SYNTHESIS OF RIGID POLYMER CONTAINING PENDANT NORBORNADIENE MOIETIES AND ITS PHOTOCHEMICAL VALENCE ISOMERIZATION

Polymers having pendant norbornadiene (NBD) moieties and rigid main ch ain were prepared from the reaction of partially brominated poly(2,6-d imethyl-p-phenylene oxide) with a potassium carboxylate derivative of the corresponding NBD using a phase transfer catalyst in chlorobenzene . The photochemical valence isomerization of pendant NBD to quadricycl ane (QC) moieties proceeded smoothly in the film state as well as poly mer solution upon the irradiation by sunlight, xenon lamp, or high-pre ssure mercury lamp. The rate of isomerization was affected by the stru cture of main chain in the polymer and the substituent groups of NBD d erivatives. The catalytic reversion of the resulting QC moiety to the original NBD proceeded smoothly in the solution with 5,10,15,20-tetrap henyl-21H,23H-porphine)cobalt(II) as the catalyst at room temperature; however, the reaction of NBD polymer containing poly(2,6-dimethyl-p-p henylene oxide) (PPO) showed lower reactivity than that of the corresp onding low molecular weight QC compound. When the cycle between the ph otochemical valence isomerization of NBD moiety to quadricyclane (QC) moiety and thermal reversion of QC moiety to NBD moiety at 160 degrees C was repeated, the NBD polymer synthesized from PPO degraded gradual ly, whereas NBD polymer prepared from poly(4-chloromethylstyrene) deco mposed easily. Therefore, the rigid PPO structure showed high resistan ce for the degradation of NBD moiety. (C) 1994 John Wiley & Sons, Inc.