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• Quaternary ammonium and zwitterion dual-functionalized PDB- b -PSB brushes on MF membrane surface were fabricated. • The membrane pore size was not significantly changed by the coating. • Surface hydrophilicity of M/PDB- b -PSB membrane enhanced obviously. • M/PDB- b -PSB membrane with passive anti-adhesive and upper active biocidal properties. • Modification strategy for ant-biofouling membrane was facile and promising. In order to improve permeability and biofouling resistance of microfiltration (MF) membranes, quaternary ammonium and zwitterion dual-functionalized diblock polyelectrolyte copolymers, poly(dimethylaminoethyl methacrylate-butylammonium bromide)- b -poly(sulfobetaine methacrylate) (PDB- b -PSB) prepared via RAFT polymerization, were immobilized on commercial poly(vinylidene fluoride) (PVDF) MF membrane surface via using a versatile and facile mussel-inspired method to fabricate hierarchical copolymer brushes. Hierarchical PDB- b -PSB brushes contained bottom passive anti-adhesive zwitterionic PSB layer and upper active biocidal quaternary ammonium PDB layer. The surface chemical composition and morphology characterizations of pure and modified membranes demonstrated that PDB- b -PSB copolymers were successfully grafted to the dopamine-modified membrane surface via thiol mediated Michael addition reaction, which did not significantly change the membrane pore structure. However, the initial contact angle of PDB- b -PSB modified membrane (M/PDB- b -PSB) was changed from 128° for pure membrane (M/pure) to 43.2° and became 0° within 10 s, indicating the enhanced hydrophilicity. More importantly, the M/PDB- b -PSB membrane exhibited active biocidal effects against E. coli and S. aureus with inhibition rates over 98% and the E. coli and S. aureus suspension fluxes of M/PDB- b -PSB membranes were 1.61 times and 1.35 times higher than those of M/pure membranes. The M/PDB- b -PSB membrane had excellent anti-biofouling property with a better water flux recovery rate of 72%, which was 30% higher than that of the M/pure membrane. Moreover, PDB- b -PSB brushes showed a good immobilization stability. Therefore, the approach of poly(dopamine)-assisted fabrication of anti-biofouling MF membranes with quaternary ammonium and zwitterion dual-functionalized diblock copolymers had a prospect application in membrane-based separation technology and water purification. [ABSTRACT FROM AUTHOR]