A polyethersulfone–bisphenol sulfuric acid hollow fiber ultrafiltration membrane fabricated by a reverse thermally induced phase separation process

A novel antifouling polyethersulfone (PES) hollow fiber membrane was modified by the addition of bisphenol sulfuric acid (BPA-PS) using a reverse thermally induced phase separation (RTIPS) process. BPA-PS was synthesized by click chemistry and was blended to improve the hydrophilicity of PES hollow fiber membranes. The performance of PES/BPA-PS hollow fiber membranes, prepared with different contents of BPA-PS and at different temperatures of the coagulation water bath, was characterized by scanning electron microscopy (SEM), pure water flux (J_w), BSA rejection rate (R), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and water contact angle measurements. SEM morphologies revealed that a finger-like cross-section emerged in the hollow fiber membrane by a non-solvent induced phase separation (NIPS) mechanism while a sponge-like cross-section appeared in the hollow fiber membrane via the RTIPS method. Both FTIR and XPS analysis indicated that the sulfate group in BPA-PS was successfully blended with the PES membranes. The results from AFM and water contact angle measurements showed that the surface roughness increased and the hydrophilicity of the PES/BPA-PS hollow fiber membrane was improved with the addition of BPA-PS. The results demonstrated that the PES/BPA-PS membrane with 1 wt% BPA-PS via RTIPS exhibited optimal properties.

A novel antifouling polyethersulfone (PES) hollow fiber membrane was modified by the addition of bisphenol sulfuric acid (BPA-PS) using a reverse thermally induced phase separation (RTIPS) process.     

Improved filtration performance and antifouling properties of polyethersulfone ultrafiltration membranes by blending with carboxylic acid functionalized polysulfone

To improve the filtration performance and antifouling properties of ultrafiltration (UF) membranes, novel polymer blend UF membranes were fabricated in this study. Carboxylic acid functionalized polysulfone (PSFNA) was synthesized by modifying polysulfone (PSF) with 6-hydroxy-2-naphthoic acid (HNA). A series of polymer blend UF membranes were fabricated by adding different amounts of PSFNA into polyethersulfone (PES) to form a homogeneous casting solution. The influences of PSFNA on the morphology, thermal stability, hydrophilicity, filtration performance and antifouling properties of the blend membranes were investigated. The results indicated that by adding PSFNA into PES membranes, the finger-like pores in the membranes became larger, and the porosity and surface hydrophilicity of the membranes were improved. Compared with the pristine PES membrane, PES/PSFNA membranes demonstrated improved filtration performance, resulting in both increased water flux and higher bovine serum albumin (BSA) rejection. At a feed pressure of 0.1 MPa, the PES/PSFNA membrane with 4.0 wt% PSFNA had a pure water flux of 478 L m⁻² h⁻¹, which was 1.7 times higher compared with the PES membrane (287 L m⁻² h⁻¹). In addition, the antifouling properties of PES membranes were also enhanced with the addition of PSFNA. The PES/PSFNA membranes with 3.0 wt% PSFNA had a total fouling ratio (TFR) of 49.6%, as compared with 62.5% for PES membranes.

Ultrafiltration membranes with improved filtration performance and antifouling properties have been synthesized through blending polyethersulfone with carboxylic acid functionalized polysulfone.     

Antifouling and antimicrobial polyethersulfone/hyperbranched polyester-amide/Ag composite

This study provided a facile approach for the development of antifouling and antibacterial polyethersulfone (PES) composite film. Mainly, hyperbranched polyester-amide (PESAM) was used as both the reducing and capping agent for the in situ formation of AgNPs. The nanoparticles were intensively investigated using Fourier transform infrared spectroscopy (FTIR), ultra-violet spectroscopy (UV-vis), scanning and transmission electron microscopy (SEM & TEM) and X-ray diffraction (XRD). AgNPs were narrowly distributed with an average particle size of about 6 nm. PESAM was mixed with PES to realize free-standing film using the phase inversion method. The inclusion of PESAM in the composite film significantly improved hydrophilicity as confirmed by the contact angle measurements. Furthermore, SEM and EDX investigations confirmed that PESAM induced the in situ formation of AgNPs not only on the film surface but also inside its macro-voids. The composite film (PES/PESAM/Ag) displayed significant antibacterial potential against Gram positive and Gram negative bacteria. Overall, the described method paves the way towards development of advanced PES composite films with antimicrobial properties for broad application areas that include desalination membranes or active packaging materials.

