Inorganic/organic polymer hybrid membranes for proton exchange membranes in fuel cell

Because of Nafion used as proton exchange membrane is confronted with high cost, high methanol permeability, and limited operating temperature (<100℃). Our study is to synthesize a series of novel inorganic/organic polymer membranes used as proton exchange membranes in direct methanol fuel cells (DMFC). At first, the introduction of the organo functional groups into polysiloxanes yields the crosslinked inorganic/organic polymer hybrid membranes. The hybrids containing crosslinked networks have the potential for high temperature stabilities and good mechanical property. Copolymer of 3-(trimethoxysilyl)propyl methacrylate (MSMA) with various ratios of functional group monomer were prepared by free radical polymerization, and then the inorganic/organic polymer hybrids were produced by sol-gel process. The structure and molecular weight of membrane is characterized by FTIR and GPC. Furthermore, TGA, DSC, SEM are used to analyze thermal properties and morphology of these membranes.
In our study, these results showed that crosslinked inorganic/organic polymer hybrid membranes with carboxylic acid group had the conductivity in the range of 10-6 to 10-4 S/cm, and those with sulfonic acid group is in the range of 10-4 to 10-2 S/cm. and showed a reduced methanol permeability (10-8 ~ 10-7 cm2/s) for Nafion 117(10-6 cm2/s). The crosslinked inorganic/organic polymer hybrid membrane was effective in reducing methanol crossover. The proton conductivity and methanol permeability can be controlled by various ratios of the two reactant monomers.