Linkage Configuration and Triad Distribution in the Copolymers of Isobutyl Vinyl Ether andN-Phenyl-maleimide Prepared in Chloroform and in Methyl Ethyl Ketone

Abstract

The radical copolymerisation of isobutyl vinyl ether (IBVE) with N-phenylmaleimide (PMI) shows a strong alternating tendency. The alternating tendency is more pronounced in the less polar solvent chloroform than in more polar methyl ethyl ketone (MEK). The monomer unit triad distribution and the proportion of cis and trans linkage configurations at cyclic PMI units in the copolymers, which are determined from the 13C NMR spectra, indicate that more alternating triads are formed when the copolymerisation is conducted in the less polar chloroform and that the amount of cis linkages, Fcis, is directly proportional to the amount of alternating triads, F101. Because the formation of the cis linkages would be a less favourable process for free monomer additions in the propagation but the cis linkages can be formed by the reaction of an electron donor/acceptor complex formed by the monomers, and because almost identical relations between Fcis and F101 are found for the copolymerisation in vastly different solvents, chloroform and MEK, it is concluded that the alternating sequences are formed via participation of a complex of the monomers.