Abstract
For improving the storage stability and the compatibility of benzoin alkyl ether (BAE) photoinitiators in photocurable formulations, the polymer-bound (or oligomeric) BAE photoinitiators were designed and their photoreactions were studied. Three kinds of functional BAE, α-(2-carboxyethyl) benzoin alkyl ether ( BAE-CA), α -methylolbenzoin alkyl ether (BAE-OH), and newly synthesized α-(2-cyanatoethyl)benzoin alkyl ether (BAE-NCO) were used for making the polymeric photoinitiators. The functional BAE's were reacted with appropriate reactive oligomers and obtained three kinds of polymer- bound BAE photoinitiators such as epoxy modified BAE (ER-BAE), PTMG-bound BAE (PTMG-BAE) and PTMG- urethane modified BAE (PTMG-U-BAE). They have BAE photoinitiator moieties in both chain-ends as well as identical chain structures with the photosensitive oligomers. The photoinitiators were used to make photocurable formurlations with photosensitive epoxy acrylate (EA), urethane acrylate (PTMG-UA) or dilue ts such as trimethylolpropane triacrylate (TMPTA) and 1, 6-hexanediol diacrylate (HDDA). The formulations were UV irradiated in thin film and the extent of photocuring was evaluated in terms of the degree of residual unsaturation (DRUS) by measuring the decrease in the intensity of IR absorption at 1405cm-1. The polymer-bound BAE photoinitiators in all the formulations exhibited higher photopolymerization efficiencies than the conventional BAE photoinitiators in the similar formulations.
