Blend membranes of sulphonated poly(arylene ether sulphone) and sulphonated polybenzimidazole and their characterization for desalination applications

Upon polycondensing, the monosodium salt of 2-sulphoterepthalic acid and 3,3′-diaminobenzidine resulted in sulphonated polybenzimidazole (s-p-PBI; amphiphilic polymer). The amphiphilic polymer was blended with commercially available sulphonated poly(arylene ether sulphone) (SPAES; acid polymer; IEC = 2.08 meq g⁻¹). The s-p-PBI content in blend composition is varied from 2.5 to 30% (w/w). ATR-FTIR spectroscopy and TG analysis were examined to identify the interactions between the polymers upon blending. Cross-sectional morphology was analysed through SEM. With amphiphilic polymer addition, chlorine (hypochlorite) stability decreased and tensile strength improved. All the blend membranes showed improved water transport or restricted salt permeability than the pristine membrane (acid polymer). Water diffusivity permeability (P_w) of blend membrane AC-AM-97.5 (i.e., 97.5% (w/w) of SPAES and 2.5% (w/w) of s-p-PBI) is 1.285 cm² s⁻¹, while the pristine membrane is 0.864 cm² s⁻¹. NaCl permeability selectivity (P_w/P_s) of AC-AM-97.5 is 0.208 × 10³, whereas pristine membrane shows 0.102 × 10³.