Photolysis of copolymers of p-methoxyacrylophenone with p-biphenyl methacrylate and 2-naphthyl methacrylate

Abstract

Copolymers of p-methoxyacrylophenone (PMeOAP) with 2-naphthyl methacrylate (2NMA) and p-biphenyl methacrylate (BMA) containing 0–4·2 wt % of 2NMA and 0–4·9 wt % of BMA were prepared. The photolysis of these copolymers under 366 nm irradiation in dilute ethyl benzoate solution at ambient temperature was studied viscometrically. Increasing content of triplet energy acceptors (2NMA and BMA) in copolymers caused decrease of quantum yields for main chain scissions. The same efficiency was observed for bound 2NMA and BMA, though naphthalene was about twice more efficient than biphenyl in intermolecular triplet energy transfer. The 25-times longer life-time of the excited triplet state of poly- p-methoxyacrylophenone (PPMeOAP) compared to polyacrylophenone does not lead to increase of intramolecular triplet energy transfer. According to Perrin's model of static quenching. the calculated radius of the quenching sphere in both copolymers of PMeOAP was about 16 A and in copolymers 1- and 2-vinylnaphthalene-acrylophenone about 13 A. The value obtained for low-molecular model compounds was about 10 A. Results indicate that there is probably no isothermic triplet energy transfer between identical p-methoxyacrylophenone chromophores.