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Polymers, Volume 3, Issue 1 (March 2011), Pages 1-661

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Open AccessReview Recombinant Spider Silks—Biopolymers with Potential for Future Applications
Polymers 2011, 3(1), 640-661; https://doi.org/10.3390/polym3010640
Received: 17 December 2010 / Revised: 12 February 2011 / Accepted: 14 March 2011 / Published: 17 March 2011
Cited by 42 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
Nature has evolved a range of materials that compete with man-made materials in physical properties; one of these is spider silk. Silk is a fibrous material that exhibits extremely high strength and toughness with regard to its low density. In this review we
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Nature has evolved a range of materials that compete with man-made materials in physical properties; one of these is spider silk. Silk is a fibrous material that exhibits extremely high strength and toughness with regard to its low density. In this review we discuss the molecular structure of spider silk and how this understanding has allowed the development of recombinant silk proteins that mimic the properties of natural spider silks. Additionally, we will explore the material morphologies and the applications of these proteins. Finally, we will look at attempts to combine the silk structure with chemical polymers and how the structure of silk has inspired the engineering of novel polymers. Full article
(This article belongs to the Special Issue Bioinspired Polymers)
Open AccessArticle Reusable Polymer-Supported Terpyridine Palladium Complex for Suzuki-Miyaura, Mizoroki-Heck, Sonogashira, and Tsuji-Trost Reaction in Water
Polymers 2011, 3(1), 621-639; https://doi.org/10.3390/polym3010621
Received: 10 January 2011 / Revised: 8 February 2011 / Accepted: 9 March 2011 / Published: 14 March 2011
Cited by 22 | PDF Full-text (682 KB) | HTML Full-text | XML Full-text
Abstract
A novel heterogeneous transition-metal catalyst comprising a polymer-supported terpyridine palladium(II) complex was prepared and found to promote the Suzuki-Miyaura, Mizoroki-Heck, Sonogashira, and Tsuji-Trost, reactions in water under aerobic conditions with a high to excellent yield. The catalyst was recovered by simple filtration and
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A novel heterogeneous transition-metal catalyst comprising a polymer-supported terpyridine palladium(II) complex was prepared and found to promote the Suzuki-Miyaura, Mizoroki-Heck, Sonogashira, and Tsuji-Trost, reactions in water under aerobic conditions with a high to excellent yield. The catalyst was recovered by simple filtration and directly reused several times without loss of catalytic activity. Full article
(This article belongs to the Special Issue New Polymer Synthesis Reactions)
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Open AccessArticle Modulating Biofunctional starPEG Heparin Hydrogels by Varying Size and Ratio of the Constituents
Polymers 2011, 3(1), 602-620; https://doi.org/10.3390/polym3010602
Received: 3 December 2010 / Revised: 24 February 2011 / Accepted: 9 March 2011 / Published: 14 March 2011
Cited by 21 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Heparin and four-armed, end-functionalized polyethylene glycol (starPEG) were recently combined in sets of covalently linked biohybrid hydrogel networks capable of directing various therapeutically relevant cell types. To extend the variability and applicability of this novel biomaterials platform, the influence of size and molar
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Heparin and four-armed, end-functionalized polyethylene glycol (starPEG) were recently combined in sets of covalently linked biohybrid hydrogel networks capable of directing various therapeutically relevant cell types. To extend the variability and applicability of this novel biomaterials platform, the influence of size and molar ratio of the two building blocks on the hydrogel properties was investigated in the present study. Heparin and starPEG were converted in various molar ratios and in different molecular weights to tune swelling, stiffness and pore size of the obtained polymer networks. Hydrogels with a range of elastic moduli could be generated by controlling either the crosslinking density or the chain length of the starPEG, whereas altering the molecular mass of heparin did not significantly affect hydrogel strength. The concentration of heparin in the swollen gels was found to be nearly invariant at varying crosslinking degrees for any given set of building blocks but adjustable by the size of the building blocks. Since heparin is the base for all biofunctionalization schemes of the gels these findings lay the ground for an even more versatile customization of this powerful new class of biomaterials. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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Open AccessArticle Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol)/Sodium Polyacrylate/Salts
