•More than 99% micropollutants in water were removed by flowing the feed water through the column of β-cyclodextrin polymers.•The optimal β-cyclodextrin polymer can remove 90% of BPA equilibrium adsorption amount within 1 min.•The maximal adsorption capacity was 113.0 mg of bisphenol A per gram of β-cyclodextrin polymer.•β-CDP shows good reproducibility after a simple and mild ethanol cleaning.Organic micropollutants in aquatic environment such as plasticizer, pesticide and pharmaceuticals, have posed a serious threat to human health and are emerging as a great challenge to humanity. Traditional water treatment techniques fail to achieve high removal efficiency for low concentration of organic micropollutants. Here we demonstrate a water-insoluble crosslinked β-cyclodextrin (β-CD) polymer able to remove a broad-spectrum of organic micropollutants from water by rapid adsorption. A family of β-CD polymers (β-CDPs) were synthesized by nucleophilic aromatic substitution of β-CD hydroxyl groups and 4,4′-difluorodiphenylsulfone. The β-CDPs were used to adsorb various organic micropollutants in water by static or dynamic adsorption process. It was found that more than 99% micropollutants in water were removed by flowing the feed water through the column of β-CDPs. The results of static adsorption experiments indicated the adsorption process was fast and the adsorption capacity was very high (the maximal value was 113.0 mg of bisphenol A per gram of β-CDP). The adsorption process was fitted well with the quasi-second-order kinetics and the Langmuir isothermal adsorption model, suggesting that it is mainly a chemical adsorption of monolayer. The water-insoluble characteristic of the β-CDPs is convenient for their separation from the treated solution after adsorption saturation for regeneration and reuse. The adsorption ability of β-CDPs was kept nearly unchanged after five filtration-regeneration cycles.

•High efficient coating of PEI layer via interfacial crosslinking on porous membranes.•High adsorption capacity of anionic dyes in acidic solution during fast permeating.•Good reusability of composite membranes after desorption in basic solution.The dye wastewater is one of the most difficult industrial wastewaters to treat. It keeps a big challenge to realize fast removal of dyes from water by membrane filtration due to the trade-off between separation selectivity and permeation flux for ultrafiltration or nanofiltration (NF) process. Here we report novel composite porous membranes which can remove anionic dyes from water by ultrafast permeating adsorption. A crosslinked polyethyleneimine (PEI) polymer with strong adsorption ability was incorporated onto a nylon microfiltration membrane by the interfacial amidation reaction between PEI and trimesoyl chloride. The obtained composite membranes were used for the decolorization of dye solution by permeation mode. It was shown that the composite membranes were able to nearly completely remove anionic dyes in acidic conditions with high permeation fluxes. In an optimized case, the adsorption capacity of Sunset Yellow for the composite membranes reached 0.7 mg/cm2 with a high flux of 85 L/m2 h under a ultralow pressure of 0.01 bar. This flux was far much higher than that of NF membranes, about 10 L/m2 h bar. The pH-dependent electrostatic interaction between PEI and anionic dyes was responsible for the rapid dye removal. The adsorption saturated membranes could be effectively regenerated by a simple alkaline washing.Download high-res image (131KB)Download full-size image

