Adsorption of Diblock Copolymers of Poly(ethylene oxide) and Poly(lactide) at Hydrophilic Silica from Aqueous Solution

The inverse osmotic compressibility of the poly(propylene imine) dendrimers in deuterated methanol has been measured as a function of concentration with small-angle neutron scattering. The experimental results reveal three different regimes. First, there is a dilute regime going up to a maximum in the inverse osmotic compressibility. This region can be subdivided into a very dilute region, where the behavior is hard-sphere-like, and a denser region, where the solvation layers overlap. The maximum, occurring around volume fraction 0.30 for each generation, is found to be the concentration where the distance between the centers of two dendrimers is twice their radius of gyration. It designates the crossover to the second regime of a semidilute phase with shrinking dendrimers. Interpenetration of the dendrimers does not seem to take place. Finally, for the higher generations, at high concentrations, the dendrimers are collapsed and the inverse osmotic compressibility starts to increase again. As dendrimers are regularly and very highly branched molecules, they can be considered as ultimately hyperbranched polymers. For both types, the experimental inverse osmotic compressibility shows similar features. The dendrimers seem to be more compact, however. Copyright 2000 Academic Press.     

聚乳酸-聚乙二醇-聚乳酸三嵌段共聚物的降解性能

以辛酸亚锡为引发剂,聚乙二醇大分子为共引发剂进行现交酯开环聚合,制备了系列聚乳酸（PLA）－聚乙二醇（PEG）－聚乳酸（PLA）三嵌段共聚物。从共聚物在生理盐水 中降解时特性粘度[η],质量和热行为的变化,考察了PEG分子量和丙交酯／PEG（摩尔比）对共聚物降解行为的影响,结果表明,PEG嵌段对共聚物的降解速率有重要影响,丙交酯／PEG一定时,PEG分子量越大,共聚物越容易降解,PEG嵌段长度一定时,丙交酯／PEG越大,共聚物降解速率越小。     

Poly（L—lactide）—Poly（ethylene glycol） Multiblock Copolymers：Synthesis and Properties

Poly (L-lactide)-poly (ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. These copolymers presented special properties, such as better miscibility between the two components, low crystallinity and better hydrophilicity, which can be modulated by adjusting the block lengths of the two components.     

聚乙二醇-聚L-丙交酯嵌段共聚物结晶形貌研究

用偏光显微镜和原子力显微镜对比研究了PEG-PLLA嵌段共聚物在110℃或120℃等温结晶后的结晶形貌.发现在110℃时只有PEG5000-PLLA2300和PEG5000-PLLA6300在偏光显微镜下呈现环带球晶形貌,在原子力显微镜高度图中显示明显的环带,并具有交替凸凹起伏形貌.而PEG5000-PLLA12000球晶中没有出现环带形貌而是生成了规则的环线.在120℃时,PEG5000-PLLA12000的球晶中才生成了规则的环带图案,原子力显微镜也显示了其球晶具有明显的交替凸凹起伏形貌,说明过冷度直接影响环带球晶的生成.产生周期性凸凹起伏和明暗交替消光是由片晶沿着球晶的半径方向周期性扭转造成的,片晶在凸起部分是Edge-on取向,在凹下部分是Flat-on取向.     

Shape Memory Properties in Poly(ethylene oxide)–Poly(ethylene terephthalate) Copolymers

Memory effects of several copolymers of poly(ethylene oxide) (PEO) and poly(ethylene terephthalate) (PET) were illustrated with photos, determined with shrinkage experiments and characterized by the recovery of samples to their original figures. Copolymers of appropriate composition could undertake an approximately full recovery which is tightly related to the annealing temperature at which shrinkage of samples occurs to some extent. Melting and recrystallization of PEO segments may be responsible for the memory effect. The memory properties of samples almost kept unchanged after many fatigue cycles (e.g. 15–20 cycles), which could make these copolymers useful in practical applications as novel shape memory materials. © 1997 John Wiley & Sons, Ltd.     

