Bulk photopolymerization of a library of synthesized multifunctional azides and alkynes was carried out toward developing structure–property relationships for CuAAC-based polymer networks. Multifunctional azides and alkynes were formulated with a copper catalyst and a photoinitiator, cured, and analyzed for their mechanical properties. Material properties such as the glass transition temperatures (Tg) show a strong dependence on monomer structure with Tg values ranging from 41 to 90 °C for the series of CuAAC monomers synthesized in this study. Compared to the triazoles, analogous thioether-based polymer networks exhibit a 45–49 °C lower Tg whereas analogous monomers composed of ethers in place of carbamates exhibit a 40 °C lower Tg. Here, the formation of the triazole moiety during the polymerization represents a critical component in dictating the material properties of the ultimate polymer network where material properties such as the rubbery modulus, cross-link density, and Tg all exhibit strong dependence on polymerization conversion, monomer composition, and structure postgelation.

Summary: High modulus two-stage reactive polymer systems are fabricated and characterized in regards to their thermomechanical properties and behavior. The polymer networks comprise thiol-acrylate formulations in which a polymer matrix is initially formed via an amine catalyzed thiol-Michael addition 'click' reaction, eventually followed by photoinitiated, free radical polymerization of the excess acrylic functional groups to result in formation of a highly crosslinked, high modulus polymer material. Composites were formed and evaluated using two distinct polymerizable thiol-acrylate formulations, each with three different filler types. Here, the fillers were used primarily to improve the mechanical performance of the polymer material following the initial Michael addition reaction though improvements were also observed in some materials following the photopolymerization as well. The fillers used were 0.7 mm methacrylated silica particles, translucent Kevlar veil and PET mesh. Thermomechanical analysis showed that the fillers resulted in a significant increase in the modulus in both the polymer networks formed at the end of each of the orthogonal reactions without a significant change in the glass transition temperatures (T g ). The two-stage matrix formed with a hexa-acrylate matrix and 20 volume % silica particles showed a 125% increase in the modulus at the end of the Michael-addition reaction and a 100% increase in the modulus after photopolymerization of the acrylates, when compared with the modulus of the unfilled polymer.