镍体系(NiCl_2/PPh_3)催化的反向原子转移自由基聚合

以 2 ,3 二氰基 2 ,3 二苯基丁二酸二乙酯 (DCDPS) NiCl2 PPh3 为引发体系 ,首次利用Ni2 + 和Ni+ 之间的变价关系 ,研究了乙烯基单体的反向ATRP .结果表明 ,苯乙烯 (St)的聚合具有活性自由基聚合的特征 ,所得PSt的分子量随转化率的增加而增加 ,并且制得的PSt可以作为大分子引发剂进行扩链反应 .但该引发体系引发甲基丙烯酸甲酯 (MMA)聚合时没有活性自由基聚合特征 ,PMMA的分子量与转化率基本无关 ,但分子量分布窄Mw Mn=1 19

A REVERSE ATRP PROCESS CATALYZED BY NICKEL-BASED(NiCl2/PPh3) SYSTEM

Radical polymerization of styrene and methyl methacrylate was investigated using a nickel based initiating system, i.e. DCDPS/NiCl 2/PPh 3,in which diethyl 2,3 dicyano 2,3 diphenyl succinate (DCDPS) is a hexa substituted ethane thermal iniferter and the nickel based catalyst reacted from Ni 2+ to Ni 1+ .The polymerization of styrene (St) was successfully controlled in bulk at 120℃.The kinetics studies showed that the kinetics is first order in monomer.The number average molecular weight M n increased linearly with conversion from 57100 to 126000,and the molecular weight distributions( M w/ M n) were around 1 5 as the monomer conversion was increased from 38% to 86%.Well defined polystyrene with α (carbethoxycyanophenyl)methyl ω chlorine end groups was obtained from the polymerization of St with DCDPS/NiCl 2/PPh 3 initiating system,and the polymerization proceeded via reverse ATRP.While the polymerization behavior of methyl methacrylate(MMA) initiated with the same system was absolutely different.The molecular weights of so obtained PMMA did not increase with the monomer conversions and at the same time the molecular weight distributions kept narrow ( M w/ M n=1 19) during the polymerization.