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Electroactive polymer Actuators and Devices (EAPAD) 2009

作者： Vargantwar, Pruthesh H. Ghosh, Tushar K. Spontak, Richard J. Departments of Chemical and Biomolecular Engineering Raleigh NC 27695 United States Materials Science and Engineering Raleigh NC 27695 United States Fiber and Polymer Science Program North Carolina State University Raleigh NC 27695 United States

ISBN: (纸本)9780819475473

Nanostructured organic materials derived from block copolymers solvated by block-selective solvents have shown considerable potential as versatile dielectric elastomers. These materials can easily be tuned to achieve the mechanical and electrical properties required for actuator applications. They are lightweight and attractive due to their facile processing, robust properties and reliable performance. Their superb actuation behavior is realized when they are used as dielectric materials under actuation conditions promoting Maxwell compression, which produces large mechanical displacements, coupling efficiencies, and energy densities. These properties generally improve when the material is subjected to mechanical pre-strain. In most cases, mechanical pre-strain is needed to safely achieve application of a desired electrical field. Requisite pre-strain generally necessitates additional overhead in terms of weight and space for the device, and promotes changes in mechanical properties. In this study a new electroactive nanostructured polymer (ENP) is prepared from a triblock copolymer and a nonvolatile block-selective solvent, and evaluated as an actuator candidate. The copolymer exhibits reasonably high actuation strains (up to 70 area%) at relatively low electric fields and energy densities up to 50 kJ/m3 without pre-strain. These performance metrics exceed those reported for conventional dielectric materials such as the VHB acrylic elastomer, as well as those of ENPs derived from styrenic triblock copolymers under no pre-strain. © 2009 SPIE.

关键词： Block copolymers

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Nylon 6/silica composite and porous nylon 6 nanofibers prepared by electrospinning

Nylon 6/silica composite and porous nylon 6 nanofibers prepa...

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fiber Society 2009 Fall Meeting and Technical Conference

作者： Shi, Quan Vitchuli, Narendiran Nowak, Joshua McCord, Marian Bourham, Mohamed Zhang, Xiangwu Fiber and Polymer Science Program Department of Textile Engineering Chemistry and Science North Carolina State University RaleighNC27695-8301 United States Department of Nuclear Engineering North Carolina State University RaleighNC27695-7909 United States

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Effect of poly(γ-glutamic acid) on the gelation of Pluronic F127

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polymers for Advanced Technologies 2009年第8期20卷 703-705页

作者： Lee, Yen-Hsien Yang, Ming-Chien Program of Biomedical Engineering National Taiwan University of Science and Technology Taipei 106 Taiwan Department of Polymer Engineering National Taiwan University of Science and Technology Taipei 106 Taiwan

The gelation of Pluronic F127 aqueous solution was investigated in the presence of sodium poly(γ-glutamate) (PGA). The gelation temperature was determined based on the tube inversion technique. The gelation temperature increased greatly when the ratio of PGA to F127 was 0.2, and then decreased at higher ratios. The enthalpy of gelation (ΔHgel) was calculated based on the model of Eldridge and Ferry. A splitting in the model was observed when the PGA/F127 ratio was 0.2 which yielded both a maximum and a minimum of ΔHgel. These results indicate that PGA can significantly affect the gelation of F127. Copyright © 2008 John Wiley & Sons, Ltd.

关键词： Enthalpy

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Silk fibroin membranes from solvent-crystallized silk fibroin/gelatin blends: Effects of blend and solvent composition

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Materials science and engineering C 2007年第3期27卷 426-431页

作者： Gil, Eun S. Frankowski, David J. Hudson, Samuel M. Spontak, Richard J. Fiber and Polymer Science Program North Carolina State University Raleigh NC 27695 United States Department of Chemical and Biomolecular Engineering North Carolina State University Raleigh NC 27695 United States Department of Materials Science and Engineering North Carolina State University Raleigh NC 27695 United States

Protein membranes have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to induce SF crystallization. Amorphous blends of these polymers appear quasi-homogeneous, as discerned from visual observation, electron microscopy and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random-coil to β-sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, as discerned from FTIR spectroscopy and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been measured as functions of blend and solvent composition. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels or generate SF membranes for biomaterial, pharmaceutical and gas-separation purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally-responsive G/SF bioconjugates. © 2006 Elsevier B.V. All rights reserved.

