</span>) of the electrochromic symmetrical displays built from different PEDOT:PSS thicknesses. Potentials of +1.6 V and −1.6 V were applied for 30 s alternatively.</p> Full article ">Figure 2
<p>Photographs of the electrochromic symmetrical displays built from PEDOT:PSS films with different thicknesses, showing an oxidized state for a potential of +1.6 V and a reduced (colored) state for a potential of −1.6 V. The corresponding measured <span class="html-italic">L*a*b*</span> parameters are mentioned at the top and bottom of the image for the oxidized (bleached) state and the neutral (colored) state, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) Color contrast <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msup> <mi>E</mi> <mo>*</mo> </msup> </mrow> </semantics></math> as a function of the chronoamperometry cycles of electrochromic displays built from PEDOT:PSS thin films with varying thickness from 109 nm to 1106 nm, (<b>b</b>) color contrast as a function of PEDOT:PSS thickness, after 10 cycles of chronoamperometry. For both graphs, applied potentials were +1.6 V for 20 s, and 1.6 V for 20 s.</p> Full article ">Figure 4
<p>(<b>a</b>) Chronoamperograms in a three-electrode cell configuration at −1.3 V for 20 s and +1.3 V for 20 s of the PEDOT:PSS layer at the optimized thickness of 880 nm, (<b>b</b>) corresponding optical transmittance spectra at oxidized and reduced states of PEDOT:PSS layer at the optimized thickness of 880 nm (the pictures of the thin films during the test are presented in the inset).</p> Full article ">Figure 5
<p>Color contrast Δ<span class="html-italic">E*</span> as a function of the number of chronoamperometry cycles, measured on an electrochromic symmetrical display built from 880 nm PEDOT:PSS thick film.</p> Full article ">Figure 6
<p>XRD pattern of the Fe<sub>2</sub>O<sub>3</sub> pigment. The red crosses indicate α-Fe<sub>2</sub>O<sub>3</sub> structure diffraction peaks (space group R-3C).</p> Full article ">Figure 7
<p>Top view SEM images of the surface morphology of two films. On the left, PEDOT:PSS film with an average thickness of 550 nm; on the right, PEDOT:PSS + 2.5% of Fe<sub>2</sub>O<sub>3</sub> film with an average thickness of 814 nm. Both films were deposited using the same wirebar (i.e., bar n°5, wet thickness 50 µm).</p> Full article ">Figure 8
<p>(<b>a</b>) Cyclic voltammograms (2<sup>nd</sup> cycle) of the electrochromic displays obtained from PEDOT-PSS + x Fe<sub>2</sub>O<sub>3</sub> thin film with varying x from 2 wt % to 3.5 wt % compared to PEDOT:PSS without Fe<sub>2</sub>O<sub>3</sub>, (<b>b</b>) cyclic voltammograms of the electrochromic displays with PEDOT:PSS +2.5% Fe<sub>2</sub>O<sub>3</sub> at different potential ranges.</p> Full article ">Figure 9
<p>This figure shows the tuning of the <span class="html-italic">L*a*b*</span> parameters by adjusting the Fe<sub>2</sub>O<sub>3</sub> content or the reduction voltage. (<b>a</b>) Image of the oxidized and reduced state of a 98%PEDOT:PSS/2%Fe<sub>2</sub>O<sub>3</sub> thin layer and display, changing from red to blue color. (<b>b</b>) <span class="html-italic">L*</span> parameter as a function of the reduction voltage for different Fe<sub>2</sub>O<sub>3</sub> contents. (<b>c</b>) Tuning of <span class="html-italic">a*b*</span> parameters by increasing Fe<sub>2</sub>O<sub>3</sub> content for oxidized state at 1.6 V and reduced state at −1.8 V (<b>d</b>); inset shows the tuning of the blue shade by varying the reduction voltage.</p> Full article ">Figure A1
<p>Current switching time as a function of PEDOT:PSS thickness in displays.</p> Full article ">
13 pages, 3378 KiB  
Article
In Situ Growth of a High-Performance All-Solid-State Electrode for Flexible Supercapacitors Based on a PANI/CNT/EVA Composite
by Xipeng Guan, Debin Kong, Qin Huang, Lin Cao, Peng Zhang, Huaijun Lin, Zhidan Lin and Hong Yuan
Polymers 2019, 11(1), 178; https://doi.org/10.3390/polym11010178 - 21 Jan 2019
Cited by 28 | Viewed by 5530
Abstract
For the development of light, flexible, and wearable electronic devices, it is crucial to develop energy storage components combining high capacity and flexibility. Herein, an all-solid-state supercapacitor is prepared through an in situ growth method. The electrode contains polyaniline deposited on a carbon [...] Read more.
For the development of light, flexible, and wearable electronic devices, it is crucial to develop energy storage components combining high capacity and flexibility. Herein, an all-solid-state supercapacitor is prepared through an in situ growth method. The electrode contains polyaniline deposited on a carbon nanotube and a poly (ethylene-co-vinyl acetate) film. The hybrid electrode exhibits excellent mechanical and electrochemical performance. The optimized few-layer polyaniline wrapping layer provides a conductive network that effectively enhances the cycling stability, as 66.4% of the starting capacitance is maintained after 3000 charge/discharge cycles. Furthermore, the polyaniline (PANI)-50 displays the highest areal energy density of 83.6 mWh·cm−2, with an areal power density of 1000 mW·cm−2, and a high areal capacity of 620 mF cm−2. The assembled device delivers a high areal capacity (192.3 mF·cm−2) at the current density of 0.1 mA·cm−2, a high areal energy (26.7 mWh·cm−2) at the power density of 100 mW·cm−2, and shows no significant decrease in the performance with a bending angle of 180°. This unique flexible supercapacitor thus exhibits great potential for wearable electronics. Full article
(This article belongs to the Special Issue Polymer-CNT Nanocomposites)
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<p>Digital photographs of four different electrodes: (<b>a</b>) conductive phase (CNT)/EVA, (<b>b</b>) CNT/EVA Cotton, (<b>c</b>) CNT paper, (<b>d</b>) 331 carbon cloth. SEM images of (<b>e</b>) CNT/EVA and (<b>f</b>) CNT paper.</p> Full article ">Figure 2
<p>(<b>a</b>) Cyclic voltammetry (CV) curves (100 mV·s<sup>−1</sup>), (<b>b</b>) galvanostatic charge-discharge (GCD) curve (0.5 mA·cm<sup>2</sup>), and (<b>c</b>) electrochemical impedance spectroscopy (EIS) measurement for flexible electrodes made from different carbon materials. (<b>d</b>) CV curves and (<b>e</b>) discharge curve for the CNT/EVA electrode.</p> Full article ">Figure 3
<p>SEM images of (<b>a</b>) CNT/EVA, (<b>b</b>) PANI-5, (<b>c</b>) PANI-10, (<b>d</b>) PANI-20, (<b>e</b>) PANI-30, and (<b>f</b>) PANI-50 electrodes. (<b>g</b>) EDS analysis of PANI–5, C element, N element, and O element.</p> Full article ">Figure 3 Cont.
<p>SEM images of (<b>a</b>) CNT/EVA, (<b>b</b>) PANI-5, (<b>c</b>) PANI-10, (<b>d</b>) PANI-20, (<b>e</b>) PANI-30, and (<b>f</b>) PANI-50 electrodes. (<b>g</b>) EDS analysis of PANI–5, C element, N element, and O element.</p> Full article ">Figure 4
<p>(<b>a</b>) CV (100 mV·s<sup>–1</sup>), (<b>b</b>) discharge curves (1 mA·cm<sup>–2</sup>), (<b>c</b>) areal capacitance and (<b>d</b>), EIS measurements of the PANI 5, 10, 20, 30, and 50 electrodes; (<b>e</b>) CV and (<b>f</b>) discharge curves of PANI–50 electrode at different scan rates and current densities; and (<b>g</b>) cycling stability of the PANI-50 electrode.</p> Full article ">Figure 4 Cont.
<p>(<b>a</b>) CV (100 mV·s<sup>–1</sup>), (<b>b</b>) discharge curves (1 mA·cm<sup>–2</sup>), (<b>c</b>) areal capacitance and (<b>d</b>), EIS measurements of the PANI 5, 10, 20, 30, and 50 electrodes; (<b>e</b>) CV and (<b>f</b>) discharge curves of PANI–50 electrode at different scan rates and current densities; and (<b>g</b>) cycling stability of the PANI-50 electrode.</p> Full article ">Figure 5
<p>Digital photographs of the PANI/CNT/EVA electrode: (<b>a</b>) mass loading, (<b>b</b>) twisted into a spiral shape or tied into a knot, stretched, and released. (<b>c</b>) CV curves of the PANI/CNT/EVA electrode under different bending angles. (<b>d</b>) CV and (<b>e</b>) discharge curves of solid-state symmetric supercapacitors at different scan rates and current densities. (<b>f</b>) Digital photographs of the assembled flexible solid-state symmetric supercapacitors (3 in series) lighting LEDs. (<b>g</b>) Ragone plots of the areal energy density and power density, and the structure of flexible solid-state symmetric supercapacitors.</p> Full article ">
10 pages, 2919 KiB  
Article
Investigation of Chitosan Nanoparticles Loaded with Protocatechuic Acid (PCA) for the Resistance of Pyricularia oryzae Fungus against Rice Blast
by The Trinh Pham, Thi Hiep Nguyen, Thuan Vo Thi, Thanh-Truc Nguyen, Tien Dung Le, Do Minh Hoang Vo, Dai Hai Nguyen, Cuu Khoa Nguyen, Duy Chinh Nguyen, Trong Tuan Nguyen and Long Giang Bach
Polymers 2019, 11(1), 177; https://doi.org/10.3390/polym11010177 - 21 Jan 2019
Cited by 30 | Viewed by 5189
Abstract
In this study, chitosan nanoparticles were used as a carrier for Protocatechuic acid (PCA) to resist Pyricularia oryzae against rice blast. The final compound was characterized using zeta potentials for its surface electricity, Fourier transform infrared (FT-IR) analysis and transmission electron microscopy (TEM) [...] Read more.
In this study, chitosan nanoparticles were used as a carrier for Protocatechuic acid (PCA) to resist Pyricularia oryzae against rice blast. The final compound was characterized using zeta potentials for its surface electricity, Fourier transform infrared (FT-IR) analysis and transmission electron microscopy (TEM) were conducted for functional groups and for particle sizes and shape, respectively. The zeta potential results showed that loading PCA causes chitosan nanoparticle (CSNP) to decrease in surface electrons. The TEM images revealed that the particle size of chitosan (CS), although increasing in size when carrying PCA molecules, showed sufficient size for reasonable penetration into fungal cells. The FT-IR analysis showed that all functional group in CSNP carried PCA matched with previous studies. The antifungal test showed that diameters of inhibition zone of CS increases significantly after loading PCA, exhibiting the strongest antimicrobial effect on the Pyricularia oryzae fungus compared with weaker effects exhibited by CSNP alone or PCA. Our results suggested that CSNP loaded with PCA could be a potential compound for eradication of Pyricularia oryzae and that further testing on in vitro rice plants is recommended to reaffirm this possibility. Full article
(This article belongs to the Special Issue Nanotechnology of Polymers and Biomaterials)
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<p>The PCA standard line.</p> Full article ">Figure 2
<p>Zeta potentials of CSNPs and CS@PCA.</p> Full article ">Figure 3
<p>FT-IR spectra of (<b>a</b>) CSNP, (<b>b</b>) PCA and (<b>c</b>) CS@PCA.</p> Full article ">Figure 4
<p>TEM images and particle size histograms of (<b>a</b>) CSNPs and (<b>b</b>) CS@PCA and their fitted by log-normal distribution function, respectively.</p> Full article ">Figure 5
<p>(<b>A</b>) Diameter of inhibition zone of PCA, CSNP and CS@PCA based on various concentrations of PCA as 500, 1000, 2500 and 5000 ppm and (<b>B</b>) Diameter of inhibition zone of CS@PCA after various ranges of time: 24, 48, 72 and 96 h.</p> Full article ">Figure 6
<p>Diameter of inhibition zone of CS@PCA in 24 h (a); 48 h (b); 72 h (c) and 96 h (d) based on various concentrations of PCA as 0 ppm, 500 ppm, 1000 ppm, 2500 ppm, 5000 ppm (C = control, 1, 2, 3 and 4, respectively).</p> Full article ">Scheme 1
<p>Synthesis of Chitosan loading Protocatechuic acid by ionic gelation method.</p> Full article ">
10 pages, 2034 KiB  
Communication
Use of Grafted Voltage Stabilizer to Enhance Dielectric Strength of Cross-Linked Polyethylene
by Wei Dong, Xuan Wang, Bo Tian, Yuguang Liu, Zaixing Jiang, Zhigang Li and Wei Zhou
Polymers 2019, 11(1), 176; https://doi.org/10.3390/polym11010176 - 20 Jan 2019
Cited by 26 | Viewed by 4526
Abstract
Aromatic voltage stabilizers can improve the dielectric properties of cross-linked polyethylene (XLPE); however, their poor compatibility with XLPE hinders their practical application. Improving the compatibility of aromatic voltage stabilizers with XLPE has, therefore, become a new research goal. Herein 1-(4-vinyloxy)phenylethenone (VPE) was prepared [...] Read more.
