The role of charge-transfer complexes in cyclocopolymerization

Abstract

ABSTRACT.Previous work from this laboratory has shown that certain 1 ,4-dienes which readily undergo cyclocopolymerization with certain alkenes also form chargetransfer complexes with the same alkenes. The results observed and the proposed cyciocopolymerization mechanism are consistent with participation of the charge-transfer complex as a distinct species in the copolymerization. This paper includes a discussion of an investigation to determine whether there was a dilution effect on the relative reactivities of the monomers in support of the charge-transfer participation concept, and whether the results of a suitable terpolymerization study would also support this postulate. In the system, divinyl ether-fumaronitrile, the maximum rate of copolymerization occurred at a monomer feed ratio of 1:2 and the composition of the copolymer was also 1:2 ata total monomer concentration of 3 moles/i. However, when the concentration was progressively lowered to 05 ml1, using the same monomer feed ratio, the fumaronitrile content of the copolymer decreased in a linear manner. In a series of terpolymerization experiments using the system, divinyl ethermaleic anhydride-acrylonitrile, it was shown that the divinyl ether-maleic anhydride ratio in the terpolymer was always greater than 1: 1 and had an upper limit of 1:2, regardless of the feed ratio of the termonomers. These results are consistent with the participation of the charge-transfer complex of divinyl ether and maleic anhydride in a copolymerization process with either maleic anhydride or acrylonitrile as the comonomer. Other systems which support these concepts are also presented. This paper emphasizes theoretical aspects of the problem rather than attempting to summarize the many examples of comonomer systems which have been found to participate in this interesting copolymerization.