聚氧化乙烯和聚醋酸乙烯酯在超声波辐照下接枝反应的研究

本文分别研究了聚氧化乙烯(PEO)和聚醋酸乙烯酯(PVAc) 在苯溶液中的超声波辐照降解,PEO与PVAc在苯溶液中的超声波辐照共聚反应。实验证明,降解反应可用Ovenall方程描述。用IR、NMR和DTA分析了在超声波辐照作用下PEO与PVAc在苯溶液中生成的共聚物的结构,证明所得产物主要为接枝共聚物,将浓度为1％的(PEO-PVAc)苯溶液在频率为18.2kHz、逆变器主迥路输入电流为2.0安的超声波强度下,辐照10分钟,共聚物的产率为10.54％,接枝点密度为33.3％,平均接枝链长为17。     

超声波辐照下聚氧化乙烯与甲基丙烯酸己酯非均相共聚反应研究

本文系统地研究了地超声波辐照下聚氧化乙烯(PEO)在其水溶液中与甲基丙烯酸己酯(HMA)的非均相共聚反应。结果表明,PEO超声降解产生的自由基可引发HMA聚合,形成PEO-HMA共聚物,该共聚物在超声波辐照下可进一步降解。通过红外光谱、裂解气相色谱及核磁共振分析表明,所得共聚物为嵌段共聚物。     

超声辐照下PEO与NaMAA嵌段共聚反应的研究

本文研究了在超声波辐照下聚氧化乙烯与甲基丙烯酸钠在水溶液中的嵌段共聚反应和共聚物结构。共聚反应按自由基聚合机理进行。反应动力学方程可用-(d[M]/(dt))=k[R·]^(1/6)[M]表示。随辐照时间或单体浓度的增加,共聚物产率和共聚物中NaMAA含量增大。将1％PEO-105％NaMAA水溶液在频率21.5kHz、阴极电流0.7A的超声强度下辐照15分钟,共聚物的产率为24.0％。用IR、MS、NMR、DSC、TEM等分析了共聚物的化学结构和聚集态结构,表明所得共聚产物为嵌段共聚物。     

在超声辐照作用下聚氧化乙烯和丙烯腈嵌段共聚的研究

本文研究了聚氧化乙烯(PEO)和丙烯腈(AN)在水溶液中的超声共聚。共聚速率和AN浓度成正比,存在AN浓度最低限。PEO的降解速率常数越大,它所共聚的AN量越大,表明AN的聚合是由PEO降解生成的大自由基引发生成的。通过元素分析和IR测定证明产物为PEO-AN共聚物。通过POM、TEM、DSC和WAXD测定证实共聚物为结晶嵌段共聚物。     

星型共聚物PEO_3-b-PDMAEMA_3的pH敏感和温敏性研究

本课题组结合阴离子开环聚合技术和原子转移自由基聚合技术,以环氧乙烷(EO)和甲基丙烯酸[2-(二甲基氨基)乙基]酯(DMAEMA)为单体,合成了分子量可控、分子量分布窄的星型嵌段共聚物PEO3-b-PDMAEMA3。基于PEO的亲水性和PDMAEMA的温敏和pH敏感性,我们用荧光光谱仪、动态激光散射仪等比较研究了该系列星型嵌段共聚物在水溶液中的温敏及pH敏行为,证明其具有温敏和pH敏感性,而且其临界胶束化pH值要小于相应的线型嵌段共聚物的临界胶束化pH值。     

新型含糖嵌段共聚物PEO-b-P(lys-ML)的合成及其在水中的聚集行为

用氨端基PEO作大分子引发剂 ,引发lys(Z) NCA开环聚合制得共聚物PEO b P(lys Z) ,经脱除保护基———苄氧羰基 (Z)后 ,与麦牙糖内酯反应制得水溶性嵌段共聚物聚环氧乙烷 b 聚 (Nε 麦芽糖酰 L 赖氨酸 )(PEO b P(lys ML) ) .用荧光方法研究了PEO b P(lys ML)在水溶液中的聚集行为 .结果表明 ,在某一临界聚集浓度 (Criticalaggregationconcentration ,简称cac)以上 ,聚合物在水中自聚集形成胶束型聚集体 ;在浓度低于cac时 ,加入与葡萄糖基团有特殊相互作用的凝集素 (ConcanavalinA ,简称ConA)也能诱导聚合物形成聚集体 ,此类聚集体对于开发新型药物载体有重要意义     

