Thin film composite membranes with modified polysulfone supports for organic solvent nanofiltration

New compositions of sulfone polymer family, namely, sulfonated poly(ether sulfide sulfone) (SPESS) based on three different diphenols such as 1,1′-Thiobis(2-naphthol) (TBN), 2,2′-thiobis(4-methyl phenol) (TBMP) and curcumin (CUR) were synthesized via aromatic nucleophilic substitution copolymerization and used for enrichment of polysulfone (PSf) support in organic solvent nanofiltration. The bulk modification of PSf support was manipulated through blending with novel copolymers. Solvent resistant thin-film composite nanofiltration (TFC-SRNF) membranes were prepared on the reinforced PSf support by in situ interfacial polymerization with poly(ethyleneimine) and iso-phthaloyl dichloride. Chemical structure, morphology and physicochemical properties of the synthesized copolymers and the resultant membranes were characterized. The solubility of SPESS copolymers as an effective factor in membrane formation via phase inversion was evaluated in highly and moderate polar solvents. Their good solubility was attributed to the presence of flexible linkages and different functional groups. Furthermore, two conceptual models were presented into two different issues: (i) the mechanism of PSf bulk modification through blending with bulky SPESS copolymers and (ii) the surface property effects of the modified PSf support on the adhesion of polyamide thin film. In order to evaluate the swelling effect and organic–organic separation performance of TFC-SRNF membranes, two dyes with identical molecular size but different charges dissolved in methanol were selected. It was found that the employing SPESS reduced swelling degree significantly and consequently improved TFC-SRNF membrane performance.