Positively charged composite nanofiltration (NF) membranes with good stability were prepared by dopamine (DA) assisted poly(ethylene imine) (PEI) deposition on a polysulfone ultrafiltration (UF) substrate followed by a cross-linking step. Attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electronic microscopy, and atom force microscopy were employed to characterize the surface chemistry and morphology of the obtained composite membranes. The DA and PEI co-deposition conditions were optimized based on knowledge of the co-deposition mechanism. The effects of the cross-linker concentration, cross-linking time, and reaction temperature on the permeation and separation properties of the prepared composite membranes were investigated in detail. Under optimized conditions, the MgCl2 rejection and permeation flux of the composite membrane reached 80.4% and 19.6 L/(m2·h), respectively (the feed was 0.01 mol/L of MgCl2 solution under a test pressure of 0.4 MPa). The rejection of various salts followed the order MgCl2≈CaCl2>MgSO4>NaCl>Na2SO4, suggesting the membranes were positively charged. The composite membranes showed good durability under alkaline aqueous conditions. This study provided new insights into the fabrication of mussel-inspired thin-film composite nanofiltration membranes.利用多巴胺改性构建一种简单制备荷正电复合纳 滤膜,解决多巴胺类改性材料耐碱性差的问题。1. 利用共沉积技术与交联反应成功制备了荷正电 复合纳滤膜;相较于传统多巴胺改性膜,该复合 膜的稳定性大大提高。2. 经过测试表征,制备得 到的纳滤膜的分离尺寸属于疏松纳滤膜范围,可 用于相应尺度的分离领域。1. 通过多巴胺与聚乙烯亚胺共沉积,首先实现二 者的表面沉积,随后通过交联剂交联制备复合膜 (图1);2. 对改性膜前后表面理化性质进行相应 表征(表2 和图3~6);3. 通过测试通量和截留等 性能及分析相关纳滤模型,表征该复合膜分离性 能(图7 和8,公式(5)和(7));4. 通过长期 分离测试及碱性溶液清洗,测试复合膜的稳定性 和耐碱性。1. 成功制备了具有荷正电性的复合纳滤膜;2. 通 过通量和截留数据拟合分析得出该膜截留尺寸 在1.5 nm 和2 nm 之间,属于疏松纳滤膜,可用 于相应尺度分离;3. 该复合膜具有良好的稳定性 及耐碱性,应用范围更广。

We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core–shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction.

•A terpolymer containing AMPS, Am and VI was designed and synthesized.•A terpolymer was used as the coating material of PA TFC membrane.•The chlorine resistance of PA TFC membrane was improved significantly.•A more neutrally-charged and hydrophilic membrane surface was created.Polyamide (PA) thin-film composite (TFC) membranes are easily degraded under the attack of active chlorine in feed water or during chemical washing. In the present work, a random terpolymer of 2-acrylamido-2-methyl propanesulfonic acid, acrylamide and 1-vinylimidazole (P(AMPS-co-Am-co-VI)) was designed as a coating material to improve the chlorine tolerance of PA TFC membrane. The terpolymer was first synthesized via conventional free radical polymerization and then coated onto commercial available PA TFC membrane by dip-coating process. The changes in surface chemistry, morphology, hydrophilicity/hydrophobicity and charge characteristics of the membrane after surface coating were investigated in detail. It was shown that the incorporation of terpolymer coating created a more neutral, hydrophilic, and smooth membrane surface. The chlorine resistance of the membranes was evaluated by comparing the permeation and separation properties of the unmodified and modified membranes after chlorine exposure. And the experimental results indicated that the chlorine tolerance of PA TFC membranes was improved significantly, especially in acid environment. The coating layer prevents the selective layer from the attack of active chlorine as a barrier layer more than a sacrificial layer. The coating material and method developed in this work can facilitate the design and manufacture of highly chlorine resistant TFC membrane for seawater desalination and industrial separation.

Free-standing symmetrical porous membranes consisting of uniform cylindrical micelles were prepared from a polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer following a process combining self-assembly and nonsolvent-induced phase separation (SNIPS). The fabricated membranes displayed an impressive ultrastructure by the overlapping of the cylindrical micelles throughout the whole membrane profile (∼65 μm). The effects of copolymer molecular weight and membrane-formation condition on membrane morphology were investigated and discussed in detail. It was concluded that the cylindrical micellar membranes could be obtained in a wide window of fabrication conditions as low molecular weight of PS-b-P4VP was used as the raw material. The permeation tests indicated that the water permeability of the symmetrical membranes reached 400 L/(h m2 bar) in neutral condition, which was comparable to that of the block copolymer (BCP) isoporous membrane reported in the literature. Significantly, the permeation and separation properties of the symmetrical membranes exhibiting a strongly pH-dependent character as the pH of feed solution varied between 1 and 6. This phenomenon was attributed to the pH-responsive conformational change of P4VP corona in the micellar aggregates of BCP. The potential application of the developed membranes in the size fractionation of nanoparticles with a wide size distribution was demonstrated.