关键词： Membranes

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Inside Front Cover: Field‐Driven Biofunctionalization of polymer fiber Surfaces during Electrospinning (Adv. Mater. 1/2007)

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Advanced Materials 2007年第1期19卷

作者： X.‐Y. Sun R. Shankar H. G. Börner T. K. Ghosh R. J. Spontak Department of Chemical & Biomolecular Engineering North Carolina State University Raleigh NC 27695 USA Department of Materials Science & Engineering North Carolina State University Raleigh NC 27695 USA Fiber & Polymer Science Program North Carolina State University Raleigh NC 27695 USA Department of Colloid Chemistry Max‐Planck Institute of Colloids & Interfaces 14424 Potsdam Germany

Surface‐biofunctionalized synthetic polymer fibers composed of a fiber‐forming host polymer and an oligopeptide conjugate can be prepared from electrospinning, report Spontak and co‐workers on p. 87. The conjugate consists of a polypeptide segment and a polymer block that is compatible with the host polymer. Because the more polarizable peptide segment migrates to the surface during electrospinning, peptide surface‐enrichment is achieved in a single step without further treatment.

关键词： Biocompatible materials Block copolymers Electrospinning fibers Peptides Poly(ethylene oxide) Surface functionalization

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Functionalized three-arm poly(ε-caprolactone) maleic acid microspheres for controlled protein release

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American Journal of Drug Delivery 2005年第4期3卷 253-267页

作者： Wu, Da-Qing Zhang, Xiang-Zheng Chu, Chih-Chang Fiber and Polymer Science Program Department of Textiles and Apparel and Biomedical Engineering Program Cornell University Ithaca NY United States Fiber and Polymer Science Program Department of Textiles and Apparel and Biomedical Engineering Program Cornell University Ithaca NY 14853-4401 United States

Introduction: The objective of this work was to fabricate a novel class of protein carriers from double-bond-functionalized multiarm poly(ε- caprolactone) maleic acid (PGCLM) microspheres and to examine protein sustained-release profiles in vitro over a period of a few months. Methods: The double-emulsion technique was used to formulate terminal functionalized three-arm PGCLM microspheres having three different types of functional groups (-OH, -COOH, and -C = C-), and one of the functional groups (>C = < bonds) was used to formulate surface-crosslinked microspheres (NPGCLM). Ovalbumin (OVA) was used as a model protein for examining its release profiles from PGCLM and NPGCLM microspheres in 0.1M phosphate-buffered saline (PBS) at 37°C. These microspheres were also characterized in terms of their morphology, size distribution, and stability. Results: The mean size of fabricated microspheres ranged from 21.9μm to 51.1μm. An OVA protein was successfully encapsulated into these biodegradable PGCLM microspheres with loading efficiency ranging from 34.2% to 46% (w/w), depending on the ratio of PGCLM to polyvinyl alcohol (PVA) stabilizer. Depending on the polymer to PVA stabilizer ratio, the cumulative OVA release % (w/w) in 0.1M PBS at 37°C ranged from 30% to 40% within 50 days. We further demonstrated the availability of the functional >C = C< bonds on the surface of PGCLM microspheres, which we expect could be used for either covalent binding of bioactive agents or imparting different chemical characteristics onto the surface of the microspheres for broadening of their applications. Discussion/Conclusion: A method for the preparation of biodegradable microspheres from water/oil emulsion of multiarm and functionalized poly(ε-caprolactone) [PGCL, PGCLM, and NPGCLM] was reported as a potential means of developing injectable therapeutic formulations for drugs. The most unique aspect of these biodegradable microspheres is the availability of two functional groups (>C = C< bon

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Nondestructive damage sensitivity and reinforcing effect of functionalized carbon nanotube and nanofiber/epoxy composites using electro-micromechanical techniques

Nondestructive damage sensitivity and reinforcing effect of ...

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2004 MRS Fall Meeting

作者： Park, Joung-Man Jung, Jin-Kyu Kim, Sung-Ju Kim, Dae-Sik Lee, Jae-Rock Kim, Tae-Wook Department of Polymer Science and Engineering Engineering Research Institute Gyeongsang National University Jinju 660-701 Korea Republic of Fiber Science Program Cornell University Ithaca NY 14853-4401 United States Advanced Materials Division Korea Research Institute of Chemical Technology Yusong Taejeon 305-600 Korea Republic of Composite Materials Group Korea Institute of Machinery and Materials Chanwon 641-010 Korea Republic of

Nondestructive damage sensing and load transfer mechanisms of thermal treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electromicromechanical technique. Carbon black (CB) was used only for the comparison. Electromicromechanical techniques were applied to obtain the fiber damage and stress transferring effect of carbon nanocomposites with their contents. Thermal treatment and temperature affected on apparent modulus and electrical properties on nanocomposites due to enhanced inherent properties of each CNMs. Coefficient of variation (COV) of volumetric electrical resistance can be used to obtain the dispersion degree indirectly for various CNMs. Dispersion and surface modification are very important parameters to obtain improved mechanical and electrical properties of CNMs for multifunctional applications. Further optimized functionalization and dispersion conditions will be investigated for the following work continuously. © 2005 Materials Research Society.