Adsorption of Diblock Copolymers of Poly(ethylene oxide) and Polylactide at Hydrophobized Silica from Aqueous Solution

The adsorption of a series of amphiphilic diblock copolymers of poly(ethylene oxide) (PEO) and poly(DL-lactide) (PL) at hydrophobized silica from aqueous solution was studied using time-resolved ellipsometry and reflectometry. The adsorbed amounts only display a weak dependence on the copolymer composition in both water and phosphate-buffered solution. For the short copolymers, the layer thickness decreases slightly with increasing length of the hydrophobic block. Furthermore, in comparison with the short copolymers, the layer thickness of the long copolymers is substantially higher. Upon degradation of the PL block, the adsorbed amount is found to decrease and approach that of the corresponding PEO homopolymer. Protein rejection studies indicate that the adsorption of fibrinogen is inhibited by copolymer preadsorption. The protein rejection is enhanced with increasing surface coverage of the preadsorbed copolymer, but largely independent of the length of the PL block and the PEO block. For all polymers investigated, essentially complete protein rejection is obtained above a critical surface coverage that is significantly lower than the saturation coverage of the copolymers. Removing the copolymer from bulk solution after preadsorption causes a partial desorption, resulting in reduced protein rejection. However, the protein rejection capacity with and without copolymer in the bulk solution is found to be similar at a given surface coverage. Contrary to the behavior of the intact copolymers, fibrinogen adsorption is found to be significant at surfaces pretreated with an extensively degraded copolymer and, in fact, quantitatively comparable to that at the hydrophobic surface in the absence of preadsorption. This finding, together with that of the effect of the copolymer composition on protein rejection, suggests that an efficient protein rejection is maintained until only a few L units remain in the copolymer, i.e., until nearly completed degradation. Copyright 2000 Academic Press.     

聚氯乙烯-聚氧乙烯共混物的反相色谱研究

用反相色谱研究了聚氯乙烯与聚氧乙烯的相容性,发现其共混物的比保留体积V_g23具有重量加和性,表明共混物可能发生了相分离。导出了相分离体系聚合物相互作用参数X₂₃的近似关系式:X₂₃=(X₁₂-X₁₃)²/2,由此式可以解释X₂₃对探针种类的依赖性。聚氯乙烯和聚氧乙烯共混体系的反相色谱实验结果基本符合这一关系式。     

Bioengineering Functional Copolymers. IX. Poly[(maleic anhydride-co-hexene-1)-g-poly(ethylene oxide)

Amphiphilic bioengineering copolymers having a combination of hydrophilic/hydrophobic linkages and polyelectrolyte behavior, along with an ability to interact with biomacromolecules, in particular with the invertase enzyme, have been synthesized by (a) complex-radical copolymerization of maleic anhydride (MA, the acceptor) and hexene-1 (H-1, the donor) monomers with benzoyl peroxide as the initiator in 1,4-dioxane at 65 degrees C under high-conversion conditions and (b) subsequent grafting (polyesterification) of synthesized poly(MA-alt-H-1) with alpha-methoxy-omega-hydroxy-poly(ethylene oxide) (PEO). Copolymerizations were also carried out in the steady state, in order to essentially reduce the effect of copolymer composition drift. The values of the monomer reactivity ratios (r(1) and r(2)) determined by using the known terminal models of Fineman-Ross (FR) and Kelen-Tüd?s (KT), as well as by nonlinear regression (NLR) analysis, are: r(1) = 0.16 and r(2) = 0.30 (FR), r(1) = 0.14 and r(2) = 0.27 (KT), and r(1) = 0.15 and r(2) = 0.29 (NLR), respectively. All the copolymers and graft copolymers were characterized by FTIR spectroscopy, (1)H{(13)C} NMR spectroscopy, viscometric measurements, and chemical (acid number), thermal (DSC and TGA), and X-ray diffraction analyses. Unlike poly(MA-alt-H-1)s, PEO macrobranched graft copolymers exhibit expressed polyelectrolyte and swelling behavior in diluted and concentrated dioxane solutions, respectively. The copolymer and its PEO hyperbranched derivatives can be used as carriers for enzyme immobilization.     

