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     

不同PEG含量对PLA/PEG共混物结晶动力学的影响

采用溶液共混法制备了一系列不同配比的聚乳酸(PLA)/聚乙二醇(PEG)共混物。通过偏光显微镜(POM)、扫描电镜(SEM)和差式扫描量热仪(DSC)研究了不同PEG含量的PLA/PEG共混物在不同结晶温度下,聚乳酸的晶体形貌、球晶生长速率及热力学性能。研究发现,PEG能够显著提高聚乳酸球晶的生长速率。当PEG含量为60%时,PLA/PEG共混物中聚乳酸球晶的生长速率最快,达到23.6μm/min,比纯聚乳酸的最快球晶生长速率(0.5μm/min)高47倍。但是,当PEG含量高于60%时,聚乳酸球晶的生长速率有所降低。同时,PLA/PEG共混物中聚乳酸球晶速率随结晶温度变化的取向,均向低温移动。另外,PLA/PEG共混物中聚乳酸球晶呈现环状花纹。DSC测试结果表明,随着PEG含量的增加,PLA/PEG共混物的玻璃化转变温度明显降低。     

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     

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.     

Surface modification of poly(ethylene terephthalate) film by coating with poly(ethylene glycol)‐grafted polystyrene

The poly(ethylene glycol) (PEG)‐grafted styrene (St) copolymer, which was formed as a nanosphere, was used as an agent to modify the surface of poly(ethylene terephthalate) (PET) film. The graft copolymer was dissolved into chloroform and coated onto the PET film by dip–coating method. The coated amount depends on the content ratios of PEG and St, the solution concentration, and the coating cycles. The graft copolymers having a low molecular weight of PEG‐ or St‐rich content was fairly stable on washing in sodium dodecyl sulfate (SDS) aqueous solution. It was confirmed that the PET surface easily altered its surface property by the coating of the graft copolymers. The contact angles of the films coated with the graft copolymers were very high (ca. 105–120°). The coated film has good antistatic electric property, which agreed with PEG content. The best condition of coating is a one‐cycle coating of 1% (w/v) graft copolymer solution. The coated surface had water‐repellency and antistatic electric property at the same time. The graft copolymer consisted of a PEG macromonomer; St was successfully coated onto PET surfaces, and the desirable properties of both of PEG macromonomer and PSt were exhibited as a novel function of the coated PE film. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1524–1530, 1999     

Comparison of micelles formed by amphiphilic poly(ethylene glycol)‐b‐poly(trimethylene carbonate) star block copolymers

In this article, we describe the synthesis and solution properties of PEG‐b‐PTMC star block copolymers via ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) monomer initiated at the hydroxyl end group of the core PEG using HCl Et₂O as a monomer activator. The ROP of TMC was performed to synthesize PEG‐b‐PTMC star block copolymers with one, two, four, and eight arms. The PEG‐b‐PTMC star block copolymers with same ratio of between hydrophobic PTMC and hydrophilic PEG segments were obtained in quantitative yield and exhibited monomodal GPC curves. The amphiphilic PEG‐b‐PTMC star block copolymers formed spherical micelles with a core–shell structure in an aqueous phase. The mean hydrodynamic diameters of the micelles increased from 17 to 194 nm with increasing arm number. As arm number increased, the critical micelle concentration (CMC) of the PEG‐b‐PTMC star block copolymers increased from 3.1 × 10^?3 to 21.1 × 10^?3 mg/mL but the partition equilibrium constant, which is an indicator of the hydrophobicity of the micelles of the PEG‐b‐PTMC star block copolymers in aqueous media, decreased from 4.44 × 10⁴ to 1.34 × 10⁴. In conclusion, we confirmed that the PEG‐b‐PTMC star block copolymers form micelles and, hence, may be potential hydrophobic drug delivery vehicles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚乙二醇中共轭烯炔化合物的合成

发展了一种在聚乙二醇介质中末端炔烃与缺电子炔烃选择性生成共轭烯炔化合物的方法。在三苯基膦氯化钯(2mol%)、溴化亚铜(4mol%)、PEG-400(1.0g)和氮气的作用下,1mmol末端炔烃与0.5mmol缺电子炔烃可以顺利地发生交叉偶联反应选择性生成相应的共轭烯炔化合物,该反应产率较高,对环境友好,且催化体系可以适当地重复使用。     

Hydrolytic Degradation of Aliphatic Polyesters Copolymerized with Poly(ethylene glycol)s

Poly(1,4-butanediol succinate) copolymers were prepared by melt polycondensation of succinic acid and 1,4-butanediol with 10–50mol% (in feed) of poly(ethylene glycol) (PEG), where molecular weight (MW) of PEG is 200–2000. The reduced specific viscosity of the copolymers increased with incorporation of the PEG component, but a higher PEG content in the copolymers reduced it. The temperature of melting (T_m) and crystallinity decreased with increasing PEG content. T_m depression of the copolymers followed approximately Flory’s equation, suggesting that these are random type copolymers. Tensile strength and elongation decreased with increasing MW and content of PEG. The weight loss of copolymer films in a buffer solution with or without lipase at 37°C, as well as water absorption, increased with increasing PEG content, implying that higher water absorption contributes to hydrolytic degradation of the films. However, the weight loss of copolymers with PEG of lower MW increased greatly in spite of lower water absorption, demonstrating that hydrolytic degradation is influenced by the concentration of degradable ester linkages between succinic acid and PEG segments rather than water absorption. © of SCI.     

