Multi-functional hybrid materials for proton conductivity

Abstract

In this paper, a new multifunctional hybrid organic–inorganic silica containing poly(ethylene glycol) [PEG] and sulfonic acid [SO₃H] groups was synthesized by a sol–gel process consisting of co-hydrolysis and co-condensation of a mixture of bis(triethoxysilylpropyl urethane)–PEG-[400, 600 and 1000] in the presence of various amounts (0, 10 and 50% molar) of a monosilylated precursor affording SH units i.e. 3-mercaptopropyltrimethoxysilane (MPTMS). These materials were characterized by ¹³C, ²⁹Si solid state NMR, IR, TGA, XPS and elemental analyses which confirm that the siloxane units in these materials remain integrally intact after chemical modification and the organic units thermally stable up to 150 °C. Evaluation of proton conductivity recorded at ambient temperature on hydrated samples indicates that by using the sol–gel process, it is possible to achieve mechanically and chemically stable hybrid materials exhibiting proton conductivity performances comparable to that of Nafion.