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Polymers
Volume 3
Issue 2
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Polymers, Volume 3, Issue 2 (June 2011) – 20 articles , Pages 662-974

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432 KiB  
Communication
A Novel Self-Assembled Liposome-Based Polymeric Hydrogel for Cranio-Maxillofacial Applications: Preliminary Findings
by Victor Joo, Thiruganesh Ramasamy and Ziyad S. Haidar
Polymers 2011, 3(2), 967-974; https://doi.org/10.3390/polym3020967 - 14 Jun 2011
Cited by 14 | Viewed by 8113
Abstract
Soft nanogels are submicron-sized hydrophilic structures engineered from biocompatible polymers possessing the characteristics of nanoparticles as well as hydrogels, with a wide array of potential applications in biotechnology and biomedicine, namely, drug and protein delivery. In this work, nanogels were obtained using the [...] Read more.
Soft nanogels are submicron-sized hydrophilic structures engineered from biocompatible polymers possessing the characteristics of nanoparticles as well as hydrogels, with a wide array of potential applications in biotechnology and biomedicine, namely, drug and protein delivery. In this work, nanogels were obtained using the physical self-assembly technique or ‘layer-by-layer’ which is based on electrostatic interactions. Liposomal vesicles were coated with alternating layers of hyaluronic acid and chitosan yielding a more viscous hydrogel formulation that previously reported core-shell nanoparticulate suspension, via simply modifying the physico-chemical characteristics of the system. Structural features, size, surface charge, stability and swelling characteristics of the nanogel were studied using scanning electron microscopy and dynamic light scattering. With a specific cranio-maxillofacial application in mind, the hydrogel was loaded with recombinant human (rh) bone morphogenetic protein-7, also known as osteogenic protein-1 or rhOP-1 and release was monitored over an extended period of 60 days. This preliminary study reports promising results on the formulation of a novel core-shell polymeric nanogel. Full article
(This article belongs to the Special Issue Polymers for Oro-Dental and Cranio- Maxillo-Facial Applications)
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<p>(<b>a</b>,<b>b</b>) macroscopic and (<b>c</b>,<b>d</b>) SEM views of L and protein loaded L(HA-CH)<sub>3</sub> hydrogel.</p> Full article ">
<p>(<b>a</b>) characterization of L(HA-CH)<sub>3</sub> hydrogel and (<b>b</b>) effect of temperature changes.</p> Full article ">
<p>(<b>a</b>) cumulative rhOP-1 release profile over 60 days and (<b>b</b>) swelling behavior studies.</p> Full article ">
573 KiB  
Article
Effect of Moisture on the Orientation Birefringence of Cellulose Esters
by Mohd Edeerozey Abd Manaf, Manami Tsuji, Shogo Nobukawa and Masayuki Yamaguchi
Polymers 2011, 3(2), 955-966; https://doi.org/10.3390/polym3020955 - 14 Jun 2011
Cited by 37 | Viewed by 8878
Abstract
Orientation birefringence and its wavelength dispersion are studied for hot-drawn films of cellulose esters such as cellulose triacetate (CTA), cellulose diacetate (CDA), and cellulose acetate propionate (CAP) exposed to three different humidities of environments. Hot-drawn CTA films show negative birefringence that decreases with [...] Read more.
Orientation birefringence and its wavelength dispersion are studied for hot-drawn films of cellulose esters such as cellulose triacetate (CTA), cellulose diacetate (CDA), and cellulose acetate propionate (CAP) exposed to three different humidities of environments. Hot-drawn CTA films show negative birefringence that decreases with increasing wavelength. On the other hand, CDA and CAP films show positive birefringence that increases with increasing wavelength, i.e., the so-called extraordinary wavelength dispersion of birefringence. Upon exposure to high humidity environment, the orientation birefringence of CDA and CAP decreases. The decrease is prominent for the samples containing a large amount of water. CTA, however, shows an increase in magnitude of its negative orientation birefringence with increasing moisture content. The results can be explained by the increase of the polarizability anisotropy perpendicular to the stretching direction in the cellulose esters. It is found from ATR-FTIR measurements that hydrogen bonds are formed between carbonyl groups of cellulose esters and water molecules. Considering that orientation birefringence of cellulose esters is determined mainly by ester groups, the formation of hydrogen bonds contributes to the polarizability anisotropy, thus affecting the orientation birefringence. Full article
(This article belongs to the Collection Polysaccharides)
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<p>Temperature dependence of <b>(a)</b> tensile storage modulus <span class="html-italic">E</span>′ and <b>(b)</b> loss modulus <span class="html-italic">E</span>″ for cellulose triacetate (CTA), unfilled circles; cellulose diacetate (CDA), filled circles; and cellulose acetate propionate (CAP), unfilled diamonds, at 10 Hz.</p> Full article ">
<p>Wavelength dependence of orientation birefringence Δ<span class="html-italic">n</span> for CTA stretched at a draw ratio of 1.5 and exposed to 0% humidity (unfilled circles), 50% humidity (filled circles) and 100% humidity (unfilled diamonds). Drawing temperature is 197 °C.</p> Full article ">
<p>Wavelength dependence of orientation birefringence Δ<span class="html-italic">n</span> for CDA stretched at a draw ratio of 1.5 and exposed to 0% humidity (open circles), 50% humidity (closed circles) and 100% humidity (open diamonds). Drawing temperature is 187 °C.</p> Full article ">
<p>Wavelength dependence of orientation birefringence Δ<span class="html-italic">n</span> for CAP stretched at a draw ratio of 1.5 and exposed to 0% humidity (unfilled circles), 50% humidity (filled circles) and 100% humidity (unfilled diamonds). Drawing temperature is 143 °C.</p> Full article ">
<p>Relation between moisture content and humidity for drawn CTA (circles), CDA (diamonds) and CAP (triangles) films exposed to three different humidities of ambiences.</p> Full article ">
<p>Relation between orientation birefringence at 589 nm and moisture content of CTA (unfilled circles), CDA (filled circles) and CAP (unfilled diamonds).</p> Full article ">
<p>ATR-FTIR spectrum of CDA exposed to 0% humidity of ambience.</p> Full article ">
<p>ATR-FTIR spectra (3,000–4,000 cm<sup>−1</sup>) of <b>(a)</b> CDA and <b>(b)</b> CTA before (0%) and after (100%) hydration.</p> Full article ">
<p>ATR-FTIR spectra (1,600–1,900 cm<sup>−1</sup>) of <b>(a)</b> CDA and <b>(b)</b> CTA before (0%) and after (100%) hydration.</p> Full article ">
813 KiB  
Article
Behavior of Na+-Polystyrene Sulfonate at the Interface with Single-Walled Carbon Nanotubes (SWNTs) and Its Implication to SWNT Suspension Stability
by Tabbetha Dobbins, Richard Chevious and Yuri Lvov
Polymers 2011, 3(2), 942-954; https://doi.org/10.3390/polym3020942 - 14 Jun 2011
Cited by 14 | Viewed by 10010
Abstract
The assembly of sodium polystyrene sulfonate (Na+-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation [...] Read more.
The assembly of sodium polystyrene sulfonate (Na+-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation believed to be the result of cation (either Na+ or H+) condensation onto the ionized polymer chain. It is well reported that cations (and also anions) adsorb preferentially onto single-walled and multi-walled carbon nanotube surfaces leading to an increased ion concentration in the near surface regions relative to the bulk solution. This work provides experimental evidence for preferentially absorbed cation condensation onto PSS anions until those cations are spaced at distances corresponding to the Bjerrum length ( B), as defined by the Manning theory of ion condensation, at the SWNT surface. The resulting electrostearic repulsions allow the SWNTs to remain suspended for days. Furthermore , coulombic repulsion among SWNT bundles after cation adsorption alone is not sufficient to form stable suspensions—but rather the stearic repulsions associated with spherically collapsed PSS at the nanotube surface is responsible for suspension stability. It is believed that the ultrasonic agitation drives cations into the small spaces between SWNT bundles and coulombic potential attracts the PSS to those regions. Full article
(This article belongs to the Special Issue Polyelectrolytes)
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<p>Monomer unit of Sodium Polystyrene Sulfonate (PSS).</p> Full article ">
<p>Zeta (<b>ζ)</b> Potential surface charge of as-purchased single-walled carbon nanotubes (SWNTs) at pH 1 to 9.</p> Full article ">
<p>SEM of Commercial MicroTechNano CNTs.</p> Full article ">
<p><b>(a)</b> 200 kX TEM of SWNTs in the as-purchased state; <b>(b)</b> 200 kX TEM of PSS-SWNTs (polystyrene sulfonate single-walled carbon nanotubes) without ultrasonication; <b>(c)</b> 63 kX TEM of SWNTs in the as-purchased state; <b>(d)</b> 63 kX TEM of PSS-SWNTs without ultrasonication; (<b>e)</b> 63 kX TEM of PSS-SWNTs after 20 hours of ultrasonication; (<b>f)</b> 63 kX TEM of PSS-SWNTs after 20 hours of ultrasonication.</p> Full article ">
<p>80 kX TEM images of PSS-SWNTs after e-beam damage which effectively removed the spherically collapsed polyelectrolyte beads.</p> Full article ">
<p>Manning Theory Bjerrum Length (ℓ<sub>B</sub>) <span class="html-italic">vs.</span> Dielectric Constant.</p> Full article ">
<p><b>(a)</b> Concentration <span class="html-italic">vs.</span> time profiles for PSS-SWNT and commercially available PABS-CNT suspensions over an 8 hour period; <b>(b)</b> at inset, PSS-SWNT suspensions 2 days after preparation using 0.36 mg/mL of SWNTs with 2 mg/mL of PSS.</p> Full article ">
629 KiB  
Communication
Physical and Chemical Characterization of Poly(hexamethylene biguanide) Hydrochloride
by Gustavo F. De Paula, Germano I. Netto and Luiz Henrique C. Mattoso
Polymers 2011, 3(2), 928-941; https://doi.org/10.3390/polym3020928 - 1 Jun 2011
Cited by 84 | Viewed by 19377
Abstract
We present the characterization of commercially available Poly(hexamethylene biguanide) hydrochloride (PHMB), a polymer with biocidal activity and several interesting properties that make this material suitable as a building block for supramolecular chemistry and “smart” materials. We studied polymer structure in water solution by [...] Read more.
