Construction and Regulation on Thiol–Acrylate\nNetworks through Binary Polymerization of Thiol–Ene Polymerization\nand Free Radical Polymerization

Thiol–acrylate\nphotopolymerization has emerged as a prevalent\napproach for network formation due to its reaction efficiency, monomer\nversatility, and simple process. However, the reaction mechanism of\nnetwork formation and eventual regulation of the network properties\nremain unclear and challenging. Different from the conventional unimechanism\nof thiol–acrylate photopolymerization, herein, thiol–acrylate\nphotopolymerization was considered as a binary polymerization between\nthiol–ene polymerization of thiol and acrylate (TEP) and free\nradical polymerization of acrylates (FRP). The kinetic behavior of\ndiacrylate and multithiols (dithiol, trithiol, and tetrathiol) was\nmonitored by real-time in situ FTIR and treated with a binary polymerization\nmodel. By simulation of the hybrid function and calculation of the\nhybrid parameters, the binary polymerization revealed that there existed\na mutual interaction instead of orthogonal behavior between TEP and\nFRP. Notably, a significant transition from inhibition to a promotion\neffect was observed with increasing thiol composition and thiol functionality.\nMoreover, the physical/mechanical properties of the photo-cross-linked\nnetworks could be easily regulated through adjusting the mutual interaction\nof TEP and FRP. By increasing thiol functionality, the gel content\nof the formed networks increased, and the uniformity of networks was\nimproved. Consequently, the reaction mechanism of thiol–acrylate\npolymerization can be perfectly interpreted by binary polymerization,\nwhich provides guidance for variable multithiol–diacrylate\nnetworks with tunable properties.