Effect of LiClO₄ and LiCl additives on the kinetics of anionic polymerization of methyl methacrylate in toluene-tetrahydrofuran mixed solvent

Abstract

The kinetics of anionic polymerization of MMA has been studied at -78 °C in toluene-THF (9:1 v/v) using 1,1'-diphenylhexyl lithium as initiator in the presence of lithium perchlorate and lithium chloride as Lewis acid additives. The control of the polymerization is lost in the absence of additives as evident from the non-linear first-order time-conversion plot and polymers with broad multimodal molecular weight distribution. The presence of LiClO₄ and LiCl in 10:1 and 5:1 ratio, respectively, over the initiator brings about sufficient control, yielding polymers of narrow unimodal distribution throughout the polymerization. The reaction in the presence of the additives follows first-order kinetics free of termination and transfer. Moreover, the order with respect to the active centers is found to be almost unity, which signifies a probable disaggregation of ion-pairs to a single complexed propagating species.