Preparation of poly(vinylidene fluoride) nanocomposite membranes based on graft polymerization and sol–gel process for polymer electrolyte membrane fuel cells

Abstract

Proton conducting nanocomposite membranes consisting of poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(styrene sulfonic acid), i.e., P(VDF-co-CTFE)-g-PSSA graft copolymer and sulfonated silica and were prepared using a sol-gel reaction and subsequent oxidation of a silica precursor, i.e., (3-mercaptopropyl) trimethoxysilane (MPTMS). The successful formation of amorphous phase nanocomposite membranes was confirmed via FT-IR and wide-angle X-ray scattering. All membranes were semi-transparent and mechanically strong, as characterized by a universal tensile machine. Transmission electron microscopy and small-angle X-ray scattering analysis revealed that silica 5-10 nm in size were homogeneously dispersed in the matrix at up to 5 wt.% of MPTMS. At higher concentrations, the silica grew to more than 50 nm in size, which disrupted the microphase-separated structure of the graft copolymer. As a result, both proton conductivity (0.12 S/cm at 25°C) and single cell performance (1.0 W/cm 2 at 75°C) were maximal at 5 wt.% MPTMS.

A Review on Catalytic Membranes Production and Applications

“…Inorganic substances, including ZrO2, TiO2, and SiO2 [31,32] are promising selections for mixing with the grafting copolymer matrix. Using hydroxyl [33] or tetraethoxysilane (TEOS) functional groups for subsequent cross linking or sol-gel reactions as a block to the side chain can improve the performance of grafting and it is a perfect way to obtain PEMs with high conductivity and enhanced stability [34].…”