Living Cationic Polymerization of Benzyl Vinyl Ether and Its Block Copolymers with Narrow Molecular Weight Distribution

Abstract

The living cationic polymerization of benzyl vinyl ether (BnVE) was achieved by the CH3CH(OiBu)OCOCH3(1)/EtAlCl2 initiating system in the presence of added bases. The effects of polymerization temperature and solvent were investigated in detail. Polymerizations in the presence of ethyl acetate at below 0°C in a non-polar solvent (toluene or CCl4) gave living polymers with a narrow molecular weight distribution (MWD) (M̅w/M̅n~1.1). The M̅n of the polymers increased in proportion to monomer conversion. The obtained living polymer was rich in isotacticity (~80%) by 1H NMR analysis. Fast living polymerization also occurred in the presence of methyl chloroacetate to synthesize higher molecular weight poly(BnVE) than >M̅n=105. Block copolymers were prepared by the sequential living polymerization of BnVE and isobutyl vinyl ether. Debenzylation of poly(BnVE) and its block copolymers was achieved by two methods [(A) HBr in toluene and (B) Na in liq. NH3] to give PVA and its block copolymers with a narrow MWD.