Synthesis of amorphous silica and sulfonic acid functionalized silica used as reinforced phase for polymer electrolyte membrane

In this work silica (SiO2) and sulfonic acid-functionalized silica (sul-SiO2) were synthesized by sol-gel method from tetraethoxysilane (TEOS) and 3-mercatopropyltrimethoxysilane (MPTMS) with various ratios between them. The synthesized materials were characterized by x-ray diffraction (XRD) for crystalline structure, Brunauer-Emmet-Teller (BET) specific surface area analysis, transmission electronic microscopy (TEM) and dynamic light scattering (DLS) for particle size analysis, and ion exchange capacity (IEC) for determining sulfur content in Sul-SiO2 materials. The initial results showed that the average particle size of amorphous SiO2 and Sul-SiO2 at different TEOS: MPTMS ratios are in narrow distribution with average diameter about 20-30 nm. The particle size of Sul-SiO2 is almost unaffected by the content of MPTMS while IEC depends strongly on it. Composite membranes of 60 mu m thickness were successfully prepared from blending of poly(vinylidene fluoride) (PVDF) and synthesized amorphous SiO2. It was shown that the latter may be used as a reinforced phase for composite membrane electrolytes based on PVDF.