Effect of molecular weight on the performance of asymmetric polysulfone membranes

The polysulfones were prepared via aromatic nucleophilic substitution (SNAr) reaction between bisphenol A (bis-A) and 4,4′-dichlorodiphenyl sulfone (DCDPS) or 4,4′-difluorodiphenyl sulfone (DFDPS). The chemical structures of the synthesized polymers were confirmed by           1H-NMR. Molecular weight and thermal stability increased in bis-A/DFDPS polymer compared to  bis-A/DCDPS, while their glass transition temperatures (Tg) were close to each other. Prepared asymmetric membrane with the higher molecular weight polymer (bis-A/DFDPS) showed higher water flux (121 L m-2 h-1), while their salt rejections were almost similar (about 75%).