We present the characterization of commercially available Poly(hexamethylene biguanide) hydrochloride (PHMB), a polymer with biocidal activity and several interesting properties that make this material suitable as a building block for supramolecular chemistry and “smart” materials. We studied polymer structure in water solution by dynamic light scattering, surface tension and capacitance spectroscopy. It shows typical surfactant behavior due to amphiphilic structure and low molecular weight. Spectroscopic (UV/Vis, FT-NIR) and thermal characterization (differential scanning calorimetry, DSC, and thermogravimetric analysis, TGA) were performed to give additional insight into the material structure in solution and solid state. These results can be the foundation for more detailed investigations on usefulness of PHMB in new complex materials and devices. Full article
(This article belongs to the Special Issue Water-Soluble Polymers)
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<p>Schematic structure of mono-protonated PHMB with chloride as counter-ion (<b>a</b>) and monomers: Hexamethylenediamine (<b>b</b>) and sodium dicyanamide (<b>c</b>).</p> Full article ">
<p>Volume distribution of particle diameter (<b>a</b>); and scattering intensity distribution for several concentrations of PHMB in water (<b>b</b>).</p> Full article ">
<p>Surface tension of PHMB in water, measured by the pendant drop method. The black lines represent curve fitting for power law (triangles) and exponential decay (squares).</p> Full article ">
<p>Capacitance at 1 KHz, 10 mV of senoidal voltage. The solid lines represent fitting of power laws to the respective points. The dotted lines are a visual guide showing the interception of extrapolations; the open circle denotes the concentration in the transition of both regimes.</p> Full article ">
<p>Differential refractivity (<span class="html-italic">η<sub>solution</sub></span>−<span class="html-italic">η<sub>water</sub></span>) of aqueous solutions of PHMB as a function of concentration (λ = 598 nm).</p> Full article ">
<p>UV absorption spectra of PHMB solution in water (black solid line), methanol (grey solid line) and ethanol (black dotted line), at 48.4 μmol dm<sup>−3</sup>.</p> Full article ">
<p>Near-infrared spectrum of pure PHMB over quartz plate (black line); deconvoluted spectrum (gray line) improves visualization of small bands.</p> Full article ">
<p>Thermogravimetric analysis of PHMB under N<sub>2</sub> flux and 10 K min<sup>−1</sup> heating rate.</p> Full article ">
334 KiB  
Article
Using Light Scattering to Screen Polyelectrolytes (PEL) Performance in Flocculation
by Maria G. Rasteiro, Ineide Pinheiro, Fernando A. P. Garcia, Paulo Ferreira and David Hunkeler
Polymers 2011, 3(2), 915-927; https://doi.org/10.3390/polym3020915 - 27 May 2011
Cited by 19 | Viewed by 8193
Abstract
Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the [...] Read more.
Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the kinetic curves for flocs growth and also for the flocs structure evolution. Flocculation kinetics, flocs size and structure, flocs resistance and reflocculation capacity could be correlated with the degree of branching of the polyelectrolytes (PEL). Furthermore, PEL with different degrees of branching corresponded to different values for the intrinsic viscosity, indicating differences in the polymer conformation, which explained well the performance differences in flocculation. Full article
(This article belongs to the Special Issue Polyelectrolytes)
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Graphical abstract

Graphical abstract
Full article ">
<p>Scattering pattern of an aggregate (slope 1—d<sub>F</sub>; slope 2—SE), <math display="inline"> <semantics id="sm4"> <mrow> <mi>q</mi> <mo>=</mo> <mfrac> <mrow> <mn>4</mn> <mi>π</mi> <msub> <mi>n</mi> <mn>0</mn></msub></mrow> <mrow> <msub> <mi>λ</mi> <mn>0</mn></msub></mrow></mfrac> <mo>sin</mo> <mrow> <mo>(</mo> <mrow> <mrow> <mi>θ</mi> <mo>/</mo> <mn>2</mn></mrow></mrow> <mo>)</mo></mrow></mrow></semantics></math>, with <span class="html-italic">n<sub>0</sub></span> the refractive index of the dispersing medium, <span class="html-italic">θ</span> the scattering angle and <span class="html-italic">λ<sub>0</sub></span> the incident light wavelength <span class="html-italic">in vacuo</span>.</p> Full article ">
<p>Kinetic curves for PELs E1, E1+, E1++ and E1++++, for three different concentrations and showing floc breakage due to sonication at 20 kHz.</p> Full article ">
<p>Particle size distribution of the flocs obtained with E1 (6 mg/g) at two different instants (2 and 14 minutes).</p> Full article ">
<p>Images of the flocs obtained with E1 (6 mg/g) at two different instants (2 minutes (<b>a</b>) and 14 minutes (<b>b</b>)).</p> Full article ">
<p>Fitting of <a href="#FD2" class="html-disp-formula">Equations 2</a> and <a href="#FD3" class="html-disp-formula">3</a> to the kinetic curves obtained with E1.</p> Full article ">
<p>Evolution of flocs structure with time (d<sub>F</sub> and SE) for PELs E1, E1+, E1++ and E1++++.</p> Full article ">
423 KiB  
Review
Synthetic Polymer Scaffolds for Stem Cell Transplantation in Retinal Tissue Engineering
by Jing Yao, Sarah L. Tao and Michael J. Young
Polymers 2011, 3(2), 899-914; https://doi.org/10.3390/polym3020899 - 26 May 2011
Cited by 53 | Viewed by 9808
Abstract
Age-related macular degeneration and retinitis pigmentosa are two leading causes of irreversible blindness characterized by photoreceptor loss. Cell transplantation may be one of the most promising approaches of retinal repair. However, several problems hinder the success of retinal regeneration, including cell delivery and [...] Read more.
Age-related macular degeneration and retinitis pigmentosa are two leading causes of irreversible blindness characterized by photoreceptor loss. Cell transplantation may be one of the most promising approaches of retinal repair. However, several problems hinder the success of retinal regeneration, including cell delivery and survival, limited cell integration and incomplete cell differentiation. Recent studies show that polymer scaffolds can address these three problems. This article reviews the current literature on synthetic polymer scaffolds used for stem cell transplantation, especially retinal progenitor cells. The advantages and disadvantages of different polymer scaffolds, the role of different surface modifications on cell attachment and differentiation, and controlled drug delivery are discussed. The development of material and surface modification techniques is vital in making cell transplantation a clinical success. Full article
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<p>Degradation of CD44 and neurocan via controlled delivery of active MMP2 enhanced stem cell integration. Retinal explants were cultured in the absence (<b>A</b>–<b>C</b>, control-PLGA) or presence (<b>D</b>–<b>F</b>, MMP2–PLGA) of active MMP2 for 1, 3 and 5 days at 37 °C, and subsequently fixed, cryosectioned and immunolabeled for GFP (green), CD44 (red) and neurocan (blue). Magnification 40×, scale bar: 25 μm. Reprinted with kind permission from Tucker, B.A.; Redenti, S.M.; Jiang, C; Swift, J.S.; Klassen, H.J.; Smith, M.E.; Wnek, G.E.; Young, M.J. The use of progenitor cell/biodegradable MMP2-PLGA polymer constructs to enhance cellular integration and retinal repopulation. <span class="html-italic">Biomaterials</span> 2010, <span class="html-italic">31</span>, 9-19.</p> Full article ">
<p>Migration and differentiation of retinal progenitor cells (RPCs) from polymer composite grafts into the Rho–/– retina. Confocal (<b>A</b>–<b>F</b>, <b>J</b>–<b>L</b>) and epifluorescent (<b>G</b>–<b>I</b>) images of the expression of neural and photoreceptor markers by RPCs were taken 2 and 4 weeks after polymer composite grafts were transplanted into the eye of adult Rho–/– mice. Recoverin co-expressing RPCs were found in the retina of Rho–/– mice at (<b>A</b>–<b>C</b>) 2 weeks and (<b>D</b>–<b>F</b>) 4 weeks after transplantation. Rhodopsin co-expressing RPCs were found in Rho–/– mice at (<b>G</b>–<b>I</b>) 2 weeks and (<b>J</b>–<b>L</b>) 4 weeks. Reprinted with kind permission from Tomita, M.; Lavik, E.; Klassen, H.; Zahir, T.; Langer, R; Young, M.J. Biodegradable Polymer Composite Grafts Promote the Survival and Differentiation of Retinal Progenitor Cells. <span class="html-italic">Stem Cells</span> 2005, <span class="html-italic">23</span>, 1579-1588.</p> Full article ">
<p>Differentiation of RPCs. GFP+ RPCs were cultured on polycaprolactone (PCL) polymer scaffolds (<b>A</b>–<b>C</b>) or glass (<b>D</b>–<b>F</b>) for 7 days. Most cells attached tightly to the PCL and expressed photoreceptor markers crx (<b>A</b>), recoverin (<b>B</b>) and rhodopsin (<b>C</b>). Almost no crx (<b>D</b>), recoverin (<b>E</b>) and rhodopsin (<b>F</b>) positive cells were found on glass. Scale bar: 200 μm.</p> Full article ">
364 KiB  
Review
Brillouin Scattering in Polymer Optical Fibers: Fundamental Properties and Potential Use in Sensors
by Yosuke Mizuno and Kentaro Nakamura
Polymers 2011, 3(2), 886-898; https://doi.org/10.3390/polym3020886 - 26 May 2011
Cited by 23 | Viewed by 9455
Abstract
We review the fundamental properties of Brillouin scattering in a perfluorinated graded-index polymer optical fiber (PFGI-POF) with 120 μm core diameter. The experiments were performed at 1.55 μm telecommunication wavelength. The Brillouin frequency shift (BFS) and the Brillouin bandwidth were 2.83 GHz and [...] Read more.
