Sulfur‐containing vinyl monomers. XIII. Cationic copolymerizations of vinyl sulfides with some vinyl monomers

Abstract

AbstractCationic copolymerizations of vinyl sulfides (VS) with some vinyl monomers with boron tri‐fluoride‐diethyl etherate catalyst were investigated to evaluate their monomer reactivities. The effects of VS on the copolymer yield and viscosity of the resulting copolymers revealed the inhibition or retardation mechanism which was explained in terms of the formation of a stable vinylsulfonium salt by the reaction between a propagating carbonium ion and VS monomer. From the results of copolymerizations of phenyl vinyl sulfide (PVS) with isobutyl vinyl ether (IBVE), β‐chloroethyl vinyl ether (CEVE), α‐methylstyrene (α‐MeSt), and styrene (St), the relative reactivities of these monomers were found to be in the following order: IBVE > CEVE > PVS > α‐MeSt > St. The relatively higher reactivity of PVS than St derivatives was explained on the basis of the conjugative and electron‐donating nature of the VS monomer. The effects of alkyl and para‐substituted phenyl groups in vinyl sulfides on their reactivities toward the propagating carbonium ion were correlated with polar factors and compared with those of the hydrolysis of α‐mercaptomethyl chlorides. The transition state for the propagation reaction in cationic polymerization of VS was proposed to be a π‐complex type structure.