Photochemical grafting of acrylated azo dyes onto polymeric surfaces. III. Effect of wavelength on the grafting of some acryloxy-substituted aromatic diazenes onto polypropylene fibres

Kinetic studies of photochemically induced grafting (1) and graft polymerization (2) onto polypropylene fibres from N,N-dimethylformamide solutions of four acryloxy-substituted aromatic diazenes, chosen as model molecules of acrylated azo dyes, were carried out at 25°C by monochromatic irradiation at various wavelengths. The effect of dye concentration was systematically investigated, and quantum efficiencies at zero concentration of dyes, as well as lifetimes for process (1) and (2), were evaluated using Stern-Volmer plots. The marked influence of wavelength and the constancy of the relatively long lifetimes at the various wavelengths support the hypothesis that quantum yields reflect efficiencies of conversion from the states populated by light absorption to reactive upper triplets.