We review the fundamental properties of Brillouin scattering in a perfluorinated graded-index polymer optical fiber (PFGI-POF) with 120 μm core diameter. The experiments were performed at 1.55 μm telecommunication wavelength. The Brillouin frequency shift (BFS) and the Brillouin bandwidth were 2.83 GHz and 105 MHz, respectively. The Brillouin gain coefficient was calculated to be 3.09 × 10−11 m/W, which was comparable to that of fused silica fibers. The Brillouin threshold power of the 100 m POF was estimated to be as high as 24 W, which can be, for practical applications, reduced by using POFs with smaller cores. These properties were compared with those of silica-based graded-index multi-mode fibers. We also investigated the BFS dependences on strain and temperature. They showed negative dependences with coefficients of −121.8 MHz/% and −4.09 MHz/K, respectively, which are −0.2 and −3.5 times as large as those in silica fibers. These BFS dependences indicate that the Brillouin scattering in PFGI-POFs can be potentially applied to high-accuracy temperature sensing with reduced strain sensitivity. Full article
(This article belongs to the Special Issue Polymers for Optical Applications)
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<p>Experimental setup for investigating the Brillouin scattering properties in the PFGI-POF. DFB-LD, distributed-feedback laser diode; EDFA, erbium-doped fiber amplifier; ESA, electrical spectrum analyzer; PC, polarization controller; PD, photo-diode.</p> Full article ">
<p><b>(a)</b> BGS in the 100 m PFGI-POF when the pump power was 20 dBm. <b>(b)</b> Magnified view around the BGS peak.</p> Full article ">
<p>Relative power of the Stokes light backscattered from 100 m PFGI-POF <span class="html-italic">vs.</span> pump power.</p> Full article ">
<p>BGS of the 100 m GI-MMF at the pump power of 15, 20, and 25 dBm.</p> Full article ">
<p>Relative Stokes power as a function of pump power in the 100 m GI-MMF.</p> Full article ">
<p><b>(a)</b> BGS dependence on strain in the PFGI-POF. <b>(b)</b> BFS as a function of applied strain.</p> Full article ">
<p><b>(a)</b> BGS dependence on temperature in the PFGI-POF. <b>(b)</b> BFS as a function of temperature.</p> Full article ">
<p><b>(a)</b> Young's modulus of bulk PMMA <span class="html-italic">vs.</span> temperature. <b>(b)</b> Density of bulk PMMA <span class="html-italic">vs.</span> temperature (plotted using the data reported in [<a href="#b47-polymers-03-00886" class="html-bibr">47</a>]).</p> Full article ">
568 KiB  
Communication
A Possibility for Construction of an Iodine Cleaning System Based on Doping for π-Conjugated Polymers
by Hiromasa Goto
Polymers 2011, 3(2), 875-885; https://doi.org/10.3390/polym3020875 - 16 May 2011
Cited by 20 | Viewed by 8437
Abstract
An iodine accumulation method using polyaniline (PANI) and a textile composite is proposed. PANI/pulp paper sheets prepared by a paper making technique are suitable for iodine adsorption, because of good processability. The PANI-based paper sheets can be applied for iodine cleanup as air [...] Read more.
An iodine accumulation method using polyaniline (PANI) and a textile composite is proposed. PANI/pulp paper sheets prepared by a paper making technique are suitable for iodine adsorption, because of good processability. The PANI-based paper sheets can be applied for iodine cleanup as air filters, water filters, and floorcloth. This concept may lead to a development of an iodine cleaning machine or iodine shield cloth based on π-conjugated polymer composites. In-situ vapor phase doping of iodine, observation of surface images, and IR measurements are carried out to examine iodine doping function for the PANI/pulp paper sheets. Full article
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<p>PANI/pulp material before paper making (<b>a</b>). PANI/pulp paper sheet prepared by traditional paper making technique (<b>b</b>). Miura folding of PANI/pulp sheet (<b>c</b>,<b>d</b>). Thermograph of the PANI/pulp paper with Miura folding upon irradiation of infra-red light (<b>e</b>).</p> Full article ">
<p>Scanning electron microscopy (SEM) images of PANI/pulp surface. (<b>a</b>) 950×. (<b>b</b>) 7,000×.</p> Full article ">
<p><span class="html-italic">In-situ</span> ESR spectra of PANI/pulp during vapor-phase doping of iodine. (Red) pristine PANI/pulp (emeraldine base (EB), no iodine doping), (blue) doping time = 1,260 s, (green) doping time = 10,260 s (171 min).</p> Full article ">
<p>ESR results during early stages of <span class="html-italic">in-situ</span> vapor phase doping of PANI/pulp with iodine. Changes in <span class="html-italic">g</span>-value, ESR intensity (<span class="html-italic">I</span><sub>pp</sub>), and linewidth (Δ<span class="html-italic">H</span><sub>pp</sub>) are presented.</p> Full article ">
<p>Infra-red (IR) absorption spectra of PANI/pulp (as polymerized, PANI = emeraldine salt (ES)), PANI/pulp (after treatment of ammonia, PANI = emeraldine base (EB)), and iodine-doped PANI/pulp (<b>a</b>). Magnification of the spectra at low wavenumbers (<b>b</b>).</p> Full article ">
<p>Optical absorption spectra of PANI (EB) in <span class="html-italic">N</span>-methyl-2-pyrrolidone (NMP) (<b>a</b>), iodine in NMP solution and PANI (EB) with iodine doping in NMP. CIE color space chromaticity diagram of PANI (EB) with iodine doping and iodine in NMP (<b>b</b>).</p> Full article ">
<p>Optical absorption spectra of PANI (EB) in <span class="html-italic">N</span>-methyl-2-pyrrolidone (NMP) (<b>a</b>), iodine in NMP solution and PANI (EB) with iodine doping in NMP. CIE color space chromaticity diagram of PANI (EB) with iodine doping and iodine in NMP (<b>b</b>).</p> Full article ">
<p>Preparation of polyaniline (PANI)/pulp composite.</p> Full article ">
714 KiB  
Article
Polarized Emission of Wholly Aromatic Bio-Based Copolyesters of a Liquid Crystalline Nature
by Kai Kan, Daisaku Kaneko and Tatsuo Kaneko
Polymers 2011, 3(2), 861-874; https://doi.org/10.3390/polym3020861 - 16 May 2011
Cited by 9 | Viewed by 8580
Abstract
A novel thermotropic liquid crystalline polymers poly{3-benzylidene amino-4-hydroxybenzoic acid (3,4-BAHBA)-co-trans-4-hydroxycinnamic acid (4HCA: trans-coumaric acid)} (Poly(3,4-BAHBA-co-4HCA)), was synthesized by the thermal polycondensation of 4HCA and 3,4-BAHBA, which was synthesized by a reaction of 3-amino-4-hydroxybenzoic acid (3,4-AHBA) with benzaldehyde. When [...] Read more.
