硫氰基/有机铜锂体系引发MMA阴离子聚合研究

采用有机锂为引发剂，以甲基丙烯酸酯（MMA）类为单体进行阴离子聚合，其副反应较严重,因为在此类单体分子中存在卢碳和羰基碳两个亲核点，引发剂进攻羰基碳则会使链终止，在聚合过程中发生各种副反应,以碱金属（Li，Na，K）为反离子的有机碳负离子化合物，其亲核性较强，倾向于进攻羰基碳，因此甲基丙烯酸酯类单体的阴离子聚合除了采用较大立体阻碍引发剂外。

Anionic Polymerization of Methyl Methacrylate Initiated by Thiocyanate-Lithium Organocuprates

Polymerizations of methyl methacrylate(MMA) initiated by lithium homocuprate and lithium heterocuprate from cuprous thiocyanate in tetrahydrofuran solution were carried out. Polymerizations initiated by lithium homocuprate were sensitive to the mass ratio of monomer to initiator and reaction temperature. At 10 ℃, with the increase of the mass ratio of monomer to initiator, the molecular weight of PMMA increased and the color of the reaction system response got more and more darker. This was often the signal of the thermal instability of organocopper. This may hint that the living end had already been destroyed. Low reaction temperature made the initiator efficiency obviously dropping. In addition, with the decrease of reaction temperature, syndiotactic degree of PMMA increased. Polymerizations initiated by lithium heterocuprate showed that heterocuprate was more efficient initiators than homocuprate. Under the same reaction conditions, PMMA from polymerization initiated by heterocuprate had narrower MWD and higher syndiotactic degree.