中国科学院机构知识库网格系统: PEO－PPO－PEO嵌段

作者：张馨予

作者郭晨
学位类别 博士
答辩日期 1999-11
授予单位 中国科学院研究生院
导师刘会洲 ; 陈家镛
关键词
其他题名 Aggregation of Polyoxyalkylene Block Copolymer and interaction with Protein
学位专业 化学工艺
中文摘要 聚环氧乙烷－聚环氧丙烷－聚环氧乙烷嵌段共聚物（PEO－PPO－PEO）在合成时可以通过控制PEO和PPO嵌段的长度，以及PPO及PEO的相对含量，改变物理化学性质，使其应用于诸多工业领域，因此，对PEO－PPO－PEO嵌段共聚物物化特性的研究具有重要的理论和实际意义。本研究的目的在于探索PEO－PPO－PEO嵌段共聚物的物化特性，及其与蛋白质的相互作用，以扩展PEO－PPO－PEO嵌段共聚物在生物工程领域的应用。本文应用傅立叶变换红外光谱（FTIR）和傅立叶变换拉曼光谱（FT－Raman）系统研究了各种PEO－PPO－PEO嵌段共聚物的蔟集行为，主要涉及嵌段共聚物在水溶液中依赖温度的胶团形成过程，以及嵌段共聚物在有机溶剂中水诱导的反胶团形成过程。分析阐述了嵌段共聚物形成胶团及形成反胶团的机理；在此基础上进一步探讨了PEO－PPO－PEO嵌段共聚物与蛋白质之间的相互作用。研究结果为PEO－PPO－PEO嵌段共聚物在生化工程领域的应用提供的科学依据。研究内容主要包括以下五个方面：1．分析研究了PEO－PPO－PEO嵌段共聚物的红外和拉曼光谱，确定了对构象变化敏感的特征谱带。使用傅立叶变换拉曼光谱和傅立叶变换红外光谱研究聚环氧乙烷－聚环氧丙烷－聚环氧乙烷（PEO－PPO－PEO）嵌段共聚物的无水样口及水溶液。提供了这些共聚物红外和拉曼光谱的定性表征。PEO－PPO－PEO嵌段共聚物的拉曼和红外光谱对结构和构象变化非常敏感。拉曼光谱和红外光谱中的其些峰与PPO／PEO比率和共聚物的构象相关。Pluronic F68和F88表现为具有一些反式构象的螺旋结构。其它嵌段共聚物随着PPO／PEO比率的增加显示出多的无序结构。同时讨论了PEO－PPO－PEO嵌段共聚物的无水样品的拉曼光谱与水溶液的拉曼光谱的比较。2．分析研究了PEO－PPO－PEO嵌段共聚物在水溶液中的依赖温度的胶团形成过程，应用去卷积方法辨析PPO和PEO嵌段不同的变化规律，阐述了PPO和PEO嵌段在胶团形成过程中的不同作用，揭示了PEO－PPO－PEO嵌段共聚物在水溶液中依赖温度的胶团形成机理。应用傅立叶变换拉曼光谱研究了四种PEO－PPO－PEO嵌段共聚物Pluronic P103、P104、P105和F88在水溶液中的依赖温度的胶团形成过程。拉曼光谱中的C－H伸缩振动区域的谱带频率和相对强度对嵌段共聚物链的极性和构象变化非常敏感，它们随温度的变化是嵌段共聚物胶团形成的标专。由此确定了这些嵌段共聚物10％水溶液的临界胶团温度。用去卷积方法解析C－H伸缩振动区域的重叠谱带，获得EO和PO嵌段的结构和微环境变化的信息。胶团外壳中的EO链段的水化程度随着温度的增加而降低，同时，EO链段的构象变得更加无序。PO链段由低温下的极性、扭曲构象变化为高温下的非极性、伸展构象。胶团形成的分子机理解释为EO和PO链段在温度影响下的结构和微环境变化。研究结果确定了疏水的PO链层在胶团形成中的决定地位，同时也揭示了亲水的EO链段的贡献。应用傅立叶变换红外光谱对聚环氧乙烷－聚环氧丙烷－聚环氧乙烷（PEO－PPO－PEO）嵌段共聚物Pluronic P105在水溶液中单体相和胶团相之间依赖温度的相转变过程进行了研究。8％的Pluronic P105水溶液的相转变温度为25 ℃。随着温度增加，PO链段表现为逐渐伸展的构象伴随着较强的链间相互作用，形成疏水的胶团核。EO链段在从单体相到胶团相的转变过程中变得更加无序，链层的堆积密度降低。EO和PO链段在相转变期间均表现出失水现象。3．分析研究了PEO－PPO－PEO嵌段共聚物在水溶液中胶团形成的热力学，分别计算了PPO和PEO嵌段的热力学参数，根据热力学参数的变化阐述了PPO和PEO嵌段在胶团形成中的不同作用，进一步确定了疏水的PO链段在胶团形成中的决定地位。应用傅立叶变化红外和拉曼光谱测量了四种PEO－PPO－PEO嵌段共聚物Pluronic P103、P104、P105和F88在水溶液中的温度依赖的胶团形成过程。使用去卷积方法分析了PPO嵌段和PEO嵌段的不同变化规律，分别计算了PPO嵌段和PEO嵌段的热力学参数。相转变温度T_m随着PPO含量的增加而降低，PPO嵌段的T_m比PEO嵌段的低；说明在相转变过程中，PPO嵌段先变化，PPO嵌段的变化引起PEO嵌段的变化；PPO含量的增加而降低，进一步说明高PPO含量的嵌段共聚物更容易发生相转变；PEO嵌段在T_m时的焓变随着PPO含量的增加而增加，表明在高PPO含量时不可忽略PEO嵌段的影响。4．分析研究了PEO－PPO－PEO嵌段共聚物在有机溶济中的反胶团形成过程。反胶团形成的机理解释为由水与水的相互作用增强而引起的聚合物分子相间互作用的加强，揭示了水在PEO－PPO－PEO嵌段共聚物的反胶团形成中的重要作用。应用傅立叶变换红外光谱技术研究了水诱导的PEO－PPO－PEO嵌段共聚物Pluronic L92在对二甲苯溶液中的反胶团形成。用去卷积和高斯曲线拟合的方法解析了水的OH伸缩振动谱带。溶解于反胶团中的水可分为单体结合水，双体结合水，自由水和束缚水。每种状态的水都随溶解水的增加而变化，水与EO的摩尔比（Z）可作为探测反胶团形成和结构变化的工具。当水比EO的摩尔比率（Z）＜ 0.35时，Pluronic L92不形成多分子胶团；当0.35 < Z < 1.3时，形成球形的胶团；当Z > 1.3时，胶团的外形可能是非球形的。水与EO的相互作作用在所考察的所有Z值情况下都很强，而水与水的相互作用在反胶团形成之前很弱，随着反胶团的形成而加强，嵌段共聚物分子的分子间相互作用也具有相同的变化规律。5．分析研究了PEO－PPO－PEO嵌段共聚物与蛋白质之间的相互作用。使用傅立叶变换红外光谱技术研究了PEO－PPO－PEO嵌段共聚物Pluronic L64在不同的水含量，存在和不存在牛血清白蛋白（BSA）的水／Pluronic L64／对二甲苯的微乳体系。考察了Pluronic L64的CO伸缩振动区域、CH伸缩振动区域和CH剪式振动区域、BA的酰胺I带，以及水的OH伸缩振动区域，获得了水－BSA相互作用、水－EO相互作用、共聚物链的分子间相互作用，PEO链的构象以及Pluronic L64微乳有BSA和没有BSA的情况下各种状态水的信息。分析比较了存在BSA和不存在BSA的微乳体系的红外光谱，获得了Pluronic L64和BSA分子之间相互作用的证据。Pluronic L64和BSA分子之间的相互作用主要是氢键作用，与Pluronic L64微乳结构有关或者说与水含量相关。BSA位于反胶团的界面双体结合水的位置。
英文摘要 Water-soluble triblock copolymers of poly (ethylene oxide) (PEO) and poly (propylene oxide) (PPO), often denoted (PEO-PPO-PEO), are commercially available nonionic macromolecular surfactant. Variation of the molecular characteristics (PPO/PEO ratio, molecular weight) of the copolymer during the synthesis allows the production of molecules with optimum properties that meet the specific requirements in different areas. They have attracted considerable attention in both fundamental research and practical application. Therefore, the purpose of this work is to explore physicochemical behavior of PEO-PPO-PEO triblock copolymer and interaction with protein, in order to develop application of polyoxyalkylene