A novel thermotropic liquid crystalline polymers poly{3-benzylidene amino-4-hydroxybenzoic acid (3,4-BAHBA)-co-trans-4-hydroxycinnamic acid (4HCA: trans-coumaric acid)} (Poly(3,4-BAHBA-co-4HCA)), was synthesized by the thermal polycondensation of 4HCA and 3,4-BAHBA, which was synthesized by a reaction of 3-amino-4-hydroxybenzoic acid (3,4-AHBA) with benzaldehyde. When the 4HCA compositions of Poly(3,4-BAHBA-co-4HCA)s were above 55 mol%, the copolymers showed a nematic, liquid crystalline phase. Differential scanning calorimetry (DSC) measurements of the copolymers showed a high glass transition temperature of more than 100 °C, sufficient for use in engineering plastics. Furthermore, the copolymers showed photoluminescence in an N-methylpyrrolidone (NMP) solution under ultraviolet (UV) light with a wavelength of 365 nm. Oriented film of Poly(3,4-BAHBA-co-4HCA) with a 4HCA composition of 75 mol% emitted polarized light, which was confirmed by fluorescent spectroscopy equipped with parallel and crossed polarizers. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
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Graphical abstract

Graphical abstract
Full article ">
<p>FT-IR spectra of the monomers and polymers.</p> Full article ">
<p><sup>1</sup>H-NMR spectra of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA) with a 4HCA composition of 50 mol% 4HCA in DMSO-<span class="html-italic">d<sub>6</sub></span>.</p> Full article ">
<p>Phase diagram of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA)s of various compositions. The inset picture is a crossed-polarizing photomicrograph of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA) with a 4HCA composition of 60 mol% at 256 °C.</p> Full article ">
<p>Crossed-polarizing optical microscope images of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA)s with a 4HCA composition of 75 mol%. (<b>a</b>–<b>c</b>) The sample was sheared to 250 °C and then supercooled to room temperature. (<b>b</b>,<b>c</b>) The image was taken under a first-order retardation plate (λ = 530 nm). (<b>b</b>) was rotated <b>90</b>°to obtain (<b>c</b>).</p> Full article ">
<p>Digital photograph of an NMP solution of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA)s under 365 nm UV light excitation. (<b>i</b>) 100/0, (<b>ii</b>) 75/25, (<b>iii</b>) 50/50, (<b>iv</b>) 25/75, (<b>v</b>) 0/100 in molar ratios.</p> Full article ">
<p>Photoluminescence excitation spectra (left), and emission spectra (right) of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA)s of various molar ratios.</p> Full article ">
<p>Photoluminescence spectra of Poly(3,4-BAHBA-<span class="html-italic">co</span>-4HCA) orientation films with the 4HCA compositions of (<b>a</b>) 75 mol% and (<b>b</b>) 100 mol% under a polarizer and analyzer irradiated at 374 nm with excited light. The table at the bottom shows direction of the polarizer, sample and analyzer.</p> Full article ">
<p>Optical train used for the photoluminescence experiments. The polarizer was placed behind the excitation shutter into the light path, and the analyzer was placed in front of the emission shutter, where the arrows indicate the polarizing and analyzing directions. Although the picture shows a parallel direction of the arrows, the polarizer and analyzer both could be rotated.</p> Full article ">
<p>Synthesis of 3,4-BAHBA.</p> Full article ">
397 KiB  
Article
Rotational Diffusion of Macromolecules and Nanoparticles Modeled as Non-Overlapping Bead Arrays in an Effective Medium
by Hengfu Wu, Umar Twahir, Alishia Davis, Ebenezer Duodo, Bahareh Kashani, Young Lee, Cindy Pena, Noni Whitley and Stuart A. Allison
Polymers 2011, 3(2), 846-860; https://doi.org/10.3390/polym3020846 - 13 May 2011
Viewed by 8472
Abstract
In this work, the retarding influence of a gel on the rotational motion of a macromolecule is investigated within the framework of the Effective Medium (EM) model. This is an extension of an earlier study that considered the effect of a gel on [...] Read more.
In this work, the retarding influence of a gel on the rotational motion of a macromolecule is investigated within the framework of the Effective Medium (EM) model. This is an extension of an earlier study that considered the effect of a gel on the translational motion of a macromolecule [Allison, S. et al. J. Phys. Chem. B 2008, 112, 5858-5866]. The macromolecule is modeled as an array of non-overlapping spherical beads with no restriction placed on their size or configuration. Specific applications include the rotational motion of right circular cylinders and wormlike chains modeled as strings of identical touching beads. The procedure is then used to examine the electric birefringence decay of a 622 base pair DNA fragment in an agarose gel. At low gel concentration (M ≤ 0.010 gm/mL), good agreement between theory and experiment is achieved if the persistence length of DNA is taken to be 65 nm and the gel fiber radius of agarose is taken to be 2.5 nm. At higher gel concentrations, the EM model substantially underestimates the rotational relaxation time of DNA and this can be attributed to the onset of direct interactions that become significant when the effective particle size becomes comparable to the mean gel fiber spacing. Full article
(This article belongs to the Special Issue Polymer Nanogels and Microgels)
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<p>Array of <span class="html-italic">N</span> Non Overlapping Beads. The bead radii, {<span class="html-italic">a<sub>j</sub></span>}, and the position of the bead centers is arbitrary.</p> Full article ">
<p><span class="html-italic">Λ<sub>1</sub></span> for a Right Circular Cylinder and Linear String of Touching Beads <span class="html-italic">versus</span> Length. The solid line is for a right circular cylinder of axial radius <span class="html-italic">R</span> and comes from <a href="#FD33" class="html-disp-formula">Equation (33)</a> [<a href="#b40-polymers-03-00846" class="html-bibr">40</a>]. The filled squares are for a linear string of touching beads of radius <span class="html-italic">a</span> and <span class="html-italic">a/R</span> = 1.207. The length of the right circular cylinder, <span class="html-italic">L</span>, is related to <span class="html-italic">N</span> and <span class="html-italic">a</span> by <a href="#FD36" class="html-disp-formula">Equation (36)</a> with <span class="html-italic">c</span> = 0.20. The gel screening parameter, <span class="html-italic">λ</span>, is set to zero (no gel).</p> Full article ">
<p>A 88 Subunit Discrete Wormlike Chain. The persistence length, <span class="html-italic">P</span>, is 65 nm and the bead radius, <span class="html-italic">a</span>, is 1.207 nm. Different configurations are generated at random as discussed in the text.</p> Full article ">
<p>Model and Experimental <span class="html-italic">Λ<sub>1</sub></span> Values for 622 bp DNA as a Function of Gel Concentration. Experimental values are denoted by the filled squares. Solid, dotted, and dashed lines denote model studies with <span class="html-italic">P</span> = 65 nm and <span class="html-italic">r<sub>g</sub></span> = 1.52, 2.0, and 2.5 nm, respectively. The temperature is 20 °C.</p> Full article ">
353 KiB  
Article
Mechanism Studies of LCP Synthesis
by Anne Buyle Padias and Henry K. Hall, Jr.
Polymers 2011, 3(2), 833-845; https://doi.org/10.3390/polym3020833 - 4 May 2011
Cited by 19 | Viewed by 13489
Abstract
The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed [...] Read more.
The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed second-order kinetics and their rate constants were comparable. In the latter stages, ketene loss leads to phenolic ends, while decarboxylation provides phenyl ester ends. Accordingly, the mechanism changes to phenolysis. A quinone methide intermediate may also intervene, as revealed by kinetics studies and MALDI-TOF spectroscopy. Tailor-made matrices and synthesis of alternating well-defined oligomers assisted our studies. Nucleophilic aromatic substitutions may play a role, and we speculate on possible chain polycondensation. Esterolysis may be a useful alternative to LCP synthesis. Complications caused by ketene loss can be averted by the use of methoxycarbonyloxy monomers. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
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<p>Copolymerization of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid.</p> Full article ">
<p>Acidolysis mechanism of <span class="html-italic">p-tert</span>-butylphenyl acetate and benzoic acid in diphenyl ether (from [<a href="#b7-polymers-03-00833" class="html-bibr">Ref. 7</a>]).</p> Full article ">
<p>Proposed mechanism for the polymerization of 4-acetoxybenzoic acid.</p> Full article ">
<p>Possible decomposition products of 4-acetoxybenzoic acid.</p> Full article ">
<p>Change of mechanism from acetolysis to phenolysis.</p> Full article ">
<p>Two possible ester-interchange reactions involving phenol.</p> Full article ">
<p>S<sub>N</sub> ar mechanism for nucleophilic aromatic substitution.</p> Full article ">
<p>Possible chain LCP polymerization.</p> Full article ">
<p>Other reaction pathways to LCP.</p> Full article ">
628 KiB  
Article
Surface Modification of Poly(L-lactic acid) Nanofiber with Oligo(D-lactic acid) Bioactive-Peptide Conjugates for Peripheral Nerve Regeneration
by Sachiro Kakinoki, Sho Uchida, Tomo Ehashi, Akira Murakami and Tetsuji Yamaoka
Polymers 2011, 3(2), 820-832; https://doi.org/10.3390/polym3020820 - 27 Apr 2011
Cited by 30 | Viewed by 9747
Abstract
In some traumatic nerve injuries, autologous nerve grafting is the first choice for bridging the gap between the severed nerve ends. However, this therapeutic strategy has some disadvantages, including permanent loss of donor function and requirement of multiple surgeries. An attractive alternative to [...] Read more.
