Growing well-defined monodispersed silica in polyimide host membranes using a surfactant assisted sol-gel process

Polyimide-silica membranes are interesting hybrid architectures that possess excellent mechanical, thermal and chemical properties. However, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems, due to the lack of favorable interactions between the hydrophobic polymer and hydrophilic silica. In this study, a new approach to forming hybrid membranes by the in situ generation of silica and functionalized silica in the polyimide matrix is presented. The new surfactant assisted sol-gel process improves the particle dispersion and the compatibility between the organic and inorganic phases. Moreover, this synthetic strategy allows the sol-gel process to proceed in the presence of a fully imidized, high molecular weight polyimide to generate a chemically well-defined silica phase. The importance of the polymer-silica and silica-surfactantfaffinities and the influence of functionalization of silica in guiding the construction of the hybrid network are also examined here.