The photopolymerized bulk copper-catalyzed azide alkyne cycloaddition (photo-CuAAC) click reaction for crosslinked networks display unique features such as, spatial and temporal control over the reaction, and delayed gelation in the network. Hence, it is explored in diverse applications like wrinkle formation and photolithography. However, defects are observed during photo-CuAAC that compromises the sample integrity on polymerizing the network under UV light, which we hypothesize is due to the decomposition of azide functional group into a reactive nitrene and nitrogen gas. We show that a Norrish Type II photoinitiating system activated using blue-light prevents azide decomposition and accelerates the bulk photo-CuAAC polymerization (&gt;75% conversion in 10 minutes), producing a glassy, transparent, and defect-free material. The photopolymerized networks are characterized using real-time Fourier transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMA). The reaction exhibits dark polymerization after irradiation is ceased enabling higher conversion. Additionally, the step-growth nature of the CuAAC polymerization exhibits a characteristic narrow glass transition temperature (T<sub>g</sub>). The incorporation of inorganic filler, such as silica, enhances the mechanical properties without compromising the positive kinetics and mechanical property attributes described for the unfilled resin. Moreover, the mechanical properties are readily tuned by using different filler size distributions. Specifically, the introduction of nano-sized and micro-sized fillers results in a 7-fold increase in modulus, from ≈2 GPa to ≈14 GPa, and a 15 °C increase in T<sub>g</sub>, making this composite material a viable substitute for traditionally employed UV-curable methacrylate and epoxy composites.

Blue-light activated bulk photo-Cu(I)-catalyzed azide-alkyne cycloaddition (photo-CuAAC) click reaction-based networks: Properties and application

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.