block copolymers in the area of biochemical engineering. In this work, aggregation behavior of PEO-PPO-PEO block copolymer in aqueous solution and organic behavior of PEO-PPO-PEO block copolymers have been studied, bands sensitive to conformation change have been determined. Fourier transform Raman (FT-Raman) and Fourier transform infrared (FTIR) spectra of poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) triblock copolymers as pure solids or liquids and in aqueous solutions have been examined. The qualitative features in Raman and FTIR spectra of these copolymers have been presented. The Raman and FTIR spectra of PEO-PPO-PEO triblock copolymers are very sensitive to the structural and conformational changes. It shows that relative intensities of several peaks in Raman spectra are dependent on PPO/PEO ratios and the conformation of copolymers. From Raman and FTIR spectra, Pluronic F68 and F88 can be considered as in helical structures with a few trans conformers. The behavior of other block copolymers has indicated that the disordered structure increases with increase of PPO/PEO ratio. The comparison of Raman spectra of pure solids or liquids PEO/PPO/PEO triblock copolymers with those in aqueous solutions has been presented. 2. Temperature-dependent micelle formation of PEO-PPO-PEO block copolymer in aqueous solution has been investigated, different roles of PPO and PEO block have been analyzed, and the mechanism of temperature-dependent micellization of PEO-PPO-PEO block copolymer been explained. The micellization of four PEO-PPO-PEO block copolymers under the trade name of Pluronic P10, P104, P105, and F88 in aqueous solutions vs. temperature was followed with FT-Raman spectroscopy. The frequencies and relative intensities of C-H stretching bands in FT-Raman spectra are sensitive to the local polarity and conformation of block copolymer chains, and their variations with temperature are indicators of micellization. Therefore, the critical micellization temperatures of these copolymers of 10% concentration in aqueous solutions were determined. The deconvolution method was used to resolve the overlapping bands in C-H stretching region and the deconvoluted spectra provide information about the structural and microenvironmental change of EO and PO blocks, respectively. The hydration of the EO chains in the corona was found to diminish with increasing temperature, while the conformation changes to a more disordered structure. The structure of PO chains changes from more polar, gauche conformation at low temperatures to less polar, stretching conformation at high temperatures. The micellization is explained by the change in structure and microenvironment of the EO and PO units. The results confirm the leading role of the hydrophobic PO units in micellization, and reveal a favorable contribution of the hydrophilic EO units. The phase transition between unimer and micellar phases of PEO-PPO-PEO triblock copolymer Pluronic P105 in aqueous solution as a function of temperature has been investigated using Fourier transform infrared FTIR spectroscopy. The transition of 8% Pluronic P105 in aqueous solution was found to occur at 25 ℃. As temperature increases, PO blocks appear to be stretched conformers and strong inter-chain interaction with the formation of a hydrophobic core in the micellar phase. The EO chains are found change to a more disordered structure with low chain packing density from the unimer phase to micellular phase. Both the EO and PO blocks exhibit dehydration during phase transition. 