This study provided a facile approach for the development of antifouling and antibacterial polyethersulfone (PES) composite film.     

Hydrophilic and antimicrobial core–shell nanoparticles containing guanidine groups for ultrafiltration membrane modification

Physical blending is a common technique to improve the water flux and antifouling performance of ultrafiltration (UF) membranes. In the present work, a novel hydrophilic and antimicrobial core–shell nanoparticle was synthesized through the chemical grafting of poly(guanidine-hexamethylenediamine-PEI) (poly(GHPEI)) on the surface of silica nanoparticles (SNP). The synthesized core–shell nanoparticles, poly(GHPEI) functionalized silica nanoparticles (SNP@PG), were incorporated into polyethersulfone (PES) to fabricate hybrid UF membranes by a phase inversion process. The chemical composition, surface and cross section morphologies, hydrophilicity, water flux and protein rejection of the membranes were evaluated by a series of characterizations. Results show that the prepared PES/SNP@PG hybrid membrane exhibits not only improved water flux, which is around 2.6 times that of the pristine PES membrane, but also excellent resistance to organic fouling and biofouling.

Hydrophilic and antimicrobial core–shell nanoparticles containing guanidine groups (SNP@PG) were applied to fabricate membranes with improved water flux and fouling resistance.     

Insights into the effects of synthesis techniques and crosslinking agents on the characteristics of cellulosic aerogels from Water Hyacinth

Aerogel cellulose materials were synthesised from Water hyacinth and different crosslinkers, such as kymene and a mixture of polyvinyl alcohol (PVA) and glutaraldehyde (GA). The effects of using a magnetic stirrer and ultrasonic methods were investigated. The results show that materials prepared using ultrasonic methods have higher porosity and lower density. The thermal conductivity of the synthesised aerogel cellulose could be as low as 0.0281 W m K⁻¹, showing the good heat insulation performance of this material. Absorption capacity was tested using diesel oil (DO), and the highest capacities of 58.82 and 52.03 g g⁻¹ of DO were found with kymene and PVA + GA as crosslinkers, respectively. The reusability of the materials was tested. After 10 cycles, the DO absorption capacity was 62.8% of the value of the first cycle for the aerogel cellulose sample with kymene as the crosslinker and 72.7% for the sample with PVA + GA as the crosslinking agent.

Aerogel cellulose materials were synthesised from Water hyacinth and different crosslinkers, such as kymene and a mixture of polyvinyl alcohol (PVA) and glutaraldehyde (GA).     

Preparation of a novel zwitterionic striped surface thin-film composite nanofiltration membrane with excellent salt separation performance and antifouling property

Thin-film composite (TFC) nanofiltration (NF) membranes were fabricated via the co-deposition of taurine, tannic acid (TA), and polyethyleneimine (PEI), followed by subsequent interfacial polymerization with trimesoyl chloride (TMC) on the surface of the polysulfone ultrafiltration substrates. The surface properties, including the roughness, hydrophilicity, surface potential, and NF performances were facilely tuned by varying the taurine content for the prepared TFC membranes. In addition, the as-prepared TFC NF membranes had an excellent antifouling property and flux recovery ratio (FRR) in humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA) filtration tests. These results also revealed that the taurine content controlled the formation of the striped surface. Thus, this work provided a viable strategy for fabricating TFC NF membranes with high selectivity and outstanding antifouling ability.

Thin-film composite (TFC) nanofiltration (NF) membranes with zwitterionic striped surface were fabricated via the co-deposition and interfacial polymerization.     