Aromatic voltage stabilizers can improve the dielectric properties of cross-linked polyethylene (XLPE); however, their poor compatibility with XLPE hinders their practical application. Improving the compatibility of aromatic voltage stabilizers with XLPE has, therefore, become a new research goal. Herein 1-(4-vinyloxy)phenylethenone (VPE) was prepared and characterized. It can be grafted onto polyethylene molecules during the cross-linking processes to promote stability of the aromatic voltage stabilizers in XLPE. Fourier transform infrared spectroscopy confirmed that VPE was successfully grafted onto XLPE, and effectively inhibited thermal migration. Thermogravimetric analysis showed that the grafted VPE/XLPE composite exhibits a better thermal stability than a VPE/PE blend composite. Evaluation of the electrical properties showed that the breakdown strength and electrical tree initiation voltage of the VPE/XLPE composite were increased by 15.5% and 39.6%, respectively, when compared to those of bare XLPE. After thermal aging, the breakdown strength and electrical tree initiation voltage of the VPE/XLPE composite were increased by 9.4% and 25.8%, respectively, in comparison to those of bare XLPE, which indicates that the grafted voltage stabilizer can effectively inhibit its migration and enhance the stability of the composite material. Full article
(This article belongs to the Special Issue Synthesis and Application of Conjugated Polymers)
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<p>FTIR and <sup>1</sup>H NMR analysis. (<b>a</b>) FTIR spectra of HAP and VPE; (<b>b</b>) <sup>1</sup>H NMR spectra of VPE.</p> Full article ">Figure 2
<p>TGA and FTIR analysis. (<b>a</b>) infrared spectrum pre-and post-extraction of VPE/PE; (<b>b</b>) infrared spectrum pre-and post-extraction of graft VPE/XLPE; (<b>c</b>) TGA of PE, VPE/PE, graft VPE/XLPE.</p> Full article ">Figure 3
<p>(<b>a</b>) breakdown strength Weibull curve of VPE/XLPE; (<b>b</b>) electrical tree initiation voltage of XLPE and composite; (<b>c</b>) electrical tree microscopic morphology of XLPE; (<b>d</b>) electrical tree microscopic morphology of VPE /XLPE.</p> Full article ">Figure 4
<p>(<b>a</b>) breakdown strength of Thermal aging before; (<b>b</b>) breakdown strength of Thermal aging after; (<b>c</b>) electrical tree initiation voltage of Thermal aging before; (<b>d</b>) electrical tree initiation voltage of Thermal aging after.</p> Full article ">Scheme 1
<p>Synthesis of VPE.</p> Full article ">Scheme 2
<p>VPE grafted onto XLPE.</p> Full article ">
11 pages, 2388 KiB  
Article
Morphology Evolution and Rheological Behaviors of PP/SR Thermoplastic Vulcanizate
by Qiang Wu, Jiafeng Fang, Minghuan Zheng, Yan Luo, Xu Wang, Lixin Xu and Chunhui Zhang
Polymers 2019, 11(1), 175; https://doi.org/10.3390/polym11010175 - 19 Jan 2019
Cited by 17 | Viewed by 5480
Abstract
The thermoplastic vulcanizates (TPVs) of polypropylene (PP)/silicone rubber (SR) were prepared by dynamic vulcanization (DV) technology. The mixing torque, morphology, viscoelasticity, and creep response of PP/SR TPVs were investigated by torque rheometer, scanning electron microscope (SEM), transmission electron microscope (TEM), rotational rheometer, and [...] Read more.
The thermoplastic vulcanizates (TPVs) of polypropylene (PP)/silicone rubber (SR) were prepared by dynamic vulcanization (DV) technology. The mixing torque, morphology, viscoelasticity, and creep response of PP/SR TPVs were investigated by torque rheometer, scanning electron microscope (SEM), transmission electron microscope (TEM), rotational rheometer, and dynamic mechanical analysis (DMA). A mixing-torque study showed that torque change and dynamic-vulcanization time increased with SR content increasing in the DV process, but DV rate was independent of SR content. TEM images indicated that the phase inversion of PP/SR-60 TPV from bicontinuous to a sea–island structure took place in the DV process, and a hot press would break the rubber aggregates and shrink a large SR phase. Dynamic-strain measurement demonstrated that PP/SR TPVs exhibit a distinct “Payne effect”, which can be attributed to the destruction and reconstruction of SR physical networks. Complex viscosity indicated that SR content did not affect the processability of PP/SR TPVs at high shear rates. Furthermore, the creep deformation and recovery of PP/SR TPVs at solid and melt states were studied, respectively. Full article
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<p>(<b>A</b>) Mixing torque change of polypropylene (PP)/silicone rubber (SR) blends in dynamic vulcanization process and (<b>B</b>) the relationship between SR content and torque change (Δ<span class="html-italic">M</span>) and dynamic vulcanization time (<span class="html-italic">t</span>).</p> Full article ">Figure 2
<p>SEM images of etched surfaces for different polypropylene (PP)/silicone rubber (SR) thermoplastic vulcanizates (TPVs). (<b>A</b>) PP/SR-30, (<b>B</b>) PP/SR-40, (<b>C</b>) PP/SR-50, (<b>D</b>) PP/SR-60, (<b>E</b>) PP/SR-70 and (<b>F</b>) SR phase size statistical result.</p> Full article ">Figure 3
<p>The relationship between different stages of polypropylene (PP)/silicone rubber (SR)-60 preparation and its morphology evolution, (<b>A</b>) Mixing torque change of PP/SR-60 preparation, (<b>B</b>) TEM image of PP/SR-60 blend at point B, (<b>C</b>) TEM image of PP/SR-60 thermoplastic vulcanizate at point C and (<b>D</b>) TEM image of PP/SR-60 TPV after hot press.</p> Full article ">Figure 4
<p>The dependence of the (<b>A</b>) dynamic storage modulus (<span class="html-italic">G</span>′) and (<b>B</b>) loss modulus (<span class="html-italic">G</span>″) on strain amplitude measured at 200 °C and 10 rad/s for different polypropylene (PP)/silicone rubber (SR) thermoplastic vulcanizates (TPVs).</p> Full article ">Figure 5
<p>Plots of (<b>A</b>) <span class="html-italic">G</span>′, (<b>B</b>) <span class="html-italic">G</span>″ and (<b>C</b>) complex viscosity (η*) vs. frequency for polypropylene (PP) and PP/ silicone rubber (SR) thermoplastic vulcanizates (TPVs) with different SR content at 200 °C.</p> Full article ">Figure 6
<p>Creep deformation and its recovery behavior of polypropylene (PP)/silicone rubber (SR) thermoplastic vulcanizates (TPVs) at (<b>A</b>) 40 °C and (<b>B</b>) 180 °C.</p> Full article ">
18 pages, 6363 KiB  
Article
Biocompatibility of Small-Diameter Vascular Grafts in Different Modes of RGD Modification
by Larisa V. Antonova, Vladimir N. Silnikov, Victoria V. Sevostyanova, Arseniy E. Yuzhalin, Lyudmila S. Koroleva, Elena A. Velikanova, Andrey V. Mironov, Tatyana S. Godovikova, Anton G. Kutikhin, Tatiana V. Glushkova, Inna Yu. Serpokrylova, Evgeniya A. Senokosova, Vera G. Matveeva, Mariam Yu. Khanova, Tatiana N. Akentyeva, Evgeniya O. Krivkina, Yulia A. Kudryavtseva and Leonid S. Barbarash
Polymers 2019, 11(1), 174; https://doi.org/10.3390/polym11010174 - 18 Jan 2019
Cited by 23 | Viewed by 5237
Abstract
Modification with Arg-Gly-Asp (RGD) peptides is a promising approach to improve biocompatibility of small-calibre vascular grafts but it is unknown how different RGD sequence composition impacts graft performance. Here we manufactured 1.5 mm poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(ε-caprolactone) grafts modified by distinct linear or cyclic [...] Read more.
Modification with Arg-Gly-Asp (RGD) peptides is a promising approach to improve biocompatibility of small-calibre vascular grafts but it is unknown how different RGD sequence composition impacts graft performance. Here we manufactured 1.5 mm poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(ε-caprolactone) grafts modified by distinct linear or cyclic RGD peptides immobilized by short or long amine linker arms. Modified vascular prostheses were tested in vitro to assess their mechanical properties, hemocompatibility, thrombogenicity and endothelialisation. We also implanted these grafts into rat abdominal aortas with the following histological examination at 1 and 3 months to evaluate their primary patency, cellular composition and detect possible calcification. Our results demonstrated that all modes of RGD modification reduce ultimate tensile strength of the grafts. Modification of prostheses does not cause haemolysis upon the contact with modified grafts, yet all the RGD-treated grafts display a tendency to promote platelet aggregation in comparison with unmodified counterparts. In vivo findings identify that cyclic Arg-Gly-Asp-Phe-Lys peptide in combination with trioxa-1,13-tridecanediamine linker group substantially improve graft biocompatibility. To conclude, here we for the first time compared synthetic small-diameter vascular prostheses with different modes of RGD modification. We suggest our graft modification regimen as enhancing graft performance and thus recommend it for future use in tissue engineering. Full article
(This article belongs to the Special Issue Functional Polymers for Biomedicine)
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<p>Study design. (<b>A</b>) A cartoon illustrating the modification of poly(3-hydroxybutyrate-<span class="html-italic">co</span>-3-hydroxyvalerate)/poly(ε-caprolactone) vascular grafts with RGD-containing peptides. Listed are RGD peptides used to modify the luminal surface of grafts and linker arm groups utilized for peptide immobilization. (<b>B</b>) General scheme for the graft surface modification, where H<sub>2</sub>N–L–NH<sub>2</sub> is a linker group.</p> Full article ">Figure 2
<p>Representative scanning electron microscopy images of grafts functionalized with distinct RGD peptides or unmodified prostheses upon the contact with human platelet-rich plasma (PRP).</p> Full article ">Figure 3
<p>Testing of adhesion and viability of endothelial cells on grafts functionalized with distinct RGD peptides or unmodified prostheses. (<b>A</b>) Representative images of endothelial colony-forming cells (ECFCs) adherent to the surface of grafts and stained with ethidium bromide (red, stains dead cells) and Hoechst 33,342 (blue, stains all cells). Scale bar = 100 μm. (<b>B</b>) Quantification of cells from experiment in A. Whiskers indicate standard deviation. <span>$</span> <span class="html-italic">p</span> &lt; 0.05 in comparison with unmodified grafts, Amine1Pep1, Amine1Pep2, Amine2Pep3; † <span class="html-italic">p</span> &lt; 0.05 in comparison with a culture plastic, Amine1Pep2, Amine1Pep3, Amine2Pep1, Amine2Pep2, Amine2Pep3; ‡ <span class="html-italic">p</span> &lt; 0.05 in comparison with all other study groups; # <span class="html-italic">p</span> &lt; 0.05 in comparison with all other study groups excepting Amine2Pep3; + <span class="html-italic">p</span> &lt; 0.05 in comparison with all other study groups excepting unmodified grafts; § <span class="html-italic">p</span> &lt; 0.05 in comparison with a culture plastic. (<b>C</b>) Relative proportion of live ECFCs on the surface of studied grafts after 72 h of culture. Whiskers indicate standard deviation. * <span class="html-italic">p</span> &lt; 0.05 in comparison with unmodified grafts, Amine1Pep1, Amine1Pep3, Amine2Pep2, Amine2Pep3; # <span class="html-italic">p</span> &lt; 0.05 in comparison with all other study groups; † <span class="html-italic">p</span> &lt; 0.05 in comparison with a culture plastic, unmodified grafts, Amine1Pep2, Amine2Pep1. (<b>D</b>) Relative proportion of dead ECFCs on the surface of studied grafts after 72 h of culture. Whiskers indicate standard deviation. * <span class="html-italic">p</span> &lt; 0.05 in comparison with all other study groups; ‡ <span class="html-italic">p</span> &lt; 0.05 in comparison with a culture plastic; # <span class="html-italic">p</span> &lt; 0.05 in comparison with a culture plastic, Amine1Pep2, Amine2Pep1.</p> Full article ">Figure 4
<p>Representative scanning electron microscopy images of endothelial colony-forming cells (ECFCs) adhered to the surface of grafts functionalized with distinct RGD peptides or unmodified prostheses after 72 h of culture.</p> Full article ">Figure 5
<p>Histological examination of grafts functionalized with distinct RGD peptides or unmodified prostheses implanted into rat abdominal aortas for 1 (<b>A</b>) and 3 (<b>B</b>) months. Haematoxylin and eosin (scale bar = 100 μm), van Gieson (scale bar = 50 μm) and alizarin red S (scale bar = 500 μm) staining.</p> Full article ">Figure 6
<p>Immunofluorescence assessment of endothelialisation of grafts functionalized with distinct RGD peptides or unmodified prostheses. (<b>A</b>) Double immunostaining for CD31 (red, mature endothelial cells) and CD34 (green, endothelial progenitor cells) with DAPI (blue, nuclei) counterstaining, representative confocal microscopy images. Scale bar = 20 μm. G means graft, L means lumen. (<b>B</b>) CD31<sup>+</sup> cell count. Whiskers indicate range, boxes bounds indicate 25th and 75th percentiles, centre lines indicate median. One-way ANOVA with Tukey’s multiple comparisons test. (<b>C</b>) CD34<sup>+</sup> cell count. Whiskers indicate range, boxes bounds indicate 25th and 75th percentiles, centre lines indicate median. One-way ANOVA with Tukey’s multiple comparisons test. (<b>D</b>) Semi-quantitative analysis of endothelial phenotype based on CD31<sup>+</sup> and CD34<sup>+</sup> cell count.</p> Full article ">
10 pages, 3123 KiB  
Communication
Towards Detection of Glycoproteins Using Molecularly Imprinted Nanoparticles and Boronic Acid-Modified Fluorescent Probe
by Lingdong Jiang, Rui Lu and Lei Ye
Polymers 2019, 11(1), 173; https://doi.org/10.3390/polym11010173 - 18 Jan 2019
Cited by 21 | Viewed by 4985
Abstract
Glycoproteins represent a group of important biomarkers for cancer and other life-threatening diseases. Selective detection of specific glycoproteins is an important step for early diagnosis. Traditional glycoprotein assays are mostly based on lectins, antibodies, and enzymes, biochemical reagents that are costly and require [...] Read more.
