Novel semi-interpenetrating polymer network hybrid membranes for proton conduction

The synthesis and characterization of new hybrid organic–inorganic membranes (HOIMs) consisting of a semi-interpenetrating polymer network, for proton conduction, are described. Silane phases (SPs) were prepared by a sol–gel route and used in the synthesis of the hybrid membranes with cellulose triacetate (CTA) as organic matrix and dinonylnaphthalenesulfonic acid (DNSA) as proton carrier. For the preparation of the SPs dichlorodimethylsilane (DCDMSi) was crosslinked with tetraethoxysilane (TEOS) or phenyltrimethoxysilane (PTMS). FTIR spectroscopy was used to optimize this procedure and solutions 1H NMR and 29Si NMR were used to characterize the SPs. The SPs and the sulfonated compound contents were varied with respect to the organic polymer in order to optimize proton conductivity performance of the membrane. The latter property and membrane stability were determined by electrochemical impedance spectroscopy (EIS). Membranes prepared with CTA, DNSA and SP(TEOS), soaked in water for 16 days, showed conductivity values of 0.08–4.14 mS/cm and those prepared with SP(PTMS) of 5.52–23.44 mS/cm. Thermal analyses carried out using DSC and TGA techniques indicate that hybrid membranes are stable up to 175 °C. Results of membrane 29Si NMR and 13C NMR, ion-exchange capacity and water uptake are also reported.