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 degrees C in inert atmosphere that induces an 87 reduction of the PDVB oxidation rate in air and slows light (lambda=405nm) induced oxidation by 56. While the thermal annealing is less effective at preventing oxidation under higher energy (lambda=365nm) 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.
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