Photochemical property of the polymer‐bearing pendant norbornadiene moiety and storage stability of the resulting quadricyclane group in the polymer

Abstract

AbstractA polymer bearing pendant norbornadiene (NBD) moieties and a low molecular weight model compound ([2‐carbobenzyloxy‐3‐phenyl‐2,5‐norbornadiene CBPNB)], were synthesized by substitution reaction of poly(p‐chloromethylstyrene) and benzyl chloride, respectively, with the potassium salt of 3‐phenyl‐2,5‐norbornadiene‐2‐carboxylic acid. Photochemical valence isomerization and storage stabilities of the resulting polymer having corresponding pendant quadricyclane (QC) groups and the low molecular weight QC compound were investigated in dichloromethane solution. It was found that the rate of photochemical valence isomerization of the pendant NBD moiety in the polymer was the same as or slightly higher than that of CBPNB, and the storage stability of the QC group in the polymer was higher than that of the QC compound resulting from CBPNB in the solution. The photochemical reaction of the pendant NBD moiety within the polymer without catalyst proceeded quantitatively in the film state. However, the photochemical reaction of the polymer films blended with 5,10,15,20‐tetraphenyl‐21H,23H‐porphine cobalt (II) catalyst (Co‐TPP) did not proceed quantitatively, and the degree of conversion of the pendant NBD moiety in the polymer decreased with increasing amounts of Co‐TPP in the film. The QC group produced in the polymer by photo‐irradiation had excellent storage stability in the film state without Co‐TPP. On the other hand, the QC group in the polymer films blended with Co‐TPP Catalyst reverted gradually to the NBD group at room temperature.