The present work aims to improve the antifouling properties and hemocompatibility of poly(vinylidene fluoride) (PVDF) membranes by polydopamine-mediated atom transfer radical polymerization (ATRP). Polydopamine (PDA) was first prepared by the oxidation and self-polymerization in basic aqueous solution. The obtained PDA was used as an additive in the preparation of PVDF membranes via non-solvent induced phase separation (NIPS). Then poly(sulfobetaine methacrylate) (PSBMA), a commonly used zwitterionic polymer, was successfully grafted from the entrapped PDA in membranes through ATRP. The changes in surface morphologies of the PVDF membranes before and after modification were observed by scanning electronic microscopy (SEM) and atomic force microscopy (AFM). Data of water contact angle measurements indicated that the surface hydrophilicity of the modified membranes was remarkably improved compared with that of the pure PVDF membrane. Results of filtration tests revealed that the water permeability and antifouling properties of the PVDF membranes were both increased after modification. Moreover, the hemocompatibility of the modified PVDF membrane was greatly improved due to the incorporation of zwitterionic brushes as demonstrated by in vitro platelet adhesion. Owing to the chemical reactivity of polydopamine as well as its strong interactions with a wide spectrum of solid substrates, this strategy can be extended to other materials and allows the development of novel functional membranes through such a blending process and secondary treatments.

Brønsted acidic ionic liquids (BAILs) are unique ionic liquids that display chemical structures similar to zwitterions, and they were typically used as solvents and catalysts. In this work, an imidazole-based BAIL monolayer was fabricated onto poly(ether sulfone) (PES) membranes via surface clicking reactions, and the multifunctionality, including ion exchange and biofouling resistance to proteins and bacteria, was demonstrated, which was believed to be one of few works in which BAIL had been considered to be a novel fouling resistance layer for porous membranes. The successful immobilization of the BAILs onto a membrane surface was confirmed by X-ray photoelectron spectroscopy analysis, contact angle measurement, and ζ potential determination. The results from Raman spectroscopy showed that, as a decisive step prior to zwitterion, the BAIL was deprotonated in aqueous solution, and biofouling resistance to proteins and bacteria was found. However, BAIL displayed ion exchange ability at lower pH, and surface hydrophilicity/hydrophobicity of membranes could be tuned on purpose. Our results have demonstrated that the BAIL grafted onto membranes will not only act as an antibiofouling barrier like zwitterions but also provide a platform for surface chemical tailoring by ion exchange, the property of which will become especially important in acidic solutions where the fouling resistance performances of zwitterions are greatly weakened.

Anti-fouling and anti-bacterial polyethersulfone (PES) membranes were developed by the addition of poly(2-dimethylaminoethyl methacrylate) grafted silica nanoparticles (SiO2-g-PDMAEMA NPs) and further post-quaternization. The SiO2-g-PDMAEMA NPs were first synthesized by grafting PDMAEMA brushes from SiO2 NPs via surface-initiated, reversible addition fragmentation chain transfer (RAFT) polymerization. PES/SiO2-g-PDMAEMA hybrid ultrafiltration (UF) membranes were then prepared from the blending solutions of PES and SiO2-g-PDMAEMA NPs via non-solvent induced phase separation (NIPS) process. The PDMAEMA chains incorporated into the PES membranes were further quaternized by reacting with 1,3-propane sultone (1,3-PS) and methyl iodide (CH3I), respectively. After treatment with 1,3-PS, the resulting zwitterionic PES membranes exhibited excellent hydrophilicity, water permeability, solute rejection and protein anti-fouling properties. The cationic membranes obtained from CH3I treatment showed strong anti-bacterial activity against Escherichia coli (E. coli) and Staphyloccocus aureus Rosenbach (S. aureus). This work presents a convenient strategy for anti-biofouling modification of polymer membranes via surface quaternization of the reactive SiO2-g-PDMAEMA NPs additive.