In some traumatic nerve injuries, autologous nerve grafting is the first choice for bridging the gap between the severed nerve ends. However, this therapeutic strategy has some disadvantages, including permanent loss of donor function and requirement of multiple surgeries. An attractive alternative to this therapeutic technique is the use of artificial nerve conduit. Poly (L-lactic acid) (PLLA) is widely used as a substrate for artificial nerve conduit because it is readily biodegradable, but it is not inherently biologically active. In this study, we developed a PLLA nanofibrous nerve conduit, modified with a conjugate of oligo (D-lactic acid) (ODLA) and the neurite outgrowth, thereby promoting peptide AG73 (RKRLQVQLSIRT) to improve nerve regeneration. PLA/ODLA-AG73 nanofibrous conduit was fabricated by electrospinning and then transplanted at the 10 mm gap of rat sciatic nerve. After six months, electrophysiological evaluation revealed that it achieved better functional reinnervation than silicone tube (used as a reference) or unmodified PLLA nanofibrous conduit. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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<p>Illustration of the surface structure of PLLA/ODLA-AG73 nanofiber.</p> Full article ">
<p>Images of different types of nerve conduit: (<b>A</b>) Whole image of a silicone tube (used as control) and PLLA/ODLA-AG73 nanofibrous conduit; (<b>B</b>,<b>C</b>) Scanning electron microscope (SEM) images of PLLA and PLLA/ODLA-AG73 nanofibrous nerve conduits, respectively.</p> Full article ">
<p>X-ray photoelectron spectroscopy (XPS) spectra of PLLA and PLLA/ODLA-AG73 nerve conduits. The inserted figure shows the spectra in the N1s region.</p> Full article ">
<p>Intraoperative photographs of different types of nerve conduit (top row, immediately after implantation; bottom row, six months after implantation): (<b>A</b>,<b>B</b>) Silicone tube (used as a control); (<b>C</b>,<b>D</b>) PLLA conduit; (<b>E</b>,<b>F</b>) PLLA/ODLA-AG73 conduit.</p> Full article ">
<p>Immunohistochemical analysis of axial cross sections of implanted silicone tube (used as a control), PLLA conduit, and PLLA/ODLA-AG73 conduit around a distal connection six months after implantation, with different stains applied: (<b>A</b>,<b>D</b>,<b>G</b>,<b>J</b>) HE stain; (<b>B</b>,<b>E</b>,<b>H</b>,<b>K</b>) GFAP-positive cells (brown); (<b>C</b>,<b>F</b>,<b>I</b>,<b>L</b>) Neurofilament (brown). Note the conduit fragments (indicated by arrows) (Scale bar = 200 μm).</p> Full article ">
<p>Electrophysiological analysis of sciatic nerves six months after implantation: (<b>A</b>) Healthy nerve; (<b>B</b>) Nerve with implanted silicone tube (used as a control); (<b>C</b>) Nerve with implanted PLLA conduit; (<b>D</b>) Nerve with implanted PLLA/ODLA-AG73 conduit.</p> Full article ">
<p>Synthesis of ODLA-AG73 conjugates.</p> Full article ">
<p>MALDI-TOF/MS spectra of AG73, ODLA, and ODLA-AG73 conjugate. Molecular weights were determined by ALDI-TOF/MS (4800 MALDI TOF/TOF Analyzer, Applied Biosystems, Foster City, CA, USA). The molecular weight of AG73, 1,496.98 Da, corresponds to the theoretical value. The molecular weight of ODLA ranges from about 700 to 1,750 Da, and after condensation with AG73 and ODLA, changes to about 1,750–2,150 Da.</p> Full article ">
<p>Adhesion and neurite outgrowth of PC12 cells on spin-coated film and on electrospun nanofibrous nonwoven PLLA or PLLA/ODLA-AG73 (scale bar = 200 μm). Spin-coated films were prepared on a glass slide with a spin coater as follows: 10 w/v% HFIP solution of PLLA or PLLA/ODLA-AG73 (including 3 w% ODLA-AG73 conjugate) was dropped on a slide and spread with a spin coater (3,000 rpm, 20 s). Nanofibrous nonwoven PLLA or PLLA/ODLA-AG73 and nanofibrous conduits were fabricated on the slide by electrospinning. PC12 cells were primed with NGF for 24 h, then, added to the samples. The samples were incubated at 37 °C for 24 h in Dulcecco's modification of Eagle's medium (DMEM) containing NGF. On spin-coated film, PLLA/ODLA-AG73 promoted the adhesion and neurite ourgrowth of PC 12 cells. On nanofibrous nonwoven PLLA and PLLA/ODLA-AG73, the PC 12 cells were slightly spread and more differentiated on PLLA/ODLA-AG73 than on PLLA.</p> Full article ">
359 KiB  
Article
Counterion Condensation and Effective Charge of PAMAM Dendrimers
by Ute Böhme, Anja Klenge, Brigitte Hänel and Ulrich Scheler
Polymers 2011, 3(2), 812-819; https://doi.org/10.3390/polym3020812 - 27 Apr 2011
Cited by 25 | Viewed by 8339
Abstract
PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino [...] Read more.
PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino groups which is monitored via the proton chemical shifts of the adjacent CH2 groups. The effective charge is determined from a combination of diffusion and electrophoresis NMR. The fraction of the charges, which are effective for the interaction with an external electric field or other charges, decreases with increasing generation (size) of the dendrimers. Full article
(This article belongs to the Special Issue Polyelectrolytes)
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<p><b>(a)</b> Branch of a PAMAM dendrimer of generation 2. The methylene groups next to the terminal primary amino groups are labeled in pink and next to the interior tertiary amino groups are labeled with blue color. <b>(b)</b> <sup>1</sup>H NMR spectra of PAMAM G2 at different pH values showing the chemical shift of the selected methylene groups as function of pH with a label of the same color as in (a).</p> Full article ">
<p>Stejskal-Tanner plot [<a href="#b4-polymers-03-00812" class="html-bibr">4</a>] of signal decay for PAMAM G2 at pH 5.</p> Full article ">
<p>Two-dimensional electrophoresis NMR spectrum of PAMAM G2 at pH 3.4.</p> Full article ">
<p>Comparison of nominal charge (blue) and effective charge (pink) PAMAM dendrimers for generations 0 to 3. On the left pH = 7.7 the primary amino groups are protonated while the tertiary amino groups are unprotonated. On the right pH = 3 all amino groups are protonated, the nominal charge is the sum of the primary and tertiary amino groups.</p> Full article ">
<p>Fraction of effective charge of fully protonated PAMAM dendrimers as a function of their generation.</p> Full article ">
607 KiB  
Review
Thermosensitive Self-Assembling Block Copolymers as Drug Delivery Systems
by Giulia Bonacucina, Marco Cespi, Giovanna Mencarelli, Gianfabio Giorgioni and Giovanni Filippo Palmieri
Polymers 2011, 3(2), 779-811; https://doi.org/10.3390/polym3020779 - 19 Apr 2011
Cited by 112 | Viewed by 18525
Abstract
Self-assembling block copolymers (poloxamers, PEG/PLA and PEG/PLGA diblock and triblock copolymers, PEG/polycaprolactone, polyether modified poly(Acrylic Acid)) with large solubility difference between hydrophilic and hydrophobic moieties have the property of forming temperature dependent micellar aggregates and, after a further temperature increase, of gellifying due [...] Read more.
Self-assembling block copolymers (poloxamers, PEG/PLA and PEG/PLGA diblock and triblock copolymers, PEG/polycaprolactone, polyether modified poly(Acrylic Acid)) with large solubility difference between hydrophilic and hydrophobic moieties have the property of forming temperature dependent micellar aggregates and, after a further temperature increase, of gellifying due to micelle aggregation or packing. This property enables drugs to be mixed in the sol state at room temperature then the solution can be injected into a target tissue, forming a gel depot in-situ at body temperature with the goal of providing drug release control. The presence of micellar structures that give rise to thermoreversible gels, characterized by low toxicity and mucomimetic properties, makes this delivery system capable of solubilizing water-insoluble or poorly soluble drugs and of protecting labile molecules such as proteins and peptide drugs. Full article
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<p>Poloxamer synthesis.</p> Full article ">
<p>Synthesis of PEG/PLA Multiblock Copolymer [<a href="#b63-polymers-03-00779" class="html-bibr">63</a>].</p> Full article ">
<p>Synthesis of PEG-PLA-PEG in presence of monohydroxyethilated PEG followed by coupling PEG-PLA with Adipoyl Chloride [<a href="#b71-polymers-03-00779" class="html-bibr">71</a>].</p> Full article ">
<p>Scheme of the synthesis pathway of the PEG-PCL multiblock copolymer according to reference [<a href="#b96-polymers-03-00779" class="html-bibr">96</a>].</p> Full article ">
<p>Gel formation and degradation behavior of PCL-PEG-PCL hydrogel according to reference [<a href="#b103-polymers-03-00779" class="html-bibr">103</a>].</p> Full article ">
<p>Structure of poly(ethylene oxide)-<span class="html-italic">b</span>-poly(propylene oxide)-<span class="html-italic">b</span>-(polyethylene oxide)-<span class="html-italic">g</span>-poly (acrylic acid) Pluronic-PAA copolymers [<a href="#b109-polymers-03-00779" class="html-bibr">109</a>].</p> Full article ">
<p>Scheme of the sol-gel transitions in Pluronic-PAA aqueous solutions [<a href="#b109-polymers-03-00779" class="html-bibr">109</a>].</p> Full article ">
<p>Structure of the cross-linked Pluronic-PAA microgel particles [<a href="#b109-polymers-03-00779" class="html-bibr">109</a>].</p> Full article ">
530 KiB  
Article
Polyelectrolyte Complex Nanoparticles of Poly(ethyleneimine) and Poly(acrylic acid): Preparation and Applications
by Martin Müller, Bernd Keßler, Johanna Fröhlich, Sebastian Poeschla and Bernhard Torger
Polymers 2011, 3(2), 762-778; https://doi.org/10.3390/polym3020762 - 12 Apr 2011
Cited by 51 | Viewed by 12391
Abstract
In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, [...] Read more.
