Cationic Polymerization of 1, 2-Dialkoxyethylenes

Abstract

1, 2-Dimethoxyethylene (DME) and 1, 2-diethoxyethylene (DEE) were polymerized by cationic catalysts in order to clarify the effect of an electron-donating group, an alkoxyl group, at an olefinic β-carbon on the reactivity of vinyl ethers in cationic polymerization. Both DME and DEE were found to be very reactive and homopolymers were easily produced at high yield, in spite of the presence of a bulky β-alkoxyl group. A partially crystalline polymer was formed in the polymerization of cis-DME catalyzed by the Al2(SO4)3-H2SO4 complex catalyst. The relative reactivities of 1, 2-dialkoxyethylenes were measured on the basis of the results of copolymerization with vinyl ethers and alkenyl ethers. BF3O(C2H5)2 and toluene were used as catalyst and solvent, respectively. The reactivity of these monomers increases as followsmethyl vinyl ether≤trans-DME<trans-methyl propenyl ether (MPE)<cis-MPE<cis-DMEand ethyl vinyl ether≈trans-DEE<cis-DEE.This order can be explained in terms of a model of the propagation step in which an attacking carbonium ion interacts with the π-electron on the olefinic double bond and the ether oxygen of vinyl ethers.