Photocurable Epoxy Acrylate with Heat Resistance and High Anticreep Properties Enabled by Enthalpy-Driven Topological Isomerization

Alkali-developable epoxy acrylate resins (EARs) are indispensable for printed circuit board (PCB) fabrication, providing essential solder-resist protection to ensure circuit security. However, EARs usually exhibit unsatisfactory thermal and mechanical properties owing to their rapid yet insufficient growth of molecular weight upon UV exposure. Here, we propose an unconventional enthalpy-driven topological reconfiguration strategy that leverages dynamic covalent chemistry to drastically enhance the properties of cured EARs via a dual-curing mechanism. Specifically, the EARs are designed to contain hindered urea bonds (HUBs) and pendant carboxyl groups, imparting the network with topological reconfiguration capability while ensuring network alkali solubility. Under thermal treatment, the HUBs are transformed into amide bonds via exchange reactions with carboxyl groups, constructing an interpenetrating network. The optimal thermal treatment parameters are investigated to guarantee sufficient heterolytic exchange within the polymer network, enabling glass transition temperature up to 173 °C. Intriguingly, the topological isomerization facilitates the localized stacking of polymer chains with ordering, thereby enabling superior creep resistance at elevated temperatures. The creep strain after stretching for 10 min at 90 °C under 1 MPa stress is only 0.28%. Overall, this work establishes enthalpy-driven topological reconfiguration as a powerful paradigm for designing high-performance electronic packaging coatings.