Construction and Regulation on Thiol–Acrylate Networks through Binary Polymerization of Thiol–Ene Polymerization and Free Radical Polymerization

Thiol–acrylate photopolymerization has emerged as a prevalent approach for network formation due to its reaction efficiency, monomer versatility, and simple process. However, the reaction mechanism of network formation and eventual regulation of the network properties remain unclear and challenging. Different from the conventional unimechanism of thiol–acrylate photopolymerization, herein, thiol–acrylate photopolymerization was considered as a binary polymerization between thiol–ene polymerization of thiol and acrylate (TEP) and free radical polymerization of acrylates (FRP). The kinetic behavior of diacrylate and multithiols (dithiol, trithiol, and tetrathiol) was monitored by real-time in situ FTIR and treated with a binary polymerization model. By simulation of the hybrid function and calculation of the hybrid parameters, the binary polymerization revealed that there existed a mutual interaction instead of orthogonal behavior between TEP and FRP. Notably, a significant transition from inhibition to a promotion effect was observed with increasing thiol composition and thiol functionality. Moreover, the physical/mechanical properties of the photo-cross-linked networks could be easily regulated through adjusting the mutual interaction of TEP and FRP. By increasing thiol functionality, the gel content of the formed networks increased, and the uniformity of networks was improved. Consequently, the reaction mechanism of thiol–acrylate polymerization can be perfectly interpreted by binary polymerization, which provides guidance for variable multithiol–diacrylate networks with tunable properties.