Synthesis and photochemical reaction of polystyrenes with pendant donor―acceptor type norbornadienes containing carbamoyl chromophores

摘要

The donor―acceptor type norbornadiene (D―A NBD) carboxylic acids containing carbamoyl groups such as di-propylcarbamoyl, methylphenylcarbamoyl, propylcarbamoyl, and phenylcarbamoyl groups were synthesized in good yields. Benzyl esters of the D―A NBD carboxylic acids were also prepared by the reaction of D―A NBD carboxylic acids with benzyl bromide as reference compounds for the polymers. Polystyrenes with pendant D―A NBDs were prepared with 100% degree of substitution by the reaction of D-A NBD carboxylic acids and poly[(p-chloromethyl)styrene] at 70 ℃ for 6 h using l,8-diazabicyclo[5.4.0]undecene-7 as a base in N-methylpyrrolidone. The photochemical valence isomerizations of the reference compounds and all the NBD polymers were examined upon UV-irradiation in THF solution or in the film state, and it was found that the polymer containing phenylcarbamoyl group had especially high photoreactivity. In addition, the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4'-bis(diethylamino)ben-zophenone as photosensitizer in the film state, and all the NBD groups of the polymers isomerized to the QC group in as little as only 20 s. The stored thermal energy of the irradiated polymers was also evaluated by DSC to be 32-52 kJ/mol.