可逆加成-断裂链转移聚合制备聚氯乙烯-b-聚乙二醇-b-聚氯乙烯共聚物

合成了含黄原酸酯端基的聚乙二醇（X-PEG-X）大分子链转移剂，并以其为可逆加成-断裂链转移试剂调控氯乙烯（VC）溶液和悬浮聚合，合成聚氯乙烯-b-聚乙二醇-b-聚氯乙烯（PVC-b-PEG-b-PVC）三嵌段共聚物。X-PEG-X调控VC溶液聚合得到的共聚物的分子量随聚合时间增加而增大，分子量分布指数小于1.65。X-PEG-X具有水/油两相分配和可显著降低水/油界面张力的特性，以X-PEG-X为链转移剂和分散剂，通过自稳定悬浮聚合也可合成PVC-b-PEG-b-PVC共聚物，共聚物颗粒无皮膜结构，分子量随聚合时间增加而增大；由于VC悬浮聚合具有聚合物富相和单体富相两相聚合特性，共聚物分子量分布指数略大于溶液聚合共聚物。通过乙酸乙烯酯（VAc）扩链反应进一步证实了PVC-b-PEG-b-PVC的“活性”，并合成PVAc-b-PVC-b-PEG-b-PVC-b-PVAc共聚物。水接触角测试表明PVC-b-PEG-b-PVC的亲水性优于PVC。

Synthesis of poly(vinyl chloride)-b-poly(ethylene glycol)-b-poly(vinyl chloride) block copolymers by reversible addition-fragmentation chain transfer polymerizations

Poly(ethylene glycol) terminated with xanthate (X-PEG-X) was synthesized and used as the reversible addition-fragmentation chain transfer (RAFT) agent for controlling vinyl chloride (VC) solution and suspension polymerizations to synthesize poly(vinyl chloride)-b-poly(ethylene glycol)-b-poly(vinyl chloride) (PVC-b-PEG-b-PVC) triblock copolymers. Results show that the molecular weights (MW) of block copolymers prepared by the solution polymerization are increased with the polymerization conversion, and the molecular weight distribution (MWD) index is lower than 1.65. X-PEG-X is amphiphilic and can effectively reduce the interfacial tension between water and oil. Thus, a novel VC RAFT suspension polymerization method was proposed to prepare PVC-b-PEG-b-PVC copolymers using X-PEG-X as the RAFT agent and a suspending agent. The block copolymer particles have no surface membranes, and MW of copolymer is increased with conversion. However, the block copolymers prepared by suspension polymerization exhibit wider MWD than the block copolymers prepared by solution polymerization, due to the two-phase mechanism of VC suspension polymerization. The chain extension of PVC-b-PEG-b-PVC with vinyl acetate (VAc) further prove the “living” nature of PVC-b-PEG-b-PVC copolymers and result the formation of PVAc-b-PVC-b-PEG-b-PVC-b-PVAc copolymer. PVC-b-PEG-b-PVC copolymers exhibit better hydrophilicity than PVC.