Polymers 2011, 3(1), 587-601; https://doi.org/10.3390/polym3010587
Received: 15 February 2011 / Accepted: 7 March 2011 / Published: 9 March 2011
Cited by 27 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text
Abstract
Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na2SO4, sodium adipate and sodium azelate) and salt concentrations on the position of
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Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na2SO4, sodium adipate and sodium azelate) and salt concentrations on the position of the binodal curve were investigated. The investigated PEG molecules had a molar mass of 2,000 to 8,000 g/mol, while that of NaPAA was 8,000 g/mol. Experimental phase diagrams, and tie lines and calculated phase diagrams, based on Flory-Huggins theory of polymer solutions are presented. Due to strong enthalpic and entropic balancing forces, the hydrophobicity of the added salt has a strong influence on the position of the binodal, which could be reproduced by model calculations. Full article
(This article belongs to the Special Issue Polyelectrolytes)
Open AccessArticle PLGA-Based Microparticles for the Sustained Release of BMP-2
Polymers 2011, 3(1), 571-586; https://doi.org/10.3390/polym3010571
Received: 9 December 2010 / Revised: 18 January 2011 / Accepted: 24 February 2011 / Published: 1 March 2011
Cited by 36 | PDF Full-text (1063 KB) | HTML Full-text | XML Full-text
Abstract
The development of growth factor delivery strategies to circumvent the burst release phenomenon prevalent in most current systems has driven research towards encapsulating molecules in resorbable polymer matrices. For these polymer release techniques to be efficacious in a clinical setting, several key points
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The development of growth factor delivery strategies to circumvent the burst release phenomenon prevalent in most current systems has driven research towards encapsulating molecules in resorbable polymer matrices. For these polymer release techniques to be efficacious in a clinical setting, several key points need to be addressed. This present study has investigated the encapsulation of the growth factor, BMP-2 within PLGA/PLGA-PEG-PLGA microparticles. Morphology, size distribution, encapsulation efficiency and release kinetics were investigated and we have demonstrated a sustained release of bioactive BMP-2. Furthermore, biocompatibility of the PLGA microparticles was established and released BMP-2 was shown to promote the differentiation of MC3T3-E1 cells towards the osteogenic lineage to a greater extent than osteogenic supplements (as early as day 10 in culture), as determined using alkaline phosphatase and alizarin red assays. This study showcases a potential BMP-2 delivery system which may now be translated into more complex delivery systems, such as 3D, mechanically robust scaffolds for bone tissue regeneration applications. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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Open AccessArticle Synthesis and Characterization of Poly(3-hexylthiophene)-b-Polystyrene for Photovoltaic Application
Polymers 2011, 3(1), 558-570; https://doi.org/10.3390/polym3010558
Received: 10 January 2011 / Revised: 12 February 2011 / Accepted: 24 February 2011 / Published: 1 March 2011
Cited by 25 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
Abstract
Poly(3-hexylthiophene)-block-polystyrene (P3HT-b-PS) was synthesized by Suzuki coupling reaction between P3HT and PS, prepared by Grignard metathesis polymerization and atom transfer radical polymerization (ATRP), respectively. The formation of block copolymer was confirmed by gel permeation chromatography (GPC) and NMR. Differential
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Poly(3-hexylthiophene)-block-polystyrene (P3HT-b-PS) was synthesized by Suzuki coupling reaction between P3HT and PS, prepared by Grignard metathesis polymerization and atom transfer radical polymerization (ATRP), respectively. The formation of block copolymer was confirmed by gel permeation chromatography (GPC) and NMR. Differential scanning calorimetry (DSC) thermogram of block copolymers showed glass transition of PS block and melting/crystallization of P3HT block, suggesting a microphase separated structure, which was also confirmed by atomic force microscopy (AFM) images and UV-vis absorption spectra. The annealing effect on the morphology of the composite films consisting of P3HT-b-PS and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was investigated. Photovoltaic cells fabricated using P3HT-b-PS and PCBM were evaluated. Full article
Open AccessArticle The Challenge of Synthesizing Oligomers for Molecular Wires
Polymers 2011, 3(1), 545-557; https://doi.org/10.3390/polym3010545
Received: 17 January 2011 / Revised: 6 February 2011 / Accepted: 23 February 2011 / Published: 28 February 2011
Cited by 5 | PDF Full-text (476 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Controlling the size of the oligomer and introducing functional groups at the ends of the oligomer that allow it to react with separate electrodes are critical issues when preparing materials for molecular wires. We demonstrate a general synthetic approach to oligophenylenevinylene (OPV) derivative
