Preparation and characterization of poly(ethylene glycol) crosslinked chitosan films

Poly(ethylene glycol) (PEG) crosslinked chitosan films with various PEG to chitosan ratio and PEG molecular weight were successfully prepared via the epoxy‐amine reaction between chitosan and PEG‐epoxy. The thermal and mechanical properties and swelling behavior were studied for the PEG crosslinked chitosan films. The mechanical strength of chitosan films were greatly enforced by the introduction of PEG‐epoxy, achieving an elongation of about 80%. It was found that the crosslinked chitosan films form hydrogel in water, achieving a swelling ratio higher than 20 times of original weight. The swelling behavior of chitosan films relied greatly on the molecular weight of the crosslinker PEG‐epoxy and the weight percent of PEG‐epoxy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Properties of Poly(vinyl chloride)/poly(ethylene oxide)/polyaniline Conductive Films: The Effect of Poly(ethylene glycol) Diglycidyl Ether

The effect of polyaniline and poly(ethylene glycol) diglycidyl ether on tensile properties, morphology, thermal degradation, and electrical conductivity of poly(vinyl chloride)/poly(ethylene oxide)/polyaniline conductive films was studied. The poly(vinyl chloride)/poly(ethylene oxide)/polyaniline conductive films were prepared using a solution casting technique at room temperature until a homogeneous solution was produced. Poly(vinyl chloride)/poly(ethylene oxide)/polyaniline/poly(ethylene glycol) diglycidyl ether conductive films exhibit higher electrical properties, tensile strength, modulus of elasticity but lower final decomposition temperature than poly(vinyl chloride)/poly(ethylene oxide)/polyaniline conductive films. Scanning electron microscopy morphology showed that the polyaniline more widely dispersed in the poly(vinyl chloride)/poly(ethylene oxide) blends with the addition of poly(ethylene glycol) diglycidyl ether as surface modifier.     

Porous poly(ethylene glycol)–polyurethane hydrogels as potential biomaterials

We report the synthesis of porous poly(ethylene glycol)–polyurethane (PEG‐PU) hydrogels using PEG‐4000 as a soft segment and 4,4′‐methylenebis(cyclohexylisocyanate) as a hard segment. The degree of swelling in the hydrogels could be controlled by varying the amount of crosslinking agent, namely 1,2,6‐hexanetriol. Structural characterization of the hydrogels was performed using solid‐state ¹³C NMR and Fourier transform infrared spectroscopy. Wide‐angle X‐ray diffraction studies revealed the existence of crystalline domains of PEG and small‐angle X‐ray scattering studies showed the presence of lamellar microstructures. For generating a porous structure in the hydrogels, cryogenic treatment with lyophilization was used. Scanning electron microscopy and three‐dimensional micro‐computed tomography imaging of the hydrogels indicated the presence of interconnected pores. The mechanical strength of the hydrogels and xerogels was measured using dynamic mechanical analysis. The observed dynamic storage moduli (E′) for the equilibrium swollen and dry gels were found to be 0.15 and 4.2 MPa, respectively. Interestingly, the porous PEG‐PU xerogel also showed E′ of 5.6 MPa indicating a similar mechanical strength upon incorporating porosity into the gel matrix. Finally, preliminary cytocompatibility studies showed the ability of cells to proliferate in the hydrogels. These gels show promise for applications as scaffolds and implants in tissue engineering. © 2014 Society of Chemical Industry     

Synthesis of unsaturated poly(ether amide)s based on amine‐terminated poly(ethylene glycol)

Novel water‐soluble unsaturated poly(ether amide)s (PEAs) were synthesized by low‐temperature polycondensation of fumaryl chloride and amine‐terminated poly(ethylene glycol) (Jeffamine®). The unsaturated copolymers were further chemically modified with thiols to provide reactive pendant functional groups. Hydrogels based on these copolymers were prepared by copolymerization of the PEA with N‐vinyl pyrrolidone exposure to ultraviolet (UV) irradiation. The resulting hydrogels exhibited a high swelling ratio, and the magnitude of swelling depended on the molecular weight of Jeffamine®. The swelling ratio and equilibrium water content tended to increase with increasing chain length of the Jeffamine® used in copolymer synthesis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 913–920, 1999     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

Synthesis,characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

BACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation. RESULTS: The copolyesters were characterized using ¹H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters. CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry     

