Benzophenone derivatives as novel organosoluble visible light Type II photoinitiators for UV and LED photoinitiating systems

Abstract Five organosoluble visible light benzophenone derivatives ( BPs ), incorporated different arylamine as electron donating groups have been synthesized and investigated for their roles as photoinitiating systems for free radical photopolymerization of acrylate monomer upon the UV and LED exposure. All the target compounds ( BP‐1 – 5 ) have confirmed through 1 H NMR, HR‐MS/EI‐MS spectra and elemental analysis. BPs displayed red‐shifted absorption, higher molar extinction coefficient and better thermal properties as compared to reference benzophenone (BP) compound. BP and BPs in combination with hydrogen donor, triethylamine (TEA), are prepared and investigated their electron spin resonance (ESR) spectroscopy and photo‐DSC (photo‐differential scanning calorimetry). ESR spectra of BP‐1 /TEA package showed the highest radical intensity among the test photoinitiator packages. In addition, BP‐1‐ based formulation exhibited the best double bond conversion efficiency than other BPs and comparable to the BP for the free radical polymerization (FRP) of TMPTA under similar UV light source. We then selected BP‐1 /TEA and BP/TEA package for FRP under LED light irradiation. Interesting, the BP‐1 /TEA system exhibited better efficiency and shorter time at maximum heat flow than BP/TEA. This result indicates BP‐1 photoinitiator not only displays good light harvesting, thermal property, but exhibits conversion efficiency under the irradiation of UV and LED.