Electrostatic enhanced surface segregation approach to self-cleaning and antifouling membranes for efficient molecular separation

Membranes with excellent antifouling properties and persistent high permeance are eternal pursuits in membrane technology. Herein, we proposed an electrostatic enhanced surface segregation approach toward the antifouling and self-cleaning membranes for molecular separation. A copolymer containing quaternary ammonium (QA) segments was designed as the surface segregation agent in the casting solution, while polysulphonic acid (PSA) was designed as the crosslinking agent in the coagulation bath. Driven by the electrostatic interactions between the positively charged QA and negatively charged sulphonic groups, the copolymer and PSA were in-situ assembled during the non-solvent induced phase separation (NIPS) processes, generating a selective separation layer on the polymeric matrix. The segregation of copolymer was enhanced, leading to a high surface coverage of ionic QA and sulphonic groups and a significantly improved surface hydrophilicity. Accordingly, the membrane exhibited a high water permeance up to 124 Lm⁻²h⁻¹bar⁻¹ with dye rejection over 95%. Moreover, the membrane exhibited excellent antifouling performance with the ultralow total permeance decline of 1.2% and the ultrahigh permeance recovery ratio of 99.8% against emulsified oil, as well as the self-cleaning property against crude oil. Hopefully, this study can afford a novel and generic approach to antifouling and self-cleaning membranes for diverse separations.