Alternating Addition Copolymerizations

Abstract

Conventional free-radical-initiated copolymerizations usually result in random copolymers. At the same time, certain monomer pairs are known to copolymerize giving regular alternation products, regardless of the composition of the monomer mixture. Behavior of the second type is characteristic of monomers differing considerably in their electron donor-acceptor character. The latter knowledge brought about a great resurgence of interest in the study of free-radical-initiated copolymerizations and many of these studies were concerned with MA. This interest was further kindled by the suggestion that the alternating tendency in some copolymerizations could arise from the participation of a 1 : 1 monomer-monomer donor-acceptor or charge-transfer complex (CTC) in the propagation reaction. Prior to this suggestion, it had generally been assumed that any alternating tendency arose as a consequence of the inherent reactivities of the monomers and radicals involved. As mentioned in Chapter 9, reactivity concepts were rationalized in terms of resonance and polar effects in semiempirical schemes such as the Q-e (1) and ``patterns''(2) concepts.