Cyclopolymerization XXVIII. Radical polymerizations of N-substituted N-methallyl-2-(methoxycarbonyl)allylamines: Polymerizability of unconjugated dienes with functional groups with low homopolymerization tendency

Radical cyclopolymerizations of N-substituted-N-methallyl-2-(methoxycarbony l)allylamines (1) were studied to compare their cyclopolymerizabilities wit h those of N-substituted-N-allyl-2-(methoxycarbonyl)allylamines (2). Monome rs 1 with a phenyl(1a) and a t-butyl(1b) group as an N-substituent were emp loyed. The phenyl group was chosen, since 2 with an N-phenyl group(2a) was reported to have exceptionally low polymerization tendency among 2. Monomer 1b was polymerized to see whether the bulky N-t-butyl group enhances the c yclization tendency of 1 or not, since 1 with an N-methyl group(1c) was rep orted to yield polymers with pendant unsaturations, though their content is low. It was found that polymerizations of 1a proceed very slowly like 2a, but the reason for their slow polymerizations was left unsolved. Polymers w ith high degree of cyclization, 96% for poly(1a) and 100% for poly(1b), wer e obtained even in their bulk polymerizations. This could be an additional support for the proposal made previously. It states that unconjugated diene s, for which monofunctional counterparts do not have homopolymerization ten dency yield highly cyclized polymers. This is because both the monofunction al counterparts of 1 are considered to have essentially no homopolymerizati on tendency. The bulky t-butyl group was found to be effective to enhance c yclization tendency also in 1. Structural studies showed that poly(1a) and poly(1b) contain both six- and five-membered rings as repeat cyclic units. Mechanism for intramolecular cyclization was discussed.