Photochemical grafting of acrylated azo dyes onto polymeric surfaces. II. Effect of wavelength on the grafting of 4-(N-ethyl-N-2-acryloxyethyl)amino-4'-nitroazobenzene onto polypropylene fibres

Quantum Yields of grafting and graft-polymerization (ph1 and ph12, respectively) of 4(N-ethyl,N-2-acryloxyethyl-amino)-4'nitro azobenzene brought into contact with polypropylene fibres by evaporation of solvent from toluene solutions were determined as a function of wavelength. A kinetic investigation of the two processes was also carried out as a function of dye concentration with a polypropylene ribbon immersed in a n-hexane solution of the dye. the marked influence of wavelength, the pronounced effect of concentration quenching on both phi1 and phi2 and the constancy of the relatively long lifetimes calculated from the Stern-Volmer plot at various wavelengths support the hypothesis that phi1 and phi2 values reflect efficiencies of conversion from the states populated by light absorption to the reactive states. The behaviour of this system is dicussed in a more general framework of photochemical reactivity of compounds which have a carbonyl group and a conjugate double bond capable of twisting in an excited state to a non planar geometry,