Thermomechanical Formation–Structure–Property Relationships in Photopolymerized Copper-Catalyzed Azide–Alkyne (CuAAC) Networks

Abstract

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 (<i>T</i>_g) show a strong dependence on monomer structure with <i>T</i>_g 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 <i>T</i>_g whereas analogous monomers composed of ethers in place of carbamates exhibit a 40 °C lower <i>T</i>_g. 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 <i>T</i>_g all exhibit strong dependence on polymerization conversion, monomer composition, and structure postgelation.