Synthesis of new photoresponsive polyesters containing norbornadiene residues by the polyaddition of donor-acceptor norbornadiene dicarboxylic acid diglycidyl ester with dicarboxylic acids and their photochemical properties

A donor-acceptor norbornadiene derivative, 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid diglycidyl ester (D-A NDGE), was synthesized by the reaction of the cesium salt of 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbomadiene-2,3-dicarboxylic acid with epibromohydrin in N-methyl-pyrrolidone (NMP). The polyaddition reactions of D-A NDGE with certain dicarboxylic acids were carried out with tetrabutylammonium bromide as a catalyst in NMP, producing corresponding polyesters containing D-A norbornadiene (NBD) residues in the main chain in fair to good yields. The photoisomerization of the D-A NBD residues in the polyesters proceeded very smoothly, forming the corresponding quadricyclane groups. The photoreactivities of the D-A NBD residues in the polymer were 50 times higher than those of the NBD residues in the film state and 60 times higher than those in a tetrahydrofuran solution. The stored energy in the quadricyclane groups of the polymers was about 45-55 kJ/mol according to differential scanning calorimetry analysis of the irradiated polymer films. (C) 2001 John Wiley & Sons, Inc.