Enhancing the Oxidation Stability of Polydivinylbenzene Films via Residual Pendant Vinyl Passivation

Polydivinylbenzene (PDVB) is a thermally stable, optically transparent, crosslinked polymer that until recently has been difficult to synthesize as a thin film. With the recent demonstration of initiated chemical vapor deposition (iCVD) of thin PDVB films, a renewed interest in the material properties of PDVB has developed. In particular, attention is now focused on its oxidation pathways and long‐term stability under the desired application use conditions. Here, we report on the thermal and environmental stability of PDVB films and show that unreacted pendant vinyl groups drive polymer oxidation upon exposure to either air or light. We demonstrate that such vinyls can be effectively passivated by a simple ex‐situ thermal annealing at ca. 300 °C in inert atmosphere that induces an 87% reduction of the PDVB oxidation rate in air and slows light (λ=405 nm) induced oxidation by 56%. While the thermal annealing is less effective at preventing oxidation under higher energy (λ = 365 nm) UV light, we demonstrate that this aging pathway is based on the presence of reactive oxygen species rather than traditional photo‐oxidation. Vinyl removal through ex‐situ thermal annealing improves the chemical stability of iCVD PDVB to continuous air (over 500 days) or light (70 hours) exposure and offers a simple option to improve its environmental aging resistance which is important for long‐term protective applications. The oxidation stability of polydivinylbenze (PDVB) thin films is improved by ex‐situ thermal annealing at ca. 280 °C. Post‐synthesis annealing eliminates unreacted vinyl bonds that are responsible for air‐driven oxidation on PDVB synthesized by initiated chemical vapor deposition (iCVD). Annealed PDVB films have up 87% slower oxidation rates than unannealed films after 500 days of air exposure and exhibit enhanced resistance against photo‐oxidation at blue (405 nm) and UV (365 nm) wavelengths.