Glycoproteins represent a group of important biomarkers for cancer and other life-threatening diseases. Selective detection of specific glycoproteins is an important step for early diagnosis. Traditional glycoprotein assays are mostly based on lectins, antibodies, and enzymes, biochemical reagents that are costly and require special cold chain storage and distribution. To address the shortcomings of the existing glycoprotein assays, we propose a new approach using protein-imprinted nanoparticles to replace the traditional lectins and antibodies. Protein-imprinted binding sites were created on the surface of silica nanoparticles by copolymerization of dopamine and aminophenylboronic acid. The imprinted nanoparticles were systematically characterized by dynamic light scattering, scanning and transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and elemental analysis. A boronic acid-modified fluorescent probe was used to detect the target glycoprotein captured by the imprinted nanoparticles. Using horseradish peroxidase as a model glycoprotein, we demonstrated that the proposed method can be applied to detect target protein containing multiple glycosylation sites. Because of their outstanding stability and low cost, imprinted nanoparticles and synthetic probes are attractive replacements of traditional biochemical reagents to develop simpler, faster, and more cost-effective analytical methods for glycoproteins. Full article
(This article belongs to the Special Issue Biomimicry through Molecular Imprinting: From Polymer Design to Devices)
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<p>Hydrodynamic particle size of silica (<b>black</b>), silica@BA (<b>red</b>), horseradish peroxidase (HRP)-imprinted MIP (<b>blue</b>), non-imprinted polymer (NIP) (<b>green</b>) measured in water.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) silica nanoparticles, (<b>b</b>) Si@BA, (<b>c</b>) HRP–MIP, and (<b>d</b>) NIP. TEM images of (<b>e</b>) silica nanoparticles, (<b>f</b>) Si@BA, (<b>g</b>) HRP–MIP, and (<b>h</b>) NIP.</p> Full article ">Figure 3
<p>FT-IR spectra of (<b>a</b>) Si, (<b>b</b>) Si@NH<sub>2</sub>, (<b>c</b>) Si@BA, and (<b>d</b>) HRP–MIP.</p> Full article ">Figure 4
<p>TGA analysis of (<b>a</b>) Si, (<b>b</b>) Si@NH<sub>2</sub>, (<b>c</b>) Si@BA, (<b>d</b>) HRP–MIP, and (<b>e</b>) NIP.</p> Full article ">Figure 5
<p>Detection of protein binding to imprinted particles using BA–FITC as a fluorescence probe. The MIP nanoparticles (3 mg) were first incubated with their corresponding protein templates (0.2–1.0 mg mL<sup>−1</sup>). After this step, BA–FITC was added, and the bound BA–FITC was measured using a fluorescence spectrometer.</p> Full article ">Figure 6
<p>Selective detection of HRP captured by HRP–MIP using BA–FITC conjugate. The different imprinted nanoparticles (BSA–MIP, OVA–MIP, TRF–MIP and HRP–MIP) and NIP nanoparticles were first incubated separately with the four proteins before being exposed to BA–FITC. The concentration of the different proteins was fixed at 1.0 mg mL<sup>−1</sup>. <span class="html-italic">P</span> values were calculated by one-way analysis of variance (ANOVA) to estimate the statistically significant differences (*** <span class="html-italic">P</span> &lt; 0.005). NS represented no significance. BSA: Bovine serum albumin, OVA: Ovalbumin, TRF: Transferrin.</p> Full article ">Scheme 1
<p>Schematic of glycoprotein imprinting using immobilized template, and detection of the molecularly imprinted polymer (MIP)-captured glycoprotein using boronic acid–fluorescein conjugate (BA–FITC) as a fluorescent probe.</p> Full article ">
12 pages, 4715 KiB  
Article
Controllable Crimpness of Animal Hairs via Water-Stimulated Shape Fixation for Regulation of Thermal Insulation
by Xueliang Xiao, Yanjia Gu, Guanzheng Wu, Diantang Zhang and Huizhen Ke
Polymers 2019, 11(1), 172; https://doi.org/10.3390/polym11010172 - 18 Jan 2019
Cited by 6 | Viewed by 4883
Abstract
Animals living in extremely cold plateau areas have shown amazing ability to maintain their bodies warmth, a benefit of their hair’s unique structures and crimps. Investigation of hair crimps using a water-stimulated shape fixation effect would control the hair’s crimpness with a specific [...] Read more.
Animals living in extremely cold plateau areas have shown amazing ability to maintain their bodies warmth, a benefit of their hair’s unique structures and crimps. Investigation of hair crimps using a water-stimulated shape fixation effect would control the hair’s crimpness with a specific wetting-drying process thereafter, in order to achieve the regulation of hair thermal insulation. The mechanism of hair’s temporary shape fixation was revealed through FTIR and XRD characterizations for switching on and off the hydrogen bonds between macromolecules via penetration into and removal of aqueous molecules. The thermal insulation of hairs was regulated by managing the hair temporary crimps, that is, through managing the multiple reflectance of infrared light by hair hierarchical crimps from hair root to head. Full article
(This article belongs to the Special Issue Shape Memory Polymers III)
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<p>Yak living in a cold plateau area with thick, warm fur and hair layers, (<b>a</b>) photograph of a yak living at Tibet plateau of more than 4000 m above sea level, (<b>b</b>) raw yak hairs with guard and down hairs, (<b>c</b>) a yak hair with natural crimps, (<b>d</b>) the stretched yak hair with more times in length than natural length, (<b>e</b>) cross section of head part of hair, and (<b>f</b>) root coarse part of hair.</p> Full article ">Figure 2
<p>How does the hair crimp? (<b>a</b>) A yak hair in free crimped state, (<b>b</b>) a crimp made of orthocortex and pi-cortical cells with different modulus E<sub>1</sub> and E<sub>2</sub> along the hair axis, and (<b>c</b>) in either cortex made of different contents of crystalline and amorphous phases for the hair crimping.</p> Full article ">Figure 3
<p>Physical properties of yak hairs. (<b>a</b>) Measured relationship of hair diameter and ratio of stretched hair length (L<sub>s</sub>) to natural crimped hair length (L<sub>o</sub>). (<b>b</b>) Distribution of crimp numbers along a mature yak hair from its coarse to fine parts.</p> Full article ">Figure 4
<p>Shape memory effect of yak hair responsive to water, in which (<b>a</b>) shows a natural crimped hair, (<b>b</b>) denotes the manually deformed yak hair soaked in water, (<b>c</b>) displays the temporarily deformed shape of hair after a drying process, and (<b>d</b>) shows the recovered crimped shape of hair stimulated by water.</p> Full article ">Figure 5
<p>A quantitative shape fixation test of yak hair, (<b>a</b>) test principle with four steps (original length (L<sub>o</sub>)→length of stretched hair in water (L<sub>s</sub>)→fixed length of hair after drying process (L<sub>f</sub>)), (<b>b</b>) the measured shape fixation ratios related to hair diameter, where the inset refers to our previous publication [<a href="#B18-polymers-11-00172" class="html-bibr">18</a>] that wetting can reduce the hair storage modulus by opening the hydrogen bonds in hair amorphous area and drying process shows the reverse function. The inset figure in (<b>b</b>) is reproduced from [<a href="#B18-polymers-11-00172" class="html-bibr">18</a>] under open access license.</p> Full article ">Figure 6
<p>Reversible hair shape fixation and recovery using characterizations from (<b>a</b>) Fourier transform infrared (FTIR) (the inset figure shows the reversible feature of hair shape memory responsive to water in terms of IR peak intensity and abscissa position, reproduced from [<a href="#B18-polymers-11-00172" class="html-bibr">18</a>] under open access license) and (<b>b</b>) X-ray diffraction (XRD) (the inset figure indicates the twin-netpoints for intact hair shape in shape memory, reproduced from [<a href="#B19-polymers-11-00172" class="html-bibr">19</a>] by permission of The Royal Society of Chemistry) for hairs in dry and wet states.</p> Full article ">Figure 7
<p>Thermal insulation of yak hairs. (<b>a</b>) Schematic illustration of thermal conductivity, convection, and radiation of yak hairs from coarse to fine crimps; (<b>b</b>) the reflectance (including absorption) measurement of visible to near infrared lights for coarse (diameter = 40 to 60 μm) and fine (diameter = 20 to 40 μm) yak hairs, using a visible- infrared spectroscopy microscope.</p> Full article ">Figure 8
<p>Thermal insulation properties of yak hairs with infrared images for (<b>a</b>) the measured relationship of hair weight (a<sub>1</sub>-0.036 g; a<sub>2</sub>-0.099 g; a<sub>3</sub>-0.124 g; a<sub>4</sub>-0.218 g) and temperature contour of hairs on a human hand (a kind of constant temperature source); (<b>b</b>) thermal insulation corresponds to hair states that (b<sub>1</sub>) shows hairs rubbed into a ball shape, (b<sub>2</sub>) shows hairs in natural state, and (b<sub>3</sub>) shows hairs in fully stretched straight state; (<b>c</b>) the fully stretched hairs in wet (c<sub>1</sub>) and dry (c<sub>2</sub>) states, using shape memory function.</p> Full article ">
12 pages, 3206 KiB  
Article
Patterned Polyvinyl Alcohol Hydrogel Dressings with Stem Cells Seeded for Wound Healing
by Tianlin Gao, Menghui Jiang, Xiaoqian Liu, Guoju You, Wenyu Wang, Zhaohui Sun, Aiguo Ma and Jie Chen
Polymers 2019, 11(1), 171; https://doi.org/10.3390/polym11010171 - 18 Jan 2019
Cited by 60 | Viewed by 7487
Abstract
Polyvinyl alcohol (PVA) hydrogel and stem cell therapy have been widely used in wound healing. However, the lack of bioactivity for PVA and security of stem therapy limited their application. In this study, an adipose-derived stem cells (ADSCs)-seeded PVA dressing (ADSCs/PVA) was prepared [...] Read more.