A facile and practical method for fabricating antifouling and antimicrobial poly(ether sulfone) (PES) membranes is developed in this work. A PES blend membrane was first fabricated by a traditional nonsolvent induced phase separation (NIPS) process with a reactive amphiphilic copolymer poly(ether sulfone)-block-poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA-b-PES-b-PDMAEMA) as the blending additive. The hydrophilic PDMAEMA chains in the copolymer additive spontaneously migrated toward the interfaces between membrane and coagulant bath (usually water) during membrane formation. The enriched PDMAEMA chains on the as-made blend membranes were then quaternized by reacting with 1,3-propane sultone (1,3-PS) and 1-bromodecane, respectively. The zwitterionic PES membranes obtained from 1,3-PS treatment showed significantly improved antifouling ability and hemocompatibility. In another case, the resulting cationic PES membranes treated with 1-bromodecane exhibited excellent antibacterial activities against Escherichia coli (E. coli) and Staphyloccocus aureus (S. aureus). The surface quaternization from the reactive polymeric additive provides a facile and versatile strategy for further functionalization of phase inversion membranes. This method is also suitable for other membrane materials. Moreover, it is easy to scale up in industrial applications.

A facile and versatile approach for the preparation of antifouling and antimicrobial polymer membranes has been developed on the basis of bioinspired polydopamine (PDA) in this work. It is well-known that a tightly adherent PDA layer can be generated over a wide range of material surfaces through a simple dip-coating process in dopamine aqueous solution. The resulting PDA coating is prone to be further surface-tailored and functionalized via secondary treatments because of its robust reactivity. Herein, a typical hydrophobic polypropylene (PP) porous membrane was first coated with a PDA layer and then further modified by poly(N-vinyl pyrrolidone) (PVP) via multiple hydrogen-bonding interactions between PVP and PDA. Data of water contact angle measurements showed that hydrophilicity and wettability of the membranes were significantly improved after introducing PDA and PVP layers. Both permeation fluxes and antifouling properties of the modified membranes were enhanced as evaluated in oil/water emulsion filtration, protein filtration, and adsorption tests. Furthermore, the modified membranes showed remarkable antimicrobial activity after iodine complexation with the PVP layer. The PVP layer immobilized on the membrane had satisfying long-term stability and durability because of the strong noncovalent forces between PVP and PDA coating. The strategy of material surface modification reported here is substrate-independent, and applicable to a broad range of materials and geometries, which allows effective development of materials with novel functional coatings based on the mussel-inspired surface chemistry.Keywords: antifouling; antimicrobial; membrane; oil/water separation; poly(N-vinyl pyrrolidone); polydopamine;

An amino-substituted polyethersulfone (PES) was synthesized by the polycondensation of a functional monomer bis(3-amino-4-hydroxyphenyl) sulfone with bis(4-fluorophenyl) sulfone. The amine groups incorporated into PES were employed as anchors to immobilize the chain transfer agents of reversible addition-fragmentation polymerization (RAFT). The resultant macro chain transfer agent was used to initiate the polymerization of the hydrophilic monomers N-isopropyl acrylamino (NIPAAm) and N, N-dimethylamino-2-ethyl methacrylate (DMAEMA), respectively. The gel permeation chromatography (GPC) results confirmed the successful synthesis of the amphiphilic copolymers PES-g-PNIPAAm and PES-g-PDMAEMA, and these two copolymers were perhaps the few examples of amphiphilic copolymer synthesized via a radical polymerization from PES main chains. The amino-substituted PES seemed a versatile precursor that showed a potential of functionalization via various strategies including click chemistry, atom transfer radical polymerization and RAFT polymerization. The synthesized amphiphilic copolymers were finally used as additives to improve the hydrophilicity and the filtration performances of PES membranes.