嵌段质量分数对手性超分子螺旋结构自组装的影响

首先,以溴代聚乙二醇单甲醚(PEO-Br)为引发剂、甲基丙烯酸丁酯(BMA)为单体,通过原子转移自由基聚合(ATRP)制备了一系列具有不同聚乙二醇(PEO)质量分数的聚甲基丙烯酸丁酯-b-聚乙二醇嵌段共聚物(PBMA-b-PEO)。在此基础上,将手性酒石酸(TA)以氢键的方式选择性掺入到嵌段共聚物的PEO相中,诱导嵌段共聚物自组装制备具有手性螺旋结构的复合薄膜PBMA-b-PEO/TA。利用小角X射线散射(SAXS)、透射电子显微镜(TEM)和圆二色光谱(CD)对嵌段共聚物复合薄膜进行表征,研究了嵌段质量分数对手性诱导嵌段共聚物螺旋结构自组装的影响。结果表明:掺入TA与嵌段共聚物质量比为0.12、0.15的TA,当PEO质量分数为0.17～0.24时,有利于嵌段共聚物相分离形成柱状螺旋结构;当PEO质量分数增加至0.26时,嵌段共聚物自组装则形成层状结构,在分子间氢键作用下虽然发生手性转移,但无法得到螺旋结构。     

F68和F108水溶液溶胶-凝胶转变过程的流变学研究

采用流变学方法研究了具有高PEO质量分数(80%)的两亲性三嵌段共聚物Pluronic F68(PEO₈₀-PPO₃₀-PEO₈₀)和F108(PEO₁₃₃-PPO₅₀-PEO₁₃₃)的水溶液在升温过程中的溶胶-凝胶转变过程, 发现对于特定浓度的嵌段共聚物水溶液, 在溶胶-凝胶转变过程中会出现一个“软凝胶”区域, 通过对F68进行区域的频率扫描实验, 推测了相应的内部结构.     

交联共聚物（ER—PEO）及其与NaSCN络合物的结构研究

环氧树脂(ER)与聚环氧乙烷(PEO)的共混物经水/乙醇萃取后的剩余物为交联ER-PEO非晶共聚物。萃取分析表明,ER/PEO中约有50wt·％的PEO与ER形成ER-PEO交联共聚物。ER/PEO与NaSCN络合后,由于Na~ 的配位络合作用,使结晶能力进一步降低。     

PEO—PPO—PEO三嵌段共聚物自组装行为的耗散粒子动力学模拟

采用耗散粒子动力学方法（DPD）,模拟了聚氧乙烯-聚氧丙烯-聚氧乙烯（PEO—PPO—PEO）三嵌段共聚物在乙醇溶液中的自组装行为,考察了该共聚物的体积分数和聚氧乙烯（PEO）嵌段链长对介观形貌的影响。当F88（PEO104-PPO39-PEO104）体积分数为20％时,胶柬由初始的均衡分散态逐渐聚合,最终形成PPO为核、PEO为壳的平衡态柱状团聚体。改变共聚物的体积分数和PEO链的长度,会形成不同的介观结构,如：球状、柱状、立体网络、层状和穿孔状结构等。结果表明,DPD方法是研究三嵌段共聚物自组装行为和介观结构形成机理的有效工具,对合成具有特定结构性能的材料有一定的指导意义。     

Studies on Ultrasonic Degradation and Block Copolymerization of Hydroxyethylcellulose and Poly(ethylene Oxide)

The ultrasonic degradation of hydroxyethylcellulose (HEC) and poly (ethylene oxide) (PEO) in aqueous solution, and the copolymerization of HEC with PEO were studied. The structure of the copolymer was identified by DTA, IR, MS, x-ray diffraction, and polarizing microscopy. The copolymer prepared is mainly block. The copolymer formed amounts to 55.07% by irradiating 0.5% HEC/PEO aqueous solution for a period of 10 min at 25°C and 18.2 kHz with 2.5 A input current on a reversed main circuit.     