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.     

聚乙二醇对聚乳酸纤维性能的改善

采用在双螺杆中熔融共混,以不同相对分子质量聚乙二醇(PEG)作为增塑剂,对聚乳酸(PLA)进行增塑改性,并把改性后的PLA进行熔融纺丝。用扫描电子显微镜(SEM)、熔体流动速率仪(MFR)、单纤维电子强力仪(EYST)和差示扫描量热仪(DSC)对改性PLA纤维进行表征。讨论了不同相对分子质量的PEG对PLA纤维性能的影响,发现随着PEG含量的增加,改性PLA的流动性增加。当PEG质量分数≤8%时,随着PEG含量的增加,改性PLA纤维强度增加,断裂伸长率增加,玻璃化转变温度(Tg)和熔点(Tm)下降。PLA与PEG组分间表现出较好的相容性。PEG200改性的PLA纤维综合效果最好。     

Drug release from poly(ortho esters)–poly(ethylene glycol) polyblend

A polyblend of poly(ortho esters)–poly(ethylene glycol) (POE–PEG) was prepared. The release behavior of the acetanilide‐loaded film of the POE–PEG polyblend was studied. Blending POE with water‐soluble PEG can promote the release of drug in pH 7.4 PBS buffer at 37°C, while POE has plasticizing effect on PEG. Infrared and X‐ray diffraction studies reveal that there is some interaction between POE and acetanilide. The SEM micrographs disclose that the porosity of the drug‐loaded film enhances with an increase immersing time. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 303–309, 1999     

Mechanical properties and morphology of poly(ethylene glycol)‐side‐chain‐modified bismaleimide polymer

Two maleimido‐end‐capped poly(ethylene glycol) (m‐PEG)‐modified bismaleimide (BMI) resins [4,4′‐bismaleimido diphenylmethane (BDM)] were synthesized from poly(ethylene glycol) (PEG) of two different molecular weights. A series of m‐PEGs and unmodified BDM were blended and thermally cured. The effect of incorporating m‐PEG side chains on the morphology and mechanical behaviors of BMI polymer were evaluated. The mechanical properties of these m‐PEG‐modified BMIs that were evaluated included flexural modulus, flexural strength, strain at break, fracture toughness, and fracture energy. The morphology of these blends was studied with scanning electron microscopy. All the m‐PEG‐modified BMI polymers showed various degrees of phase separation depending on the molecular weights and concentrations of the m‐PEG used. The effects of these morphological changes in the m‐PEG‐modified BMI polymers were reflected by the improved fracture toughness and strain at break. However, there was a reduction in the flexural moduli in all m‐PEG‐modified BMI polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 715–724, 2002     

Enhanced dynamic mechanical and shape‐memory properties of a poly(ethylene terephthalate)–poly(ethylene glycol) copolymer crosslinked by maleic anhydride

Dimethyl terephthalate (DMT) and ethylene glycol (EG) were used for the preparation of poly(ethylene terephthalate) (PET), and poly(ethylene glycol) (PEG) was added as a soft segment to prepare a PET–PEG copolymer with a shape‐memory function. MWs of the PEG used were 200, 400, 600, and 1000 g/mol, and various molar ratios of EG and PEG were tried. Their tensile and shape‐memory properties were compared at various points. The glass‐transition and melting temperatures of PET–PEG copolymers decreased with increasing PEG molecular weight and content. A tensile test showed that the most ideal mechanical properties were obtained when the molar ratio of EG and PEG was set to 80:20 with 200 g/mol of PEG. The shape memory of the copolymer with maleic anhydride (MAH) as a crosslinking agent was also tested in terms of shape retention and shape recovery rate. The amount of MAH added was between 0.5 and 2.5 mol % with respect to DMT, and tensile properties and shape retention and recovery rate generally improved with increasing MAH. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 27–37, 2002     

Synthesis and characterization of novel block copolymer from trans‐4‐hydroxy‐L‐proline and poly(ethylene glycol)

