The copolymerization of methyl methacrylate and isoprene in the presence of ethyl aluminium sesquichloride: role of monomer complexes

Abstract

The kinetics of the spontaneous copolymerization of methyl methacrylate and isoprene in the presence of ethyl aluminium sesquichloride in toluene and at temperatures between 0° and 40°C have been investigated. Irreproducible fast initial rates of copolymerization are followed by slower reproducible rates. The structures of the copolymer and the accompanying Diels-Alder adduct have been determined by 1H and 13C n.m.r.; the copolymers produced under a wide range of conditions are equimolar and highly alternating. The concentrations of various binary and ternary complexes have been assessed through 1H n.m.r. chemical shift measurements; it is shown that the mechanism of copolymerization cannot involve simply the effective homopolymerization of ternary isoprene-methyl methacrylate-ethyl aluminium sesquichloride complexes.