Thermoreversible hydrogels. XIX. Synthesis and swelling behavior and drug release behavior for the N‐isopropylacrylamide/poly(ethylene glycol) methylether acrylate copolymeric hydrogels

A series of thermosensitive copolymeric hydrogels were prepared from various molar ratios of N‐isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methylether acrylate (PEGMEA_n), which was synthesized from acryloyl chloride and poly(ethylene glycol) mono methylether with three oxyethylene chain lengths. Investigation of the effect of the chain length of oxyethylene in PEGMEA_n, and the amount of the PEGMEA_n in the NIPAAm/PEGMEA_n copolymeric gels, on swelling behavior in deionized water was the main purpose of this study. Results showed that the swelling ratio for the present copolymeric gels increased with increasing chain length of oxyethylene in PEGMEA_n and also increased with increase in the amount of PEGMEA_n in the copolymeric gels. However, the gel strength and effective crosslinking density of these gels decreased with increase in swelling ratio. Some kinetic parameters were also evaluated in this study. Finally, the drug release and drug delivery behavior for these gels were also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1683–1691, 2003     

Synthesis and property evaluations of photocrosslinkable chitosan derivative and its photocopolymerization with poly(ethylene glycol)

Photocrosslinkable polymers are clean and convenient materials for the biomedical uses. Chitosan, which owns excellent biocompatible and antimicrobial properties, is one of the choices while it is introduced with photosensitive functional groups. In this study, chitosan was N‐phthaloylated to react with acryloyl chloride in the organic solvent homogeneously and the result has been verified by the solubility test. Fourier transformed infrared spectrometry and nuclear magnetic resonance spectrometer analysis indicated that the modification with the attachment of the photosensitive functional group, the acryloyl group, onto chitosan and poly(ethylene glycol) (PEG) was feasible. The differential scanning calorimetry analysis further indicated that the melting points of the N‐phathaloylated chitosan were decreased as compared with the untreated chitosan control. Then photocrosslinkable chitosan derivative (CH‐PAA) was photocopolymerized with PEG diacrylate (PEGA) under UV irradiation. The adhesion strength characterization and swelling capacity evaluation for this photocopolymer have shown obvious raises of the adhesiveness and water‐adsorption abilities as compared with the photopolymer of CH‐PAA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1794–1801, 2006     

Synthesis of amphiphilic poly(phthalazinone ether sulfone ketone)‐graft‐poly(ethylene glycol) graft copolymers via Williamson etherification

Amphiphilic graft copolymers consisting of poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) (PEG) side chains were synthesized via reaction of chloromethylated PPESK (CMPPESK) with a sodium alkoxide of methoxyl PEG (PEG‐ ONa). The reactive precursor, CMPPESK, was prepared by the chloromethylation of PPESK with chloromethylether (CME) using concentrated H₂SO₄ as reaction medium. FTIR spectroscopy, ¹H‐NMR and Solid‐state ¹³C CP‐MAS NMR analysis confirmed the covalent linking of PEG with PPESK backbones. The PEG content in the graft copolymers from ¹H‐NMR analysis varied from 21.0 to 37.2 wt %, which was approximately in agreement with that calculated from TGA tests. The graft products have good solubility in many aprotic polar solvents and can be slightly swelled by water and ethanol, but water insoluble. Contact angle measurements revealed that the hydrophilicity of PPESK was significantly improved by the introduction of PEG graft chains, indicating the graft copolymer is a potential hydrophilic additive for PPESK membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

Synthesis and characterization of cleavable surfactants derived from poly(ethylene glycol) monomethyl ether

A series of noncyclic acetal-linked cleavable surfactants were simply prepared by condensation of aldehydes with poly(ethylene glycol) monomethyl ethers. All of the products were characterized by¹H nuclear magnetic resonance. Their hydrophile-lipophile balance, surface tension, cloud point, critical micelle concentration, and foam height were determined. Hydrolysis kinetic studies, followed by gas chromatography, showed that they had higher hydrolytic reactivity in acidic solution than cyclic acetal-linked cleavable surfactants.     

