Synthesis and photochemical property of polymers with pendant donor-acceptor-type norbornadiene moieties

The donor-acceptor-type norbornadiene (D-A NBD) 1,4,5,6-tetramethyl-3-pheny l-2,5-NBD-2-carboxylic acid was prepared by the Diels-Alder reaction of met hyl 3-phenylprop-2-ynoate with 1,2,3,4-tetramethyl-1,3-cyclopentadiene. 1,4 ,5,6,7-Pentamethyl-3-phenyl-2,5-NBD-2-carboxylic acid was also synthesized in the same way. Styrene-type polymers with pendant D-A NBD moieties were p repared with a 100% degree of substitution (DS) by the reaction of D-A NBD carboxylic acids with poly[(p-chloromethyl)styrene] with 1,8-diazabicyclo[5 .4.0]undecene-7 in dimethyl sulfoxide at 70 degreesC for 6 h. In the reacti on of D-A NBD carboxylic acids with poly(2-chloroethyl vinyl ether), the DS s were about 60%. The photochemical valence isomerizations of all the NBD p olymers proceeded smoothly with UV irradiation in tetrahydrofuran solutions and in the film state. In addition, the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4 ' -bis(di ethylamino)benzophenone as a photosensitizer in a film state. The stored th ermal energy of the irradiated polymers was also evaluated by differential scanning calorimetry to be 55-74 kJ/mol. (C) 2001 John Wiley & Sons, Inc.