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Controlling the size of the oligomer and introducing functional groups at the ends of the oligomer that allow it to react with separate electrodes are critical issues when preparing materials for molecular wires. We demonstrate a general synthetic approach to oligophenylenevinylene (OPV) derivative molecules with a molecular length up to 9–10 nm which allow for the introduction of aromatic thioacetate functionality in fully conjugated oligomer systems. Oligomers containing 3–15 phenyl units were synthesized by step wise Horner-Wadsworth-Emmons (HWE) reactions of a bifunctional OPV-monomer, which demonstrated good control of the size of the OPVs. Workup after each reaction step ensures a high purity of the final products. End group functionalization was introduced as a last step. Full article
(This article belongs to the Special Issue Single Molecular Wire)
Open AccessArticle A 3D Electroactive Polypyrrole-Collagen Fibrous Scaffold for Tissue Engineering
Polymers 2011, 3(1), 527-544; https://doi.org/10.3390/polym3010527
Received: 5 January 2011 / Revised: 6 February 2011 / Accepted: 24 February 2011 / Published: 28 February 2011
Cited by 22 | PDF Full-text (571 KB) | HTML Full-text | XML Full-text
Abstract
Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal or muscular cells. Here we report on the fabrication of polypyrrole-incorporated collagen-based fibers via interfacial polyelectrolyte complexation (IPC).
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Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal or muscular cells. Here we report on the fabrication of polypyrrole-incorporated collagen-based fibers via interfacial polyelectrolyte complexation (IPC). The mean ultimate tensile strength of the fibers is 304.0 ± 61.0 MPa and the Young’s Modulus is 10.4 ± 4.3 GPa. Human bone marrow-derived mesenchymal stem cells (hMSCs) are cultured on the fibers in a proliferating medium and stimulated with an external electrical pulse generator for 5 and 10 days. The effects of polypyrrole in the fiber system can be observed, with hMSCs adopting a neuronal-like morphology at day 10, and through the upregulation of neural markers, such as noggin, MAP2, neurofilament, β tubulin III and nestin. This study demonstrates the potential of this fiber system as an attractive 3D scaffold for tissue engineering, where collagen is present on the fiber surface for cellular adhesion, and polypyrrole is encapsulated within the fiber for enhanced electrical communication in cell-substrate and cell-cell interactions. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
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Open AccessReview Biopolymers for Hard and Soft Engineered Tissues: Application in Odontoiatric and Plastic Surgery Field
Polymers 2011, 3(1), 509-526; https://doi.org/10.3390/polym3010509
Received: 23 December 2010 / Revised: 24 January 2011 / Accepted: 15 February 2011 / Published: 28 February 2011
Cited by 8 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
Abstract
The goal of modern dentistry and plastic surgery is to restore the patient to normal function, health and aesthetics, regardless of the disease or injury to the stomatognathic and cutaneous system respectively. In recent years tissue engineering and regenerative medicine have yielded many
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The goal of modern dentistry and plastic surgery is to restore the patient to normal function, health and aesthetics, regardless of the disease or injury to the stomatognathic and cutaneous system respectively. In recent years tissue engineering and regenerative medicine have yielded many novel tissue replacements and implementation strategies. Scientific advances in biomaterials, stem cell isolation, growth and differentiation factors and biomimetic environments have created unique opportunities to fabricate tissues in the laboratory. Repairing of bone and skin is likely to become of clinical interest when three dimensional tissue reconstructive procedures and the appropriate supporting biomimetic materials are correctly assembled. In the present review, we provide an overview of the most promising biopolymers that may find clinical application in dento-maxillo-facial and plastic surgery. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
Open AccessArticle Cellulose Chemistry Meets Click Chemistry: Syntheses and Properties of Cellulose-Based Glycoclusters with High Structural Homogeneity
Polymers 2011, 3(1), 489-508; https://doi.org/10.3390/polym3010489
Received: 6 January 2011 / Accepted: 6 February 2011 / Published: 24 February 2011
Cited by 19 | PDF Full-text (967 KB) | HTML Full-text | XML Full-text
Abstract
b-1,4-Glucans having oligosaccharide appendages (O-/N-linked b-maltoside and O-/N-linked b-lactoside) at 6C positions of all repeating units can be readily prepared from cellulose through a two step strategy composed of: (1) regio-selective and quantitative bromination/azidation to afford
