Epoxy monoacrylate synthesis and photopolymerization in a thiol-ene/cationic hybrid system

Thiol-ene/cationic hybrid materials were designed and synthesized to address the challenges of the low glass transition temperature (Tg) and low storage modulus of thiol-ene materials. Two bifunctional monomers with methacrylate and epoxy groups were synthesized via a semiesterification reaction and characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The resultant bifunctional monomers were used as coupling agents in two thiol-ene/cationic hybrid systems that comprised tetrafunctional thiol, trifunctional/ difunctional ene, and difunctional epoxycyclohexyl monomers. Real-time Fourier transform infrared spectroscopy, which was applied to monitor the conversion of the functional groups, indicated that both thiol and alkene conversion improved upon the addition of the coupling agent while allyl conversion decreased slightly after irradiation for 120 s. Dynamic mechanical analysis indicated that the storage modulus and Tg values of the thiol-ene/cationic hybrid materials with coupling agents were higher than those of thiol-ene materials in both rigid and flexible systems, respectively.