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

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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Synthesis and characterization of biodegradable poly(L-aspartic acid-co-PEG)

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Journal of polymer science 2000年第16期36卷

作者： Chee-Youb Won Chih-Chang Chu Jong Doo Lee Fiber and Polymer Science Program and Biomedical Engineering Program Cornell University Ithaca New York 14853 Department of Materials Science and Engineering Cornell University Ithaca New York 14853

The melt polycondensation reaction of the prepolymer prepared from N -(benzyloxycarbonyl)- L -aspartic acid anhydride ( N -CBz- L -aspartic acid anhydride) and low molecular weight poly(ethylene glycol) (PEG) using titanium isopropoxide (TIP) as a catalyst produced the new biodegradable poly( L -aspartic acid- co -PEG). This new copolymer had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the preparation of the prepolymer were obtained by using a 0.12 mol % of p -toluenesulfonic acid with PEG 200 for 48 h. The weight-average molecular weight of the prepolymer increased from 1,290 to 31,700 upon melt polycondensation for 6 h at 130°C under vacuum using 0.5 wt % TIP as a catalyst. The synthesized monomer, prepolymer, and copolymer were characterized by FTIR, 1 H- and 13 C-NMR, and UV spectrophotometers. Thermal properties of the prepolymer and the protected copolymer were measured by DSC. The glass transition temperature ( T g ) of the prepolymer shifted to a significantly higher temperature with increasing molecular weight via melt polycondensation reaction, and no melting temperature was observed. The in vitro hydrolytic degradation of these poly( L -aspartic acid- co -PEG) was measured in terms of molecular weight loss at different times and pHs at 37°C. This pH-dependent molecular weight loss was due to a simple hydrolysis of the backbone ester linkages and was characterized by more rapid rates of hydrolysis at an alkaline pH. These new biodegradable poly( L -aspartic acid- co -PEG)s may have potential applications in the biomedical field. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2949–2959, 1998

关键词： aspartic acid anhydride poly(ethylene glycol) poly(L-aspartic acid-co-PEG) biodegradable polymers

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A new copolymerization process leading to poly(propylene carbonate) with a highly enhanced yield from carbon dioxide and propylene oxide

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Journal of polymer science 2000年第12期37卷

作者： M. Ree J. Y. Bae J. H. Jung T. J. Shin Department of Chemistry Polymer Research Institute and School of Environmental Engineering Pohang University of Science & Technology San 31 Hyoja-dong Pohang 790-784 Korea

Using excessively loaded propylene oxide (PO) as a solvent, the copolymerization of carbon dioxide (CO 2 ) and PO was carried out with zinc glutarate catalyst, consequently producing poly(propylene carbonate) of high molecular weight in a high yield (64–70 g polymer per gram of catalyst) never achieved before. Both the PO used as solvent and the excessively loaded CO 2 were fully recoverable, respectively, and reusable for their copolymerization, indicating that this is a clean, green polymerization process to convert CO 2 to its polycarbonate. The polymer yield was further improved by scaling up the copolymerization process. Among zinc glutarate catalysts prepared through several synthetic routes, one from zinc oxide delivered the highest yield in the copolymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1863–1876, 1999

关键词： carbon dioxide propylene oxide aliphatic polycarbonate zinc glutarate copolymerization

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Copolymerization of carbon dioxide and propylene oxide using an aluminum porphyrin system and its components

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Journal of polymer science 2000年第16期37卷

作者： J. H. Jung M. Ree T. Chang Department of Chemistry Polymer Research Institute and School of Environmental Engineering Pohang University of Science & Technology San 31 Hyoja-dong Pohang 790-784 Korea

The catalytic activities of tetraphenylporphinatoaluminum chloride (TPPAlCl) and its propylene oxide adduct (TPPAl(PO) 2 Cl) were investigated in detail together with a quarternary salt Et 4 NBr for the copolymerization of carbon dioxide and propylene oxide. In addition, for the components and starting raw materials of the catalyst systems, catalytic activities were examined for the copolymerization. The TPPAlCl catalyst delivered oligomers containing ether linkages to a large extent, regardless of its PO adduction. And cyclic propylene carbonate, as byproduct, was formed in a very small portion. Using the TPPAlCl coupled with Et 4 NBr as a catalyst system, the formation of ether linkages was reduced significantly in the copolymerization; however, the obtained oligomer still contained ether linkages of 25.0 mol % in the backbone. On the other hand, the formation of cyclic carbonate was increased to 22.4 mol % relative to the oligomer product. The results indicate that the salt, which was coupled with the TPPAlCl catalyst, plays a key role in reducing the formation of ether linkage in the oligomer and, however, in enhancing the formation of cyclic carbonate. Similar results were obtained for the copolymerization catalyzed by the TPPAl(PO) 2 Cl/Et 4 NBr system. That is, the formation of ether linkages was not restricted further by the PO adduction of the TPPAlCl component in the catalyst system. Only oligomers with a relatively high molecular weight were produced. This indicates that the PO adduction of the TPPAlCl component contributes highly to the initiation and propagation step in the oligomerization, consequently leading to a relatively high molecular weight oligomer. In contrast, the Et 4 NBr, as well as the Et 2 AlCl, produced only cyclic carbonate in a very low yield. Furthermore, tetraphenylporphine exhibited no catalytic activity, regardless of using together with Et 4 NBr. On the other hand, the Et 2 AlCl coupled with Et 4 NBr provided a low molecular weigh

