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Abstract A polyvinyl chloride (PVC)-based positively-charged nanofiltration membrane was fabricated from polyvinyl chloride- graft -poly(N,N -dimethylaminoethyl methacrylate) by heating and crosslinking treatment. We characterized the surface chemical compositions, membranes structures, surface hydrophilicity and surface charges of the prepared membrane. The estimated membrane pore diameter is 1.98 nm and the pore diameters are in the range of 0.5–2.0 nm. The membrane exhibits excellent water permeability (9.3 L m−2 h−1 bar−1) and salt rejection (93.1% with MgCl 2 solution). Both the heating treatment and crosslinking reaction can diminish the pore size of the precursor membrane. The membrane hydrophilicity is improved after quaternization, leading to higher water permeability compared with the membrane treated by heating only. Moreover, surface quaternization and crosslinking offer the membrane excellent pressure resistance and long-term stability. The prepared nanofiltration membrane has great promise in many applications including water softening and multivalent ion removal. Highlights • Positively charged nanofiltration membrane was directly fabricated from polyvinyl chloride copolymer. • The membrane was formed after the heating treatment and crosslinking reaction. • The membrane exhibited 9.3 L m−2 h−1 bar−1 of water permeability and 93.1% of MgCl 2 rejection. • The membrane had excellent pressure resistance and long-term stability. [ABSTRACT FROM AUTHOR]

Abstract Different from the typical interfacial polymerization for nanofiltration membrane fabrication, we proposed a novel method to prepare charged nanofiltration membrane via rapid immersion thermal annealing process with the ultrafiltration membrane, which was prepared from the amphiphilic copolymer, poly(vinyl chloride) -g- poly(2-(dimethylamino)ethyl methacrylate) (PVC -g- PDMA) via non-solvent induced phase separation. The pore structures and chemical properties of the membranes, and annealing conditions including the media where the membrane was annealed, annealing temperature and time, were investigated in detail. It is found that the porous separation layer was collapsed to be a stable, defect-free, and smooth film as the dense separation layer of nanofiltration membrane when it was annealed in n -heptane above its glass transition temperature (T g) for only 1 min while the pore size cutoff was tailored from 20 nm to 2 nm. Salt rejections were in the order of MgCl 2 > NaCl > MgSO 4 > Na 2 SO 4 at neutral condition due to Donnan repulsion, indicating a typical positively charged nanofiltration membrane. Overall, this rapid immersion thermal annealing process provides a facile and effective strategy to tailor ultrafiltration membrane toward nanofiltration applications for amphiphilic copolymer based membranes. Graphical abstract fx1 Highlights • NF membrane was formed rapidly via thermal annealing from ultrafiltration membrane. • Pore size of NF membrane could be tailored by the annealing condition. • The positively charged NF membranes showed high divalent cations rejection and water permeace. • Outstanding adhesive strength between the supports and the separation layer was attained. [ABSTRACT FROM AUTHOR]

In this study, a stable zwitterionic layer on the surface of a membrane was developed to improve antifouling properties of the membrane, whereby negatively-charged membranes were modified by a positively-charged zwitterionic copolymer via surface adsorption and a cross-linking reaction. Here, 2-methacryloyloxyethyl phosphorylcholine and 2-aminoethyl methacrylate hydrochloride copolymer (P(MPC- co -AEMA)) was used as a model zwitterionic copolymer that can be adsorbed onto negatively-charged surfaces, and cross-linked by glutaraldehyde. The surface chemical compositions, morphology, hydrophilicity, charge, and antifouling properties of the membranes were characterized. Furthermore, the stability of the coating layer was evaluated. The results indicated that the surface hydrophilicity and antifouling properties of the membrane were clearly improved after surface modification. In addition, the stability of the coating layer was significantly increased after cross-linking compared to that after only surface adsorption. This is likely due to the cross-linking of the interpenetrating polymer networks inside the porous structure on the surface. Our findings provide a simple and effective method for surface modification via surface adsorption for use in practical applications. • P(MPC- co -AEMA) was immobilized on surface via adsorption and cross-linking. • The membrane showed improved the antifouling property. • The stability of P(MPC-co-AEMA) was increased after cross-linking. [ABSTRACT FROM AUTHOR]