In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, media and structural parameters. Especially, mixing order, mixing ratio, PEL concentration, pH and molecular weight, were found to be sensible parameters to regulate the size (diameter) of spherical PEI/PAC nanoparticles, in the range between 80–1,000 nm, in a defined way. Finally, applications of dispersed PEI/PAC particles as additives for the paper making process, as well as for drug delivery, are outlined. PEI/PAC nanoparticles mixed directly on model cellulose film showed a higher adsorption level applying the mixing order 1. PAC 2. PEI compared to 1. PEI 2. PAC. Surface bound PEI/PAC nanoparticles were found to release a model drug compound and to stay immobilized due to the contact with the aqueous release medium. Full article
(This article belongs to the Special Issue Polyelectrolytes)
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<p>(From [<a href="#b18-polymers-03-00762" class="html-bibr">18</a>] with kind permission of Research Trends) Scheme of the polyelectrolyte (PEL) complex (PEC) formation process supported by experiment and simulation [<a href="#b17-polymers-03-00762" class="html-bibr">17</a>].</p> Full article ">
<p>Structural formulae and pH dependence of branched poly(etyhleneinmine) (PEI) and linear poly(acrylic acid) (PAC).</p> Full article ">
<p>DLS data on PEC-0.6 (0.001 M) for (<b>A</b>) 1. PEI 2. PAC (related to full circle in <a href="#f4-polymers-03-00762" class="html-fig">Figure 4</a>); (<b>B</b>) 1. PAC 2. PEI (related to broken circle in <a href="#f4-polymers-03-00762" class="html-fig">Figure 4</a>).</p> Full article ">
<p>Size of PEI/PAC particles <span class="html-italic">versus</span> n<sub>−</sub>/n<sub>+</sub>, c<sub>PEL</sub> = 0.001 M, pH = 10/4.</p> Full article ">
<p>Count rate (CR) of PEI/PAC <span class="html-italic">versus</span> mixing ratio.</p> Full article ">
<p>Size of PEI/PAC particles <span class="html-italic">versus</span> n<sub>−</sub>/n<sub>+</sub>, c<sub>PEL</sub> = 0.001 M, pH = 10/4.</p> Full article ">
<p>Intensity distributions from DLS data on PEC-0.6 dispersions of PEI/PAC in dependence of PEL concentration (c<sub>PEL</sub>).</p> Full article ">
<p>Hydrodynamic diameter D<sub>H</sub> and count rate (CR) of PEC-0.6 dispersions of PEI/PAC in dependence of PEL concentration (c<sub>PEL</sub>).</p> Full article ">
<p>Intensity distributions from DLS data on PEC-1.5 dispersions of PEI/PAC for various pH settings [<span class="html-italic">i.e.</span>, pH(PEI)/pH(PAC)]. (n<sub>−</sub>/n<sub>+</sub> = 1.5, c<sub>PEL</sub> = 0.005 M).</p> Full article ">
633 KiB  
Review
Hydrogels for Cardiac Tissue Engineering
by Zhenqing Li and Jianjun Guan
Polymers 2011, 3(2), 740-761; https://doi.org/10.3390/polym3020740 - 9 Apr 2011
Cited by 155 | Viewed by 19477
Abstract
Cardiac tissue regeneration is an integrated process involving both cells and supporting matrix. Cardiomyocytes and stem cells are utilized to regenerate cardiac tissue. Hydrogels, because of their tissue-like properties, have been used as supporting matrices to deliver cells into infarcted cardiac muscle. Bioactive [...] Read more.
Cardiac tissue regeneration is an integrated process involving both cells and supporting matrix. Cardiomyocytes and stem cells are utilized to regenerate cardiac tissue. Hydrogels, because of their tissue-like properties, have been used as supporting matrices to deliver cells into infarcted cardiac muscle. Bioactive and biocompatible hydrogels mimicking biochemical and biomechanical microenvironments in native tissue are needed for successful cardiac tissue regeneration. These hydrogels not only retain cells in the infarcted area, but also provide support for restoring myocardial wall stress and cell survival and functioning. Many hydrogels, including natural polymer hydrogels, synthetic polymer hydrogels, and natural/synthetic hybrid hydrogels are employed for cardiac tissue engineering. In this review, types of hydrogels used for cardiac tissue engineering are briefly introduced. Their advantages and disadvantages are discussed. Furthermore, strategies for cardiac regeneration using hydrogels are reviewed. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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<p>The aligned structure of cardiomyocytes in the myocardium [<a href="#b8-polymers-03-00740" class="html-bibr">8</a>]. The alignment is uniform in each layer with a gradual transition of alignment between layers from the endocardium to the epicardium.</p> Full article ">
<p>Frank-Starling law for mechanical behaviors of the ventricle muscle [<a href="#b9-polymers-03-00740" class="html-bibr">9</a>-<a href="#b11-polymers-03-00740" class="html-bibr">11</a>].</p> Full article ">
<p>Myocardial infarction and the remodeling process: (<b>A</b>) normal myocardium, with clear nucleus and elongated actin fibers and (<b>B</b>) 12–18 h post-MI, the nucleus starts to dissociate and a wavy actin fiber emerge at the infracted sites; (<b>C</b>) 24 h post-MI, macrophages (cells with multiple nuclei) start to penetrate and the dead cells are removed by phagocytosis; (<b>D</b>) 3 weeks post-MI, fibroblasts are attracted to the infracted area and start to deposit collagen fibers in the area; (<b>E</b>) 3 months post-MI, the remodeling process is nearly complete. Collagen scar tissue has formed [<a href="#b12-polymers-03-00740" class="html-bibr">12</a>].</p> Full article ">
<p>Decellularized heart matrix by H&amp;E staining: (<b>A</b>) intact acellular matrix before lyophilization, a porous structure can be clearly seen; (<b>B</b>) acellular matrix before being milled; (<b>C</b>) normal heart tissue before decellularization [<a href="#b22-polymers-03-00740" class="html-bibr">22</a>]. Scale bars are 100 μm.</p> Full article ">
<p>The pacing signal of cultured cardiomyocytes in an (<b>A</b>) “aligned” and (<b>B</b>) “isotropic” construct. The contract force generated by cells on aligned fibers shows a higher force compared to those on isotropic fibers under electric stimulus (<b>C</b>) and Lillies' trichrome staining for (<b>D</b>) “isotropic” and (<b>E</b>) “aligned” samples. The aligned cell construct has a thicker cell layer compared to that of isotropic structure [<a href="#b28-polymers-03-00740" class="html-bibr">28</a>].</p> Full article ">
<p>Poly(ethylene glycol) molecular structure: (<b>A</b>) PEG; (<b>B</b>) PEG-diacrylate.</p> Full article ">
<p>Chemical structure of PHEMA.</p> Full article ">
<p>Chemical structure of (<b>A</b>) polyacrylamide, (<b>B</b>) polymethacrylamide, and (<b>C</b>) poly(N-isopropylacrylamide).</p> Full article ">
<p>Human umbilical endothelial cells cultured on bare PEG gel (left) and PEG/RGD gel (right) surfaces [<a href="#b50-polymers-03-00740" class="html-bibr">50</a>]. Scale bars are 100 μm. Cells on RGD modified PEG surface showed an elongated morphology, while the cells on the bare PEG surface showed a round morphology.</p> Full article ">
1875 KiB  
Article
Multiblock Copolymers of Styrene and Butyl Acrylate via Polytrithiocarbonate-Mediated RAFT Polymerization
by Bastian Ebeling and Philipp Vana
Polymers 2011, 3(2), 719-739; https://doi.org/10.3390/polym3020719 - 31 Mar 2011
Cited by 23 | Viewed by 13868
Abstract
When linear polytrithiocarbonates as Reversible Addition-Fragmentation chain Transfer (RAFT) agents are employed in a radical polymerization, the resulting macromolecules consist of several homogeneous polymer blocks, interconnected by the functional groups of the respective RAFT agent. Via a second polymerization with another monomer, multiblock [...] Read more.
