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.
Anionic polymerization of methyl methacrylate (MMA), n-butyl methacrylate (nBMA) and glycidyl methacrylate (GMA) initiated by nBuCu(NCy2)Li (1) in tetrahydrofuran (THF) at -50 degrees C to -10 degrees C was investigated. It was found that the polymerization of MMA and nBMA initiated by 1 proceeded quantitatively in THF to afford PMMA and PBMA with polydispersity index 1.15-1.30 and nearly 100% initiator efficiencies at -10 degrees C. The molecular weights increased linearly with the ratio of [monomer]/[1]. However, a post-polymerization experiment carried out on this system revealed a double polymer peak by GPC when fresh monomer was added after an interval of 10 min. Polymerization of styrene could be initiated by 1, but the initiator efficiency was low.