Preparation of collagen‐immobilized poly(ethylene glycol)/poly(2‐hydroxyethyl methacrylate) interpenetrating network hydrogels for potential application of artificial cornea

To enhance the mechanical strength of poly(ethylene glycol)(PEG) gels and to provide functional groups for surface modification, we prepared interpenetrating (IPN) hydrogels by incorporating poly(2‐hydroxyethyl methacrylate)(PHEMA) inside PEG hydrogels. Formation of IPN hydrogels was confirmed by measuring the weight percent gain of the hydrogels after incorporation of PHEMA, as well as by ATR/FTIR analysis. Synthesis of IPN hydrogels with a high PHEMA content resulted in optically transparent and extensively crosslinked hydrogels with a lower water content and a 6 ～ 8‐fold improvement in mechanical properties than PEG hydrogels. Incorporation of less than 90 wt % PHEMA resulted in opaque hydrogels due to phase separation between water and PHEMA. To overcome the poor cell adhesion properties of the IPN hydrogels, collagen was covalently grafted to the surface of IPN hydrogels via carbamate linkages to hydroxyl groups in PHEMA. Resultant IPN hydrogels were proven to be noncytotoxic and cell adhesion study revealed that collagen immobilization resulted in a significant improvement of cell adhesion and spreading on the IPN hydrogel surfaces. The resultant IPN hydrogels were noncytotoxic, and a cell adhesion study revealed that collagen immobilization improved cell adhesion and spreading on the IPN hydrogel surfaces significantly. These results indicate that PEG/PHEMA IPN hydrogels are highly promising biomaterials that can be used in artificial corneas and a variety of other load‐bearing tissue engineering applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and surface properties of polystyrene‐graft‐poly(ethylene glycol) copolymers

Polystyrene‐graft‐poly(ethylene glycol) copolymers (PS‐g‐PEG) were successfully synthesized using the “grafting‐through” method. The graft copolymers and the surface properties of their coats were characterized by 1 H‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), static contact angle measurement, and atomic force microscopy (AFM). Both DSC and TEM indicated that the graft copolymers had a microphase separated structure. AFM showed the microphase separated structure also occurred at the coat surface, especially at high PEG content, which could also be indirectly confirmed by the XPS and contact angle results. The formation mechanism of the microphase separated structure was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1458–1465, 2007     

聚乙二醇/聚己内酯三嵌段共聚物的合成与表征

以甲苯二异氰酸酯 (TDI)为偶联剂 ,合成了聚乙二醇 (PEG) /聚己内酯 (PCL)两亲性三嵌段共聚物 (PEG-b-PCL -b -PEG ,PECL) ,采用IR、1 H-NMR、DSC和WAXD分析和研究了PECL的结构与性能。实验结果表明 ,PECL的结构和组成与设计相一致 ,结晶度和熔点均低于均聚物 ,且随着PECL中PCL嵌段含量的增加 ,PCL嵌段熔点升高。透射电镜照片显示PECL纳米粒呈核 /壳结构的球形。     

Influence of racemization on stereocomplex‐induced gelation of water‐soluble polylactide–poly(ethylene glycol) block copolymers

Ring‐opening polymerization of L ‐ or D ‐lactide was realized at 140 °C for a period of 7 days in the presence of dihydroxyl poly(ethylene glycol) (PEG), with M?_n = 4000 g mol^?1, using zinc lactate as initiator. The resulting poly(L ‐lactide)–PEG–poly(L ‐lactide) and poly(D ‐lactide)–PEG–poly(D ‐lactide) triblock copolymers are water soluble with polylactide (PLA) block length ranging from 11 to 17 units. Both the tube inverting method and rheological measurements were used to evaluate the gelation properties of aqueous solutions containing single copolymers or L /D copolymer pairs. Stereocomplexation between poly(L ‐lactide) and poly(D ‐lactide) blocks is observed for mixed solutions. Hydrogel formation is detected in the case of relatively long PLA blocks (DP _PLA = 17), but not for copolymers with shorter PLA blocks (DP _PLA = 11–13) due to partial racemization of L ‐lactyl units. Racemization is largely reduced when the reaction time is shortened to 1 day. Under these conditions, DP _PLA of 8 is sufficient for the stereocomplexation of PLA–PEG block copolymers, and DP _PLA above 10 leads to the formation of hydrogels of PLA–PEG block copolymers. On the other hand, racemization appears as a general phenomenon in the (co)polymerization of L ‐lactide with Zn(Lac)₂ as initiator, although it is negligible or undetectable in the case of high molar mass polymers. Therefore, racemization is the limiting factor for the stereocomplexation‐induced gelation of water‐soluble PLA–PEG block copolymers where the PLA block length generally ranges from 10 to 30. Reaction conditions including initiator, time and temperature should be strictly controlled to minimize racemization. Copyright © 2010 Society of Chemical Industry     

