Effect of reaction medium on the ionizing radiation‐initiated cationic copolymerization of styrene derivatives

Abstract

AbstractThe influence of reaction medium polarity on the ionizing radiation‐initiated copolymer‐ization of styrene derivatives involving unpaired carbocations is examined. In the copo‐lymerization of nonpolar monomers such as p‐CH3styrene/styrene, a small effect consistent with that predicted by Laidler‐Eyring theory is found. In the copolymerization of nonpolar/polar monomer pairs such as p‐CH3styrene/p‐Clstyrene and styrene/p‐Clstyrene, any such effect is masked by specific solvation phenomena. A competition between such phenomena appears to exist, in which the different cations are dominated by different interactions. The p‐Clstyryl cation appears to undergo strong intramolecular complexation with the penultimate aromatic ring in nonpolar conditions; thus, this cation displays increased se‐lectivity toward monomers best able to disrupt the complex. The p‐CH3styryl and styryl cations do not appear to be subject to such strong complexation; thus, in nonpolar solvent, their selectivity tends towards monomers with the highest cation‐solvating ability. The differing copolymerization behavior of the p‐Clstyryl cation is consistent with the findings of previous investigations of the effect of reaction medium on chain transfer with these monomers. © 1995 John Wiley & Sons, Inc.