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions, a novel hydrophilic nanofiltration (NF) membrane was fabricated by simply dipping polysulfone (PSf) ultrafiltration (UF) substrate in dopamine solution. The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane. The surface hydrophilicity of membranes was evaluated through water contact angle measurements. It was found that membrane hydrophilicity was significantly improved after coating a polydopamine (pDA) layer, especially after double coating. The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue, congo red and methyl orange with a pure water flux of 83.7 L/(m2·h) under 0.6 MPa. The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process. The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment. It was demonstrated that the salts rejections followed the sequence: NaCl < Na2SO4 < MgSO4 < MgCl2 < CaCl2, and the rejection to CaCl2 reached 68.7%. Moreover, the composite NF membranes showed a good stability in water-phase filtration process.

Amphiphilic graft copolymers having poly(vinylidene fluoride) (PVDF) backbones and poly(N-isopropylacrylamide) (PNIPAAm) side chains were synthesized via γ-ray pre-irradiation induced graft polymerization in water phase suspension. No organic solvent was used in the synthesis process, which was harmless to environment. The resulting copolymers, PVDF-g-PNIPAAm, were characterized by nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA). It was showed that the PNIPAAm chains were successfully grafted onto PVDF main chains, and the weight percentage of PNIPAAm chains in the graft copolymers increased almost linearly with the increase of the monomer concentration in reaction solution. The synthesized PVDF-g-PNIPAAm was used as an additive in the preparation of PVDF porous membranes by immersion precipitation. The surface chemical compositions of the prepared blend membranes were analyzed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found the weight fraction of PNIPAAm chains on membrane surface was much higher than that in PVDF-g-PNIPAAm copolymer due to the surface segregation of hydrophilic chains. The membrane hydrophilicity, surface morphology and water permeability were evaluated by water contact angle measurement, scanning electron microscopy (SEM) observation and water permeation experiment, respectively. It was indicated that both water contact angle and water permeability exhibited an abrupt change when the temperature was elevated to above low critical solution temperature (LCST, 32 °C) due to the shrinkage of PNIPAAm chains.Research highlights▶ PVDF-g-PNIPAAm was synthesized via γ-ray pre-irradiation induced graft polymerization without using any organic solvent. ▶ The grafting percentage of PVDF-g-PNIPAAm increased almost linearly with the monomer concentration. ▶ The concentration of PNIPAAm on membrane surface reached a level comparable to that in PVDF-g-PNIPAAm due to the surface segregation of hydrophilic PNIPAAm chains.

It is well-known that cellulose is difficult to dissolve in common organic solvent and be directly processed into porous membrane. In this work, using ionic liquid, 1-allyl-3-methylimidazolium chloride (AMIMCl) as solvent, high flux and anti-fouling cellulose nanofiltration (NF) membranes were fabricated by phase inversion method from 8.0 wt.% of cellulose/AMIMCl solutions. Pure water was employed as the non-solvent in phase inversion process. From the result of polarized light microscopy, we found that cellulose was completely dissolved in the AMIMCl at 90 °C. The characterizations of Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopies showed that no obvious changes occurred in the chemical structure of cellulose after membrane formation, but the crystallinity had a remarkable decreased. Membrane morphologies of the fabricated cellulose membranes including the cross-section and the surface were analyzed by scanning electron microscopy (SEM). It was found that the AMIMCl had a distinctive effect on phase inversion process and the cellulose selective layer displayed a macrovoid-free and relatively dense layered structure. Based on the filtration experimental results, the pure water permeation flux of the membranes reached 128.5 L/m2h under 0.4 MPa, and the molecular weight cut-off was less than 700 Da. The membranes exhibited a good stability and anti-fouling ability in water-phase separation process, and were suitable as NF membranes to separate the organic compounds with a medium molecular weight.Highlights► Cellulose NF membranes were fabricated using ionic liquid as solvent. ► The pure water flux of membrane reached to 128.5 L/m2h under 0.4 MPa. ► The molecular weight cut-off was less than 700 Da. ► The membranes exhibited a good stability and anti-fouling capability.

