A Highly Reactive, Bifunctional α-Hydroxyalkylphenone-Based Cyclopolymerizable Photoinitiator

A novel photoinitiator (CTI) containing two I2959 groups and 1,6-heptadiene moiety is prepared by esterification reaction between 2,2'-(oxybis(methylene))diacrylic acid (TBEED-COOH) and I2959. Thermal copolymerization of CTI and TBEED in solution using 2,2 '-azobis(isobutyronitrile) (AIBN) at 80 degrees C gives a linear polymeric PI (P-CTI) indicating high cyclization tendency of CTI. Photoreactivity of CTI as a PI and as a monomer is investigated at different concentrations with a variety of monomers such as 2-hydroxyethyl methacrylate (HEMA), triethyleneglycol dimethacrylate (TEGDMA), trimethylolpropane triacrylate (TMPTA), and TBEED under UV-visible light irradiation by differential scanning photocalorimetry. The absorption, steady state photolysis, and migration properties of both CTI and P-CTI are investigated. The results demonstrate that modification of I2959 results in improved migration stability and faster photopolymerization kinetics at lower concentrations than parent I2959.