Polydimethylsiloxane Modified Chitosan IV. Preparation and Characterization of Porous Hybrid Membranes

This paper deals with the synthesis of organic-inorganic hybrid membranes prepared by modified chitosan with epoxy terminated polydimethylsiloxane and γ–glycidoxypropyltrimetoxysilane as cross-linking agents. The transformation of amino groups of chitosan through the reaction with epoxy groups was confirmed by FT-IR analysis. As proved by electron and atomic force microscopy, the hybrid membrane are phase segregated materials with spherical domains of silica core covered by hydrophobic siloxane in a hydrophilic chitosan matrix. The water contact angles of hybrid membranes (85°–96°) and pure chitosan membranes (72°) indicated a lower hydrophilic character of modified chitosan. As a result of the crosslinking and of increased hydrophobicity, the hybrid membranes were characterized by a smaller water swelling degree (about 30%) as compared to pure chitosan membrane (700%). However, the presence of the pores in hybrid membranes determined an increase of the water adsorption (maximum swelling degree, about 200%). The hybrid membranes possess a higher thermal stability as compared to chitosan, but a lower one as compared to polydimethylsiloxane.