Cationic copolymerization of vinyl ethers with styrene derivatives and their model reactions: selectivity of a growing carbocation

Abstract

In order to assess the possibility of cross propagation in cationic copolymerization, vinyl ethers were copolymerized with styrene derivatives using BF 3O(C 2H 5) 2 catalyst in toluene and methylene chloride at −78°C, and the monomer reactivity ratios were determined. The experimental results were compared with the relative reactivity of these olefins in the electrophilic addition of diethyl acetal and of Ph 3CSnCl 5. The addition of diethyl acetal could be a model for the reaction of vinyl ether-type propagating species, and that of Ph 3CSnCl 5 for styrene-type propagating species. Either in the copolymerizations or in the model reactions a carbocation preferred to react with one having a similar structure to the two olefinic compounds, provided that a steric interruption between the carbocation and the olefins is not significant.