Swelling behaviors of proton exchange membranes in alcohols

Abstract

Swelling behaviors of physically crosslinked polymer membranes were observed in water and alcohols across a wide range of temperatures. Swelling of proton exchange membranes (PEM) was related to specific interactions at lower temperature. In average swelling ratio (SR) analysis, more hydrophobic PEMs showed lower expansion in water and methanol (MeOH), but higher SRs in other alcohols. The average SR was highest for MeOH and decreased as the carbon number increased. When hydrogen bonding is strongest, more hydrophobic PEMs had higher SRs in alcohols with more carbon. The total volume changes in alcohols was highest in MeOH and decreased as the carbon number increased. At high temperature, a PEM with flexible structure showed higher total volume change. A new equation based on Flory-Rehner's theory was proposed to describe the swelling behavior of PEMs. The new equation had fewer parameters and better represented the experimental volume expansion data than previous models.