PES/Quaternized-PES Blend Anion Exchange Membranes: Investigation of Polymer Compatibility and Properties of the Blend

Polyethersulfone (PES)-based anion exchange blend membranes were prepared from quaternized-PES (Q-PES) and N-Methyl-2-pyrrolidone (NMP) casting solutions with water as coagulant via non-solvent induced phase inversion. The compatibility of the blend system was investigated through thermodynamic studies while membrane formation was determined using the cloud point technique. The properties of the membranes were investigated using atomic force microscopy (AFM), contact angle measurements and SurPASS Electrokinetic analysis. The ion exchange capacity (IEC) and the swelling of the membranes were also investigated. The PES/Q-PES blend system was compatible at the mass ratio of 0.70:0.30, thus leading to delay in demixing of the solvent and non-solvent during phase inversion. Below 0.70:0.30 mass ratio, the blend system is incompatible, leading to instantaneous demixing of the solvent and non-solvent during the phase inversion process. The roughness and surface charge density increased with the increasing addition of Q-PES while the total surface energy decreased. The IEC increased with the addition of Q-PES while the swelling decreased. Therefore, a suitable compatibility of PES:Q-PES at a mass ratio of 0.70:0.30 and below is the prerequisite for an eff ective blend system. The conductivity and electrical resistance of the blend membranes were enhanced by the addition of Q-PES additive, while the tensile strength was compromised.