水分散体系中苯乙烯和甲基丙烯酸甲酯梯度共聚物的合成与表征

Synthesis and Characterization of Gradient Copolymer Composed of Styrene and Methyl Methacrylate in Water Dispersion System

以 2 -溴代异丁酸乙酯 ( EBi B)为引发剂 ,Cu Br/Cu Br2 /1 ,1 0 -邻二氮菲 ( phen)为复合催化剂 ,十二烷基磺酸钠 ( SLS)为乳化剂 ,考察了水分散体系中苯乙烯 ( St)和甲基丙烯酸甲酯 ( MMA)的原子转移自由基共聚合的可控性和相对反应活性 .在此基础上 ,通过反应进料法在水分散体系中进行了 St和 MMA的梯度共聚合 ,反应表现出“活性”聚合的特征 ,即所得共聚物的数均分子量随着单体转化率的增加而增大 ,分子量分布较窄 ( Mw/Mn<1 .5 0 ) .用 1 H NMR跟踪分析了聚合反应过程中共聚物微观组成的变化规律 ,结果表明 ,共聚物链中 MMA链节的累积含量和瞬时含量都随着共聚物相对链长的增加而增加 ,即随着聚合物相对链长的增加共聚物的微观组成从 St链节占主导地位逐渐变化为以 MMA链节占主导地位 ,表明确实形成了 St和MMA的梯度或渐变共聚物 .

The controllability as well as the monomer reactivity for the atom transfer radical copolymerization of styrene(St) and methyl methacrylate(MMA) in water dispersion system was examined with ethyl 2-bromoisobutyrate as the initiator,CuBr/CuBr_2/1,10-phenanthroline as catalyst and sodium laurylsulfonate as surfactant,respectively. The gradient copolymerization of St and MMA was performed in the water dispersion system with continuous addition of the second monomer MMA into the copolymerization system. The experimental results showed that the water dispersion gradient copolymerization proceeded in a living fashion,producing well-defined copolymers with narrow polydispersities and controlled molecular weights. The increase of the cumulative composition and instantaneous composition of MMA unit along the copolymer chain length demonstrated that the gradient copolymer composed of St and MMA was successfully synthesized in such a water dispersion system. [WT5HZ]