黄原酸酯调控的氯乙烯的可逆-加成断裂链转移聚合

Reversible addition-fragmentation chain transfer polymerization of vinyl chloride controlled by xanthate

以三种不同结构的黄原酸酯为调控剂,进行氯乙烯(VC)溶液和细乳液可逆加成-断裂链转移(RAFT)聚合,发现O-乙基黄原酸丙酸乙酯对VC聚合的调控效果良好,氯乙烯RAFT细乳液聚合速率明显大于溶液聚合,VC聚合12h转化率大于90%,但聚氯乙烯(PVC)的分子量分布宽于溶液聚合产物。核磁共振和紫外可见吸收光谱分析证明合成的PVC具有黄原酸酯基端基结构,结构缺陷少。含黄原酸酯基PVC可进一步调控VC及醋酸乙烯酯聚合,进行扩链或得到嵌段共聚物。结合聚合动力学,说明黄原酸酯调控的氯乙烯聚合具有活性特征。

Three xanthates with different structures were prepared and employed in vinyl chloride(VC)solution and miniemulsion polymerizations as reversible addition-fragmentation chain transfer(RAFT)agents.It was found that VC polymerization could be well controlled by using O-ethyl-S-(1-ethoxycarbonyl)ethyl dithiocarbonate as the RAFT agent.The rate of VC RAFT miniemulsion polymerization was obviously higher than that of RAFT solution polymerization,and the conversion of VC was higher than 90%for the miniemulsion polymerization running for 12 h,while the molecular weight distribution of poly(vinyl chloride)(PVC)prepared by RAFT miniemulsion polymerization was wider than that of PVC prepared by RAFT solution polymerization.The 1H NMR and UV-Vis absorption spectroscopy analysis of PVC-xanthate proved the presence of chain-end functional groups and the absence of structural defects.PVC-xanthate could be further used as macro-RAFT agent for VC and vinyl acetate polymerization,to prepare chain extended PVC and poly(vinyl chloride)-b-poly(viny acetate)copolymer,respectively.Combined with polymerization kinetics study,the living characters of xanthate-mediated solution and miniemulsion polymerizations of VC were verified.