Polyvinyl alcohol (PVA) hydrogel and stem cell therapy have been widely used in wound healing. However, the lack of bioactivity for PVA and security of stem therapy limited their application. In this study, an adipose-derived stem cells (ADSCs)-seeded PVA dressing (ADSCs/PVA) was prepared for wound healing. One side of the PVA dressing was modified with photo-reactive gelatin (Az-Gel) via ultraviolet (UV) irradiation (Az-Gel@PVA), and thus ADSCs could adhere, proliferate on the PVA dressings and keep the other side of the dressings without adhering to the wound. The structure and mechanics of Az-Gel@PVA were determined by scanning electron microscopy (SEM) and material testing instruments. Then, the adhesion and proliferation of ADSCs were observed via cell counts and live-dead staining. Finally, in vitro and in vivo experiments were utilized to confirm the effect of ADSCs/PVA dressing for wound healing. The results showed that Az-Gel was immobilized on the PVA and showed little effect on the mechanical properties of PVA hydrogels. The surface-modified PVA could facilitate ADSCs adhesion and proliferation. Protein released tests indicated that the bioactive factors secreted from ADSCs could penetrated to the wound. Finally, in vitro and in vivo experiments both suggested the ADSCs/PVA could promote the wound healing via secreting bioactive factors from ADSCs. It was speculated that the ADSCs/PVA dressing could not only promote the wound healing, but also provide a new way for the safe application of stem cells, which would be of great potential for skin tissue engineering. Full article
(This article belongs to the Special Issue Functional Polymers for Biomedicine)
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<p>Optical images (<b>A</b>(a) and <b>A</b>(b)) and scanning electron microscope (SEM) images (<b>B</b> and <b>C</b>) of patterned PVA dressings: the honeycomb mould (<b>A</b>(a)), the patterned PVA dressings (<b>A</b>(b)), Az-Gel@PVA dressings (<b>B</b>) and PVA dressings (<b>C</b>).</p> Full article ">Figure 2
<p>Elongation (<b>A</b>), energy at break (<b>B</b>) maximum strength (<b>C</b>) and young’s modulus (<b>D</b>) of PVA and Az-Gel@PVA dressings. Error bars represent standard deviation for <span class="html-italic">n</span> = 3.</p> Full article ">Figure 3
<p>Cell counts of ADSCs on the different dressings after 1 and 4 d culture: tissue culture plate (TCP) (<b>a</b>), PVA (<b>b</b>), Az-Gel@PVA with and without UV irradiation (<b>c</b>,<b>d</b>). * <span class="html-italic">p</span> &lt; 0.05, <span class="html-italic">n</span> = 4.</p> Full article ">Figure 4
<p>Fluorescence micrographs of live-dead staining of ADSCs on the different dressings after 1, 4, 24 and 48 h culture using Calcein-AM (Cal-AM) for live cells (green) and propidium iodide (PI) for dead ones(red). Scale bar lengths at 2, 4 and 24 h are 100 μm, while scale bar length at 48 h is 500 μm.</p> Full article ">Figure 5
<p>Total protein and basic fibroblast growth factor (bFGF) release from different dressings after incubated in serum-free medium for 48 h: Az-Gel@PVA dressings without ADSCs seeded (<b>a</b>), Az-Gel@PVA dressings with 3 × 10<sup>5</sup> (<b>b</b>) and 6 × 10<sup>5</sup> (<b>c</b>) cells/cm<sup>2</sup> ADSCs seeded. * <span class="html-italic">p</span> &lt; 0.05, <span class="html-italic">n</span> = 4.</p> Full article ">Figure 6
<p>The ADSCs-seeded PVA dressings promoted NIH-3T3 cell proliferation and migration. (<b>A</b>) Cell Counting Kit-8 (CCK-8) test of NIH-3T3 proliferation covered with different dressings for 1 d and 4 d: control (a); Az-Gel@PVA dressing without ADSCs seeded (b); Az-Gel@PVA dressings with 3 × 10<sup>5</sup> (b) and 6 × 10<sup>5</sup> (c) cells/cm<sup>2</sup> ADSCs seeded. * <span class="html-italic">p</span> &lt; 0.05, <span class="html-italic">n</span> = 4. (<b>B</b>) The scratch closure in NIH-3T3 cells cultured for 24 h covered with Az-Gel@PVA dressings with (B(b)) and without (B(a)) ADSCs seeded. All scale bar lengths are 200 μm (px = μm in these images).</p> Full article ">Figure 7
<p>Photographs (<b>A</b>) and measurements (<b>B</b>) of wound healing of full thickness square defects in rats after different periods of time.</p> Full article ">Scheme 1
<p>Schematic illustration of patterned polyvinyl alcohol (PVA) dressings seeded with adipose-derived stem cells (ADSCs) for wound healing.</p> Full article ">
14 pages, 5049 KiB  
Article
Analysis and Identification of the Mechanism of Damage and Fracture of High-Filled Wood Fiber/Recycled High-Density Polyethylene Composites
by Yong Guo, Shiliu Zhu, Yuxia Chen and Dagang Li
Polymers 2019, 11(1), 170; https://doi.org/10.3390/polym11010170 - 18 Jan 2019
Cited by 12 | Viewed by 4502
Abstract
The damage and fracture of fiber reinforced polymer composites are vital constraints in their applications. To understand the mechanism of damage of wood fiber (WF) reinforced high density polyethylene (HDPE) composites, we used waste WF and recycled HDPE (Re-HDPE) as the raw materials [...] Read more.
The damage and fracture of fiber reinforced polymer composites are vital constraints in their applications. To understand the mechanism of damage of wood fiber (WF) reinforced high density polyethylene (HDPE) composites, we used waste WF and recycled HDPE (Re-HDPE) as the raw materials and prepared high-filled WF/Re-HDPE composites via extrusion. The damage and fracture mode and failure mechanism of the composites with different WF contents (50%, 60%, and 70%) was studied under a three-point bending test by combining the acoustic emission (AE) technique and scanning electron microscope (SEM) analysis. The results show that AE technology can better assist in understanding the progress of damage and fracture process of WF/Re-HDPE composites, and determine the damage degree, damage accumulation, and damage mode. The damage and fracture process of the composites presents three main stages: the appearance of initial damage, damage accumulation, and destructive damage to fracture. The matrix deformation, fiber breakage, interface delamination, fiber-matrix debonding, fiber pull-out, and matrix cracking were the dominant modes for the damage of high-filled WF/Re-HDPE composites under bending load, and the AE signal changed in different damage stages and damage modes. In addition, the WF content and repeated loading had a significant influence on the composite’s damage and fracture. The 50% and 60% WF/Re-HDPE composites produced irreversible damage when repeated load exceeded 75% of the maximum load, while 25% of the maximum load could cause irreversible damage for 70% WF/Re-HDPE composites. The damage was accumulated owing to repeated loading and the mechanical properties of the composites were seriously affected. Full article
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<p>Schematic of the three-point bending test and the acoustic emission signal acquisition.</p> Full article ">Figure 2
<p>Acoustic emission (AE) accumulative counts vary with stress-strain during three-point bending test. The black curve represents stress-strain curve; the green curve represents AE accumulative counts; and the blue circle represents amplitude.</p> Full article ">Figure 3
<p>Scanning electron microscope (SEM (analysis of damage and fracture mode and characteristics ((<b>a</b>,<b>b</b>)—Fiber breakage; (<b>c</b>,<b>d</b>)—Fiber pull-out (interface friction); (<b>e</b>)—Matrix cracking; (<b>f</b>)—Fiber-matrix debonding (interface delamination) and matrix deformation).</p> Full article ">Figure 4
<p>Five AE characteristic waveforms corresponding to the damage and fracture mode. (<b>a</b>) Type I (Matrix deformation); (<b>b</b>) Type II (Fiber breakage); (<b>c</b>) Type III (Interface delamination); (<b>d</b>) Type IV (Interface friction); and (<b>e</b>) Type V (Matrix cracking).</p> Full article ">Figure 5
<p>Distribution of damage and fracture stage and mode. The black curve represents stress-strain curve; the green curve represents AE accumulative counts; and the blue circle represents amplitude.</p> Full article ">Figure 6
<p>The AE amplitude, ringing counts, and stress-strain curves of wood fiber (WF)/recycled high density polyethylene (Re-HDPE) composites with different WF contents. The blue circle represents amplitude and ringing counts in (<b>a</b>–<b>f</b>), respectively.</p> Full article ">Figure 7
<p>The interface morphology of WF/Re-HDPE composites with different WF contents ((<b>a</b>) 50% WF/Re-HDPE, (<b>b</b>) 60% WF/Re-HDPE, and (<b>c</b>) 70% WF/Re-HDPE).</p> Full article ">Figure 8
<p>The AE accumulative ringing counts, accumulative energy, and stress-strain curve of WF/Re-HDPE composites with different WF content. The blue circle represents accumulative counts and accumulative energy in (<b>a</b>–<b>f</b>), respectively.</p> Full article ">Figure 9
<p>Time-strain curve and AE amplitude of WF/Re-HDPE composites with different WF content. The blue circle represents amplitude in <a href="#polymers-11-00170-f009" class="html-fig">Figure 9</a>.</p> Full article ">Figure 10
<p>Time-strain curve, AE accumulative counts, and ringing counts of WF/Re-HDPE composites with different WF contents. The blue circle represents accumulative counts and ringing counts in (<b>a</b>–<b>f</b>), respectively.</p> Full article ">
14 pages, 5645 KiB  
Article
Preparation of a Water-Based Photoreactive Azosulphonate-Doped Poly(Vinyl Alcohol) and the Investigation of Its UV Response
by Philipp Nothdurft, Jörg Guido Schauberger, Gisbert Riess and Wolfgang Kern
Polymers 2019, 11(1), 169; https://doi.org/10.3390/polym11010169 - 18 Jan 2019
Cited by 4 | Viewed by 5083
Abstract
Two different azosulphonate dyes were synthesised and purified for the preparation of a water-based photoreactive azosulphonate-doped poly(vinyl alcohol). The aim was the investigation of a novel azosulphonate-poly(vinyl alcohol) photoresist with decreased water solubility after illumination, setting a focus on environmentally benign substances. The [...] Read more.
Two different azosulphonate dyes were synthesised and purified for the preparation of a water-based photoreactive azosulphonate-doped poly(vinyl alcohol). The aim was the investigation of a novel azosulphonate-poly(vinyl alcohol) photoresist with decreased water solubility after illumination, setting a focus on environmentally benign substances. The electron distribution of the aromatic rings of the two different azosulphonate molecules were changed by the UV-induced cleavage of the –N=N–SO3− groups, which was evidenced by UV spectroscopy. The formation of ester groups was detected by Fourier-transform infrared and 13C nuclear magnetic resonance spectroscopy. UV–Vis spectroscopy was used to investigate the photoreactivity of the prepared films. Photolithographic experiments demonstrated the applicability of these newly produced materials as photoresist materials. In addition, these materials provide high thermal stability. Full article
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<p>Decomposition mechanism of aryl azosulphonate compounds dependent on the chemical environment, as published by Nuyken, Voit and Riess (copyright permission by Riess) [<a href="#B23-polymers-11-00169" class="html-bibr">23</a>,<a href="#B26-polymers-11-00169" class="html-bibr">26</a>].</p> Full article ">Figure 2
<p>Two-step synthesis of water-soluble aryl azosulphonates.</p> Full article ">Figure 3
<p><sup>1</sup>H (<b>a</b>) and <sup>13</sup>C (<b>b</b>) NMR spectra of AZOII dissolved in deuterated water.</p> Full article ">Figure 4
<p><sup>1</sup>H (<b>a</b>) and <sup>13</sup>C (<b>b</b>) NMR spectra of AZOIII dissolved in deuterated water.</p> Full article ">Figure 5
<p>FTIR analysis of the AZOII (<b>a</b>) and AZOIII (<b>b</b>) dye on CaF<sub>2</sub> platelets at different illumination times.</p> Full article ">Figure 6
<p>UV–Vis absorption spectra of aqueous solutions of (<b>a</b>) AZOII and (<b>b</b>) AZOIII upon exposure to UV light.</p> Full article ">Figure 7
<p>TGA curves (weight loss in relation to the initial sample weight) and the corresponding heat flow of (<b>a</b>) AZOII and (<b>b</b>) AZOIII.</p> Full article ">Figure 8
<p>Mechanism of coupling reaction of aryl azosulphonates to PVA via polymer analogous esterification reaction: (<b>a</b>) crosslinking of PVA by coupling of AZOII; (<b>b</b>) coupling of monovalent AZOIII to PVA.</p> Full article ">Figure 9
<p><sup>13</sup>C NMR of PAII.5 (comprising 20 wt % of AZOII) before (<b>a</b>) and after (<b>b</b>) annealing at 100 °C for 60 min.</p> Full article ">Figure 10
<p><sup>13</sup>C NMR of PAIII.5 (comprising 20 wt % of AZOII) before (<b>a</b>) and after (<b>b</b>) annealing at 100°C for 60 min.</p> Full article ">Figure 11
<p>FTIR spectra of AZOII-PVA (<b>left</b>) and AZOIII-PVA (<b>right</b>) polymers; (<b>a</b>) neat PVA; (<b>b</b>) the respective AZO dye; (<b>c</b>) PAII.5/PAIII.5 containing 20 wt % of AZO dye; (<b>d</b>) PVA-AZO after 60 min of annealing at 100 °C.</p> Full article ">Figure 12
<p>UV–Vis absorption spectra (<b>a</b>) of annealed PAII.5 and (<b>b</b>) of annealed thin PAIII.5 films coated onto a CaF<sub>2</sub> substrate.</p> Full article ">Figure 13
<p>Phase contrast image of thin patterned PAII.1 films (<b>a</b>) and after development in deionised water (<b>b</b>).</p> Full article ">Figure 14
<p>Phase contrast image of thin patterned PAIII.1 films (<b>a</b>) and after development in deionised water (<b>b</b>).</p> Full article ">Figure 15
<p>Gas bubble formation upon the development of patterned samples (100 μm features; dose: 45 Jcm<sup>−2</sup>) in deionised water using phase contrast imaging mode. (<b>a</b>) PAII.5; (<b>b</b>) PAIII.5.</p> Full article ">
19 pages, 2699 KiB  
Article
Influence of the Characteristics of Expandable Graphite on the Morphology, Thermal Properties, Fire Behaviour and Compression Performance of a Rigid Polyurethane Foam
by Pablo Acuña, Zhi Li, Mercedes Santiago-Calvo, Fernando Villafañe, Miguel Ángel Rodríguez-Perez and De-Yi Wang
Polymers 2019, 11(1), 168; https://doi.org/10.3390/polym11010168 - 18 Jan 2019
Cited by 56 | Viewed by 6877
Abstract
Three types of expandable graphite (EG) differing in particle size and expansion volume, are compared as flame retardant additives to rigid polyurethane foams (RPUFs). In this paper we discuss microstructure, thermal stability, fire behavior, and compression performance. We find that ell size distributions [...] Read more.
