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• Three kinds of comb-shaped amphiphilic PEME triblock copolymers were synthesized. • Effects of PEME with different hydrophilic block length on membrane structure-property relationship. • M-2 membrane exhibited high BSA solution flux (150 L·m−2·h−1) and excellent rejection (99.99%). • M-2 membrane overcame the permeability-selectivity trade-off for BSA solution separation. In order to reduce membrane fouling and fabricate highly selective membranes with high water permeability, three kinds of comb-shaped amphiphilic triblock copolymers, poly[poly(ethylene glycol) methacrylate]- b -poly(methyl methacrylate)- b -poly[poly(ethylene glycol) methacrylate] (PPEGMA- b -PMMA- b -PPEGMA, named as PEME), were synthesized via RAFT polymerization and used as modifiers to prepare poly(vinylidene fluoride) (PVDF) blend membranes by the non-solvent induced phase separation (NIPS) method. The effects of PEME with different hydrophilic PPEGMA length on the surface chemical structure, morphology, permeability and antifouling properties of the blend membranes were investigated detailedly. The results from ATR-FTIR and XPS tests confirmed that hydrophilic PPEGMA segments in PEME were enriched on the membrane surface due to PEME induced surface segregation. With the increase of the hydrophilic chain length in PEME, the mean pore size, porosity and roughness of the blend membrane increased gradually, indicating the modifier had the ability to adjust the membrane pore structure. Compared with pure membrane, the hydrophilicity of blend membranes was enhanced and the protein adsorption of representative bovine serum albumin (BSA) decreased obviously. After three cycles of the water-BSA-water, the M-2 blend membrane exhibited high BSA solution flux (150 L·m−2·h−1), excellent rejection (up to 99.99%) and satisfactory antifouling performance. In addition, compared with the recently published PVDF blend ultrafiltration membranes prepared by NIPS method, the M-2 membrane with surface small pore size, high flux, high selectivity and low fouling properties overcame the permeability-selectivity trade-off for BSA solution separation and showed a good application prospect for efficiently protein separation. [ABSTRACT FROM AUTHOR]

[Display omitted] • N -oxide zwitterionic anti-fouling loose nanofiltration membranes were fabricated via bio-inspired co-deposition. • Zwitterionic N -oxide moieties in ZPEI regulate membrane surface micro-morphology, hydrophilicity, electronegativity, and pore structure. • ZPEI-LNM exhibits high water permeance and dyes rejection and low salts rejection. • The outstanding surface hydrophilicity and low roughness enable the membranes with excellent antifouling performance to organic foulants. Developing anti-fouling loose nanofiltration membranes (LNMs) that can achieve dye desalination of saline textile wastewater through dye retention and salt permeation for resource utilization remains an urgent challenge that needs to be addressed. Inspired by the biomimetic adhesion of mussels and the excellent fouling resistance of saltwater fish surfaces, novel LNMs were prepared through co-deposition strategy using dopamine (DA) and N -oxide zwitterionic polyethyleneimine (ZPEI) as biomimetic functional materials. There are multiple interactions between them, including Schiff base reaction, Michael addition reaction, cation-π interaction and covalent polymerization. Compared with PEI-LNM prepared under the similar method, the optimized ZPEI-LNM displays more uniform surface, smaller average roughness (6 nm vs 22 nm), and denser pore size (0.69 nm vs 0.79 nm), indicating the zwitterionic N -oxide moieties in ZPEI regulate the deposition process and the cross-linking structure of the selective layer. ZPEI-LNM exhibits a high pure water flux of 203.0 L m−2h−1 under 0.6 MPa. Importantly, ZPEI-LNM shows high retention towards different dyes, including Congo red (CR, negative, 696.8 g/mol) of 100.0 %, Acid fuchsin (AF, negative, 585.5 g/mol) of 99.5 %, Crystalline violet (CV, positive, 408.0 g/mol) of 98.2 %, and Indigo carmine (negative, 466.4 g/mol) of 96.0 %, while the rejection of NaCl (8.7 %) and Na 2 SO 4 (12.7 %) are both lower. As expected, for the mixture solution of AF/NaCl, the dyes are efficiently rejected, while salts can pass through, indicating that ZPEI-LNM displays an excellent dye desalination capability. Furthermore, multiple-cycle antifouling tests for bovine serum albumin (BSA) and sodium alginate (SA) reveal that the flux recovery ratios are higher than those of PEI-LNM (BSA: 90.4 % vs 81.9 %; SA: 86.6 % vs 80.5 %), indicating ZPEI-LNM exhibits better anti-fouling performance towards different model foulants owing to the outstanding hydration layer caused by zwitterionic N -oxide moieties and lower surface roughness. Consequently, the work offers a new viewpoint for the fabrication of anti-fouling LNMs via biomimetic strategy for dye desalination. [ABSTRACT FROM AUTHOR]

Inspired by trimethylamine N -oxide (TMAO) secreted by saltwater fish, a novel ultra-low fouling material of N -oxide zwitterion (PTMAO) was introduced to the membrane surface via a dual-biomimetic strategy for efficient oil–water separation at near "zero pressure". [Display omitted] • Synthesized a novel N -oxide zwitterionic (PTMAO) material with ultra-low fouling. • Direct linkage of positive and negative charges (N+-O−) in PTMAO provided excellent hydrophilicity. • Bioinspired PTMAO was introduced into the membrane surface by biomimetic co-deposition chemistry. • PTMAO was introduced to endow the membrane with super-hydrophilic and oil repellent properties. • Membrane prepared by dual-biomimetic strategy showed efficient oil–water separation property. Superwetting membranes have good prospective for treatment of oil-containing wastewaters. However, development of simple and environment-friendly membranes with efficient oil–water separation performance remains a great challenge that needs to be addressed urgently. In this study, inspired by the secretion of trimethylamine- N -oxide (TMAO) by saltwater fish, we report a novel N ‑oxide zwitterionic polymer (PTMAO) with ultralow fouling property possessing directly linked opposite charges in their molecules and superior hydrophilicity, as compared to conventional zwitterionic ones. Using biomimetic co-deposition technique of dopamine (DA) and PTMAO, a zwitterionic polymer network was formed via self-polymerization of DA and followed by hydrogen bonding and cation-π effects between the oxidatively generated polydopamine (PD) and PTMAO. As expected, the fabricated membrane exhibited excellent superhydrophilicity and underwater superoleophobicity. The M–PD/PT/2:2 membrane achieved high efficiency of oil–water separation performance under ultra-low-pressure conditions, with an oil–water emulsion flux of 1121.1 L/m2 h, a recovery rate of 93.1%, and oil rejection as high as 99.2% in the cyclic oil–water emulsion separation process. Meanwhile, the M–PD/PT/2:2 membrane showed excellent stability. Therefore, this work provides a new idea for the preparation of superwetting membranes using dual-biomimetic techniques for effective separation of oil–water emulsion. [ABSTRACT FROM AUTHOR]