Synthesis and properties of photosensitive rubbers. I. Direct addition reaction of α,β-unsaturated carboxylic acids to polydienes and polypentenamer

The addition reaction of α,β-unsaturated carboxylic acids to polydienes, such as cis-1,4-polybutadiene, 1,2-polybutadiene, and polypentenamer, was investigated in the presence of acid catalysts in order to obtain photosensitive rubbers. The structures of products obtained were identified as cyclized polydiene rubbers having pendent α,β-unsaturated carboxylate groups. The amount of the incorporated substrates increased up to the maximum of around 20 mole %, and the amount of the residual unsaturated groups in the polymer backbone decreased because of cyclization of the double bond. The products had two glass transition temperatures. These glass transition temperatures were identified as follows: a lower transition, owing to the original polydiene segment where the incorporated carboxylate groups were located; and a higher one, owing to cyclic segment. These two thermal transitions on the polymer backbone indicate that the cyclic structure exists as a block segment in the polymer and the carboxylate group is incorporated at random in a polydiene structure. The synthetic condition needed to obtain a desired amount of the incorporated substrate and the degree of the cyclization of polydienes and polypentenamer were investigated.