Radical cyclopolymerizations of N-methyl-N-methallyl-2-(methoxycarbonyl) (1) were studied to see the validity of the proposal made previously. It states that the use of functional groups with a higher conjugative nature together with no homopolymerization tendency is essential for the design of 1,6-dienes with not only a high cyclization tendency but also high polymerizability. Monomer 1 was designed, since non-homopolymerizability of both the monofunctional counterparts of 1 could be assumed reasonably based on the reported polymerization behavior of compounds with similar structures. The alpha-substituted acryloyl group of 1 was found to have high conjugative nature and polymerizations of 1 proceeded rapidly to yield polymers with degree of cyclization of 97% even in its bulk polymerizations. The results thus obtained were fundamentally in accordance with what had been expected from the proposal. Structural studies showed that poly(1) consists almost exclusively of six-membered rings as repeat cyclic units. Mechanism for intramolecular cyclization during the cyclopolymerization of 1 was discussed based on the structural characteristics of poly(1) along with those reported for the polymers obtained from diallyl monomers. (C) 2000 Elsevier Science Ltd. All rights reserved.