A series of novel ABA‐type block copolymers were synthesized by polymerization of trans‐4‐hydroxy‐L ‐proline (HyP) in the presence of various molecular weight poly(ethylene glycol)s (PEGs), a bifunctional OH‐terminated PEG using stannous octoate as catalyst. The optimal reaction conditions for the synthesis of the copolymers were obtained with 5 wt % stannous octoate at 140°C under vacuum (20 mmHg) for 24 h. The synthesized copolymers were characterized by IR spectroohotometry, proton nuclear magnetic resonance, differential scanning calorimetry, and Ubbelohde viscometer. The glass transition temperature (T_g) of the copolymers shifted to significantly higher temperature with increasing the number average degree of polymerization and HyP/PEO molar ratio. In contrast, the melting temperature (T_m) decreased with increasing the HyP/PEO molar ratio. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1581–1587, 2001     

Synthesis and hydrophilicity of poly(butylene 2,6‐naphthalate)/poly(ethylene glycol) copolymers

Poly(butylene 2,6‐naphthalate) (PBN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two‐step melt copolymerization process of dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) with 1,4‐butanediol (BD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structures, thermal properties, and hydrophilicities of these copolymers were studied by ¹H NMR, DSC, TGA, and by contact angle and moisture content measurements. In particular, the intrinsic viscosities of PBN/PEG copolymers increased with increasing PEG molecular weights, but the melting temperatures (T_m)_, the cold crystallization temperatures (T_cc)_, and the heat of fusion (ΔH_f) values of PBN/PEG copolymers decreased on increasing PEG contents or molecular weights. The thermal stabilities of the copolymers were unaffected by PEG content or molecular weight. Hydrophilicities as determined by contact angle and moisture content measurements were found to be significantly increased on increasing PEG contents and molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2677–2683, 2006     

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     

Decomposition of poly(ethylene glycol) in nanocomposites

Poly(ethylene glycol) (PEG) has been widely used in studies of polymer–clay nanocomposites because it readily intercalates in smectite clays. Nanocomposites were formed from PEG with molecular weights (M_w) ranging from 300 to 20,000, as evidenced by expansion of the basal planar spacing of the clay (d₀₀₁) in X‐ray diffraction. However PEG with high molecular weight (≥ 10,000) readily underwent degradation during preparation of composites when heated at low temperature (60°C) due to oxidative attack. Molecular weight distribution determined by gel permeation chromatography showed that this degradation always happened with or without the presence of clay and it became more serious when the molecular weight was higher. The reduction in pH of aqueous PEG solutions after degradation increased with molecular weight. Since d₀₀₁ was independent of molecular weight over a wide range, such degradation cannot be detected by this method. Precautions against oxidative attack are therefore recommended to avoid decomposition when preparing PEG–clay nanocomposites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 548–552, 2004     

聚乙二醇中咪唑与芳基硼酸的N-芳基化反应

N-芳基咪唑类化合物是一类非常重要的结构单元,常见于药物、农药以及生物分子中,因此寻找新的合成N-芳基咪唑类物质的方法成为有机合成化学家关注的热点问题之一。在绿色化学的倡导下,研究发展了一个促进咪唑类底物与芳基硼酸N-芳基化反应的催化体系,它是以Cu_2O(10%)为催化剂,以聚乙二醇400为反应介质,在室温下反应。研究结果表明,该催化体系适用于咪唑类底物与各种具有不同取代基的芳基硼酸的N-芳基化反应,为N-芳基咪唑类化合物提供一个简单、有效、绿色的合成方法。     

Crystallization and morphology of cholesterol end‐capped poly(ethylene glycol)

Crystallization and morphology of polyethylene glycol with molecular weight M_n = 2000 (PEG2000) capped with cholesterol at one end (CS‐PEG2000) and at both ends (CS‐PEG2000‐CS) were investigated. It is found that the bulky cholesteryl end group can retard crystallization rate and decrease crystallinity of PEG, especially for CS‐PEG2000‐CS. Isothermal crystallization kinetics shows that the Avrami exponent of CS‐PEG2000 decreases as crystallization temperature (T_c). The Avrami exponent of CS‐PEG2000‐CS increases slightly with T_c, but it is lower than that of CS‐PEG2000. Compared to the perfect spherulite morphology of PEG2000, CS‐PEG2000 exhibits irregular and leaf‐like spherulite morphology, while only needle‐like crystals are observed in CS‐PEG2000‐CS. The linear growth rate of CS‐PEG2000 shows a stronger dependence on T_c than PEG2000. The cholesterol end group alters not only the free energy of the folding surface, but also the temperature range of crystallization regime. The small angle X‐ray scattering (SAXS) results show that lamellar structures are formed in all these three samples. By comparing the long periods obtained from SAXS with the theoretically calculated values, we find that the PEG chains are extended in PEG2000 and CS‐PEG2000, but they are once‐folded in CS‐PEG2000‐CS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2464–2471, 2007