Microstructure and protonic conductivity of H₃PO ₄-doped polyethylenimine-siloxane chemically covalently organic-inorganic hybrids

The chemically covalent polyethylenimine-siloxane hybrids doped with various amounts of ortho-phosphoric acid (H₃PO₄) were prepared and characterized by FTIR, DSC, TGA, and solid-state NMR spectra. The protonic conduction behavior of these materials was also investigated by means of impedance measurements. These observations indicate that the hydrogen bonding and protonic interactions exist between the dopant H₃PO₄ and the hybrid host, resulting in an increase in T_g of polyethylenimine segments. These hybrids are thermally stable up to 200°C from TGA analysis. Conductivity studies show an Arrhenius behavior characteristic and the Grotthus-like proton conduction, and a high conductivity of 10^-2-10^-3 S cm^-1 at 110°C in dry atmosphere for the hybrid membrane with H₃PO₄/EI of 0.5.