Synthesis and photolysis of copolymers with 1-(4-carbethoxyphenyl)-2-propen-1-one structural units

Abstract

New light-sensitive copolymers containing 1-(4-carbethoxyphenyl)-2-propen-1-one (PCOOEt) chromophore and as comonomer styrene (S), vinyl acetate (VAC), ethyl acrylate (EA), phenyl acrylate (PhA), acrylonitrile (AN) and 1-buten-3-one (MVK) were prepared. Copolymers with MVK were crosslinked. In the copolymerization with VAC, an oligomer with M GPC about 5000 Dalton and rich in PCOOEt is formed initially. Later, after consumption of PCOOEt, VAC polymerizes to high molecular weight. The oligomers are built in the main chain of VAC. Since the ketone-containing structures are only in the oligomeric part and in the side-chains, no decrease of the molecular weight, as followed by viscometry, was observed during photolysis. Copolymers of PCOOEt with EA, PhA, S and AN degrade under 366 nm irradiation in benzene or dimethylformamide solution with a quantum yield of main chain scission of the same order of magnitude as homopolymer. The quenching of the photolysis of copolymers shows that the reactivity of the triplet state is influenced by the comonomer. A comparison of quenching constants for copolymers with those of homopolymers indicate that self-quenching is not an important deactivation route of the triplet carbonyl group.