When linear polytrithiocarbonates as Reversible Addition-Fragmentation chain Transfer (RAFT) agents are employed in a radical polymerization, the resulting macromolecules consist of several homogeneous polymer blocks, interconnected by the functional groups of the respective RAFT agent. Via a second polymerization with another monomer, multiblock copolymers—polymers with alternating segments of both monomers—can be prepared. This strategy was examined mechanistically in detail based on subsequent RAFT polymerizations of styrene and butyl acrylate. Size-exclusion chromatography (SEC) of these polymers showed that the examined method yields low-disperse products. In some cases, resolved peaks for molecules with different numbers of blocks (polymer chains separated by the trithiocarbonate groups) could be observed. Cleavage of the polymers at the trithiocarbonate groups and SEC analysis of the products showed that the blocks in the middle of the polymers are longer than those at the ends and that the number of blocks corresponds to the number of functional groups in the initial RAFT agent. Furthermore, the produced multiblock copolymers were analyzed via differential scanning calorimetry (DSC). This work underlines that the examined methodology is very well suited for the synthesis of well-defined multiblock copolymers. Full article
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<p>General structure of the employed RAFT agents.</p> Full article ">
<p><b>(a)</b> SEC curve (solid line: RI signal, dashed line: UV signal) of the polyfunctional RAFT agent <b>A</b>; <b>(b)</b> SEC curves (solid lines: RI signal, dashed lines: UV signal) of the polyfunctional RAFT agents <b>C</b> (red, obtained by rinsing with CS<sub>2</sub>) and <b>D</b> (black, obtained by rinsing with THF).</p> Full article ">
<p><b>(a)</b> <span class="html-italic">M̅</span><sub>n</sub> (black circles) and polydispersity index (PDI, red squares, RI signal) as a function of monomer conversion for polymerization <b>4</b>; dashed line: linear regression for <span class="html-italic">M̅</span><sub>n</sub>; <b>(b)</b> Corresponding SEC curves (solid lines: RI signal, dashed lines: UV signal) and SEC curve of the employed RAFT agent <b>C</b>.</p> Full article ">
<p>SEC curves (solid lines: RI signal, dashed lines: UV signal, calibration for polystyrene) for copolymerization <b>III</b>.</p> Full article ">
<p><b>(a)</b> SEC curves of polymer <b>1d</b> before (dashed line) and after (solid line) aminolysis; <b>(b)</b> SEC curves of polymer <b>2d</b> before (dashed line) and after (solid line) aminolysis. (The numbers in the diagrams indicate the maxima of the number-weighted distributions.); <b>(c)</b> SEC curves of polymer <b>5d</b> before (dashed line) and after (solid line) aminolysis. Figure 6. DSC curves of polymer samples 6c and Va-Vd; curves are shifted vertically for clarity.</p> Full article ">
<p>DSC curves of polymer samples <b>6c</b> and <b>Va</b>–<b>Vd</b>; curves are shifted vertically for clarity.</p> Full article ">
<p>General strategy for the synthesis of multiblock copolymers using polytrithiocarbonate RAFT agents.</p> Full article ">
1939 KiB  
Article
Low Molecular Weight pDMAEMA-block-pHEMA Block-Copolymers Synthesized via RAFT-Polymerization: Potential Non-Viral Gene Delivery Agents?
by Olga Samsonova, Christian Pfeiffer, Markus Hellmund, Olivia M. Merkel and Thomas Kissel
Polymers 2011, 3(2), 693-718; https://doi.org/10.3390/polym3020693 - 28 Mar 2011
Cited by 69 | Viewed by 14419
Abstract
The aim of this study was to investigate non-viral pDNA carriers based on diblock-copolymers consisting of poly(2-(dimethyl amino)ethyl methacrylate) (pDMAEMA) and poly(2-hydroxyethyl methacrylate) (pHEMA). Specifically the block-lengths and molecular weights were varied to determine the minimal requirements for transfection. Such vectors should allow [...] Read more.
The aim of this study was to investigate non-viral pDNA carriers based on diblock-copolymers consisting of poly(2-(dimethyl amino)ethyl methacrylate) (pDMAEMA) and poly(2-hydroxyethyl methacrylate) (pHEMA). Specifically the block-lengths and molecular weights were varied to determine the minimal requirements for transfection. Such vectors should allow better transfection at acceptable toxicity levels and the entire diblock-copolymer should be suitable for renal clearance. For this purpose, a library of linear poly(2-(dimethyl amino)ethyl methacrylate-block-poly(2-hydroxyl methacrylate) (pDMAEMA-block-pHEMA) copolymers was synthesized via RAFT (reversible addition-fragmentation chain transfer) polymerization in a molecular weight (Mw) range of 17–35.7 kDa and analyzed using 1H and 13C NMR (nuclear magnetic resonance), ATR (attenuated total reflectance), GPC (gel permeation chromatography) and DSC (differential scanning calorimetry). Copolymers possessing short pDMAEMA-polycation chains were 1.4–9.7 times less toxic in vitro than polyethylenimine (PEI) 25 kDa, and complexed DNA into polyplexes of 100–170 nm, favorable for cellular uptake. The DNA-binding affinity and polyplex stability against competing polyanions was comparable with PEI 25 kDa. The zeta-potential of polyplexes of pDMAEMA-grafted copolymers remained positive (+15–30 mV). In comparison with earlier reported low molecular weight homo pDMAEMA vectors, these diblock-copolymers showed enhanced transfection efficacy under in vitro conditions due to their lower cytotoxicity, efficient cellular uptake and DNA packaging. The homo pDMAEMA115 (18.3 kDa) self-assembled with DNA into small positively charged polyplexes, but was not able to transfect cells. The grafting of 6 and 57 repeating units of pHEMA (0.8 and 7.4 kDa) to pDMAEMA115 increased the transfection efficacy significantly, implying a crucial impact of pHEMA on vector-cell interactions. The intracellular trafficking, in vivo transfection efficacy and kinetics of low molecular weight pDMAEMA-block-pHEMA are subject of ongoing studies. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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Graphical abstract

Graphical abstract
Full article ">
<p><sup>1</sup>H NMR spectra of (<b>A</b>) CPT in CDCl<sub>3</sub>, (<b>B</b>) pDMAEMA in D<sub>2</sub>O and (<b>C</b>) pDMAEMA-<span class="html-italic">block</span>-pHEMA in D<sub>2</sub>O; the numbers designate the atoms within the molecules.</p> Full article ">
<p>A, B The library of diblock copolymers sorted according to an increasing amount of pDMAEMA (<b>A</b>). The proportion and weight of each block-part in the various pDMAEMA-pHEMA copolymers were calculated according to the repeating units (<b>B</b>).</p> Full article ">
<p><b>A, B, C, D.</b> Electrophoretic mobility of free and complexed DNA in agarose gel (Each row starts with free DNA and is continued by N/P 0.5, 1, 2 complexes with the indicated polymers. Polymers are separated by white vertical lines).</p> Full article ">
<p><b>A, B, C, D.</b> Heparin assay: displacement of DNA from polyplexes with polyanion on agarose gel.</p> Full article ">
<p><b>A, B.</b> Polyplex sizes and zeta potentials of all synthesized polymers in isotonic glucose. Significant differences in size and zeta potential comparing N/P 15 <span class="html-italic">versus</span> all other N/P 10 and 20 of one polymer according to two-way ANOVA are labeled (***p &lt; 0.001, **p &lt; 0.005 and *p &lt; 0.01).</p> Full article ">
<p><b>A, B.</b> Polyplex sizes and zeta potential of pDMAEMA<sub>115</sub> derivatives in isotonic glucose.</p> Full article ">
<p>Polyplex behavior of homo- and diblock-copolymers in isotonic glucose and NaCl as a function of incubation time.</p> Full article ">
<p><b>A, B.</b> Cytotoxic effects of copolymers in L929 mouse fibroblasts after incubation for 24 h, ***p &lt; 0.001 &amp; **p &lt; 0.01 according to two-way ANOVA.</p> Full article ">
<p>Cytotoxicity (MTT) of pDNA-polymer complexes, N/P 15 in L929, exposed for 4 h.</p> Full article ">
955 KiB  
Article
Spectroscopic Investigation of Composite Polymeric and Monocrystalline Systems with Ionic Conductivity
by Darya V. Radziuk and Helmuth Möhwald
Polymers 2011, 3(2), 674-692; https://doi.org/10.3390/polym3020674 - 24 Mar 2011
Cited by 13 | Viewed by 8235
Abstract
The conductivity mechanism is studied in the LiCF3SO3-doped polyethylene oxide by monitoring the vibrations of sulfate groups and mobility of Li+ ion along the polymeric chain at different EO/Li molar ratios in the temperature range from 16 to [...] Read more.
