Copolymeric systems bearing side-chain thioxanthone and alpha-aminoacetophenone moieties as photoinitiators for ultraviolet-curable pigmented coatings

Copolymers of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-methacryloyloxy propyl)]aminopropan-1-one and of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-methacryloyloxypropyl)]aminobutan-1-one with 1-[(2-methacryloyloxy)ethoxycarbonyl]thioxanthone were prepared and structurally characterized. The above systems were also checked in the ultraviolet cure of an acrylic mixture upon irradiation over 380 nm, thus simulating the conditions of a TiO2-pigmented formulation. The curing results were compared with those obtained in the presence of the mixtures of the corresponding homopolymers as well a; of their low-molecular-weight models. The copolymeric systems display synergistic effects of activity with respect to the structural models but show lower photoinitiation efficiency against the homopolymers mixtures. These data are discussed and interpreted in terms of structural requirements and photochemical mechanistic aspects of the above systems. (C) 1997 John Wiley & Sons, Inc.