Three types of expandable graphite (EG) differing in particle size and expansion volume, are compared as flame retardant additives to rigid polyurethane foams (RPUFs). In this paper we discuss microstructure, thermal stability, fire behavior, and compression performance. We find that ell size distributions were less homogeneous and cell size was reduced. Furthermore, thermal conductivity increased along with EG loading. Thermogravimetric analysis (TGA) showed that EG only increased residue yield differently. The results indicate that a higher expansion of EG increased the limiting oxygen index (LOI) value, whereas a bigger particle size EG improved the rating of the vertical burning test (UL94). Results from the cone calorimeter test showed that a bigger particle size EG effectively reduced peak of heat release rate (pHRR). Furthermore, a higher expansion, led to a decrease in smoke production (TSP). The combination of both characteristics gives extraordinary results. The physical–mechanical characterization of the EG/RPUF foams revealed that their compression performance decreased slightly, mostly due to the effect of a bigger size EG. Full article
(This article belongs to the Special Issue Multi-functional Polymer Composites and Structures)
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<p>SEM micrographs of the growth plane of rigid polyurethane foam (RPUF) samples.</p> Full article ">Figure 2
<p>Cell size distribution for (<b>a</b>) EG1, (<b>b</b>) EG2, and (<b>c</b>) EG3 RPUF samples.</p> Full article ">Figure 2 Cont.
<p>Cell size distribution for (<b>a</b>) EG1, (<b>b</b>) EG2, and (<b>c</b>) EG3 RPUF samples.</p> Full article ">Figure 3
<p>SEM micrograph of EG3-10 sample in the RPUF matrix.</p> Full article ">Figure 4
<p>(<b>a</b>) TGA and (<b>b</b>) DTG curves for RPUF samples containing EG1, EG2, and EG3 at 10 wt % loading.</p> Full article ">Figure 5
<p>(<b>a</b>) Heat release rate (HRR), (<b>b</b>) Total heat released (THR), and (<b>c</b>) Total smoke production (TSP) curves for RPUF samples containing EG1, EG2, and EG3 at 10 wt % loading.</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>) Heat release rate (HRR), (<b>b</b>) Total heat released (THR), and (<b>c</b>) Total smoke production (TSP) curves for RPUF samples containing EG1, EG2, and EG3 at 10 wt % loading.</p> Full article ">
22 pages, 7284 KiB  
Review
Recent Advances in Organic Thermoelectric Materials: Principle Mechanisms and Emerging Carbon-Based Green Energy Materials
by Yinhang Zhang, Young-Jung Heo, Mira Park and Soo-Jin Park
Polymers 2019, 11(1), 167; https://doi.org/10.3390/polym11010167 - 18 Jan 2019
Cited by 101 | Viewed by 14559
Abstract
Thermoelectric devices have recently attracted considerable interest owing to their unique ability of converting heat to electrical energy in an environmentally efficient manner. These devices are promising as alternative power generators for harvesting electrical energy compared to conventional batteries. Inorganic crystalline semiconductors have [...] Read more.
Thermoelectric devices have recently attracted considerable interest owing to their unique ability of converting heat to electrical energy in an environmentally efficient manner. These devices are promising as alternative power generators for harvesting electrical energy compared to conventional batteries. Inorganic crystalline semiconductors have dominated the thermoelectric material fields; however, their application has been restricted by their intrinsic high toxicity, fragility, and high cost. In contrast, organic thermoelectric materials with low cost, low thermal conductivity, easy processing, and good flexibility are more suitable for fabricating thermoelectric devices. In this review, we briefly introduce the parameters affecting the thermoelectric performance and summarize the most recently developed carbon-material-based organic thermoelectric composites along with their preparation technologies, thermoelectric performance, and future applications. In addition, the p- and n-type carbon nanotube conversion and existing challenges are discussed. This review can help researchers in elucidating the recent studies on carbon-based organic thermoelectric materials, thus inspiring them to develop more efficient thermoelectric devices. Full article
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<p>(<b>a</b>) How heat can be converted to electricity (Seebeck coefficient) using thermoelectric materials; and (<b>b</b>) how electrical power can be transformed to cooling or heating (Peltier effect).</p> Full article ">Figure 2
<p>Thermal conduction in amorphous polymers.</p> Full article ">Figure 3
<p>Thermal conduction in ideal crystalline materials.</p> Full article ">Figure 4
<p>Thermal conductivity in crystalline filler-based polymer composites with discontinuous filler network.</p> Full article ">
15 pages, 5699 KiB  
Article
Mechanical and Water-Resistant Properties of Eco-Friendly Chitosan Membrane Reinforced with Cellulose Nanocrystals
by Haiquan Mao, Chun Wei, Yongyang Gong, Shiqi Wang and Wenwen Ding
Polymers 2019, 11(1), 166; https://doi.org/10.3390/polym11010166 - 18 Jan 2019
Cited by 70 | Viewed by 9071
Abstract
Environmentally benign and biodegradable chitosan (CS) membranes have disadvantages such as low mechanical strength, high brittleness, poor heat resistance and poor water resistance, which limit their applications. In this paper, home-made cellulose nanocrystals (CNC) were added to CS to prepare CNC/CS composite membranes [...] Read more.
Environmentally benign and biodegradable chitosan (CS) membranes have disadvantages such as low mechanical strength, high brittleness, poor heat resistance and poor water resistance, which limit their applications. In this paper, home-made cellulose nanocrystals (CNC) were added to CS to prepare CNC/CS composite membranes through mechanical mixing and solution casting approaches. The effects of CNC dispersion patterns and CNC contents on the properties of composite membranes were studied. The analysis of the surface and cross-section morphology of the membranes showed that the dispersion performance of the composite membrane was better in the case that CNC was dissolved in an acetic acid solution and then mixed with chitosan by a homogenizer (Method 2). CNC had a great length-diameter ratio and CNC intensely interacted with CS. The mechanical properties of the composite membrane prepared with Method 2 were better. With a CNC content of 3%, the tensile strength of the composite membrane reached 43.0 MPa, 13.2% higher than that of the CNC-free membrane. The elongation at break was 41.6%, 56.4% higher than that of the CNC-free membrane. Thermogravimetric, contact angle and swelling analysis results showed that the addition of CNC could improve the heat and water resistance of the chitosan membrane. Full article
(This article belongs to the Special Issue Processing and Molding of Polymers)
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<p>(<b>a</b>) Cellulose molecule, (<b>b</b>) Chitosan molecule.</p> Full article ">Figure 2
<p>The process of forming polyelectrolyte complex (PEC) between cellulose nanocrystals (CNC) and chitosan (CS) molecules.</p> Full article ">Figure 3
<p>Preparation procedure of composite membranes with Method 1.</p> Full article ">Figure 4
<p>Preparation procedure of composite membranes with Method 2.</p> Full article ">Figure 5
<p>(<b>a</b>) Particle size distribution, (<b>b</b>) TEM image, and (<b>c</b>) Zeta potential distribution of CNC.</p> Full article ">Figure 6
<p>Polarizing microscopy results of (<b>a</b>) CNC suspension and (<b>b</b>–<b>f</b>) composite membranes prepared with 1–5% CNC suspensions (Method 1).</p> Full article ">Figure 7
<p>Polarizing microscopy results of (<b>a</b>) CS and (<b>b</b>–<b>f</b>) composite membranes prepared with 1–5% CNC suspensions (Method 2).</p> Full article ">Figure 8
<p>SEM images of (<b>a</b>) surface of CS membrane, (<b>b</b>) cross section of 3 wt % CNC composite membrane (Method 1), (<b>c</b>) cross section of CS membrane, and (<b>d</b>) cross section of 3 wt % CNC composite membrane (Method 2).</p> Full article ">Figure 9
<p>Effect of CNC contents on the mechanical properties of CNC/CS composite membranes prepared with (<b>a</b>) Method 1 and (<b>b</b>) Method 2, respectively.</p> Full article ">Figure 10
<p>FTIR spectra of CNC, CS and CNC/CS composite membranes.</p> Full article ">Figure 11
<p>XRD patterns of CNC, CNC/CS membrane, CS membrane, and CS powder.</p> Full article ">Figure 12
<p>(<b>a</b>) TG and (<b>b</b>) DTG analysis results of CNC/CS composite membranes.</p> Full article ">Figure 13
<p>Effect of CNC content on the contact angle properties of CNC/CS composite membranes.</p> Full article ">Figure 14
<p>Effect of CNC content on the swelling properties of CNC/CS composite membranes.</p> Full article ">Figure 15
<p>Biodegradation performances of the composite membrane.</p> Full article ">
14 pages, 3575 KiB  
Article
Layer-by-Layer Assembly and Electrochemical Study of Alizarin Red S-Based Thin Films
by Wei Ma, Yanpu Zhang, Fei Li, Donghui Kou and Jodie L. Lutkenhaus
Polymers 2019, 11(1), 165; https://doi.org/10.3390/polym11010165 - 18 Jan 2019
Cited by 8 | Viewed by 6253
Abstract
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the [...] Read more.
