Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives

Abstract

The possibility of copolymer formation and the effect of polymerization conditions on monomer reactivity ratios (MRR) were investigated for cationic copolymerizations of a vinyl ether with styrene derivatives. 2-Chloroethyl vinyl ether (CEVE) was used as the vinyl ether, and p-methoxystyrene (pMOS), p-methylstyrene (pMS) and α-methylstyrene (αMS) as styrene derivatives. Copolymerization was carried out in toluene or methylene chloride, being catalyzed by BF3·O(C2H5)2 or SnCl4·CCl3CO2H at −78°C. The copolymer composition was determined from each monomer consumption through gas chromatography. The copolymer formation was confirmed by fractionation and NMR spectrum of the product. In CEVE–αMS system, the relative reactivity of each monomer was independent of the kind of the propagating chain ends (r1×r2≅1). In contrast, composition curves showed an S-shape in CEVE-pMOS and CEVE–pMS systems (r1×r2>1). This difference may be attributed to the difference in stability between the growing carbonium ions of αMS and the ring-substituted styrenes. It was found that polymerization conditions significantly affect MRR; the CEVE content in the copolymer was greater for BF3·O(C2H5)2 than for SnCl4·CCl3CO2H, and greater in toluene than in methylene chloride.