Synthesis and photochemical reaction of poly(ester)s containing donor-acceptor type norbornadiene residues in the both main and side chains

The synthesis and photochemical valence isomerization of polymers containing donor-acceptor type norbornadiene (D-A NBD) residues in both main and side chains, by the polyaddition of 5-(4-methoxyphenyl)1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid diglycidyl ester (D-A NDGE) with terephthaloyl chloride follows by substitution reactions of the resulting polymer with potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl -3-methylester-2,5-NBD-2-carboxylate, potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-3-(N,N-dipropylcarbamoyl) -2,5-NBD-2-carboxylate, and potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-3-(N-methyl-N-phenylcarbamoyl)-2,5-NBD-2-carboxylate, respectively. The photochemical valence isomerization of the synthesized poly(ester)s (P-1-P-4, and P-5a-c) was examined in tetrahydrofuran solution or in the film state upon irradiation with a 500-W xenon lamp, and it was found that each photochemical reaction proceeded very smoothly. It was also observed that the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4'-bis(diethylamino)benzophenone (BEBP) as a photo-sensitizer in the film state. The stored thermal energies of the irradiated polymers were evaluated by DSC analysis to be 75-153 J/g.