Adsorption and Exchange Dynamics in Aging Hydroxyethylcellulose Layers on Silica

The adsorption kinetics of hydroxyethylcellulose (HEC) on silica and relaxations in adsorbed HEC layers were probed using total internal reflectance fluorescence and near-Brewster reflectivity. Like many random-coil polymers, HEC was found to adsorb at the transport-limited rate. Relaxations occurred at nearly constant interfacial mass when HEC layers were exposed to aqueous solvent, causing the subsequent exchange of chains between the layer and the free solution to become increasingly hindered. Eventually, on the time scale of a day, layers became immobilized and unable to accommodate chains from free solution. A continued fluorescence decay, beyond time scales that could be probed with self exchange, suggested further relaxations of the adsorbed HEC. The polydisperse HEC system (with an average molecular weight near 450,000) behaved qualitatively similar to molecular weight standard polyethylene oxide (PEO) layers on silica. For instance, relaxations in PEO layers occurred on a time scale of 10-20 h, like the HEC layers. Young layers of the latter, however, exhibited self-exchange kinetics that were an order of magnitude slower than PEO layers of similar age. This difference in adsorbed layer dynamics was attributed to HEC's stiffer backbone, compared with flexible PEO. Copyright 2000 Academic Press.     

Adsorption of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers at the silica-water interface

The adsorption of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) and poly(ethylene oxide)-b-poly(gamma-methyl-epsilon-caprolactone) copolymers in aqueous solution on silica and glass surfaces has been investigated by flow microcalorimetry, small-angle neutron scattering (SANS), surface forces, and complementary techniques. The studied copolymers consist of a poly(ethylene oxide) (PEO) block of M(n) = 5000 and a hydrophobic polyester block of poly(epsilon-caprolactone) (PCL) or poly(gamma-methyl-epsilon-caprolactone) (PMCL) of M(n) in the 950-2200 range. Compared to homoPEO, the adsorption of the copolymers is significantly increased by the connection of PEO to an aliphatic polyester block. According to calorimetric experiments, the copolymers interact with the surface mainly through the hydrophilic block. At low surface coverage, the PEO block interacts with the surface such that both PEO and PCL chains are exposed to the aqueous solution. At high surface coverage, a dense copolymer layer is observed with the PEO blocks oriented toward the solution. The structure of the copolymer layer has been analyzed by neutron scattering using the contrast matching technique and by tapping mode atomic force microscopy. The experimental observations agree with the coadsorption of micelles and free copolymer chains at the interface.     

EFFECT OF OVERLAP CONCENTRATION AND PERSISTENCE LENGTH ON DNA SEPARATION IN POLYMER SOLUTIONS BY ELECTROPHORESIS

The persistence length and the overlap concentration(c~*) of poly(ethylene oxide)(PEO) and hydroxyethylcellulose(HEC) with similar molecular weight in 1×TBE buffer were studied by laser light scattering and viscometry.Their effect on DNA separation was investigated by capillary electrophoresis.It was determined that the persistence length of HEC was at least 5 times higher than that of PEO.Therefore,the c~* of HEC was smaller than that of PEO by a factor of ca.2.5.It was also found that the c~* values de...     

A Simple and Effective Approach to Vesicles and Large Compound Vesicles via Complexation of Amphiphilic Block Copolymer With Polyelectrolyte in Water

This work reports for the first time a simple and effective approach to trigger a spheres‐to‐ vesicles morphological transition from amphiphilic block copolymer/polyelectrolyte complexes in aqueous solution. Vesicles and large compound vesicles (LCVs) were prepared via complexation of polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) with poly(acrylic acid) (PAA) in water and directly visualized using cryo‐TEM. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on the PAA and PEO blocks of the block copolymer. The findings in this work suggest that complexation between amphiphilic block copolymer and polyelectrolyte is a viable approach to vesicles and LCVs in aqueous media.     

