苯乙烯的单电子转移活性自由基聚合

以2,2-二溴甲基-1,3-二溴丙烷（PEBr4）为引发剂，Cu0粉/三（2-二甲氨基乙基）胺（Me6-TREN）为催化体系，在二甲亚砜（DMSO）和H2O的混合溶剂中实现了苯乙烯（St）的单电子转移活性自由基聚合（SET-LRP）。 通过1H NMR和GPC分析表明，所得聚合物为星形结构并具有较窄的分子量分布Mw/Mn=1.20（MGPCn=25.3×103，转化率为42.6%），且聚合物的链端保留了-Br端基。 考察了溶剂、反应温度及相转移催化剂对聚合的影响，结果表明，混合溶剂中H2O的体积分数由10%增加至20%导致了聚合速率的降低，表观聚合速率常数（kappp）由0.026 4 h-1减小至0.019 7 h-1；升高反应温度、增加催化剂用量以及相转移催化剂的加入分别导致聚合体系的kappp增加，同时，催化剂用量的增加和相转移催化剂的加入使聚合物的分子量分布系数降低。

Single Electron Transfer Living Radical Polymerization of Styrene

The polystyrene(PSt) was synthesized by a single electron transfer living radical polymerization(SET-LRP) in a binary mixture of dimethyl sulfoxide(DMSO) and water using 2,2-dibromomethyl-1,3-dibromopropane as the multifunctional initiator, Cu0 powder and tris-(2-dimethylamino ethyl)amine (Me6-TREN) as catalytic system. The resulting polymers were analyzed by 1H NMR and GPC, the results showed that the distribution of the resulting polymer was narrow(Mw/Mn=1.20, MGPCn=25.3×103, 42.6% conversion) and the polymers prepared were star shape and had perfect chain ends -Br retention. In addition, the kinetic plots of polymerization were first order, which indicated a living polymerization process. The various factors which had affected the SET-LRP of St such as solvent, polymerization temperature and phase transfer catalyst(PTC) were studied, and the results showed that the H2O content in the binary mixtures increasing form 10% to 20%(volume fraction) led to a reduction in polymerization rate, which could be revealed by the apparent polymerization rate constant(kappp) of 0.019 7 h-1 reducing from 0.026 4 h-1. Meanwhile the kappp increased in according with enhancing the polymerization temperature, increasing the amount of catalyst or adding the PTC. The addition of PTC or increasing the amount of catalyst could improve the control of the polymerization.