Synthesis and characterization of poly(vinyl alcoho)-based membranes for direct methanol fuel cell

Membranes made of poly(vinyl alcohol) (PVA) and its ionic blends with sodium alginate (SA) and chitosan were synthesized and characterized for their ion-exchange capacity (IEC) and swelling index values to investigate their applicability in direct methanol fuel cells (DMFCs). These membranes were assessed for their intermolecular interactions, thermal stabilities, and mechanical strengths with Fourier transform infrared spectroscopy, Xray diffraction methods, differential scanning calorimetry, thermogravimetric analysis, and tensile testing, respectively. Methanol permeability and proton conductivity were also estimated and compared to that of Nation 117. In addition to being effective methanol barriers, the membranes had a considerably high IEC and thermal and mechanical stabilities. The addition of small amounts of anionic polymer was particularly instrumental in the significant reduction of methanol permeability from 8.1 x 10(-8) cm(2)/s for PVA to 6.9 X 10(-8) cm(2)/s for the PVA-SA blend, which rendered the blend more suitable for a DMFC. Low methanol permeability, excellent physicomechanical properties, and above all, cost effectiveness could make the use of these blends in DMFCs quite attractive. (C) 2005 Wiley Periodicals, Inc.