丙二腈存在下苯乙烯-甲基丙烯酸甲酯的活性无规共聚研究

Malononitrile as Additive for Random Copolymerization of Styrene with Methyl Methacrylate Mediated by Stable Free Radical Polymerization

研究了少量丙二腈对稳定自由基（TEMPO）存在下苯乙烯（St）和甲基丙烯酸甲酯（MMA）无规共聚的影响．发现丙二腈对于该共聚体系具有明显的加速效果．丙二腈与TEMPO的摩尔比在2．5：1时加速效果最好．在125℃下聚合30min转化率可达93％，共聚产物分子量随转化率增大而增大．分子量分布较窄（1．1～1．5）．聚合速率随St在单体中的比例提高而减小．在MMA的单体比例较大时仍能得到分散性小的共聚物．

The living free radical random copolymerizations of styrene with methyl methaerylate initiated by henzoyl peroxide （BPO） were studied in the presence of TEMPO （2,2,6,6-tetramethylpiperidinyl-l-oxy） with the addition of malononitrile （MN）. It was found that eopolymerization was distinctly accelerated by the addition of small amount of MN. In comparison with the homopoly-merization of St with MMA, these systems represented a dramatic improvement. The copolymerization of St with MMA achieved high conversion （93%） in 30 minutes at 125℃ ,when fst, is 0.2,[-MN] ： [-TEMPO] ： FBPO] = 3 ： 1.2 ： 1. The rate of polymerization is nearly 50 times higher than that without MN. Even at less styrene ratios at the monomer （fst=0.2） ,the molecular weight of the copolymer gradually increased with time and maintained a low polydispersity. The eopolymerization of styrene with MMA proceeded in a living fashion indicated by the increase in molecules weight with time and conversion and relatively low polydispersity. The molecular weights can be controlled from 10000 to 23000 amu and polydispersities can be controlled from 1.1 to 1.5. In the all ^1HNMR spectra of polymers using MN as additive,we didn＇t find the peaks refered to additive and the peaks of end groups of polymers were still existed.