Sorption and Transport Properties of the Semi-Interpenetrating Network Based on Crosslinked Poly(vinyl alcohol) and Poly(styrene sulfonic acid-co-maleic anhydride) as Proton-Conducting Membranes

This study investigates the sorption and transport properties of hydrocarbon membranes based on poly(vinyl alcohol) network and poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA). The water and methanol self-diffusion coefficients through an 80 wt % PSSA-MA interpenetrating SIPN-80 membrane measured 3.75 x 10(6) and 5.47 x 10(7) cm(2)/s, respectively. These results are lower than the corresponding values of Nafion (R) 115 (8.89 x 10(-6) cm(2)/s for water and 8.63 x 10(-6) cm(2)/s for methanol). The methanol permeability of SIPN-80 membranes is 4.1 x 10(-7) cm(2)/s, or about one-fourth than of Nafion (R) 115. The difference in self-diffusion behaviors of Nafion (R) 115 and SIPN-80 membranes is well correlated with their sortion characteristics. The solvent uptake of Nafion (R) 115 increased as the methanol concentration increased up to a methanol mole fraction of 0.63, and then decreased. However, the solvent uptake of the SIPN-80 membranes decreased sluggishly as the methanol concentration increased. The lambda values of water and methanol (i.e., lambda(H2O) and lambda(CH3OH)) in Nafion (R) 115 are quite close, indicating no sorption preference between water and methanol. In contrast, the lambda(CH3OH) value is only one-third lambda(H2O) for a SIPN-80 membrane. Accordingly, the SIPN membranes are regarded as candidates for direct methanol fuel cell applications. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 342-350, 2009.