Recent developments in polymerization by an alternating intra-intermolecular mechanism

Recent developments in polymerization by an alternating intra-intermolecular mechanism are summarized and discussed briefly. The methods used to prove the structure of typical polymers, which in turn established the mechanism of polymerization, are reviewed. A study of larger ring formation by Marvel and Garrison is also summarized. Ring of sizes from 7 to 21 members were formed from α-diolefins in yields of from 4 to 25%. A study of certain unsymmetrical dienes has shown that cyclization occurs in yields up to 60%, but that gelation eventually occurs because of the difference in relative reactivities of the two olefinic double bonds. Copolymerization of certain 1,4-dienes with certain olefins to produce linear copolymers containing six-membered rings is discussed. In an effort to explain the strong driving force to close a six-membered ring during polymerization of 1,6-diolefins, a pronounced interaction between the double bonds, which can be represented by several resonance forms of the molecule, is proposed.