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the complementary polymer. Unconventional LbL methods, including co-adsorption of ARS and poly(4-styrene sulfonate) (PSS) with BPEI to assemble (BPEI/(ARS+PSS))n, as well as pre-complexation of ARS with BPEI and further assembly with PSS to fabricate ((BPEI+ARS)/PSS)n, are designed for investigation and comparison. Film growth patterns, UV–Vis spectra and surface morphology of the three types of LbL assemblies are measured and compared to reveal the formation mechanism of the LbL films. Electrochemical properties including cyclic voltammetry and spectroelectrochemistry of (BPEI/ARS)120, (BPEI/(ARS+PSS))120 and ((BPEI+ARS)/PSS)120 films are studied, and the results show a slight color change due to the redox reaction of ARS. ((BPEI+ARS)/PSS)120 shows the best stability among the three samples. It is concluded that the manner of dye- incorporation has a great effect on the electrochemical properties of the resultant films. Full article
(This article belongs to the Special Issue Polyelectrolytes and Polyelectrolyte Complexes-in Memory of Prof. Paul Dubin)
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<p>Chemical structure of Alizarin Red S (<b>1</b>) and its ionized structures (<b>2</b> and <b>3</b>).</p> Full article ">Figure 2
<p>Photographs of (<b>a</b>) (BPEI/ARS)<sub>n</sub>, (<b>b</b>) (BPEI/(ARS+PSS))<sub>n</sub> and (<b>c</b>) ((BPEI+ARS)/PSS)<sub>n</sub> on ITO-coated glass; UV–Vis spectra of (<b>d</b>) (BPEI/ARS)<sub>n</sub>, (<b>e</b>) (BPEI/(ARS+PSS))<sub>n</sub> and (<b>f</b>) ((BPEI+ARS)/PSS)<sub>n</sub> on ITO-coated glass; (<b>g</b>) UV–Vis spectra of ARS, ARS+BPEI and ARS+PSS; (<b>h</b>) UV–Vis spectra of BPEI+ARS solution, (BPEI/ARS)<sub>120</sub>, (BPEI/(ARS+PSS))<sub>120</sub> and ((BPEI+ARS)/PSS)<sub>120</sub> on ITO-coated glass; (<b>i</b>) Relationship of the number of bilayers or layers pairs and the absorbance of the films at the maximum absorption wavenumber.</p> Full article ">Figure 3
<p>Hydrogel formed during assembly of ((BPEI+ARS)/PSS)<sub>120</sub> under wet conditions, (<b>a</b>) dark background and (<b>b</b>) bright background.</p> Full article ">Figure 4
<p>Relationship between the number of bilayers (or layer pairs) and thickness for when n is 20, 40, 60, 80, 100 and 120.</p> Full article ">Figure 5
<p>Atomic force microscopy 3D height images of (<b>a</b>) (BPEI/ARS)<sub>20</sub>, (<b>b</b>) (ARS/(PSS+ARS))<sub>20</sub> and (<b>c</b>) ((BPEI+ARS)/PSS)<sub>20</sub> films.</p> Full article ">Figure 6
<p>CVs of (BPEI/ARS)<sub>120</sub> (<b>a</b>), (BPEI/(ARS+PSS))<sub>120</sub> (<b>b</b>) and ((BPEI+ARS)/PSS)<sub>120</sub> (<b>c</b>) on ITO-coated glass in 0.1 M NaCl.</p> Full article ">Figure 7
<p>CVs of ARS (<b>a</b>), ARS+PSS (<b>b</b>) and ARS+BPEI (<b>c</b>) solutions in 0.1 M NaCl.</p> Full article ">Figure 8
<p>UV–Vis spectra of (<b>a</b>) (BPEI/ARS)<sub>120</sub>, (<b>b</b>) (BPEI/(ARS+PSS))<sub>120</sub> and (<b>c</b>) ((BPEI+ARS)/PSS)<sub>120</sub> LbL films in 0.1 M NaCl aqueous solutions: after the 1st and 2nd electrochemical reduction (at voltage of −1.18 V vs. Fe(CN)<sub>6</sub><sup>4−</sup>/Fe(CN)<sub>6</sub><sup>3−</sup>) and oxidation (at voltage of −0.38 V vs. Fe(CN)6<sup>4−</sup>/Fe(CN)<sub>6</sub><sup>3−</sup>) processes.</p> Full article ">Scheme 1
<p>Schematics of LbL assemblies in this study: (<b>a</b>) (BPEI/ARS)<sub>n</sub>, (<b>b</b>) (BPEI/(PSS+ARS))<sub>n</sub> and (<b>c</b>) ((BPEI+ARS)/PSS)<sub>n</sub>.</p> Full article ">
23 pages, 7401 KiB  
Article
Electrospun Graphene Nanosheet-Filled Poly(Trimethylene Terephthalate) Composite Fibers: Effects of the Graphene Nanosheet Content on Morphologies, Electrical Conductivity, Crystallization Behavior, and Mechanical Properties
by Chien-Lin Huang, Hsuan-Hua Wu, Yung-Ching Jeng and Wei-Zhi Liang
Polymers 2019, 11(1), 164; https://doi.org/10.3390/polym11010164 - 17 Jan 2019
Cited by 15 | Viewed by 4475
Abstract
In this study the effects of increased graphene nanosheet (GNS) concentration on variations in the structure and properties of electrospun GNS-filled poly(trimethylene terephthalate) (PTT/GNS) composite fiber, such as its morphologies, crystallization behavior, mechanical properties, and electrical conductivity, were investigated. The effects of GNS [...] Read more.
In this study the effects of increased graphene nanosheet (GNS) concentration on variations in the structure and properties of electrospun GNS-filled poly(trimethylene terephthalate) (PTT/GNS) composite fiber, such as its morphologies, crystallization behavior, mechanical properties, and electrical conductivity, were investigated. The effects of GNS addition on solution rheology and conductivity were also investigated. GNSs were embedded in the fibers and formed protrusions. The PTT cold crystallization rate of PTT/GNS composite fibers increased with the gradual addition of GNSs. A PTT mesomorphic phase was formed during electrospinning, and GNSs could induce the PTT mesomorphic phase significantly during PTT/GNS composite fiber electrospinning. The PTT/GNS composite fiber mats (CFMs) became ductile with the addition of GNSs. The elastic recoveries of the PTT/GNS CFMs with 170 °C annealing were better than those of the as-spun PTT/GNS CFMs. Percolation scaling laws were applied to the magnitude of conductivity to reveal the percolation network of electrospun PTT/GNS CFMs. The electrical conductivity mechanism of the PTT/GNS CFMs differed from that of the PTT/GNS composite films. Results showed that the porous structure of the PTT CFMs influenced the performance of the mats in terms of electrical conductivity. Full article
(This article belongs to the Special Issue Graphene-Polymer Composites II)
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<p>Concentration dependence of the specific viscosity of the PTT solutions.</p> Full article ">Figure 2
<p>Transmission electron microscope (TEM) images of GNS the deposited GNS on the TEM grid prepared from the ortho-dichlorobenzene (<span class="html-italic">o</span>-DCB) solution.</p> Full article ">Figure 3
<p>Effect of GNS content on the viscoelastic properties of PTT solutions: (<b>a</b>) dynamic storage modulus <span class="html-italic">G′</span>, (<b>b</b>) dynamic loss modulus <span class="html-italic">G″</span>, and (<b>c</b>) complex viscosity <span class="html-italic">η</span>* at 25 °C. The PTT/trifluoroacetic acid (TFA) concentration is 14 wt %.</p> Full article ">Figure 3 Cont.
<p>Effect of GNS content on the viscoelastic properties of PTT solutions: (<b>a</b>) dynamic storage modulus <span class="html-italic">G′</span>, (<b>b</b>) dynamic loss modulus <span class="html-italic">G″</span>, and (<b>c</b>) complex viscosity <span class="html-italic">η</span>* at 25 °C. The PTT/trifluoroacetic acid (TFA) concentration is 14 wt %.</p> Full article ">Figure 4
<p>Functional domain for electrospinning of 14 wt % PTT solution with various GNS contents. The domains indicate the range of operating electrical fields required for the stable cone-jet mode. (Filled symbols for lower bond applied voltage and open symbols for upper bond applied voltage).</p> Full article ">Figure 5
<p>Scanning electron microscope (SEM) and TEM images of electrospun PTT fibers filled with: (<b>a</b>,<b>b</b>) 1 wt %, (<b>c</b>,<b>d</b>) 3 wt %, (<b>e</b>,<b>f</b>) 5 wt %, and (<b>g</b>,<b>h</b>) 7 wt % GNS. The positions of GNSs and nanofibrils are indicated by the thick and thin arrows, respectively.</p> Full article ">Figure 5 Cont.
<p>Scanning electron microscope (SEM) and TEM images of electrospun PTT fibers filled with: (<b>a</b>,<b>b</b>) 1 wt %, (<b>c</b>,<b>d</b>) 3 wt %, (<b>e</b>,<b>f</b>) 5 wt %, and (<b>g</b>,<b>h</b>) 7 wt % GNS. The positions of GNSs and nanofibrils are indicated by the thick and thin arrows, respectively.</p> Full article ">Figure 6
<p>Schematic models of various dispersion types of GNSs in PTT fiber: (<b>1</b>) GNSs are individually dispersed in the PTT fiber at intervals. (<b>2</b>) GNSs are close together in the PTT fiber. (<b>3</b>) Some parts of the GNSs overlap with one another in the PTT fiber. <span class="html-italic">L<sub>GNS</sub></span> indicates the inter-GNS distance assemblies in the PTT composite fiber. (<b>4</b>) The GNS are layered in the PTT fiber. When the GNS content is increased, the resulting dispersion form gradually changes.</p> Full article ">Figure 7
<p>(<b>a</b>) Wide-angle X-ray diffraction (WAXD) intensity profiles of the as-spun PTT/GNS composite fibers, and (<b>b</b>) differential scanning calorimetry (DSC) heating traces of the as-spun PTT/GNS composite fibers.</p> Full article ">Figure 8
<p>Fourier transform infrared spectroscopy (FTIR) spectra of (<b>a</b>) neat PTT and (<b>b</b>) PTT/GNS 99/1 composite fibers during stepwise heating to 225 °C.</p> Full article ">Figure 9
<p>(<b>a</b>) Normalized area of the 948 and 935 cm<sup>−1</sup> bands (<span class="html-italic">A</span><sub>935+948</sub>) and (<b>b</b>) variation in the absorbance peak at 875–870 cm<sup>−1</sup> for the neat PTT and PTT/GNS 99/1 composite fibers during stepwise heating.</p> Full article ">Figure 10
<p>WAXD intensity profiles of (<b>a</b>) neat PTT and (<b>b</b>) PTT/GNS 99/1 composite fibers during stepwise heating to 240 °C.</p> Full article ">Figure 11
<p>Schematic of the microstructure change of the PTT/GNS composite fibers during cold crystallization.</p> Full article ">Figure 12
<p>Stress-strain curves of PTT/GNS CFMs with and without annealing at 170 °C for 30 min. The solid lines indicate the as-spun PTT/GNS CFMs, and the dashed lines indicate PTT/GNS CFMs with annealing at 170 °C.</p> Full article ">Figure 13
<p>(<b>a</b>) Conductivity versus GNS volume contents of PTT/GNS CFMs and HP-PTT/GNS CFM composites. (<b>b</b>) Percolation scaling law between <span class="html-italic">σ</span> and <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> − <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math><span class="html-italic"><sub>c</sub></span> for PTT/GNS CFMs. (<b>c</b>) Schematic representation of electrospun PTT/GNS fiber. (<b>d</b>) Schematic representation of GNS-GNS conductive path in the PTT/GNS CFMs.</p> Full article ">
17 pages, 2887 KiB  
Article
Micelle Structure Details and Stabilities of Cyclic Block Copolymer Amphiphile and Its Linear Analogues
by Brian J. Ree, Toshifumi Satoh and Takuya Yamamoto
Polymers 2019, 11(1), 163; https://doi.org/10.3390/polym11010163 - 17 Jan 2019
Cited by 15 | Viewed by 7219
Abstract
In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b [...] Read more.
In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b-PEO and l-PBA-b-PEO-b-PBA) by using synchrotron X-ray scattering and quantitative data analysis. The comprehensive scattering analysis gives details and insights to the micellar architecture through structural parameters. Furthermore, this analysis provides direct clues for structural stabilities in micelles, which can be used as a good guideline to design highly stable micelles. Interestingly, in water, all topological polymers are found to form ellipsoidal micelles rather than spherical micelles; more interestingly, the cyclic polymer and its linear triblock analog make oblate-ellipsoidal micelles while the linear diblock analog makes a prolate-ellipsoidal micelle. The analysis results collectively inform that the cyclic topology enables more compact micelle formation as well as provides a positive impact on the micellar structural integrity. Full article
(This article belongs to the Special Issue Cyclic Polymers)
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<p>Chemical structures of the amphiphilic block copolymers used in this study.</p> Full article ">Figure 2
<p>A representative X-ray scattering intensity <span class="html-italic">I</span>(<span class="html-italic">q</span>) profile and data analysis results of the <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO micelle formed in deionized water with a concentration of 0.5 wt % at 25 °C, which were performed using (<b>a</b>) spherical CFS model, (<b>b</b>) two-phase ellipsoid model, and (<b>c</b>) three-phase ellipsoid model. (<b>d</b>–<b>f</b>) Kratky representations of the scattering data of the <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO micelle fitted by spherical CFS, two-phase ellipsoid, and three-phase ellipsoid models, respectively. In each figure, the open dot symbols are the measured data and the red solid line represents the sum of the corresponding analysis profile (blue line) and blob contribution (green line). Here, <span class="html-italic">q</span> = (4π/<span class="html-italic">λ</span>)sin<span class="html-italic">θ</span> in which 2<span class="html-italic">θ</span> is the scattering angle and <span class="html-italic">λ</span> is the wavelength of the X-ray beam used.</p> Full article ">Figure 3
<p>Deviation between the measured scattering data and the data analysis results obtained by various analysis schemes over the <span class="html-italic">q</span>-range of 0.15 to 1.5 nm<sup>−1</sup>: (<b>a</b>) <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO micelle; (<b>b</b>) <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO-<span class="html-italic">b</span>- PBA micelle; (<b>c</b>) <span class="html-italic">c</span>-PBA-<span class="html-italic">b</span>-PEO micelle. Each value of deviation was calculated by the following formula [(<span class="html-italic">I</span><sub>obs</sub> − <span class="html-italic">I</span><sub>calc</sub>)/<span class="html-italic">I</span><sub>obs</sub>] × 100% where <span class="html-italic">I</span><sub>obs</sub> is the measured scattering intensity and <span class="html-italic">I</span><sub>calc</sub> is calculated scattering intensity from data analysis. The colored circles represent the deviations from results of spherical CFS (red circles), two-phase ellipsoid (green circles), and three-phase ellipsoid (blue circles) models. The deviations in <span class="html-italic">q</span>-range of 1.5 to 3.5 nm<sup>−1</sup> are not shown due to the insignificantly large deviations arising from the high levels of noise in the raw scattering data in high-<span class="html-italic">q</span> regions.</p> Full article ">Figure 4
<p>A representative X-ray scattering intensity <span class="html-italic">I</span>(<span class="html-italic">q</span>) profile and data analysis results of the <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO-<span class="html-italic">b</span>-PBA micelle formed in deionized water with a concentration of 0.5 wt % at 25 °C, which were performed using (<b>a</b>) a spherical CFS model, (<b>b</b>) a two-phase ellipsoid model, and (<b>c</b>) a three-phase ellipsoid model. (<b>d</b>–<b>f</b>) Kratky representations of the scattering data of the <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO micelle fitted by spherical CFS, two-phase ellipsoid, and three-phase ellipsoid models, respectively. In each figure, the open dot symbols are the measured data and the red solid line represents the sum of the corresponding analysis profile (blue line) and blob contribution (green line). <span class="html-italic">q</span> = (4π/<span class="html-italic">λ</span>)sin<span class="html-italic">θ</span> in which 2<span class="html-italic">θ</span> is the scattering angle and <span class="html-italic">λ</span> is the wavelength of the X-ray beam used.</p> Full article ">Figure 5
<p>A representative X-ray scattering intensity <span class="html-italic">I</span>(<span class="html-italic">q</span>) profile and data analysis results of the <span class="html-italic">c</span>-PBA-<span class="html-italic">b</span>-PEO micelle formed in deionized water with a concentration of 0.5 wt % at 25 °C, which were performed using (<b>a</b>) spherical CFS model, (<b>b</b>) two phase ellipsoid model, and (<b>c</b>) three phase ellipsoid model. (<b>d</b>–<b>f</b>) Kratky representations of the scattering data of the <span class="html-italic">l</span>-PBA-<span class="html-italic">b</span>-PEO micelle fitted by spherical CFS, two phase ellipsoid, and three phase ellipsoid models, respectively. In each figure, the open dot symbols are the measured data and the red solid line represents the sum of the corresponding analysis profile (blue line) and blob contribution (green line). <span class="html-italic">q</span> = (4π/<span class="html-italic">λ</span>)sin<span class="html-italic">θ</span> in which 2<span class="html-italic">θ</span> is the scattering angle and <span class="html-italic">λ</span> is the wavelength of the X-ray beam used.</p> Full article ">Figure 6
<p>Size distribution curves of the micelles of topological block copolymers which are expressed based on the equatorial radius <span class="html-italic">R</span><sub>e,micelle</sub> of micelles extracted by the scattering data analyses using a three-phase ellipsoid scheme.</p> Full article ">Figure 7
<p>Schematic representations of the micelle structures of amphiphilic topological block copolymers based on the structural parameters obtained from the quantitative X-ray scattering data analyses using a three-phase ellipsoid scheme.</p> Full article ">
12 pages, 3197 KiB  
Article
Role of Molecular Weight in Polymer Wrapping and Dispersion of MWNT in a PVDF Matrix
by Muthuraman Namasivayam, Mats R. Andersson and Joseph Shapter
Polymers 2019, 11(1), 162; https://doi.org/10.3390/polym11010162 - 17 Jan 2019
Cited by 6 | Viewed by 5725
Abstract
The thermal and electrical properties of a polymer nanocomposite are highly dependent on the dispersion of the CNT filler in the polymer matrix. Non-covalent functionalisation with a PVP polymer is an excellent driving force towards an effective dispersion of MWNTs in the polymer [...] Read more.
