Anhydrous proton conductivity of sulfonated polysulfone/deep eutectic solvents (DESs) composite membranes: Effect of sulfonation degree and DES composition

Abstract The potential use of deep eutectic solvents (DESs) for anhydrous conductivity of sulfonated polysulfone membrane is presented. To this end, different molar ratios of sodium bromide as hydrogen bond acceptor (HBA) and ethylene glycol as hydrogen bond donor (HBD) are used for the synthesis of DESs. Two sulfonation degrees (DS) of 30 and 40% are also adjusted for the synthesis of sulfonated polysulfones. The synthesized DESs have suitable thermal stability as well as low viscosity to provide interconnected ionic pathways within the membranes. The proton conductivity of membranes is mainly influenced by the HBD/HBA molar ratio of DES as well as the DS of sulfonated polymer. The maximum proton conductivity of 301 mS/cm at 100 °C is obtained for the polymer with 40% DS containing a DES with a higher HBD/HBA molar ratio. The prepared composite membranes have great potential for fuel cell performance, especially in anhydrous conditions.