关键词： Carbon nanotubes

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Pore structure analysis of swollen dextran-methacrylate hydrogels by SEM and mercury intrusion porosimetry

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Journal of biomedical Materials Research Part B: Applied Biomaterials 2002年第3期53卷

作者： Sin–hee Kim Chih–Chang Chu Fiber and Polymer Science Program Department of Textiles & Apparel and Biomedical Engineering Program Cornell University Ithaca NY 14853

The objectives of this study were to visually examine the surface and interior morphology of a new class of biodegradable hydrogels based on dextran-methacrylate and to quantify the porous structure of these hydrogels in swollen state. Two techniques (scanning electron microscopy and mercury intrusion porosimetry) were used to analyze pore structure of dextran-methacrylate hydrogels as a function of the degree of methacrylate substitution. SEM was used to observe 3-dimensional network structure of cryofixed and fractured swollen dextran-methacrylate hydrogels. Image analysis of the SEM data revealed different pore shapes and sizes, depending on the degree of substitution and the location within the hydrogel. A higher methacrylate-substituted dextran hydrogel showed a compact and rigid pore structure, while a lower substituted hydrogel showed a delicate and fragile pore structure. Mercury intrusion porosimetry analysis of the pore structure of dextran-methacrylate hydrogels provided useful and more reliable quantitative data of pore characteristics, such as total pore area, average pore diameter, their distribution, and bulk density. The total pore area and average pore diameter of swollen dextran-methacrylate hydrogels decreased with an increase in degree of methacrylate substitution, while bulk density increased with an increase in degree of substitution. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 53: 258–266, 2000

关键词： dextran-methacrylate hydrogel pore structure scanning electron microscopy mercury intrusion porosimetry morphology image analysis

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Biodegradable dextran-polylactide hydrogel network and its controlled release of albumin

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Journal of biomedical Materials Research Part B: Applied Biomaterials 2000年第1期54卷

作者： Yeli Zhang Chih-Chang Chu Fiber and Polymer Science Program Department of Textiles and Apparel & Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

The objective of this paper was to study the release of bovine serum albumin (BSA) from a series of biodegradable hydrogels having a wide range of hydrophilicity to hydrophobicity, swelling, and biodegradation properties. BSA was incorporated into a series of biodegradable hydrogels made from a dextran derivative of allyl isocyanate (dex-AI, as the hydrophilic constituent) and poly( DL -lactic acid) diacrylate macromer (PDLLAM, as the hydrophobic constituent). The release kinetics of BSA from these dex-AI/PDLLAM hydrogels was studied. Laser confocal scanning microscopy was used to investigate the morphological change of the hydrogels, as well as BSA distribution in the hydrogels, as a function of dex-AI to PDLLAM composition ratio and incubation time. We found that the incorporation of PDLLAM into dex-AI reduced the initial burst release of BSA due to its more homogeneous distribution in the hydrogels. As the PDLLAM component increased, the rate of formation of a loose three-dimensional (3D) network structure increased; consequently, the sustained rate and extent of BSA release increased. Both release index and diffusion coefficient (from release kinetics data) increased as the PDLLAM component increased in the hydrogels. The data suggest that the release of BSA was controlled by both diffusion of BSA through swelling of the hydrophilic phase during an early stage, and degradation of the hydrophobic phase during a late stage, and also that the magnitude of diffusion versus degradation controlled release is dependent on composition ratio and immersion time. © 2000 John Wiley & Sons, Inc.

关键词： dextran poly(lactic acid) hydrogel controlled release albumin laser confocal microscope biodegradation

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Synthesis and characterization of biodegradable network hydrogels having both hydrophobic and hydrophilic components with controlled swelling behavior

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Journal of polymer science 2000年第24期37卷

作者： Yeli Zhang Chee-Youb Won Chih-Chang Chu Fiber and Polymer Science Program Department of Textiles and Apparel & Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

A new class of biodegradable hydrogels, consisting of hydrophobic poly( D , L )lactic acid (PDLLA) and hydrophilic dextran segments with a polymer network structure, was synthesized with UV photopolymerization. Unsaturated vinyl groups first were introduced onto the PDLLA and dextran polymer backbones, then followed by a crosslinking reaction of diacrylate-terminated PDLLA and dextran acrylate. The chemical crosslinking forced the hydrophobic PDLLA and hydrophilic dextran segments to mix with each other in the network hydrogels. The new polymers were characterized by standard polymer characterization methods such as NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. The effects of reaction time, temperature, and molar ratio of the reactants on the incorporation of acrylate onto the polymer backbone were examined. A series of hydrogels with different dextran/PDLLA composition ratios was prepared, and their swelling behaviors were studied. These new bicomponent network hydrogels had a wide range of hydrophilicity to hydrophobicity that was difficult to achieve in totally hydrophilic hydrogels. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4554–4569, 1999

关键词： biodegradable hydrogel dextran poly(D,L)lactic acid polymer network photocrosslinking acrylate biodegradable polymers swelling ratio

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