Grafting styrene onto poly(vinyl acetate) by free radical chain transfer reactions

Abstract

Poly(vinyl acetate– graft-styrene) graft copolymers were prepared by the free radical polymerization of styrene (St) in the presence of a poly(vinyl acetate– co-vinyl iodoacetate) (PVAc-I) statistical copolymer as a macromolecular chain transfer agent. The chain transfer agent was prepared by the radical copolymerization of vinyl acetate and vinyl chloroacetate, followed by the replacement of the chlorine atoms in the copolymer with iodine atoms through reaction with KI in acetone. The resulting iodoacetate moieties acted as chain transfer sites during St polymerization in the presence of PVAc-I. No crosslinking was noticed during the polymerization under the experimental conditions employed. As polymerization proceeded, the amount of both graft copolymer and homopolySt, and also St content of the graft copolymer increased, while the amount of non-grafted macromolecular chain transfer agent decreased. The efficiency of the grafting process was not very high, as at about 40% St conversion the raw material contained 17 wt% homopolySt, 11 wt% non-grafted PVAc-I, and only 72 wt% graft copolymer. The synthesized graft copolymers were characterized by 1H NMR and DSC measurements.