In the last years a considerable attention has  been paid to the preparation and characterization of the organic-inorganic hybrid materials like the organo- substituted phosphazene/SiO₂ network used in preparing the membranes intended to be used in the selective separation processes. In fact the phosphazene macromolecules within the silica matrix are known to improve the toughness of the ceramic network while the stiffness of the phosphazene phase being highly improved by the silica matrix.

In this paper the preparation of nine phosphazene based composite membranes (M0-M8) by making use of solution casting method is presented. The casting solutions were prepared from N−methylpyrrolidone (NMP), 0.1% organo-substituted phosphazene/SiO₂ matrix and 12-22% polymer support (polysulfone). The organo-substituted phosphazene/SiO₂ matrix was obtained by the acid catalyzed sol-gel reaction of tetraethoxysilane (TEOS) with siloxane monomer. The siloxane monomer was synthesized from hexachlorocyclotriphosphazene (N₃P₃CI₆) and 3-(trimethoxysilyl)-propylamine (H₂N-(CH₂)₃-Si(OCH₃)₃). The resulting composite membranes were characterized by IR spectroscopy, SEM microscopy and gasometrical determination (medium diameter).