Photoluminescence of an epoxy resin: role of imidazole catalyst, oxidized groups and evolution during curing

Photoluminescence spectroscopy is a powerful tool to monitor chemical changes in polymer networks. However, interpreting epoxy resin luminescence is challenging due to complex molecular structures and the emergence of new spectral bands during crosslinking. In this paper, we examine in-depth the excitation and emission properties of an epoxy resin cured with an imidazole catalyst. Some emission bands in the cured resin are consistent with contributions from the initial constituents (DGEBF and imidazole), whereas others emerge during curing. An emission around 315 nm provides a reliable kinetic marker of reaction progress. Longer-wavelength emissions show non-monotonic behavior, indicating that luminescence during curing depends on additional evolving chemical and physical parameters. Comparison with chemiluminescence measured during curing (from previous work) highlights complementary sensitivity to oxidation-related excited states. Although definitive molecular assignment is not possible from PL/CL alone, these techniques reveal strong correlations between excited states and process stages. • Epoxy resin photoluminescence evolves strongly during imidazole curing • New emissive species emerge during crosslinking • Oxidized and imidazole groups contribute significantly to the photoluminescence • A 315 nm band quantitatively follows curing kinetics • Photo- and chemiluminescence probe complementary aspects