氯乙烯活性自由基聚合及其嵌段共聚物的合成与自组装

Living radical polymerization (LRP) of vinyl chloride (VC) remains enormously challenging due to a high chain transfer constant to the monomer, nonsolubility of PVC in its monomer and poor thermal stability of PVC. Till now, few attention has been paid to the synthesis and self-assembly of VC block copolymers. Single-electron transfer degenerative chain transfer (SET-DT) and reversible addition fragmentation-chain transfer (RAFT) polymerizations of VC will be carried out in this work. The approaches to improve the controlling of SET-DT polymerization and polymerization rate will be explored based on the combined considering of polymerization chemistry mechanism, mass transfers between different phases and particle formation mechanism of aqueous VC suspension and suspended emulsion SET-DT polymerizations. Several xanthate chain transfer agents which can effectively mediate RAFT suspension and (mini)emulsion polymerizations of VC would be synthesized, and the polymerization mechanism and kinetics would be investigated. Through above research, the novel methods to prepare PVC with low structure defects and good thermal stability would be proposed. Furthermore, block copolymers consisting of PVC and different hydrophilic polymer blocks would be synthesized using living PVC as macro-initiator or macro-chain transfer agent, and effects of block copolymer structures on the self-assembly behavior in bulk and solution states would be investigated. The theories related to living radical polymerization of chlorine-containing monomers and condensed structures of block copolymers would be extended.

氯乙烯(VC)自由基聚合向单体链转移反应显著、PVC不溶于单体且热稳定性差，造成VC活性自由基聚合难度大、可控性差，进一步合成VC嵌段共聚物及嵌段共聚物自组装的研究很少。本项目开展VC单电子转移-蜕化链转移(SET-DT)和可逆加成-断裂链转移(RAFT)聚合研究，结合水相悬浮和悬浮态乳液SET-DT聚合化学机理、聚合过程相际传质和成粒机理，探索提高SET-DT聚合可控性和反应速率的有效途径；合成能有效调控VC单体RAFT水相悬浮和细(乳液)聚合的黄原酸酯类链转移剂，并研究聚合机理和动力学；建立合成化学缺陷结构少、热稳定性好的PVC的新方法。以活性PVC为大分子引发剂或链转移剂，进一步制备由PVC和不同特性亲水聚合物链段构成的嵌段共聚物，研究嵌段共聚物结构对其本体和溶液自组装行为的影响。通过以上研究，拓展与含氯单体活性自由基聚合和嵌段共聚物凝聚态结构相关的理论。

采用传统自由基聚合合成的聚氯乙烯(PVC)的分子量分布较宽且化学缺限结构含量较高。此外，PVC还存在韧性和亲水性差等不足。无规共聚和接枝共聚是目前工业PVC化学改性的主要方法，而VC活性自由基聚合和嵌段共聚尚未工业化应用。单电子转移-蜕化链转移(SET-DT)和可逆加成-断裂链转移(RAFT)聚合是两种具有工业化应用前景的VC活性自由基聚合方法，但采用水相悬浮和细乳液(即微悬浮)等工业常用聚合方法时，聚合速率和可控性尚有待提高。本项目首先开展VC水相悬浮和细乳液SET-DT和RAFT聚合研究，结合聚合化学、传递扩散机理和PVC成粒过程，研究了聚合方法、聚合体系组成、工艺条件等对聚合动力学和PVC分子量及分子量分布的影响，实现了水相悬浮SET-DT聚合速率的显著提高，建立了优选黄原酸酯RAFT试剂调控的VC自稳定RAFT悬浮聚合、VC细乳液RAFT聚合、VC-VAc细乳液RAFT无规和嵌段共聚等方法。其次，以碘封端活性PVC为大分子引发剂，通过溶液和反相乳液SET-DT聚合合成了VC与丙烯酸、甲基丙烯酸、甲基丙烯酸二氨基乙酯、N-异丙基丙烯酰胺、N,N-二甲基丙烯酰胺及N-丙烯酰吗啉的三嵌段共聚物；通过含黄原酸酯基团的聚乙二醇(PEG)和聚醋酸乙烯酯(PVAc)调控的溶液、悬浮和细乳液RAFT聚合制备了PVC-PEG和PVAc-PVC嵌段共聚物(醇解得到PVA-PVC嵌段共聚物)，得到嵌段共聚动力学和嵌段共聚物分子量及分子量分布变化规律。再次，研究了含不同亲水链段、不同嵌段分子量的VC嵌段共聚物的本体自组装、溶液水相自组装、溶液旋涂和静态呼吸图成膜特性，得到嵌段共聚物结构对本体相结构、临界胶束浓度、胶束形貌和尺寸、膜形貌的影响规律。最后，利用两亲性VC嵌段共聚物的自组装特性，制备了嵌段共聚物改性的抗生物玷污或具有pH响应的PVC分离膜、可作为拉曼光谱增强基底的嵌段共聚物蜂窝多孔膜；又以两亲嵌段共聚物为模板，制备了纳米氧化钛多孔膜。项目研究拓展了VC活性自由基聚合、VC嵌段共聚合、两亲性VC嵌段共聚物自组装理论，为嵌段共聚改性PVC的制备和应用提供了基础。

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