Photochemical grafting of acrylated azo dyes onto polymeric surfaces. I. Grafting of 4-(N-ethyl, N-2-acryloxyethyl) amino, 4′-nitro, azobenzene onto polyamide and polypropylene fibers

In the reported experiments, photochemically induced grafting and graft polymerization of 4-(N-ethyl, N-2-acryloxyethyl)amino, 4'-nitro, azobenzene(I), brought into contact with polyamide and polypropylene fibers by evaporation of solvent from toluene solutions, has been investigated kinetically at 45 degree C. Two constant-rate periods were observed. The first one was interpreted on the basis of an autosensitized grafting mechanism of monomeric or oligomeric species of (I), photochemically initiated by hydrogen abstraction from the polymer surface. This first step occurred at a rate dependent on the chemical nature of the substrate being faster for polyamide than for polypropylene by a factor of about 1. 25; it was followed by a brief induction period, after which a transient autoacceleration led to a second constant rate process, independent of the substrate. This latter step was explained as an autosensitized photochemically induced graft polymerization of (I) on the first grafted layer.