A novel sulfur‐containing photoinitiator based on benzophenone derivatives for rapid photopolymerization

Abstract In this study, a series of benzophenone (BP)‐based photoinitiators (PIs), designated as BP‐Sn, were synthesized by the integration of small molecule hydrogen donors into the BP scaffold. This design aims to minimize reliance on co‐initiators, reduce potential odors and toxicities, and enhance initiation efficiency of PIs under LED irradiation. Additionally, the incorporation of thioether linkages imparts a distinctive dual functionality to PIs, enabling them to exhibit both hydrogen‐abstracting (Type II) and bond‐breaking (Type I) characteristics. The photophysical and photoinitiation properties of BP‐Sn were evaluated using electron paramagnetic resonance, UV‐visible spectrophotometry, and real‐time Fourier‐transform Infrared spectroscopy. The findings demonstrate that BP‐Sn exhibit remarkable efficacy as a single‐component PI for free‐radical polymerization, achieving a final conversion efficiency approaching 95% and a photoinitiation rate exceeding 20% s −1 for the polymerization of tripropylene glycol diacrylate without the need for additional co‐initiators. Furthermore, the polymerization experiment revealed that exposure to 365 nm LED light for just 2 min results in the formation of a colorless and well‐defined patterned texture, with a thickness of 5 mm and a diameter of 7 cm, demonstrating its potential practical applications.