Polymers containing side-chain benzophenone chromophores: a new class of highly efficient polymerization photoinitiators

In the present paper the efficiency of side-chain benzophenone chromophores containing polymers has been tested in the u.v. photoinitiated polymerization of acrylic monomers. Poly(4-acryloxybenzophenone) (poly(ABP)) and copolymers of acryloxybenzophenone (ABP) with (-)-menthyl acrylate (MtA), methyl acrylate (MA) and 1-acryloxy-2-ethoxyethane (AEE) exhibit much higher efficiency than that observed for the low molecular weight model compound 4-(2-methylpropionyloxy)benzophenone (IBP). The experimental findings indicate that the efficiency of the copolymer as photoinitiator depends markedly on the nature of benzophenone non-containing co-units and on the sequence length of ABP monomeric units. When poly(ABP) is used as photoinitiator in combination with a tertiary amine such as N,N-dimethylaniline (DMA) or poly[4-(N,N-dimethylamino)styrene] (poly(DMAS)), its efficiency is higher than that observed for the corresponding IBP/DMA and IBP/poly(DMAS) systems. Only in the case of the substantially alternating copolymer of ABP with DMAS is the efficiency of the macromolecular photoinitiator lower with respect to that of the mixture of the monomeric analogues (IBP + DMA).