PREPARATION AND PHOTOREACTION OF COPOLYMERS DERIVED FROM N-(1-PHENYLETHYL)ACRYLAMIDE AND 7-ACRYLOYLOXY-4-METHYL COUMARIN

The copolymers containing photoreactive 4-methyl coumarin pendant grou ps have been prepared by radical copolymerization of N-(1-phenylethyl) acrylamide (Ml) and 7-acryloyloxy-4-methyl coumarin (M2) in DMF at 70 -degrees-C. The monomer reactivity ratios (MRR) of M1 and M2 are estim ated by Finenam-Ross, Kelen-Tudos, Mayo-Lewis, and YBR methods to be a bout r1 = 0.12-0.16 and r2 = 1.13-1.28. Dilute dioxane solutions of th e copolymers (10(-4)-10(-5) M of 4-methyl coumarin chromophores) are f irst photocrosslinked intramolecularly by irradiating 350 nm light (di merization of 4-methyl coumarin) and then photocleaved at 254 nm (symm etric cleavage of cyclobutane). Tracing by an UV-visible spectrophotom eter, it is found that photocrosslinking and photocleavage proceed sim ultaneously when 254 nm is the light source and finally reaches to a d ynamic equilibrium. However, only photocrosslinking can be observed un der 350 nm light. Kinetic results show that both photocrosslinking and photocleavage are first-order reactions. Moreover, photocrosslinking rate constant increases with mole fraction Of M2 in the copolymer (F2) . On the contrary, rate constant of photocleavage decreases with incre asing F2. (C) 1994 John Wiley & Sons, Inc.