3. Thermodynamics of aggregation of PEO-PPO-PEO block copolymers has been investigated. The micellization of four PEO-PPO-PEO block copolymers under the trade name of Pluronic P103, P104, P105, and F88 in aqueous solutions vs. temperature was followed with FT-Raman and FTIR spectroscopy. The deconvolution method was used to resolve PPO and PEO block. Enthalpies (ΔH_m) and temperatures (T_m) during phase transition of each block have been obtained. T_m decrease with increase of PPO content, and T_m of PPO block is lower than that of PEO block. This explains the transition of PEO block is induced by that of PPO block during process of phase transition. ΔH_m of PPO block decreases with increase of PPO content, and that of PEO block increase with increase of PPO content. It shows that the effect of PEO block on micellization could not be overlooked for block copolymer with high PPO/PEO ratio. 4. Reverse micelle formation of PEO-PPO-PEO block copolymer in organic solvent has been investigated. The mechanism of reverse micelle formation is explained by the strengthening of the intermolecular interactions of copolymers, which was originated from the water-water interaction. The results confirm the leading role of water in the reverse micelle formation of PEO-PPO-PEO block copolymer. The water-induced reverse micelle formation of PEO-PPO-PEO block copolymer, Pluronic L92, in p-Xylene solution has been investigated by FTIR spectroscopic technique. The OH stretching band of water has been resolved by deconvolution and Gaussian curve fitting. The solubilized water can be classified into monomer bound water, dimer bound water, free water and trapped water. Each state of water is sensitive to the amount of water. Therefore, their variations with the water to EO molar ratio (Z) have been employed for the detection of the reverse micelle formation and structural change. It showed that the Pluronic L92 did not form polymolecular micelles when the molar ratio of water to EO (Z) is less than 0.35. For 0.35 < Z < 1.3, spherical micelles were formed and for Z > 1.3, the shape of micelles could be nonspherical. The water-EO interaction dominates at all water content studied. As water was added in the Pluronic L92-p-Xylene system, the water-water interaction strengthened during micellization and structural change of micelles. In the meantime, the block copolymer molecules showed stronger intermolecular interactions as compared with those before transition. 5. Interaction between PEO-PPO-PEO block polymer and protein has been investigated. The study of water-in-oil (w/o) micoemulsions of PEO-PPO-PEO block copolymer, Pluronic L64, in p-Xylene with different water content both in the absence and in the presence of bovine serum albumin (BSA) has been carried out by FT-IR spectroscopy. The information on water-BSA interaction, water-EO interaction, intermolecular interaction of copolymer chains, conformation of PEO chains, and various water states in Pluronic L64 microemulsions with or without the addition of BSA, was obtained from investigating of CO stretching band, CH stretching band, and CH scissoring band of Pluronic L64, amide I band of BSA, and OH stretching band of water. Evidence of molecular interactions between Pluronic L64 and BSA was obtained from the comparative analysis of spectra in the presence of BSA with those in the absence of BSA. Such interaction depends on the structure of Pluronic L64 micromemulsions or the content of water, with hydrogen bonding is primarily involved. The localization of BSA in reverse micelles is at the interface where the dimer bound water molecules reside.
语种中文
公开日期 2013-09-27
页码 134
源URL []
专题过程工程研究所_研究所（批量导入）

推荐引用方式
GB/T 7714 郭晨. PEO－PPO－PEO嵌段共聚物蔟集及蛋白质的相互作用[D]. 中国科学院研究生院. 1999.