Design and Synthesis of Co-initiators via Base-Catalysed Sequential Conjugate Addition: Application in Photoinduced Radical Polymerisation Reaction

Applications of photochemistry are becoming very popular in modern-day life due to its operational simplicity, environmentally friendly and economically sustainable nature in comparison to thermochemistry. In particular photoinduced radical polymerisation (PRP) reactions are finding more biological applications and especially in the areas of dental restoration processes, tissue engineering and artificial bone generation. A type-II photoinitiator and co-initiator-promoted PRP turned out to be a cost-effective protocol, and herein we report the design and synthesis of a new efficient co-initiator for a PRP reaction via a barrierless sequential conjugate addition reaction. Experimental mechanistic observations have been further complemented by computational data. Time for newly synthesised 1,2-benzenedithiol (DTH) based co-initiator promoted polymerisation of urethane dimethacrylate (UDMA, 70 %) and triethylene glycol dimethacrylate (TEGDMA, 30 %) in presence of 450 nm LED (15 W) under the aerobic conditions is 38 seconds. Polymeric material has high glass transition temperature, improved mechanical strength (860 BHN) and longer in-depth polymerisation (3 cm). A highly efficient synthesis of a co-initiator for a type-II photoinitiator promoted photoinduced radical polymerzation reaction via a barrierless catalytic sequential conjugate addition reaction. The computational study confirms the presence of a low HOMO-LUMO gap for the newly developed addition reaction. The 1,2-benzenedithiol-based co-initiator turned out to be very efficient for the polymerization and the resultant polymeric material has excellent physical properties for dental restoration and 3D-printing.image

Automated summary

Applications of photochemistry are gaining popularity due to its simplicity, environmental friendliness, and economic sustainability compared to thermochemistry. Photoinduced radical polymerization (PRP) reactions are finding more biological applications, especially in dental restoration, tissue engineering, and artificial bone generation. A new efficient co-initiator has been designed and synthesized for a PRP reaction via a barrierless sequential conjugate addition reaction.