异端基遥爪聚乙二醇的合成

采用3种新式引发剂,即2-(苄氧基）乙醇钾、2-(四氢-2H-吡喃-2-氧基)乙醇钾、单丙烯基乙二醇钾引发环氧乙烷阴离子开环聚合,反应条件为25 ℃、48 h、醇与萘钾摩尔比例1∶1,得到3种异端基遥爪聚乙二醇。以2-(苄氧基）乙醇钾引发聚合所得产物为起始物,经一系列反应,得到两种两端均为活性基团的异端基遥爪聚乙二醇,这种方法具有普适性。通过1HNMR及GPC手段,表征了产物的结构、分子量及分子量分布。结果表明可以得到高产率、分子量可控且分布窄的异端基遥爪聚乙二醇。     

Relaxational behavior and swelling‐pH master curves of poly[(diethylaminoethyl methacrylate)‐graft‐(ethylene glycol)] hydrogels

Poly[(diethylaminoethyl methacrylate)‐graft‐(ethylene glycol)] hydrogels were prepared with a molar ratio of 10:1 of diethylaminoethyl methacrylate to poly(ethylene glycol) of number‐average molecular weights (M_n) 200, 400 and 1000 g mol^?1 using tetra(ethylene glycol) dimethacrylate to give a crosslinking ratio between 0.5 and 4.0 %. Glucose oxidase and catalase were immobilized in the matrix during polymerization. The maximum enzyme loading used was 6.6 × 10^?4 g of glucose oxidase per g of polymer. The equilibrium and dynamic swelling properties of these hydrogels were investigated. The pH‐dependent equilibrium swelling characteristics showed a sharp transition between the swollen and the collapsed state at pH 7.0. The dynamic response of the hydrogel discs to pH was analyzed in pulsatile pH conditions. The effects of particle size, crosslinking and molecular weight of poly(ethylene glycol) (PEG) on the dynamic swelling response were investigated. The pulsatile nature of the response was analyzed using Boltzmann superposition. Swelling–pH master curves were obtained. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers

Poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. The reaction was carried out under mild conditions, using dicyclohexylcarbodiimide as the coupling agent and dimethylaminopyridine as the catalyst. The resulting copolymers were characterized by various analytical techniques, such as GPC, viscometry, ¹H‐NMR, FTIR, DSC, X‐ray diffractometry, and contact angle measurement. The results indicated that these copolymers presented outstanding properties pertinent to biomedical use, including better miscibility between the two components, low crystallinity, and hydrophilicity. Moreover, the properties of the copolymers can be modulated by adjusting the block length of the two components or the reaction conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1729–1736, 2002; DOI 10.1002/app.10580     

Synthesis of bismaleimide resin containing the poly(ethylene glycol) side chain: Curing behavior and thermal properties

Two maleimido end‐capped poly(ethylene glycol) (m‐PEG) of different molecular weights were synthesized and blended at various proportions with bismaleimide resin (4,4′‐bismaleimido diphenylmethane) (BDM). The curing behavior and the thermal properties of the m‐PEG/BDM blends were studied and presented here. It was found that the addition of m‐PEG enhanced the processability of the BDM resin significantly. The processing window of the BDM resin was increased from approximately 20 to 80°C. The addition of m‐PEG modified resins, however, resulted not only in the reduction in the thermal stability of the blended BDM resin but also elevation of the coefficients of thermal expansion. The changes in thermal/mechanical properties of the blends were found to be proportional to the amounts of m‐PEG incorporated. It was observed that the curing behavior, and thermal and mechanical properties, of the blends were independent of the molecular weight of the PEG segment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2935–2945, 2002     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Formation of honeycomb films from poly(L‐lactide)‐block‐poly(ethylene glycol) via water‐droplet templating

The fabrication of honeycomb‐patterned films from amphiphilic poly(L ‐lactide)‐block‐poly(ethylene glycol) (PLEG) in a high‐humidity atmosphere is reported. The influence of the solution concentration on pattern formation was investigated. Moreover, by comparing the different conditions of fabricating regular structures between PLEG and poly(phenylene oxide), the mechanism of the regular pattern formation was studied. Finally, by adding sodium dodecylsulfate to a concentrated solution of 1 g L^?1 PLEG? CHCl₃ which otherwise could not form regular pores, we found that regular pores could be obtained. The PLEG honeycomb films are expected to be of use in cell culture, tissue engineering and many other areas. Copyright © 2007 Society of Chemical Industry