Influence of free and copolymerized triplet quenchers on the photolysis of poly(vinyl phenyl ketone) in solution

The influence of free, diffusion-control quenchers of triplets (naphthalene, biphenyl, 2,5-dimethyl-2,4-hexadiene) on the photolysis of poly(vinyl phenyl ketone) in benzene solution has been investigated. The Stern-Volmer plots for quenching of main-chain scission were linear, and the quenching constants were independent of the macroviscosity of the solutions. Copolymers of vinyl phenyl ketone with 1-vinylnaphthalene and 2-vinylnaphthalene containing as much as 10% (by weight) vinylnaphthalene were prepared. The photolysis of the copolymers was compared with the photolysis of poly(vinyl phenyl ketone) in the presence of free naphthalene. It was found that the quenching efficiency of found naphthalene units was about 21 times higher. The possibility of migration of the absorbed energy along the polymer chain is discussed. The relation between average-number molecular weight M _n and intrinsic viscosity η] has been determined osmometrically. For unfractionated poly(vinyl phenyl ketone) in benzene at 30°C, the relation η] = 2.82 × 10^?5 M _n^0.84 has been found.