SYNTHESIS AND STUDY OF IODONIUM BORATE SALTS AS PHOTOINITIATORS

Iodonium butyltriphenylborate salts (Ar-I+-Ar'. Ph3B--R), (R=Bu) were found to be more efficient than iodonium tetraphenylborate salts (R=Ph ) when used as photoinitiators for the polymerization of acrylates. Re lative photodecomposition rates were also different. It was found from a study of the photoreaction of iodonium berate salts with a model mo nomer, methyl methacrylate, that iodonium butyltriphenylborate salts s imultaneously produce a butyl radical from the berate anion and an ary l radical from the iodonium cation upon irradiation. Both radicals ini tiate polymerization. Iodonium tetraphenylborate salts were found to r elease an aryl radical, but only from the iodonium cation. Iodonium be rate salts exhibit strong absorption below 300 nm with a tail absorpti on above 400 nm. Thus, iodonium butyltriphenyl berate salts are effici ent photoinitiators even when used with visible light. When a photosen sitizer such as 5,7-diiodo-3-butoxy-6-fluorone is employed, iodonium b utyltriphenylborate salts are rendered much more efficient for visible light photopolymerization. (C) 1998 John Wiley & Sons, Inc.