In this work, the polypropylene glycol (PPG) was observed showing obvious hydrophilicity improvement to polyethersulfone (PES) membranes when it was introduced. The water contact angles of the blend membranes were significantly lowered to 50° when contents of PPG were 25 wt % in the as-formed membranes. The stability test presented a good durability of PPG when blend membranes suffered a 70 days water washing. Surface constitution analysis revealed that PPG concentration in the near surface was nearly two times higher than the theoretic value, indicating the surface enrichment of PPG in membranes. A pore-forming effect was also observed though the porosity increase was not obvious. The results of platelet adhesion, flux recovery, and protein adsorption indicated a nice fouling-resistance property of blend membranes. The molecular folding as well as the surface aggregation of PPG was explored as a reason for the hydrophilic improvement to blend membranes.

This study aims to explore the fundamental surface characteristics of polydopamine (pDA)-coated hydrophobic polymer films. A poly(vinylidene fluoride) (PVDF) film was surface modified by dip coating in an aqueous solution of dopamine on the basis of its self-polymerization and strong adhesion feature. The self-polymerization and deposition rates of dopamine on film surfaces increased with increasing temperature as evaluated by both spectroscopic ellipsometry and scanning electronic microscopy (SEM). Changes in the surface morphologies of pDA-coated films as well as the size and shape of pDA particles in the solution were also investigated by SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The surface roughness and surface free energy of pDA-modified films were mainly affected by the reaction temperature and showed only a slight dependence on the reaction time and concentration of the dopamine solution. Additionally, three other typical hydrophobic polymer films of polytetrafluoroethylene (PTFE), poly(ethylene terephthalate) (PET), and polyimide (PI) were also modified by the same procedure. The lyophilicity (liquid affinity) and surface free energy of these polymer films were enhanced significantly after being coated with pDA, as were those of PVDF films. It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates. This information provides us with not only a better understanding of biologically inspired surface chemistry for pDA coatings but also effective strategies for exploiting the properties of dopamine to create novel functional polymer materials.

Based on the self-polymerization and strong adhesion characteristics of dopamine in aqueous solution, a novel and convenient approach was developed to immobilize protein onto porous polyethylene (PE) membranes. A thin polydopamine (pDA) layer was formed and tightly coated onto PE membrane by dipping simply the membrane into dopamine aqueous solution for a period of time. Subsequently, bovine serum albumin (BSA) was bound onto the obtained PE/pDA composite membranes via the coupling between BSA and the reactive polydopamine layer. The firm immobilization of polydopamine layer and BSA was verified by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results of water contact angle measurement showed that the hydrophilicity of PE membrane was significantly improved after coating polydopamine and binding BSA. The experiments of blood platelet adhesion indicated that BSA-immobilized PE membrane had better blood compatibility than the unmodified PE and the PE/pDA composite membranes. The investigations on hepatocyte cultures and cell viability revealed that the polydopamine coating endowed PE membrane with significantly improved cell compatibility. Compared to BSA surface, polydopamine surface is more favorable for cell adhesion, growth, and proliferation.Graphical abstract.Highlights► Porous PE membrane was successfully surface-modified via dopamine self-polymerization and firm attachment to membrane surface followed by BSA binding in mild aqueous environments. ► The hydrophilicity of PE membrane was significantly improved by the polydopamine coating and BSA immobilization. ► The BSA-immobilized PE membrane had better blood compatibility than the unmodified PE and the PE/pDA composite membranes. ► Compared to BSA surface, polydopamine surface is more favorable for cell adhesion, growth, and proliferation.

