UV stability of self-healing poly(methacrylate) network layers

•Rarely studied UV stability of Diels-Alder crosslinked networks is explored.•Spectroscopic and thermal testing proves networks are stable under UV-ageing.•Importantly, self-healing properties are fully retained after UV-ageing.•Solar heat initiated self-healing is possible, allowing photovoltaic applications. The applicability of high-modulus poly(methacrylate) networks containing reversible Diels-Alder crosslinks as self-healing coatings for outdoor applications, like photovoltaics, is evaluated. The materials are compared before and after accelerated UV-ageing using a combination of spectroscopic techniques, as well as thermogravimetric analysis and kinetic simulations, illustrating polymer network stability. In addition, it is proven by differential scanning calorimetry that the reversibility of the Diels-Alder bonds persists after ageing. Using dynamic mechanical analysis, it is shown that all pristine and UV-aged reversible networks maintain their structural integrity between -80 °C and 120 °C, and that they exhibit self-healing of micro-defects, allowing the restoration of thermomechanical properties. Furthermore, kinetic modelling is used to simulate the thermal effect on the Diels-Alder conversion during a typical day cycle for photovoltaic modules. The modelling shows that the total Diels-Alder conversion stays high (above 77%), ensuring mechanical robustness of these materials by maintaining a high crosslink density during high temperature exposure and/or temperature cycling, hence illustrating their thermal stability and supporting the potential use of such materials in outdoor photovoltaic applications.