关键词： carbon dioxide propylene oxide oligomeric propylene carbonate cyclic propylene carbonate aluminum porphyrin catalysts

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A rapid-injection NMR study of the effect of lithium alkoxides on the butyllithium-initiated polymerization and propagation of styrene

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Journal of polymer science 2000年第8期37卷

作者： Craig A. Ogle Xiao Li Wang Clifford M. Carlin Frederick H. Strickler Bernard Gordon III Department of Chemistry University of North Carolina at Charlotte Charlotte North Carolina 28223 Department of Materials Science and Engineering Polymer Science Program Pennsylvania State University University Park Pennsylvania 16802

In studies carried out in THF at −80°C, lithium n -butoxide was found to speed up the initiation and to an even greater extent the rate of propagation in the alkyllithium-initiated polymerization of styrene. Bulky alkoxides were found to slow down the rate of polymerization by slowing both initiation and propagation although initiation was decreased to a greater extent than propagation. Five equivalents of lithium tert -butoxide stopped the initiation completely under these reaction conditions when n -butyllithium was used as an initiator. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1157–1168, 1999

关键词： butyllithium polymerization styrene lithium alkoxides NMR

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Structure development and physical properties achieved in the drawing and/or annealing of PEN fibers

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Journal of polymer science 2000年第11期38卷

作者： Gang Wu Ming Liu Xiaoning Li John A. Cuculo College of Material Science and Engineering Beijing University of Chemical Technology Beijing 100029 China Department of Fibrous Material Engineering Beijing Institute of Clothing Technology Beijing 100029 China Fiber & Polymer Science Program College of Textiles North Carolina State University Raleigh North Carolina 27695

As-spun poly(ethylene-2,6-naphthalate) (PEN) fibers (i.e., precursors) prepared from high molecular weight polymer were drawn and/or annealed under various conditions. Structure and property variations taking place during the treatment process were followed via wide-angle X-ray scattering (WAXS), small-angle X-ray scattering, differential scanning calorimetry (DSC), and mechanical testing. Both the WAXS and DSC measurements of the cold-drawn samples stretched from a low-speed-spun amorphous fiber indicate that strain-induced crystallization can occur at a temperature below the glass-transition temperature and that the resultant crystal is in the α-form modification. In contrast, when the same precursor was subjected to constrained annealing, its amorphous characteristics remained unchanged even though the annealing was performed at 200 °C. These results may imply that the application of stretching stress is more important than elevated temperatures in producing α-form crystallization. The crystalline structure of the hot-drawn samples depends significantly on the morphology of the precursor fibers. When the precursor was wound at a very low speed and in a predominantly amorphous state, hot drawing induced the formation of crystals that were apparently pure α-form modification. For the β-form crystallized precursors wound at higher speeds, a partial crystalline transition from the β form to the α form was observed during the hot drawing. In contrast with the mechanical properties of the as-spun fibers, those of the hot-drawn products are not improved remarkably because the draw ratio is extremely limited for most as-spun fibers in which an oriented crystalline structure has already formed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1424–1435, 2000

关键词： poly(ethylene-2,6-naphthalate) fiber drawing annealing structural change crystalline transition

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Control of various morphological changes of poly(meth)acrylate microspheres and their swelling degrees by SPG emulsification

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Journal of polymer science 2000年第22期38卷

作者： Sumalee Tawonsree Shinzo Omi Suda Kiatkamjornwong Multidisciplinary Program of Petrochemistry and Polymer Science Faculty of Science Chulalongkorn University Bangkok 10330 Thailand Graduate School of Bio-Application and System Engineering Tokyo University of Agriculture and Technology 2-24-16 Nakamachi Koganei Tokyo 184 Japan Department of Imaging and Printing Technology Faculty of Science Chulalongkorn University Bangkok 10330 Thailand