The thermal and electrical properties of a polymer nanocomposite are highly dependent on the dispersion of the CNT filler in the polymer matrix. Non-covalent functionalisation with a PVP polymer is an excellent driving force towards an effective dispersion of MWNTs in the polymer matrix. It is shown that the PVP molecular weight plays a key role in the non-covalent functionalisation of MWNT and its effect on the thermal and electrical properties of the polymer nanocomposite is reported herein. The dispersion and crystallisation behaviour of the composite are also evaluated by a combination of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Full article
(This article belongs to the Special Issue Nanotechnology of Polymers and Biomaterials)
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<p>(<b>A</b>) Structure of PVP and P4VP; (<b>B</b>) computer model of PVP wrapping arrangement on a carbon nanotube [<a href="#B15-polymers-11-00162" class="html-bibr">15</a>].</p> Full article ">Figure 2
<p>Optical image showing dispersion of MWNT and PVP treated MWNT in DMF: After being treated with sonication (<b>A</b>,<b>B</b>) and after being statically placed for 120 h (<b>C</b>) and 240 h (<b>D</b>).</p> Full article ">Figure 3
<p>Thermal conductivity measure of three different PVP functionalised MWNT/PVDF composites.</p> Full article ">Figure 4
<p>Electrical conductivity measure of three different PVP functionalised MWNT/PVDF composites.</p> Full article ">Figure 5
<p>Thermal Properties of PVP<sub>10000</sub> functionalised MWNT/PVDF composite.</p> Full article ">Figure 6
<p>Crystallisation vs. wt % of PVP@MWNT/PVDF composite.</p> Full article ">Figure 7
<p>SEM image (Anterior) of MWNT/PVDF composite: (<b>a</b>) PVP@MWNT/PVDF composites; (<b>b</b>) PVP<sub>10000</sub> at 2.44 wt %; (<b>c</b>) PVP<sub>40000</sub> at 9.09 wt %; (<b>d</b>) PVP<sub>55000</sub> at 23.08 wt %, SEM image (fractured side view) of MWNT/PVDF composite; (<b>e</b>) PVP@MWNT/PVDF composites; (<b>f</b>) PVP<sub>10000</sub> at 2.44 wt %; (<b>g</b>) PVP<sub>40000</sub> at 9.09 wt % and (<b>h</b>) PVP<sub>55000</sub> at 23.08 wt %.</p> Full article ">Figure 7 Cont.
<p>SEM image (Anterior) of MWNT/PVDF composite: (<b>a</b>) PVP@MWNT/PVDF composites; (<b>b</b>) PVP<sub>10000</sub> at 2.44 wt %; (<b>c</b>) PVP<sub>40000</sub> at 9.09 wt %; (<b>d</b>) PVP<sub>55000</sub> at 23.08 wt %, SEM image (fractured side view) of MWNT/PVDF composite; (<b>e</b>) PVP@MWNT/PVDF composites; (<b>f</b>) PVP<sub>10000</sub> at 2.44 wt %; (<b>g</b>) PVP<sub>40000</sub> at 9.09 wt % and (<b>h</b>) PVP<sub>55000</sub> at 23.08 wt %.</p> Full article ">Figure 8
<p>Thermal conductivity measure of PVP and P4VP functionalised MWNT/PVDF composite.</p> Full article ">
11 pages, 2415 KiB  
Article
Differential Colonization Dynamics of Marine Biofilm-Forming Eukaryotic Microbes on Different Protective Coating Materials
by Yanhe Lang, Yuan Sun, Miao Yu, Yubin Ji, Lei Wang and Zhizhou Zhang
Polymers 2019, 11(1), 161; https://doi.org/10.3390/polym11010161 - 17 Jan 2019
Cited by 7 | Viewed by 3231
Abstract
In this study, the actual anti-biofouling (AF) efficacy of three protective coatings, including a chlorinated rubber-based coating (C0) and two polydimethylsiloxane (PDMS)-based coatings (P0 and PF), were estimated via the static field exposure assays. The surface properties of [...] Read more.
In this study, the actual anti-biofouling (AF) efficacy of three protective coatings, including a chlorinated rubber-based coating (C0) and two polydimethylsiloxane (PDMS)-based coatings (P0 and PF), were estimated via the static field exposure assays. The surface properties of these protective coatings, including surface wettability and morphology features, were characterized using the static water contact angle (WCA) and scanning electron microscope (SEM). The colonization and succession dynamics of the early-adherent biofilm-forming eukaryotic microbial communities occupied on these protective coatings were explored using the Single-stranded Conformation Polymorphism (SSCP) technique. The field data clearly revealed that coating P0 and PF performed better in the long-term static submergence, as compared with the C0 surface, while coating PF showed excellent AF efficacy in the field. Fingerprinting analysis suggested that the diversity, abundance, the clustering patterns, and colonization dynamics of the early-colonized eukaryotic microbes were significantly perturbed by these protective coatings, particularly by the PF surfaces. These differential AF efficacy and perturbation effects would be largely ascribed to the differences in the wettability and surface nanostructures between the C0, P0 and PF surfaces, as evidenced by WCA and SEM analysis. Full article
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<p>The scanning electron microscope (SEM) images of the three coatings (i.e., C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces.) before immersion for comparison. The scale bars are 2 μm in main figures, and 200 nm in inset.</p> Full article ">Figure 2
<p>Images of the tested steel substrates coated with different coatings (i.e., C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces) immersed in the natural seawater at different exposure times. Stage I: Oct.19, 2013-Mar.18, 2014, 150 days; Stage II: Mar.25, 2014-July.13, 2014,110 days.</p> Full article ">Figure 3
<p>The Single-stranded Conformation Polymorphism (SSCP) patterns of the early biofilm-forming eukaryotic microbial communities developed on the C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces.</p> Full article ">Figure 4
<p>Comparison of the diversity indices of pioneer eukaryotic microbial communities colonized on the C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces, including (<b>a</b>) Shannon diversity index, (<b>b</b>) Abundance, (<b>c</b>) Simpson index and (<b>d</b>) Evenness index. Error bars represent the standard deviation (SD) of the mean. One asterisk (*) represents significant difference (P &lt; 0.05), whereas two asterisks (**) represent extremely significant difference (P &lt; 0.01).</p> Full article ">Figure 5
<p>Clustering pattern of pioneer biofilm-forming eukaryotic communities formed on the C0, P<sub>0</sub> and P<sub>F</sub> surfaces. (<b>a–c</b>) the clustering patterns of pioneer biofilm-forming the eukaryotic communities adhering to the C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces (EC<sub>0</sub>, EP<sub>0</sub> and EP<sub>F</sub>) based on the Unweighted Pair-Group Method with Arithmetic means (UPGMA) method. (<b>d</b>) the multidimensional scale (MDS) analysis of the clustering patterns of the early pioneer eukaryotic communities (EC<sub>0</sub>, EP<sub>0</sub> and EP<sub>F</sub>) on the C<sub>0</sub>, P<sub>0</sub> and P<sub>F</sub> surfaces.</p> Full article ">
15 pages, 5808 KiB  
Article
Effect of Thermal Ageing on the Impact Damage Resistance and Tolerance of Carbon-Fibre-Reinforced Epoxy Laminates
by Irene García-Moreno, Miguel Ángel Caminero, Gloria Patricia Rodríguez and Juan José López-Cela
Polymers 2019, 11(1), 160; https://doi.org/10.3390/polym11010160 - 17 Jan 2019
Cited by 36 | Viewed by 5647
Abstract
Composite structures are particularly vulnerable to impact, which drastically reduces their residual strength, in particular, at high temperatures. The glass-transition temperature (Tg) of a polymer is a critical factor that can modify the mechanical properties of the material, affecting its [...] Read more.
