SYNTHESIS OF SELF-PHOTOSENSITIZING POLYESTERS CARRYING PENDANT NORBORNADIENE (NBD) MOIETIES AND BENZOPHENONE GROUPS AND THEIR PHOTOCHEMICAL-REACTIONS

Various epoxy monomers containing benzophenone (BP) groups were synthe sized by reactions of potassium or lithium salts of BP derivatives wit h excess epichlorohydrin or epibromohydrin using tetrabutylammonium br omide (TBAB) as a phase transfer catalyst (PTC). The copolymerization of glycidyl piperidylcarbonyl)-2,5-norbornadiene-2-carboxylate (GPNC), which was prepared by the reaction of epichlorohydrin with potassium carboxylate of a norbornadiene (NBD) derivative using a PTC, and (glyc idyloxy)benzophenone with phthalic anhydride(PAn) proceeded in 93% yie ld using TBAB as a catalyst in sulfolane at 100 degrees C for 24 h to give self-photosensitizing polyester P-l containing a pendant NBD moie ty and a pendant 4-oxybenzophenone group. Copolymerizations of various epoxy monomers containing certain NBD moieties and BP groups with PAn produced corresponding polyesters with pendant NBD moieties and BP gr oups in good yields. The photochemical valence isomerizations of the N BD moieties and the photosensitizing isomerizations of the NBD moietie s due to the energy transfer from excited BP groups to the NBD moietie s in the polymers were performed in the film state or in dichlorometha ne solution. From this result, it was found that rates of the photoche mical isomerization of the NBD moieties in the polymers were strongly enhanced by the introduction of the pendant BP, N-alkyl-N,N',N'-trimet hyl-4,4'-diaminobenzophenone (TBP), group. Furthermore, the photochemi cal isomerization of the NBD moieties in the polymers having a pendant TBP group proceeded effectively in a diluted dichloromethane solution compared with the mixtures of NBD polymers and low molecular weight p hotosensitizers such as 4,4'-bis(N,N-diethylamino)benzophenone. Glass transition temperatures (T-g's) of the prepared polyesters having NBD moieties and stored thermal energy in the corresponding quadricyclane (QC) residues in the polymers were measured by DSC analysis. Then, it was found that T-g's of NBD polyesters were 30-85 degrees C, and photo irradiated polyesters having QC residues released their stored thermal energies (about 90 kJ/mol) at temperatures above the T-g's of the cor responding NBD polymers.