A metal-organic composite membrane with sub-2 nm pores was developed via interfacial coordination reaction in biphasic systems for the first time. Herein, tannic acid (TA) was dissolved in water, as aqueous phase; iron(III) acetylacetonate (Fe(acac) 3), used as Fe(III) source, was dissolved in n -hexane as organic phase. A detailed study was conducted to obtain the defect-free TA-Fe(III) separation layer, including the salt concentration in aqueous solution, pH of the aqueous solution and the ratio of TA to Fe(acac) 3. The results indicated that the defect-free TA-Fe(III) composite membrane formed when the tris-complex (TA 3 -Fe(III)) was achieved. The optimal condition for preparing TA-Fe(III) composite membrane was using aqueous solution containing 0.4 M NaCl at pH = 6 with the ratio of TA to Fe(acac) 3 of 10. Different from the typical separation layer formed on the membrane surface by interfacial polymerization, the TA-Fe(III) separation layer was formed in the pores of the substrate, which is attributed to the higher diffusion coefficient of Fe(acac) 3 from organic phase to aqueous phase. This work provided a novel strategy to fabricate metal-organic composite membrane with sub-2 nm pores; meanwhile, the new-prepared membrane shows a high Na 2 SO 4 rejection of 97.3% with the water permeance of 8.6 L m−2 h−1 bar−1, and a high VB 12 rejection of 97.6%, indicating an excellent ion/molecule separation performance. Image 1 • TA-Fe(III) composite membrane with sub-2 nm pores was fabricated via interfacial coordination reaction for the first time. • Defect-free TA-Fe(III) composite membrane formed when the tris-complex (TA 3 -Fe(III)) was achieved. • Separation layer is formed in the pores of the substrate. • The membrane exhibited 8.6 L m−2 h−1 bar−1 of water permeance and 97.3% of Na 2 SO 4 rejection. [ABSTRACT FROM AUTHOR]

• Flexible PMIA separator and Li-S cathode were successfully integrated with excellent robustness via a simple NIPS method. • The cells assembled with the integrated electrodes can deal with volume expansion of sulfur, diffusion of polysulfides and dendrite growth of Li simultaneously. • The resultant cell exhibits a capacity of 773.6 mAh g−1 at 1 C and after 600 cycles,the capacity still remains at 565.5 mAh g−1 with the calculated capacity fade of 0.045% per cycle. Lithium−sulfur (Li−S) batteries are of great interest in next-generation flexible electronic devices for their much higher energy density. However, current Li−S batteries are still facing the problem about rational construction of the flexible power sources. Herein, a novel flexible and integrated electrode is fabricated through a non-solvent induced phase separation (NIPS) method with poly(m-phenylene isophthalamide) (PMIA) as the flexible support for Li-S batteries. Notably, the integrated electrode shows the capability of adapting the volume expansion of cathode materials, inhibiting the diffusion of lithium polysulfides and suppressing the dendrite growth of Li. As a result, battery assembled with the fabricated electrode exhibits a capacity of 773.6 mAh g−1 at 1 C. After 600 cycles, the capacity still remains at 565.5 mAh g−1 with the calculated capacity fade of 0.045% per cycle. This proposed strategy is advanced and feasible, which has great potential in next-generation portable electronic devices. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Nanofiltration membranes (NFMs) with negatively-charged nanochannels (NCNs) are of critical significance for enhancing the rejection of divalent anions. Herein, NFMs with NCNs are fabricated through a facile coating-heating route. Sulfonated polysulfone (SPSF) nanoparticles (13–40 nm) dispersed in aqueous phase are used to generate a dense layer on PES ultrafiltration (UF) membranes with different molecular weight cut-off (MWCO). It is found that the differences in the roughness of the substrates have significant contributions to the packing process of the SPSF nanoparticles, which indicate the smooth surface can be the better one. Scanning electron microscopy (SEM) images suggest the successful fabrication of the dense layer about 200 nm on different substrates. The resultant membranes feature selective layers with the nanochannels from 0.7 to 1.2 nm in average and zeta potential measurements indicate the nanochannel layers are negatively charged, causing the salts rejection in the following sequence: Na 2 SO 4 > NaCl > MgSO 4 > MgCl 2. Furthermore, the constructed membranes exhibit an excellent separation performance with the water flux of 7.2 L m−2 h−1 bar−1 and the rejection rate for Na 2 SO 4 of 94%, which demonstrates a novel economic and effective approach towards fabrication of nanofiltration membranes. Image 1 • Negatively-charged nanochannels were successfully fabricated from aqueous sulfonated polysulfone nanoparticles. • A smoother substrate is benefit to the coating of the SPSF nanoparticles for a better performance. • The prepared nanofiltration membranes exhibited enhanced rejection of divalent anions. [ABSTRACT FROM AUTHOR]