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b-1,4-Glucans having oligosaccharide appendages (O-/N-linked b-maltoside and O-/N-linked b-lactoside) at 6C positions of all repeating units can be readily prepared from cellulose through a two step strategy composed of: (1) regio-selective and quantitative bromination/azidation to afford 6-azido-6-deoxycellulose; and (2) the subsequent Cu+-catalyzed coupling with oligosaccharides having terminal alkyne. The resultant cellulose derivatives showed improved water solubility in comparison to native cellulose; they, however, bound to carbohydrate-binding proteins in a rather non-specific manner. Molecular dynamics calculations revealed that these properties are attributable to rigid sheet-like structures of the cellulose derivatives and the subsequent exposure of their hydrophobic moieties to solvents. Full article
(This article belongs to the Special Issue Click Chemistry in Polymer Science)
Open AccessReview Bioinspired Poly(2-oxazoline)s
Polymers 2011, 3(1), 467-488; https://doi.org/10.3390/polym3010467
Received: 30 November 2010 / Revised: 12 December 2010 / Accepted: 6 February 2011 / Published: 11 February 2011
Cited by 85 | PDF Full-text (1081 KB) | HTML Full-text | XML Full-text
Abstract
Poly(2-oxazoline)s are regarded as pseudopeptides, thus bioinspired polymers, due to their structural relationship to polypeptides. Materials and solution properties can be tuned by varying the side-chain (hydrophilic-hydrophobic, chiral, bioorganic, etc.), opening the way to advanced stimulus-responsive materials and complex colloidal structures. The
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Poly(2-oxazoline)s are regarded as pseudopeptides, thus bioinspired polymers, due to their structural relationship to polypeptides. Materials and solution properties can be tuned by varying the side-chain (hydrophilic-hydrophobic, chiral, bioorganic, etc.), opening the way to advanced stimulus-responsive materials and complex colloidal structures. The bioinspired “smart” solution and aggregation behavior of poly(2-oxazoline)s in aqueous environments are discussed in this review. Full article
(This article belongs to the Special Issue Bioinspired Polymers)
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Open AccessArticle Electrically Conductive Epoxy Adhesives
Polymers 2011, 3(1), 427-466; https://doi.org/10.3390/polym3010427
Received: 31 December 2010 / Accepted: 8 February 2011 / Published: 10 February 2011
Cited by 20 | PDF Full-text (795 KB) | HTML Full-text | XML Full-text
Abstract
Conductive adhesives are widely used in electronic packaging applications such as die attachment and solderless interconnections, component repair, display interconnections, and heat dissipation. The effects of film thickness as functions of filler volume fraction, conductive filler size, shape, as well as uncured adhesive
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Conductive adhesives are widely used in electronic packaging applications such as die attachment and solderless interconnections, component repair, display interconnections, and heat dissipation. The effects of film thickness as functions of filler volume fraction, conductive filler size, shape, as well as uncured adhesive matrix viscosity on the electrical conduction behavior of epoxy-based adhesives are presented in this work. For this purpose, epoxy-based adhesives were prepared using conductive fillers of different size, shape, and types, including Ni powder, flakes, and filaments, Ag powder, and Cu powder. The filaments were 20 μm in diameter, and 160 or 260 μm in length. HCl and H3PO4 acid solutions were used to etch and remove the surface oxide layers from the fillers. The plane resistance of filled adhesive films was measured using the four-point method. In all cases of conductive filler addition, the planar resistivity levels for the composite adhesive films increased when the film thickness was reduced. The shape of resistivity-thickness curves was negative exponential decaying type and was modeled using a mathematical relation. The relationships between the conductive film resistivities and the filler volume fractions were also derived mathematically based on the experimental data. Thus, the effects of surface treatment of filler particles, the type, size, shape of fillers, and the uncured epoxy viscosity could be included empirically by using these mathematical relations based on the experimental data. By utilizing the relations we proposed to model thickness-dependent and volume fraction-dependent conduction behaviors separately, we were able to describe the combined and coupled volume fraction-film thickness relationship mathematically based on our experimental data. Full article
(This article belongs to the Special Issue Conductive Polymers)
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Open AccessReview Electrospun Nanofibrous Materials for Neural Tissue Engineering
Polymers 2011, 3(1), 413-426; https://doi.org/10.3390/polym3010413
