Application of Potassium Alkoxide and Potassium Phenoxide in Anionic Polymerization of MMA

The anionic polymerization of methyl methacrylate(MMA) initiated by n-butyl lithium(n-BuLi) was conducted in tetrahydrofuran (THF) solvent,in which potassium t-butoxide (t-BuOK) and potassium phenolate (POK) were added as the side reaction inhibitors.The molecular weight,molecular weight distribution (MWD) and molecular structure of the polymers were characterized by Gel Permeation Chromatography (GPC) and proton Nuclear Magnetic Resonance (¹H-NMR).Results revealed that the lithium counterion (Li⁺) in the active species was replaced by K⁺ via the ion exchange reaction between t-BuOK and n-BuLi.By means of the substitution reaction,the side reactions of MMA could be inhibited to some extent.When the molar ratio of t-BuOK to n-BuLi was greater than 10,the controllable anionic polymerization of MMA could be realized at 0℃.The MWD of PMMA was as narrow as 1.22 and the number-average molecular weight (M_n) was consistent with the theoretical value well.This means the side reaction in the anionic polymerization of MMA was suppressed well.Furthermore,POK could associate with K⁺ in the active species in the system,which further promoted the inhibition effect on the side reactions.As a result,the controllable anionic polymerization of MMA could be realized at higher temperature (40℃),the MWD of the synthesized PMMA was narrow (1.24) and M_n was approximate to the theoretical value.