F127-based (F127, PEO-b-PPO-b-PEO) amphiphilic block copolymers containing poly(N,N–dimethylamino-2-ethyl methacrylate) (PDMAEMA) end blocks (F127-b-PDMAEMAn) were used as additives in the polyethersulfone (PES) porous membranes preparation by phase inversion method. The membrane properties and morphologies were characterized by contact angle measurements, porosity analysis, scanning electron microscope (SEM) and water permeation tests. Compared to the F127, water contact angle results showed that the synthesized copolymers were more effective in improving the membranes hydrophilicity, and better hydrophilicity was obtained for additives with longer PDMAEMA blocks. Porosity data and SEM observation showed that the usage of F127-b-PDMAEMAn led to smaller pore size compared with F127, which might attribute to the altered membrane-forming process by an increased entanglement of F127-b-PDMAEMA with PES. The water permeation results indicated that the additives F127-b-PDMAEMA had endowed membranes with smart properties that responded to temperature and pH stimulations. While the synthesized additives caused the blend membranes to adsorb more proteins than the F127 did, which was assigned to the weak polyelectrolyte property of the PDMAEMA blocks.Research highlights▶ To improve the reservation of F127 in membrane, F127 was lengthened while amphiphilic property was remained. ▶ The usage of a modified F127 with PDMAEMA blocks in modification of PES membranes has not been found. ▶ The F127-b-PDMAEMA altered membrane-forming path, and showed pH-/temperature responsive behavior.

Based on the self-polymerization and strong adhesion characteristic of dopamine in wet conditions, the hydrophobic polyethylene (PE) porous membranes were surface-modified via simply immersing them into dopamine aqueous solution for 24 h. Subsequently, heparin was immobilized covalently onto the resultant membrane by the coupling between heparin and reactive polydopamine layer. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were utilized to determine the chemical compositions of membrane surface, which confirmed the successful introduction of polydopamine and immobilization of heparin molecules. Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the changes in surface morphologies after surface modification. The data of water contact angle measurements indicated that the hydrophilicity of PE membranes was remarkably improved after polydopamine coating and heparin immobilization. The results of in vitro hemocompatibility test proved that surface heparinization significantly suppressed the adhesion of platelet and enhanced the anticoagulation ability of PE membranes. This work offered a convenient approach to improve the permeability and biocompatibility of inert PE porous membranes for their biomedical and blood-contacting applications.Research highlights▶ Surface heparinization is regarded as an effective way to improve the blood compatibility of hydrophobic polymeric membrane. ▶ The polydopamine could form a stable reactive layer that tightly attached upon the membrane, which affords opportunities to further surface modification and functionalization such as heparinization in present study. ▶ After dopamine modification and heparin immobilization, the hydrophilicity of PE membranes has been remarkably improved, and the heparin-immobilized PE membranes show very good hemocompatibility.

Hydrophobic polymer membranes were surface-modified by coating 3,4-dihydroxyphenylalanine (DOPA) and dopamine. The DOPA and dopamine self-polymerized and adhered firm to the membrane surfaces in mild aqueous environments. The membrane surface hydrophilicity was evaluated through water contact angle measurement. It was found that the water contact angle of the modified membranes reduced remarkably compared with the corresponding original membranes, suggesting that the membrane hydrophilicity was significantly improved. The changes in the chemical compositions of membrane surfaces were determined by X-ray photoelectron spectroscopy (XPS). Morphological changes of membrane surfaces were described using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The experimental results indicated the polymer layers containing carboxyl, hydroxyl and amino groups were substantially attached onto the membranes by the strongly interaction between poly(DOPA)/poly(dopamine) and membrane surfaces. This facile method was effectual to polyolefin porous membranes including polyethylene (PE), poly(vinylidene fluoride) (PVDF) and polytetrafluoroethylene (PTFE). The water fluxes for these membranes were also elevated after coating.