Received: 31 December 2010 / Revised: 24 January 2011 / Accepted: 28 January 2011 / Published: 9 February 2011
Cited by 61 | PDF Full-text (855 KB) | HTML Full-text | XML Full-text
Abstract
The use of biomaterials processed by the electrospinning technique has gained considerable interest for neural tissue engineering applications. The tissue engineering strategy is to facilitate the regrowth of nerves by combining an appropriate cell type with the electrospun scaffold. Electrospinning can generate fibrous
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The use of biomaterials processed by the electrospinning technique has gained considerable interest for neural tissue engineering applications. The tissue engineering strategy is to facilitate the regrowth of nerves by combining an appropriate cell type with the electrospun scaffold. Electrospinning can generate fibrous meshes having fiber diameter dimensions at the nanoscale and these fibers can be nonwoven or oriented to facilitate neurite extension via contact guidance. This article reviews studies evaluating the effect of the scaffold’s architectural features such as fiber diameter and orientation on neural cell function and neurite extension. Electrospun meshes made of natural polymers, proteins and compositions having electrical activity in order to enhance neural cell function are also discussed. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
Open AccessLetter A Pendulum-Like Motion of Nanofiber Gel Actuator Synchronized with External Periodic pH Oscillation
Polymers 2011, 3(1), 405-412; https://doi.org/10.3390/polym3010405
Received: 20 December 2010 / Accepted: 6 February 2011 / Published: 8 February 2011
Cited by 18 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we succeeded in manufacturing a novel nanofiber hydrogel actuator that caused a bending and stretching motion synchronized with external pH oscillation, based on a bromate/sulfite/ferrocyanide reaction. The novel nanofiber gel actuator was composed of electrospun nanofibers synthesized by copolymerizing acrylic
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In this study, we succeeded in manufacturing a novel nanofiber hydrogel actuator that caused a bending and stretching motion synchronized with external pH oscillation, based on a bromate/sulfite/ferrocyanide reaction. The novel nanofiber gel actuator was composed of electrospun nanofibers synthesized by copolymerizing acrylic acid and hydrophobic butyl methacrylate as a solubility control site. By changing the electrospinning flow rate, the nanofiber gel actuator introduced an anisotropic internal structure into the gel. Therefore, the unsymmetrical motion of the nanofiber actuator was generated. Full article
(This article belongs to the Special Issue Biofunctional Polymers for Medical Applications)
Open AccessArticle The Effect of Polyterpenol Thin Film Surfaces on Bacterial Viability and Adhesion
Polymers 2011, 3(1), 388-404; https://doi.org/10.3390/polym3010388
Received: 20 November 2010 / Revised: 23 December 2010 / Accepted: 25 January 2011 / Published: 28 January 2011
Cited by 24 | PDF Full-text (646 KB) | HTML Full-text | XML Full-text
Abstract
The nanometer scale surface topography of a solid substrate is known to influence the extent of bacterial attachment and their subsequent proliferation to form biofilms. As an extension of our previous work on the development of a novel organic polymer coating for the
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The nanometer scale surface topography of a solid substrate is known to influence the extent of bacterial attachment and their subsequent proliferation to form biofilms. As an extension of our previous work on the development of a novel organic polymer coating for the prevention of growth of medically significant bacteria on three-dimensional solid surfaces, this study examines the effect of surface coating on the adhesion and proliferation tendencies of Staphylococcus aureus and compares to those previously investigated tendencies of Pseudomonas aeruginosa on similar coatings. Radio frequency plasma enhanced chemical vapor deposition was used to coat the surface of the substrate with thin film of terpinen-4-ol, a constituent of tea-tree oil known to inhibit the growth of a broad range of bacteria. The presence of the coating decreased the substrate surface roughness from approximately 2.1 nm to 0.4 nm. Similar to P. aeruginosa, S. aureus presented notably different patterns of attachment in response to the presence of the surface film, where the amount of attachment, extracellular polymeric substance production, and cell proliferation on the coated surface was found to be greatly reduced compared to that obtained on the unmodified surface. This work suggests that the antimicrobial and antifouling coating used in this study could be effectively integrated into medical and other clinically relevant devices to prevent bacterial growth and to minimize bacteria-associated adverse host responses. Full article
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