Studies on the charge‐transfer complex and polymerization. XI. Donor‐acceptor interaction in alternating radical copolymerization

Abstract

AbstractThe microstructure of the copolymer of butadiene with maleic anhydride has been shown by IR spectra to be rich in cis‐1,4 structure (about 70% at 60°C.), whereas the butadiene homopolymer by radical mechanism is rich in trans‐1,4 structure. The copolymer rich in cis‐1,4 structure was also observed in the copolymerization of butadiene with sulfur dioxide, but the copolymers of butadiene with styrene, acrylonitrile, dimethyl maleate, diethyl fumarate, or fumaronitrile were rich in trans‐1,4 structure. Because the free butadiene monomer exists as the transoid structure, the activation of butadiene through the cisoid complex is assumed in the copolymerization with maleic anhydride. This shows that the donor‐acceptor interaction between butadiene and maleic anhydride or sulfur dioxide participates in this alternating radical copolymerization, and the small alternating tendency observed between butadiene and acrylonitrile, maleate, or fumarate comes from the stabilization of the transition state by electrostatic interaction or electron transfer.