Incorporating tertiary amine and thioether in polyarylene sulfide sulfone membranes for multiple separations

Polymers have been widely applied for membrane separations; however, most polymer membranes lack adjustable pores and cannot serve in multiple separations once fabricated. Here, a novel block copolymer, polyarylene sulfide sulfone/amide tertiary amine (PASS/ATA), containing tertiary amine and thioether groups was designed for membrane fabrication as it can be self-assembled into a well-defined, uniform, and continuous pores. Via a facile oxidization procedure, the tertiary amine and thioether groups in the membrane molecular chains were converted into amine oxide and sulfone groups, respectively, which dramatically narrows down the pores of the membranes and greatly improves dye rejection, altering the application of the membranes from ultrafiltration (UF) to nanofiltration (NF). Furthermore, after the thioether units were oxidized into sulfone groups, the solvent resistance of the membranes was greatly increased, ensuring the application of the oxidized membranes in organic solvent nanofiltration (OSN). Dissipative particle dynamics (DPD) simulation was applied to shed insight on the formation mechanisms and transformation processes, as well as to explain the decrease of pore size combined with the enhancement of solvent resistance. As a result, combing tertiary amines with thioether groups in polymer chains endows the membrane with multiple functionalities, allowing for multiple separations including UF, NF, and OSN.