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%).