Permeability and conductivity studies on ionomer-polysilsesquioxane hybrid materials

Hybrid materials based on sulphonated poly(ether ether ketone) (SPEEK, ionomer) and (RSIO_1.5)_n network (polysilsequioxane) were prepared by sol-gel process. Two different precursors namely aminopropyl trimethoxysilane (APTMS) and imidazoleglycidoxypropyl trimethoxysilane (IGPTMS) were utilized to generate (RSiO_1.5)_n in SPEEK matrix by sol-gel process. ²⁹Si MAS NMR confirmed the formation of RSiO _3/2 network structure inside the matrix. Characterisation of the hybrid materials showed lower methanol and water permeability compared to the plain SPEEK. They are therefore promising materials as membranes for direct methanol fuel cells applications. The hybrid material derived from amino group was more effective in decreasing the permeability than the material derived from imidazole group. However, the proton conductivity of the latter was higher than the material derived from amino group. The results indicate that hybrid material prepared from imidazole containing silane is more suitable as a membrane for direct methanol fuel cell than the one prepared from aniino carrying silane because it fulfils the two main requirements, namely low methanol permeability and reasonably good proton conductivity.