聚乙二醇-聚乳酸共聚物药物载体

本文综述了聚乙二醇与聚乳酸共聚亲水改性的最新进展, 包括嵌段和星型结构聚乙二醇-聚乳酸共聚物(PEG-PLA)及其端基化衍生物的合成。同时概述了该共聚物以胶束、微粒、水凝胶和囊泡形式担载亲水、疏水及蛋白质类药物的应用,特别介绍了静电纺丝制备的PEG-PLA超细纤维载体及其释药特性。     

Compatibility of Poly(vinyl chloride) with Polyalkyleneoxides. I. Poly(methylene oxide) and Poly(ethylene oxide)

The compatibility of poly(vinyl chloride) (PVC) with linear polyethers is examined over the entire composition range. This study examines blends with poly(methylene oxide) (PMO) and poly(ethylene oxide) (PEO) of medium (MMW) and high (HMW) molecular weight. The techniques used are dynamic mechanical analysis, DSC, and optical microscopy (phase contrast and polarizing). The results indicate that all polyethers show limited miscibility in the melt at high PVC contents. Proper analysis of the T_m data using the Kwei-Frisch and Hoffman-Weeks procedures allows the determination of the thermodynamic interaction parameter, which is found to be close to zero for all pairs of blends.     

Radiation Degradation of Copolymers. III. Poly(styrene-co-methyl Acrylate)

The distribution of volatile products from γ-irradiation of copolymers of styrene and methyl acrylate is independent of the composition of the copolymer and the same as that obtained from poly(methyl acrylate). The yields are less than proportional to the methyl acrylate content, Indicating a protective effect from the styrene units as observed previously in copolymers of styrene with methyl methacrylate. The flexural strengths of the copolymers, measured at 1°C, decrease with radiation dose for high styrene content, but increase for high methyl acrylate content. Samples irradiated in air have appreciably lower strengths than those irradiated in vacuum. Gel measurements show intermediate behavior for the copolymers between the homopolymers.     

Crystallization and Physical Ageing of Poly (2-vinyl pyridine)-b-poly(ethylene oxide) Diblock Copolymers

Summary: A set of melt miscible Poly(2-vinyl pyridine)-b-Poly(ethylene oxide) (P2VP-b-PEO) block copolymers of different compositions were studied. Transmission electron microscopy shows phase separation in the materials during the crystallization process of the PEO block as crystalline lamellae are observed for all compositions evaluated. The isothermal crystallization kinetics of PEO is progressively retarded as the P2VP content in the copolymer increases, since P2VP hinders molecular mobility in the miscible amorphous phase. Polarized light optical microscopy demonstrated that the glassy P2VP block has a negative effect on the secondary nucleation of the PEO. Finally, physical ageing experiments performed in the glassy state of the amorphous mixed phase, at different ageing times, demonstrated that a nucleating effect can be induced in the glassy state as a consequence of the reorganization of the amorphous regions. This nucleating effect significantly alters the cold crystallization rate upon subsequent heating above the glass transition temperature.     

苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的受限结晶行为的反气相分析

 采用反气相法研究了苯乙烯 氧乙烯 苯乙烯三嵌段结晶聚合物 (PS PEO PS)的结晶熔融相变 ,测定了PS PEO PS的结晶度、熔点以及熔程 ,探讨了正构烷烃探针分子的碳链长度对测定结果的影响。研究结果表明 :PS PEO PS的微相分离对PEO链段的结晶行为有较大的影响 ,其晶体结构中存在由多种不完善PEO结晶和PS非结晶构成的中间层 ;正构烷烃探针分子的碳链长度对测定PS PEO PS的熔点和熔程无影响 ,但对结晶度测定和PEO结晶熔融相变的检测影响较大 ,所测得PS PEO PS的结晶度随正构烷烃探针分子碳链的增长而降低。     

共聚酯PEIT-PEG结构与性能的研究

PET与PEG共聚可改善PET的抗静电性，但PEG含量的增加，会使共聚物的结晶温度大幅度地降低，不利于纤维加工，且伴随着结晶的发生，纤维的抗静电性也受到影响。在共聚体系中添加间苯二甲酸(IPA)，不仅能破坏大分子链结构的规整性、降低共聚酯的结晶性，而且能提高共聚酯纤雏的抗静电性能。用DSC与TG对共聚酯(PEIT-PEG)的聚集态结构、热性能、结晶性能等进行了表征。     

Poly(ethylene oxide)s hydrophobically modified. Adsorption and spreading at the air-water interface

A comparative study of spread and adsorbed monolayer of poly(ethylene oxide)s of different molecular weight hydrophobically modified with alkyl isocyanates of different length chain is reported. The modification of the polymer was carried out according to reported procedures. The polymers obtained were studied at the air-water interface by Langmuir isotherms for spread monolayers and by Gibbs isotherms for the adsorption process. Isotherms obtained are interpreted in terms of the hydrophobic and hydrophilic balance of the polymers. Limiting area per repeating unit (A(0)) and collapse pressure (pi(c)) from spread monolayers were obtained. Spread monolayers of the hydrophobically modified polymers show larger collapse pressure values than unmodified polymer monolayers. In the adsorption process the excess surface concentration Gamma(infinity), area per repeat unit sigma, and efficiency of the adsorption were determined. The values of the area occupied per repeat unit in adsorbed monolayer (sigma) were larger than those of the spread monolayer. The efficiency of the adsorption of poly(ethylene oxide)s increases with the hydrophobic modification and with the alkyl chain length.     

