화학공학소재연구정보센터
Journal of Polymer Science Part A: Polymer Chemistry, Vol.45, No.14, 2978-2988, 2007
Synthesis of self-photosensitizing polyesters containing donor-acceptor norbornadiene moieties and benzophenone groups and their photochemical reactions
The ring-opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor-acceptor norbornadiene (D-A NBD) dicarboxylic acid, 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarbox ylic acid, monoglycidyl ester derivatives with D-A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self-photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D-A NBD moieties in these polymers was higher than that of the D-A NBD moieties in the polymer having rto photosensitizing group. Furthermore, the rate of the photoisomerization of the D-A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo-irradiated polymers having QC moieties released thermal energies of 146-180 J/g. The D-A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15-30% after 50 repeated cycles of interconversion. (c) 2007 Wiley Periodicals, Inc.