Composite structures are particularly vulnerable to impact, which drastically reduces their residual strength, in particular, at high temperatures. The glass-transition temperature (Tg) of a polymer is a critical factor that can modify the mechanical properties of the material, affecting its density, hardness and rigidity. In this work, the influence of thermal ageing on the low-velocity impact resistance and tolerance of composites is investigated by means of compression after impact (CAI) tests. Carbon-fibre-reinforced polymer (CFRP) laminates with a Tg of 195 °C were manufactured and subjected to thermal ageing treatments at 190 and 210 °C for 10 and 20 days. Drop-weight impact tests were carried out to determine the impact response of the different composite laminates. Compression after impact tests were performed in a non-standard CAI device in order to obtain the compression residual strength. Ultrasonic C-scanning of impacted samples were examined to assess the failure mechanisms of the different configurations as a function of temperature. It was observed that damage tolerance decreases as temperature increases. Nevertheless, a post-curing process was found at temperatures below the Tg that enhances the adhesion between matrix and fibres and improves the impact resistance. Finally, the results obtained demonstrate that temperature can cause significant changes to the impact behaviour of composites and must be taken to account when designing for structural applications. Full article
(This article belongs to the Collection Assessment of the Ageing and Durability of Polymers)
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<p>(<b>a</b>) Standard impact specimens according to ASTM D7136 recommendations. (<b>b</b>) Programmable oven used for the thermal ageing treatments.</p> Full article ">Figure 2
<p>Experimental setup for drop-weight impact test. (<b>a</b>) Drop-weight column device. (<b>b</b>) Compression after impact (CAI) support fixture according to ASTM D7136 standard.</p> Full article ">Figure 3
<p>Impact damage response histories of typical composite laminates under drop-weight impact test: (<b>a</b>) force–time history, (<b>b</b>) energy–time history, and (<b>c</b>) force–displacement history [<a href="#B3-polymers-11-00160" class="html-bibr">3</a>].</p> Full article ">Figure 4
<p>Experimental setup of phased array ultrasonic testing. (<b>a</b>) Olympus Omniscan SX. (<b>b</b>) Phased-array transducer of 64 elements at 5 MHz with coupled encoder. (<b>c</b>) Details of the raster scan scheme for the composite laminates.</p> Full article ">Figure 5
<p>(<b>a</b>) Description of the non-standard adjustable CAI device proposed in this study. (<b>b</b>) Experimental setup for CAI testing.</p> Full article ">Figure 6
<p>(<b>a</b>) Average energy and (<b>b</b>) force histories and (<b>c</b>) force–displacement curves of non-aged [0/90/±45]<sub>2s</sub> quasi-isotropic composite laminates with different ageing processes.</p> Full article ">Figure 7
<p>Ultrasonic C-scanning images of the damaged area of [0/90/±45]<sub>2s</sub> quasi-isotropic composite laminates aged at different temperatures and periods of time. The effect of ageing on the impact damage response. (E<sub>impact</sub> = 20 J).</p> Full article ">Figure 8
<p>CAI test of thermal-aged [0/90/±45]<sub>2s</sub> quasi-isotropic laminates. (<b>a</b>) Averaged CAI stress–displacement curves. (<b>b</b>) Average CAI results and standard deviation.</p> Full article ">Figure 9
<p>CAI damage profiles during the CAI test of [0/90/±45]<sub>2s</sub> quasi-isotropic laminates aged at 190 °C and 210 °C for 10 and 20 days. An impact load of 20 J was applied on the front face.</p> Full article ">Figure 10
<p>Details of the CAI damage profiles during the CAI test of [0/90/±45]<sub>2s</sub> quasi-isotropic laminates aged at 190 °C for 10 days and 210 °C for 20 days.</p> Full article ">
11 pages, 2273 KiB  
Article
Solubility Difference between Pectic Fractions from Creeping Fig Seeds
by Ri-si Wang, Xiao-hong He, Hong Lin, Rui-hong Liang, Lu Liang, Jun Chen and Cheng-mei Liu
Polymers 2019, 11(1), 159; https://doi.org/10.3390/polym11010159 - 17 Jan 2019
Cited by 9 | Viewed by 4709
Abstract
Crude water-extracted pectin (WEP) isolated from creeping fig seeds were mainly fractionated into WEP-0.3 and WEP-0.4 fractions. Fractions were confirmed to be nonstarch, nonreducing sugars, nonpolyphenols and protein-unbounded acidic polysaccharides. Interestingly, a significant difference in solubility was found between WEP-0.3 (higher solubility than [...] Read more.
Crude water-extracted pectin (WEP) isolated from creeping fig seeds were mainly fractionated into WEP-0.3 and WEP-0.4 fractions. Fractions were confirmed to be nonstarch, nonreducing sugars, nonpolyphenols and protein-unbounded acidic polysaccharides. Interestingly, a significant difference in solubility was found between WEP-0.3 (higher solubility than WEP) and WEP-0.4 (remarkably insoluble), which was consistent with the amorphous and porous sponge-like structure of WEP-0.3 as well as the crystalline and dense rod-like state of WEP-0.4. However, the result of the FT-IR spectra was contradicted by the solubility of WEP-0.4, which possessed the lowest degree of methoxylation and ought to possess the highest solubility. Through mineral analysis, a considerably high content of Ca2+ was found in WEP-0.4, suggesting that the low solubility of WEP-0.4 was probably attributable to the formation of microgels during dialysis. Therefore, metal divalent cations in the dialysate were suggested to be depleted for the dialysis of low methoxyl pectin. Full article
(This article belongs to the Special Issue Polysaccharides)
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<p>The profile of water-extracted pectin (WEP) on anion-exchange chromatography was eluted with distilled water and a stepwise gradient of NaCl aqueous solutions (0.1–0.5 M NaCl), detected by the phenol-sulphuric acid method at 490 nm and the m-hydroxybiphenyl method at 525 nm.</p> Full article ">Figure 2
<p>The solubility of WEP, WEP-0.3 and WEP-0.4 in water as a function of dissolution time.</p> Full article ">Figure 3
<p>X-ray diffraction patterns of WEP and its fractions. (<b>a</b>) WEP; (<b>b</b>) WEP-0.3; (<b>c</b>) WEP-0.4.</p> Full article ">Figure 4
<p>Environmental scanning electron microscopy images of WEP and its fractions. (<b>a</b>) WEP (×400); (<b>b</b>) WEP (×800); (<b>c</b>) WEP-0.3 (×400); (<b>d</b>) WEP-0.3 (×800); (<b>e</b>) WEP-0.4 (×400); (<b>f</b>) WEP-0.4 (×800).</p> Full article ">Figure 5
<p>Fourier transform-infrared spectra of WEP and its fractions.</p> Full article ">
14 pages, 12706 KiB  
Article
Sol–Gel-Processed Organic–Inorganic Hybrid for Flexible Conductive Substrates Based on Gravure-Printed Silver Nanowires and Graphene
by Xinlin Li, Nahae Kim, Seongwook Youn, Tae Kyu An, Juyoung Kim, Sooman Lim and Se Hyun Kim
Polymers 2019, 11(1), 158; https://doi.org/10.3390/polym11010158 - 17 Jan 2019
Cited by 8 | Viewed by 4216
Abstract
In this study, an organic–inorganic (O–I) nanohybrid obtained by incorporating an alkoxysilane-functionalized amphiphilic polymer precursor into a SiO2–TiO2 hybrid network was successfully utilized as a buffer layer to fabricate a flexible, transparent, and stable conductive substrate for solution-processed silver nanowires [...] Read more.
In this study, an organic–inorganic (O–I) nanohybrid obtained by incorporating an alkoxysilane-functionalized amphiphilic polymer precursor into a SiO2–TiO2 hybrid network was successfully utilized as a buffer layer to fabricate a flexible, transparent, and stable conductive substrate for solution-processed silver nanowires (AgNWs) and graphene under ambient conditions. The resulting O–I nanohybrid sol (denoted as AGPTi) provided a transmittance of the spin-coated AgNWs on an AGPTi-coated glass of 99.4% and high adhesion strength after a 3M tape test, with no visible changes in the AgNWs. In addition, AGPTi acted as a highly functional buffer layer, absorbing the applied pressure between the conductive materials, AgNWs and graphene, and rigid substrate, leading to a significant reduction in sheet resistance. Furthermore, gravure-printed AgNWs and graphene on the AGPTi-based flexible substrate had uniform line widths of 490 ± 15 and 470 ± 12 µm, with 1000-cycle bending durabilities, respectively. Full article
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<p>Fabrication of AgNW (or graphene) electrodes with high conductivities and adhesion strengths by mechanical pressing techniques on the AGPTi (or GPTi) buffer layer. (<b>a</b>) spray coating of AgNWs or graphene, (<b>b</b>) applying pressure to the film.</p> Full article ">Figure 2
<p>Images of the bare glass and AGPTi- and GPTi-coated glasses used for the fabrication of highly transparent electrodes.</p> Full article ">Figure 3
<p>Optical microscopic images before and after the 3M taping tests on AgNWs/bare glass (<b>a</b>,<b>a-1</b>), graphene/bare glass (<b>b</b>,<b>b-1</b>), AgNWs/AGPTi (<b>c</b>,<b>c-1</b>), graphene/AGPTi (<b>d</b>,<b>d-1</b>), AgNWs/GPTi (<b>e</b>,<b>e-1</b>), and graphene/GPTi (<b>f</b>,<b>f-1</b>).</p> Full article ">Figure 4
<p>Changes in the sheet resistances of the AgNWs and graphene after the taping tests on the bare glass and AGPTi- and GPTi-coated glasses.</p> Full article ">Figure 5
<p>OM and SEM images of the AgNWs and graphene before (<b>a</b>,<b>b</b>) and after (<b>c</b>,<b>d</b>) the mechanical pressing, respectively.</p> Full article ">Figure 6
<p>AFM images of the AgNWs and graphene on AGPTi and GPTi before ((<b>a</b>) AgNWs/AGPTi/glass, (<b>b</b>) AgNWs/GPTi/glass, (<b>c</b>) graphene/AGPTi/glass, and (<b>d</b>) graphene/GPTi/glass), and after ((<b>a-1</b>) P-AgNWs/AGPTi/glass, (<b>b-1</b>) P-AgNWs/GPTi/glass, (<b>c-1</b>) P-graphene/AGPTi/glass, and (<b>d-1</b>) P-graphene/GPTi/glass) the mechanical pressing process.</p> Full article ">Figure 7
<p>Gravure-printed lines of AgNWs and graphene on AGPTi ((<b>a</b>) G-AgNWs/AGPTi/PET and (<b>c</b>) G-graphene/AGPTi/PET) and GPTi ((<b>b</b>) G-AgNWs/GPTi/PET and (<b>d</b>) G-graphene/GPTi/PET), which were predeposited on PET.</p> Full article ">Figure 8
<p>(<b>a</b>) Relationship between the printing speed and line width. (<b>b</b>) Change in line resistance as a function of the line width.</p> Full article ">Figure 9
<p>(<b>a</b>) Normalized line resistances of the gravure-printed AgNWs and graphene on AGPTi and GPTi as a function of the bending cycle. Optical images of the gravure-printed AgNWs and graphene on AGPTi ((<b>b</b>) G-AgNWs/AGPTi/PET and (<b>c</b>) G-graphene/AGPTi/PET) and GPTi ((<b>d</b>) G-AgNWs/GPTi/PET and (<b>e</b>) G-graphene/GPTi/PET) after 1000 bending cycles.</p> Full article ">
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Article
Synthesis of Propylene-co-Styrenic Monomer Copolymers via Arylation of Chlorinated PP and Their Compatibilization for PP/PS Blend
by Xiangming Fu, Xijun Liu, Chunyu Zhang, Heng Liu, Yanming Hu and Xuequan Zhang
Polymers 2019, 11(1), 157; https://doi.org/10.3390/polym11010157 - 17 Jan 2019
Cited by 6 | Viewed by 4346
Abstract
A series of propylene-co-styrenic monomer copolymers were synthesized using the Friedel–Crafts alkylation reaction between chlorinated PP and substituted benzene, and the effects of these copolymers on a PP/PS (80/20) blend were investigated by using the impact test, morphology observation, thermo- and [...] Read more.
A series of propylene-co-styrenic monomer copolymers were synthesized using the Friedel–Crafts alkylation reaction between chlorinated PP and substituted benzene, and the effects of these copolymers on a PP/PS (80/20) blend were investigated by using the impact test, morphology observation, thermo- and dynamic mechanical analysis, and rheology measurements. The results showed that the compatibilization efficiency varied as the variation of the substitute on the benzene ring of the styrenic monomer unit was incorporated in the PP chain in an order of methyl > ethyl > methoxyl. The copolymers bearing a crystalline isotactic polypropylene chain sequence and rubbery propylene-co-styrene-like unit chain segments may prepossess imaginable applications, giving an example for the synthesis and applications of PP-based copolymers, initiating a new way to broaden the polyolefin-based material family. Full article
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Graphical abstract
Full article ">Figure 1
<p><sup>1</sup>H-NMR spectrum of chlorinated polypropylene.</p> Full article ">Figure 2
<p><sup>1</sup>H-NMR spectra of propylene-<span class="html-italic">co</span>-styrenic monomer copolymers represented by tertiary carbon linkage: (<b>a</b>) P1, (<b>b</b>) P2, (<b>c</b>) P3.</p> Full article ">Figure 3
<p>Impact strength of blends with varied amounts of compatibilizers.</p> Full article ">Figure 4
<p>SEM micrographs of the impact fractured surface of the PP/PS blend (<b>a</b>) and that using 2 wt.% of compatibilizers ((<b>b</b>) P1, (<b>c</b>) P2, (<b>d</b>) P3 and (<b>e</b>) SEBS).</p> Full article ">Figure 5
<p>SEM images of the PP/PS blend (<b>a</b>), and that compatibilized using varied amounts of P1 ((<b>b</b>) 1 wt.%, (<b>c</b>) 2 wt.%, (<b>d</b>) 3 wt.%, (<b>e</b>) 4 wt.%).</p> Full article ">Figure 6
<p>The <span class="html-italic">T</span><sub>g</sub> of PS in the PP/PS blend and that of the blend with 2 wt.% of compatibilizer.</p> Full article ">Figure 7
<p>Variation of crystallization temperature (<span class="html-italic">T</span><sub>c</sub>) (<b>a</b>) and crystallinity (X<sub>c</sub>) (<b>b</b>) of blends with varied amounts of compatibilizer.</p> Full article ">Figure 8
<p>Rheological behaviors of PP, PS, and binary PP/PS (80/20) and the ternary blend with 2 wt.% of P1.</p> Full article ">Scheme 1
<p>Friedel–Crafts alkylation and chain scission reaction mechanisms.</p> Full article ">
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