聚氧乙烯大单体与甲基丙烯酸甲酯的共聚合及其共聚物的研究

研究了聚氧乙烯（ＰＥＯ）大单体与甲基丙烯酸甲酯的溶液共聚合，考察了引发剂用量，单体总浓度、投料比、反应时间对共聚物组成和分子量的，ＩＲ、ＨＮＭＲ、ＧＰＣ、ＶＰＯ、ＤＳＣ航透射电等测定结果表明，经纯化的共聚物具有预期的结构，且呈现微相分离，体外人体正常抗凝血浆复钙时间测定结果显示：共聚物的抗凝血明显好于玻璃和ＰＭＭＡ均聚物，且随共聚物中ＰＥＯ含量的增加而增强，经水化处理的共聚物的抗凝血性比未经处理的     

聚左旋乳酸-聚乙二醇二嵌段共聚物的非等温结晶行为研究

通过变温广角X射线衍射(WAXD)、 差示扫描量热法(DSC)和偏光显微镜(POM)研究了聚左旋乳酸-聚乙二醇(PLLA-PEG)二嵌段共聚物的非等温结晶行为, 并用Ozawa方程分析了PLLA-PEG的非等温结晶动力学. 实验结果表明, 高熔点的硬段PLLA结晶符合Ozawa理论, 而低熔点的软段PEG对PLLA的结晶起到了稀释剂的作用; 当软段PEG开始结晶时, 已经结晶完全的硬段PLLA限制了PEG的结晶, 使得软段PEG的结晶不符合Ozawa理论. 此外, 不同降温速率下的结晶形貌研究结果表明, 随着降温速率的增加, 晶体经历了从环带球晶、 环带和十字消光的混合球晶到典型的十字消光球晶的转变, 并且球晶的尺寸也明显变小.     

共聚酯PEIT-PEG结晶性能的研究

通过偏光显微镜、广角X衍射与FTIR三种测试手段对共聚酯PEIT-PEG的结晶性能进行了系统的研究，重点分析了间苯二甲酸(IPA)、聚乙二醇(PEG)分子量和含量对共聚酯结晶性的影响。研究表明，PEIT与PEG之间发生了共聚反应，IPA的引入使PET结晶性能下降，晶粒尺寸减少，结晶度降低。引入PEG后，当PEG分子量和含量较低时，共聚酯结晶性能提高；当PEG含量较高时，在PEG分子量不变的情况下，随着PEG含量的增加，结晶性能下降；若PEG重量含量相同，PEG分子量越高，结晶性能越好。     

The Degradation of Poly(ethylene terephthalate)

The penetration of new markets by polyester fibers has emphasized the need for increased stability of the polyester toward a variety of degradative reactions. Extensive studies of the nature of the thermal, hydrolytic, oxidative, and radiation-induced degradation reactions have been reported. The interpretation of kinetic investigations and the identification of the reaction products have been facilitated by using suitable esters as model compounds in place of the polymeric species.     

Application of New Modified Poly(ethylene Oxide)-Block-Poly(propylene oxide)-Block-Poly(ethylene oxide) Copolymers as Demulsifier for Petroleum Crude Oil Emulsion

Water soluble nonionic amphiphilic block copolymers based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(propylene glycol) (PPG) were prepared. Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymers, PEG-PPG-PEG, were prepared in the normal condition. The chemical composition and molecular weights of the prepared copolymers were determined from ¹H NMR and GPC techniques. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The prepared nonionic surfactants were evaluated as demulsifiers for water in crude-oil emulsions that were pronounced at different ratios of crude oil: water at 318 K and 333 K. The experimental results showed that the dehydration rate of the prepared demulsifiers reached 100% based on demulsifier chemical compositions and concentrations.