Crosslinked poly(meth)acrylate polymers with a variety of morphologies were synthesized with two steps. In the first step, a microporous glass membrane (Shirasu Porous Glass, SPG) was employed to prepare uniform emulsion droplets by applying an adequate pressure to the monomer phase, which was composed of the ADVN initiator, solvent of toluene or heptane or their mixture, and a mixture of (meth)acrylate monomers. The droplets were formed continuously through the membrane and suspended in the aqueous solution, which contained a PVA-127 suspending agent, SLS emulsifier, and NaNO 2 inhibitor to suppress the nucleation of secondary particles. SPG pore sizes of 0.90, 5.25, and 9.25 μm were used. Then the emulsion droplets were polymerized at 343 K with a rotation rate 160 rpm for 24 h. The (meth)acrylate monomers 2-ethylhexyl acrylate (2-EHA), 2-ethylhexyl methacrylate (2-EHMA), cyclohexyl acrylate (CHA), methyl methacrylate (MMA), lauryl acrylate (LA), and lauryl methacrylate (LMA) were used in this research. The influences of the ratios of the monomer and crosslinking agent EGDMA, the amount of diluents, the monomer type on the polymer particle morphology, the swelling degree, and the polymer particle size were investigated. It was found that an increase in the concentrations of EGDMA and heptane resulted in higher coarse porous spheres and smaller polymer particle sizes. A coefficient with a variation close to 10%, or a standard deviation of about 4, was obtained. The capacity of these spheres as solvent absorption materials was examined. The highest swelling degrees of heptane and toluene were obtained when LA was employed as the monomer with 30% (by weight) of EGDMA and 70% (by weight) of heptane as an inert solvent. The highest capacity of the solvent absorption was obtained when using a polymer particle size of 4.81 μm, as prepared by SPG pore size 0.9 μm. The polymer particles were able to absorb aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and

关键词： Shirasu porous glass 2-ethyl hexyl acrylate 2-ethyl hexyl methacrylate cyclohexyl acrylate methyl methacrylate lauryl acrylate swelling degree crosslinking agent diluent solvent absorption

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Amino acid-based bioanalogous polymers. Synthesis, and study of regular poly(ester amide)s based on bis(α-amino acid) α,ω-alkylene diesters, and aliphatic dicarboxylic acids

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Journal of polymer science 2000年第4期37卷

作者： R. Katsarava V. Beridze N. Arabuli D. Kharadze C. C. Chu C. Y. Won Centre for Medical Polymers and Biomaterials of Ministry of Health and Institute of Molecular Biology & Biophysics of Georgian Academy of Sciences P.O. Box 24 380079 Tbilisi-79 Georgia Fiber and Polymer Science Program Department of Textiles & Apparel & Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

The purpose of this research was to synthesize new regular poly(ester amide)s (PEAs) consisting of nontoxic building blocks like hydrophobic α-amino acids, α,ω-diols, and aliphatic dicarboxylic acids, and to examine the effects of the structure of these building block components on some physico-chemical and biochemical properties of the polymers. PEAs were prepared by solution polycondensation of di- p -toluenesulfonic acid salts of bis-(α-amino acid) α,ω-alkylene diesters and di- p -nitrophenyl esters of diacids. Optimal conditions of this reaction have been studied. High molecular weight PEAs ( M w = 24,000–167,000) with narrow polydispersity ( M w / M n = 1.20–1.81) were prepared under the optimal reaction conditions and exhibited excellent film-forming properties. PEAs obtained are mostly amorphous materials with T g from 11 to 59°C. α-Chymotrypsin catalyzed in vitro hydrolysis of these new PEA substrates was studied to assess the effect of the building blocks of these new polymers on their biodegradation properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 391–407, 1999

关键词： α-amino acids biodegradable polymers regular poly(ester amide)s α-chymotrypsinolysis

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Relaxation of Anisotropic Thermal Diffusivity in a polymer Melt Following Step Shear Strain

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Physical Review Letters 1999年第2期82卷 366-366页

作者： David C. Venerus Jay D. Schieber Hadjira Iddir Job D. Guzman Andrew W. Broerman Department of Chemical and Environmental Engineering and Center of Excellence in Polymer Science and Engineering Illinois Institute of Technology Chicago Illinois 60616

Forced Rayleigh light scattering is used to examine anisotropic thermal heat conduction due to deformation in a polymeric liquid. Thermal diffusivity is measured in both the flow and neutral directions in a polyisobutylene melt following the imposition of a step shear strain. The thermal diffusivity in the flow and neutral directions increases and decreases, respectively, immediately following the deformation before relaxing to an equilibrium value. Comparison of the difference between measured flow and neutral direction thermal diffusivities with the analogous flow-induced birefringence supports arguments for a proportionality between stress and thermal diffusivity.

关键词： .shear strain polymer melt equilibrium value anisotropic thermal ow-induced Following Step following the imposition neutral direction

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