GROUP-TRANSFER POLYMERIZATION OF N-BUTYL ACRYLATE WITH LEWIS-ACID CATALYSTS .1. KINETIC INVESTIGATION USING HGI2 AS A CATALYST IN TOLUENE

The group transfer polymerization (GTP) of n-butyl acrylate using 1-me thoxy-1-(trimethylsiloxy)-2-methyl-1-propene as an initiator and HgI2 as a catalyst in toluene is much slower compared to nucleophilic-catal yzed GTP; half-lives are in the range of minutes to hours. Induction p eriods are observed which are attributed to the formation of trimethyl silyl iodide (TMSI). The polymerization follows first-order kinetics w ith respect to the concentrations of initiator and catalyst. With resp ect to concentration of monomer the reaction is of first-order interna lly but follows an external reaction order of 1.52 due to the higher p olarity of the reaction medium at higher monomer concentrations. The d egree of polymerization is controlled by the ratio [M](0)/[I](0), and the molecular weight distribution is narrow and can be described by a modified Poisson distribution. Generally, M(w)/M(n) less than or equal to 1.2. It is proposed that the active species are formed from initia tor, catalyst, and TMSI.