POLYMERIC PHOTOINITIATORS HAVING BENZOIN METHYL-ETHER MOIETIES CONNECTED TO THE MAIN-CHAIN BY THE BENZOYL GROUP AND THEIR ACTIVITY FOR ULTRA-VIOLET CURABLE COATINGS

Homopolymers of 4-acryloyloxybenzoin methyl ether (ABME) and 4-acryloy loxy-alpha-methylbenzoin methyl ether (AMBE) [poly(ABME) and poly(AMBE )] as well as copolymers of AMBE with (-)-menthyl acrylate (MtA) and w ith different N,N-dialkylaminoethyl acrylates have been employed in th e photoinitiated polymerization and crosslinking of a standard acrylic formulation for u.v. clear curable coatings. The photoinitiation acti vity of the above systems, detected by microwave dielectrometry, has b een compared with that found for the corresponding low molecular weigh t structural models. The results clearly indicate that high and low mo lecular weight photoinitiators promote u.v. curing at a similar rate; however, a significant decrease of the induction period and hence an i mproved overall activity is found for the polymeric systems. An interp retation of the experimental findings, related to the behaviour of pre viously reported polymeric photoinitiators based on the benzoin methyl ether moiety, is also reported.