荧光探针技术研究共溶剂对PEO-PPO-PEO嵌段共聚物溶液胶束的形成及内部结构的影响

选择了甲醇、乙醇、正丙醇、乙二醇、乙二胺、乙醇胺及２甲氧基乙醇等七种包括单官能团和双官能团共溶剂、与水组成混合溶剂,并利用荧光探针技术研究了共溶剂对环氧乙烷环氧丙烷环氧乙烷（ＰＥＯＰＰＯＰＥＯ）共聚物水溶液胶束形成及其结构的影响,结果表明,一些共溶剂与水和共聚物ＰＰＯ段都具有较好的混溶性,使形成胶束的ＣＭＴ升高,而其它共溶剂的引入则使得形成胶束的ＣＭＴ降低．从共溶剂对所形成胶束的微结构影响看,能与共聚物链有较强作用的双官能团的共溶剂和有较小分子尺寸的共溶剂有利于使形成的胶束具有较紧密的结构,在此条件下,形成胶束的紧密程度决定了胶束内微极性的大小,而与引入共溶剂的极性大小关系不大．     

Two Gel States of a PEO‐PPO‐PEO Triblock Copolymer Formed by Different Mechanisms

Two gel states of a PEO‐PPO‐PEO (Pluronic P103) triblock copolymer in water are investigated using small‐angle X‐ray scattering, rheology and differential scanning calorimetry. The first gel state turns out to be the hexagonal microphase while the second gel state, showing turbidity change with four distinct regions, is somewhat disrupted. The second gel is moreover not thermoreversible as evidenced by rheology. Based upon the present study, two different gelation mechanisms for aqueous PEO‐PPO‐PEO solutions are proposed.     

P123(PEO20-PPO70-PEO20)嵌段共聚物水溶液物理凝胶化行为的耗散粒子动力学模拟

采用耗散粒子动力学(Dissipative particle dynamics, DPD)方法研究了P123(PEO20-PPO70-PEO20)嵌段共聚物水溶液常温下的物理凝胶化行为. 在体积分数(2%~10%)较低时, P123在水溶液中形成球形胶束. 当P123的水溶液体积分数升高到20%时, 会形成柱状胶束. 在P123的水溶液体积分数为30%和40%时, 观察到具有三维网络结构的凝胶. 这些模拟结果不仅与实验结果一致, 而且证明了耗散粒子动力学方法是一种非常适合研究物理凝胶化行为的重要方法. 另外, 在P123的水溶液体积分数为40%时, 研究了凝胶随着时间发展的形成过程.     

部分水解聚丙烯酰胺-羟乙基纤维素的水相pH响应性自组装

为考察无规共聚物在全水相环境中的自组装行为, 合成了结构类似于无规共聚物的低相对分子质量的部分水解聚丙烯酰胺(HPAM). 尝试改变水溶液pH值来诱导HPAM与羟乙基纤维素(HEC)发生自组装, 采用透射电子显微镜(TEM)观察到不同pH值时分别获得了100 nm的似正方体胶束, 200 nm×100 nm的类椭球胶束, 100 nm的串珠状胶束以及500 nm×300 nm×50 nm的半月形胶束等pH响应性核壳型聚合物胶束. 建立了金在胶束表面原位还原耦合TEM表征方法, 用于检测低衬度聚合物胶束的纳米细节; 配合电子探针X射线微区分析(EPMA)和扫描电子显微镜(SEM), 证实了半月形聚合物胶束的精致分级构造为亲水性内囊@疏水性连续囊壁@亲水性外壳的多泡囊泡, 并证实pH=0.9时多泡囊泡崩解为疏水性内核@亲水性外壳的10 nm类球体小胶束. 通过分析链节质子化状态的pH响应性, 结合zeta电位和吸光度测定结果, 阐释了不同pH值时组成聚合物胶束的核和壳的链段归属, 获得了全水相中HPAM自组装驱动力和形貌方面的全新知识.