Preparation and photochemical properties of polymers containing 1-(4-benzylphenyl)-2-propen-1-one or 1-(4-benzoylphenyl)-2-propen-1-one structural units

Abstract

The new monomers 1-(4-benzylphenyl)-2-propen-1-one (4) and 1-(4-benzoylphenyl)-2-propen-1-one (6) and their homopolymers P4 and P6 and copolymers with styrene P4/S and P6/S were prepared. The polymers exhibit an n—π* band in their UV spectra and vibrationally well-resolved low-temperature phosphorescence. Both properties are characteristic of photoreactive polyketones. Polymers containing structure 6 show greater near-UV absorption and lower triplet energy in films at 77 K than the photoreactive polyvinylketones. The absorption and emission spectra of the transients, their lifetimes and their quenching by triplet quenchers in benzene at 300 K were determined by laser flash photolysis. Lamp photolysis of the title polymers at 366 nm in benzene results in a decrease in the molecular mass due to the Norrish type II reaction. The quantum yields of main-chain scission are comparable with those of other reactive polyvinylketones (around 0.2). The Stern—Volmer constants based on photolysis and transient quenching indicate the involvement of the long-lived triplet state in the chain scission process.