甲基丙烯酸甲酯原子转移自由基聚合等规度研究

在0～100℃温度范围内,由原子转移自由基聚合方法,采用助催化和非助催化体系,引发甲基丙烯酸甲酯聚合,利用¹³CNMR测定聚甲基丙烯酸甲酯的等规度.发现原子转移自由基聚合仍以间同立构为主,随着聚合温度的升高间同立构等规度降低,与通常自由基聚合对有规立构控制特征相似.助催化剂异丙醇铝和活性端羰基配位,对聚合物的立构规整性有一定的影响.

Studies on the Tacticity of Poly(methyl methacrylate) Synthesized by Atom Transfer Radical Polymerization

Two series of PMMA samples have been synthesized by Atom Transfer Radical Polymerization(ATRP) with and without catalytic promoter(aluminum isopropoxide, (i-PrO)₃Al in the temperature range of 0~100 ℃. Their tacticity has been determined by ¹³C Nuclear Magnetic Resonance(NMR). The results showed that the polymers by ATRP were all predominantly syndiotactic, and the tendency to form syndiotactic sequences decreased with the polymerization temperature increase. The tacticity of PMMA was influenced by catalytic promoter, [(i-PrO)₃Al], because it coordinates with the ester carbonyl group of polymer chain end. The activation parameters governing the tacticity of ATRP were calculated. The results indicate that the same type of active species is present in ATRP and conventional radical system.