Microstructure and Water Vapor Barrier Performance of Organic-Bridged Polysilsesquioxane/Carbon Quantum Dots Composite Coatings

Developing siloxane-based coatings with excellent water vapor barrier ability is of great importance due to their wide applications for various optical-related fields. To improve the water vapor barrier ability of polysilsesquioxane coatings, this research proposes a strategy of introducing carbon quantum dots (CQDs) into organic-bridged polysilsesquioxane coatings to enhance their water vapor barrier property. The CQDs are prepared by the pyrolysis of citric acid and then the composite coatings are prepared by thioether-ester-bridged silsesquioxane precursor in situ hydrolysis and condensation in the presence of CQDs. The experimental results show that the CQDs disperse well in the polysilsesquioxane matrix which is conducive to provide long diffusion pathway of water vapor molecules and also introduce individual "bubble pores" into the composite coatings. Thus-obtained composite coatings not only show fivefold enhancement in water vapor barrier ability compared to the polysilsesquioxane coating without CQDs, but also perform good light transparence and good UV radiation-resistant property, which would satisfy the requirements of optical-related moisture-resistant application fields. This work proposes a strategy to improve the water vapor barrier ability of siloxane-based coatings by the incorporation of carbon quantum dots. Carbon quantum dots not only act as water vapor blocker, but also act as foaming agent to make even individual "bubble pores" throughout the coatings. Thus-obtained composite coatings perform enhanced water vapor barrier property and optical transparency.image (c) 2023 WILEY-VCH GmbH