Synthesis of Self-Photosensitizing Polyesters Carrying Pendant Norbornadiene (NBD) Moieties and Benzophenone Groups and Their Photochemical Reactions

Abstract

Various epoxy monomers containing benzophenone (BP) groups were synthesized by reactions of potassium or lithium salts of BP derivatives with excess epichlorohydrin or epibromohydrin using tetrabutylammonium bromide (TBAB) as a phase transfer catalyst (PTC). The copolymerization of glycidyl 3-(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 (glycidyloxy)benzophenone with phthalic anhydride (PAn) proceeded in 93% yield using TBAB as a catalyst in sulfolane at 100°C for 24 h to give self-photosensitizing polyester P-1 containing a pendant NBD moiety 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 groups in good yields. The photochemical valence isomerizations of the NBD moieties and the photosensitizing isomerizations of the NBD moieties due to the energy transfer from excited BP groups to the NBD moieties in the polymers were performed in the film state or in dichloromethane solution. From this result, it was found that rates of the photochemical isomerization of the NBD moieties in the polymers were strongly enhanced by the introduction of the pendant BP, N′,, group. Furthermore, the photochemical 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 photosensitizers 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 Tg's of NBD polyesters were 30-85°C, and photoirradiated polyesters having QC residues released their stored thermal energies (about 90 kJ/mol) at temperatures above the Tg's of the corresponding NBD polymers.

Synthesis and photochemical properties of novel pentamethylated norbornadiene containing polyimides

“…Although all values of restored energy match those reported in the literature,17, 18, 20, 22, 34 it is interesting to note that the highest values are obtained when the polymer T g is lower or similar to starting conversion temperature. This is observable with the P2a–P2d polymers.…”

“…Because the experiences were performed with very thin polymer films, it was assumed that the Beer Lambert's law was applicable. So, in this study, this relation was used according to the work published in the literature 18, 20, 31, 33…”

“…The introduction of NBD groups into the polymer chains as a side groups were performed either by chemical polymer modification,14–18 by cationic polymerization of NBD containing vinylic monomers,19 or by ring‐opening copolymerization of glycidyl esters containing NBD moieties with carboxylic anhydrides 20…”

Ring-opening copolymerization (ROCOP): synthesis and properties of polyesters and polycarbonates

“…A photosensitizer addition was required to achieve the conversion, however, Nishikubo et al successfully synthesized a self-photosensitizing polyester using a mixture of epoxides, with norbornadiene (NBD) and benzophenone substituents, copolymerized with PA. 50 The reactivity of photoisomerization was increased, while the energy storage capacity remains the same (90 kJ mol À1 ). Nevertheless these polymers are hampered by relatively low photoreactivity and material fatigue.…”

Palladium‐Catalyzed Three‐Component Coupling Reaction of Allyl Carboxylates, Norbornenes and Diboronates Involving Sequential Olefins Insertion and Borylation Reaction

“…Norbornene derivatives, a group of inexpensive and practical organic molecules, are widely applied in the acquisition of biologically active molecules, functional polymers, solar-energy-storage materials and synthetic intermediates. [1] Consequently, turning norbornene derivatives into multiple new desired skeletons with high efficiency has emerged as an attractive goal in modern organic synthesis. [2] In recent years, continuous studies in the construction of C-C, C-N, C-X bonds by functionalization of norbornene derivatives in a two-molecule reaction systems have been carried out by our group (Scheme 1).…”