A novel TiO2 nanoparticle self-assembly membrane was prepared based on ultrahigh molecular weight poly(styrene-alt-maleic anhydride)/poly(vinylidene fluoride) (SMA/PVDF) blend membrane. TiO2 nanoparticle solution was beforehand prepared via the controlled hydrolysis of titanium tetraisopropoxide. The diameter (10 nm or less) and anatase crystal structure were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The SMA/PVDF blend membranes prepared by the phase inversion method were immersed into the TiO2 nanoparticle solution for a week to produce TiO2 self-assembly membranes. The chemical compositions in membrane surface were analyzed by X-ray photoelectron spectroscopy (XPS). The membrane morphologies were measured by scanning electron microscopy (SEM). Finally, the membrane hydrophilicity, protein anti-fouling property and the molecular weight cutoff (MWCO) were characterized by water contact angle measurement, static protein absorption and filtration experiments, respectively. It is demonstrated that, in comparison to PVDF/SMA blend membrane, the permeability and anti-fouling ability of TiO2 self-assembly membranes were significantly improved.

The present work aims to improve the antifouling properties and hemocompatibility of poly(vinylidene fluoride) (PVDF) membranes by polydopamine-mediated atom transfer radical polymerization (ATRP). Polydopamine (PDA) was first prepared by the oxidation and self-polymerization in basic aqueous solution. The obtained PDA was used as an additive in the preparation of PVDF membranes via non-solvent induced phase separation (NIPS). Then poly(sulfobetaine methacrylate) (PSBMA), a commonly used zwitterionic polymer, was successfully grafted from the entrapped PDA in membranes through ATRP. The changes in surface morphologies of the PVDF membranes before and after modification were observed by scanning electronic microscopy (SEM) and atomic force microscopy (AFM). Data of water contact angle measurements indicated that the surface hydrophilicity of the modified membranes was remarkably improved compared with that of the pure PVDF membrane. Results of filtration tests revealed that the water permeability and antifouling properties of the PVDF membranes were both increased after modification. Moreover, the hemocompatibility of the modified PVDF membrane was greatly improved due to the incorporation of zwitterionic brushes as demonstrated by in vitro platelet adhesion. Owing to the chemical reactivity of polydopamine as well as its strong interactions with a wide spectrum of solid substrates, this strategy can be extended to other materials and allows the development of novel functional membranes through such a blending process and secondary treatments.

Anti-fouling and anti-bacterial polyethersulfone (PES) membranes were developed by the addition of poly(2-dimethylaminoethyl methacrylate) grafted silica nanoparticles (SiO2-g-PDMAEMA NPs) and further post-quaternization. The SiO2-g-PDMAEMA NPs were first synthesized by grafting PDMAEMA brushes from SiO2 NPs via surface-initiated, reversible addition fragmentation chain transfer (RAFT) polymerization. PES/SiO2-g-PDMAEMA hybrid ultrafiltration (UF) membranes were then prepared from the blending solutions of PES and SiO2-g-PDMAEMA NPs via non-solvent induced phase separation (NIPS) process. The PDMAEMA chains incorporated into the PES membranes were further quaternized by reacting with 1,3-propane sultone (1,3-PS) and methyl iodide (CH3I), respectively. After treatment with 1,3-PS, the resulting zwitterionic PES membranes exhibited excellent hydrophilicity, water permeability, solute rejection and protein anti-fouling properties. The cationic membranes obtained from CH3I treatment showed strong anti-bacterial activity against Escherichia coli (E. coli) and Staphyloccocus aureus Rosenbach (S. aureus). This work presents a convenient strategy for anti-biofouling modification of polymer membranes via surface quaternization of the reactive SiO2-g-PDMAEMA NPs additive.