Green one-pot synthesis and processing of polyimide–silica hybrid materials

Abstract

Inorganic–organic hybrid materials allow for combining features typical of the inorganic component with those of the organic component in one material. Generally, the preparation of organic and inorganic compounds requires considerably different synthesis conditions. Hence, the development of one-pot routes to inorganic–organic hybrid materials is challenging. We herein report a fully green one-pot synthesis of polyimide/silica (PI/SiO₂) hybrids. Specifically, we co-condense both components hydrothermally, using nothing but the respective precursors and water. Furthermore, we show that the PI and the SiO₂ component can be covalently connected under hydrothermal conditions, using the compatibilizer (3-aminopropyl)-triethoxysilane. We thoroughly investigate the effect of different reaction conditions, including temperature, pH, precursor concentration and reaction time on the morphology and crystallinity of the final materials. The polyimide component, poly(hexamethylene pyromellitimide) was chosen for its thermoplasticity, which allows for processing both the PI and the PI/SiO₂via sintering. For being a solvent-free method, sintering qualifies as a green processing technique. This work is the first report of the simultaneous hydrothermal condensation of an inorganic and an organic material.