The conductivity mechanism is studied in the LiCF3SO3-doped polyethylene oxide by monitoring the vibrations of sulfate groups and mobility of Li+ ion along the polymeric chain at different EO/Li molar ratios in the temperature range from 16 to 90 °С. At the high EO/Li ratio (i.e., 30), the intensity of bands increases and a triplet appears at 1,045 cm−1, indicating the presence of free anions, ionic pairs and aggregates. The existence of free ions in the polymeric electrolyte is also proven by the red shift of bands in Raman spectra and a band shift to the low frequency Infra-red region at 65 < T < 355 °С. Based on quantum mechanical modeling, (method MNDO/d), the energies (minimum and maximum) correspond to the most probable and stable positions of Li+ along the polymeric chain. At room temperature, Li+ ion overcomes the intermediate state (minimum energy) through non-operating transitions (maximum energy) due to permanent intrapolymeric rotations (rotation of C, H and O atoms around each other). In solid electrolyte (Li2SO4) the mobility of Li+ ions increases in the temperature range from 20 to 227 °С, yielding higher conductivity. The results of the present work can be practically applied to a wide range of compact electronic devices, which are based on polymeric or solid electrolytes. Full article
(This article belongs to the Special Issue New Polymer Synthesis Reactions)
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<p>The diagram illustrating conductivity σ (S·cm<sup>−1</sup>), which compares polyethylene oxide with other materials.</p> Full article ">
<p>Raman spectra of LiCF<sub>3</sub>SO<sub>3</sub> + (EG)<sub>11</sub>DME (EO/Li = 10) at room temperature. (EG)<sub>11</sub>DME is dimethyl ethylene glycol with the chain length n = 11 and EO/Li = 10 is the inverse molar ratio of LiCF<sub>3</sub>SO<sub>3</sub> to elements of ethylene oxide oligomer. Where ‘vs’, ‘s’ and ‘m’ are spectral bands with ‘very strong’, ‘strong’ and ‘medium’ intensity, respectively. The assignments ‘sh’ indicates a band shoulder, ‘w’—a bandwidth, ‘<span class="html-italic">δ</span>’ and ‘<span class="html-italic">v</span>’—the deformations and valency vibrations in the corresponding molecular groups, respectively.</p> Full article ">
<p>Raman spectra of dimethyl ethylene glycol with the chain lengths 2 (<b>A</b>) and 11 (<b>B</b>) (EG)<sub>2</sub>DME and (EG)<sub>11</sub>DME and EO/Li = 10 inverse molar ratio of LiCF<sub>3</sub>SO<sub>3</sub> to elements of ethylene oxide oligomer in a temperature range of 289 K to 363 K.</p> Full article ">
<p>Raman spectra of dimethyl ethylene glycol with chain lengths 2 (<b>A</b>) and 11 (<b>B</b>) LiCF<sub>3</sub>SO<sub>3</sub> + (EG)<sub>n</sub>DME at a concentration of EO/Li inverse molar ratio of LiCF<sub>3</sub>SO<sub>3</sub> to elements of ethylene oxide oligomer from 10 to 30 at room temperature (A).</p> Full article ">
<p>Band decomposition of symmetric valence vibration of SO<sub>3</sub><sup>−</sup> in LiCF<sub>3</sub>SO<sub>3</sub> + (EG)<sub>11</sub>DME at EO/Li = 10 at room temperature.</p> Full article ">
<p>The dependence of Li<sub>2</sub>SO<sub>4</sub> ν<sub>1</sub> (469 cm<sup>−1</sup>), ν<sub>2</sub> (646 cm<sup>−1</sup>) and ν<sub>3</sub> (1,123 cm<sup>−1</sup>) vibrations on temperature in the range from 55 to 300 °C.</p> Full article ">
<p>The quantum mechanical modeling (MNDO/d method) of the Li<sup>+</sup> ion locations along the polymeric chain of polyethylene oxide with the chain fragment [CH<sub>2</sub>-CH<sub>2</sub>-O]<sub>n</sub> (n = 4). The capital letters A, C, E, G and J are assigned to the states of Li<sup>+</sup> ion with the local minimum energy (<span class="html-italic">i.e.</span>, E<sub>A</sub> = −3,287.18 kkal·mol<sup>−1</sup>, EC= −3,286.61 kkal·mol<sup>−1</sup>, E<sub>E</sub>= −3,286.82 kkal·mol<sup>−1</sup>, E<sub>G</sub>= −3,286.60 kkal·mol<sup>−1</sup>, E<sub>J</sub>= −3,318.75 kkal·mol<sup>−1</sup>). The intermediate states of Li<sup>+</sup> ion along the polymeric chain fragment are ascribed to B, D, F, H and K states with the local minimum energy (<span class="html-italic">i.e.</span>, E<sub>B</sub> = −3,304.13 kkal·mol<sup>−1</sup>, E<sub>D</sub>= −3,304.63 kkal·mol<sup>−1</sup>, E<sub>F</sub>= −3,304.61 kkal·mol<sup>−1</sup>, E<sub>H</sub>= −3,319.30 kkal·mol<sup>−1</sup>, E<sub>K</sub>= −3,330.75 kkal·mol<sup>−1</sup>).</p> Full article ">
<p>The quantum mechanical calculation of the Li<sup>+</sup> ion local energies with the non-operating transitions L and M (E<sub>L</sub>= −3,283.80 kkal·mol<sup>−1</sup> and E<sub>M</sub>= −3,287.19 kkal·mol<sup>−1</sup>) which exist between the intermediate states (B, <span class="html-italic">etc.</span>).</p> Full article ">
943 KiB  
Review
Routes to Nanoparticle-Polymer Superlattices
by Sara Mehdizadeh Taheri, Steffen Fischer and Stephan Förster
Polymers 2011, 3(2), 662-673; https://doi.org/10.3390/polym3020662 - 24 Mar 2011
Cited by 30 | Viewed by 11073
Abstract
Nanoparticles can self-assemble into highly ordered two- and three-dimensional superlattices. For many practical applications these assemblies need to be integrated into polymeric matrices to provide stability and function. By appropriate co-assembly of nanoparticles and polymers it has become possible to tailor the nanoparticle [...] Read more.
Nanoparticles can self-assemble into highly ordered two- and three-dimensional superlattices. For many practical applications these assemblies need to be integrated into polymeric matrices to provide stability and function. By appropriate co-assembly of nanoparticles and polymers it has become possible to tailor the nanoparticle superlattice structure via the length and stiffness of the polymer chains. The present article outlines and discusses established routes to nanoparticle-polymer superlattices. Recent progress has been remarkable so that the integration into functional devices has become the next challenge. Full article
(This article belongs to the Special Issue Nano-Structures of Block Copolymers)
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<p>(<b>a</b>) TEM image of a two-dimensional array of gold nanoparticles [<a href="#b1-polymers-03-00662" class="html-bibr">1</a>] and (<b>b</b>) SEM-image of a three-dimensional, highly ordered FePt nanoparticle microcrystal [<a href="#b3-polymers-03-00662" class="html-bibr">3</a>]. From Ref. [<a href="#b1-polymers-03-00662" class="html-bibr">1</a>] and [<a href="#b3-polymers-03-00662" class="html-bibr">3</a>].</p> Full article ">
<p>Various routes to nanoparticle superlattices. The two major routes involve the use of preformed nanoparticles that are subsequently integrated into a polymer matrix (1) or the use of polymer microdomains to synthesize nanoparticles from precursors within the polymer matrix (2). Both routes are designed to finally lead to the controlled assembly of nanoparticle-polymer superlattices. The numbers indicate the corresponding figures in the manuscript.</p> Full article ">
<p>Block copolymer micelles filled with precursor (<b>a</b>), micelles with many gold nanoparticles after fast reduction (<b>b</b>), and preformed CdS nanoparticles solubilized into block copolymer microdomains (<b>c</b>). From Refs. [<a href="#b14-polymers-03-00662" class="html-bibr">14</a>] and [<a href="#b19-polymers-03-00662" class="html-bibr">19</a>].</p> Full article ">
<p>Nanoparticles (<b>a</b>) and after phase separation (<b>b</b>), and after growth and fusion (<b>c</b>) in block copolymer superlattices. The large volume fraction of nanoparticles allows the fusion into nanowires. From Ref. [<a href="#b16-polymers-03-00662" class="html-bibr">16</a>].</p> Full article ">
<p>SEM-images (<b>a</b>, <b>b</b>) of a monolayer of gold-nanoparticles obtained by precursor reduction in block copolymer micelles. The distance between the nanoparticles can be controlled via the polymer block length. From Ref. [<a href="#b11-polymers-03-00662" class="html-bibr">11</a>].</p> Full article ">
<p>SEM-image of silica nanoparticles obtained from a sol/gel synthesis in micellar cores. From Ref. [<a href="#b17-polymers-03-00662" class="html-bibr">17</a>].</p> Full article ">
<p>TEM-images of bare nanoparticles covered with low molecular weight ligand (oleic acid) (<b>a</b>) and polystyrene coated nanoparticles (<b>b</b>). The distance between the nanoparticles can be controlled via the polymer chain length. From Ref. [<a href="#b25-polymers-03-00662" class="html-bibr">25</a>].</p> Full article ">
<p>SEM-image of a highly ordered two-dimensional magnetite/polystyrene monolayer (<b>a</b>) and SAXS-curves of ordered three-dimensional CdSe/polystyrene nanocomposites (<b>b</b>); where the distance between the nanoparticles was controlled via the chain length of the polystyrene chains. From Ref. [<a href="#b26-polymers-03-00662" class="html-bibr">26</a>].</p> Full article ">
<p>TEM-image of highly ordered two-dimensional gold/DNA monolayers [<a href="#b31-polymers-03-00662" class="html-bibr">31</a>] (<b>a</b>) and SAXS-curves of ordered three-dimensional gold/DNA nanocomposites (<b>b</b>); where the distance between the nanoparticles was controlled via the number of base pairs of the DNA-chain [<a href="#b32-polymers-03-00662" class="html-bibr">32</a>]. From Refs. [<a href="#b31-polymers-03-00662" class="html-bibr">31</a>] and [<a href="#b32-polymers-03-00662" class="html-bibr">32</a>].</p> Full article ">
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