Evaluation of the formation and antifouling properties of a novel adsorptive homogeneous mixed matrix membrane with in situ generated Zr-based nanoparticles

In situ generation is a powerful technique used to prepare homogenous adsorptive mixed matrix membranes (MMMs) containing functional nanoparticles, although the mechanism of formation of the membranes is not yet clear and there have been few published evaluations of membrane fouling. We therefore used this method to prepare a novel homogeneous adsorptive Zr-based nanoparticle–polyethersulfone (PES) MMM and systematically studied the mechanism of membrane formation at the atomic level. As the amount of ZrOCl₂·8H₂O in the casting solution increased, the phase inversion kinetics changed from instantaneous demixing due to the thermodynamic enhancement effect to a delayed demixing process caused by viscosity hindrance. The in situ generation of nanoparticles in these MMMs can be divided into three stages: the migration stage, the exfoliation stage and the stable stage. Our findings provide a fundamental understanding of the interface chemistry in the development of in situ generated MMMs. M2 showed a higher adsorption of As(v) than the pure PES membrane and could be reused after regeneration. The removal of As(v) from the M2 filtration system mainly took place via adsorption rather than size exclusion, as confirmed by EDS and experimental data. The presence of humic acid slightly inhibited the removal of As(v) during the filtration process as a result of the barrier effect caused by the formation of a filter cake via humic acid fouling. The filtration of a bovine serum albumin solution showed that the MMM with in situ generated nanoparticles had better antifouling properties than the PES membrane alone in multiple applications as a result of the enhanced hydrophilic surface.

A homogeneous in situ generated Zr-based NPs/PES mixed matrix membrane with enhanced adsorptive and antifouling performance was developed.     

PEGylated polyvinylidene fluoride membranes via grafting from a graphene oxide additive for improving permeability and antifouling properties

Polyvinylidene fluoride (PVDF) porous membranes with enhanced hydrophilicity and antifouling performance were developed via surface PEGylation (PEG, polyethylene glycol) via a reactive graphene oxide (GO) additive. PVDF/GO blended membranes were first fabricated via a non-solvent-induced phase separation process. Then the carboxyl groups of GO sheets immobilized on the membrane surface acted as initiating sites for grafting amine-functionalized PEG (PEG-NH₂) chains via an amination reaction. Analysis of the X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy-attenuated total reflectance results confirmed the successful grafting of hydrophilic PEG molecular chains on PVDF membrane surfaces. The water contact angle of the PEGylated PVDF membrane decreased to 59.9°, indicating improved hydrophilicity. As a result, the antifouling performance was enhanced significantly. After surface PEGylation, the flux recovery rate is reached 90.2%, the total fouling ratio was as low as 20.7%, and reversible fouling plays a dominant role during the membrane fouling process. This work provides a valuable strategy to fabricate PEGylated membranes via the introduction of a reactive GO additive.

Polyvinylidene fluoride (PVDF) porous membranes with enhanced hydrophilicity and antifouling performance were developed via surface PEGylation (PEG, polyethylene glycol) via a reactive graphene oxide (GO) additive.     

Surface modification of a PES membrane by corona air plasma-assisted grafting of HB-PEG for separation of oil-in-water emulsions

The main goal of this study is to modify a polyethersulfone (PES) membrane by grafting with hyperbranched polyethylene glycol (HB-PEG) using corona air plasma to intensify the anti-fouling properties of the prepared membrane. The separation efficiency and fouling tendency of the modified membranes were evaluated for the treatment of a synthetic oily wastewater. A mechanism was proposed for the HB-PEG grafting on the surface of the corona treated PES membranes and all steps of the grafting were described in detail. The effects of corona treatment operating conditions on the morphology, surface properties, separation performance and anti-fouling efficiency of the modified PES membranes were investigated. Also, the HB-PEG grafted PES membranes were characterized by FTIR, AFM and contact angle analysis. Finally, the HB-PEG grafting on the surface of the PES membranes altered the surface hydrophilicity and led to the improvement of the anti-fouling property and oil–water permeation flux of all modified membranes without any remarkable changes in oil rejection.

The main goal of this study is to modify a polyethersulfone (PES) membrane by grafting with hyperbranched polyethylene glycol (HB-PEG) using corona air plasma to intensify the anti-fouling properties of the prepared membrane.     

Preparation of lignin nanospheres based superhydrophobic surfaces with good robustness and long UV resistance

Lignin is an ideal substance for preparation of functional materials. Specifically, lignin nanospheres (LNPs) are formed by self-assembly of lignin molecules and show great application prospects in drug delivery, electrochemistry, catalysis, etc. At present, most superhydrophobic surfaces are mainly built using non-degradable inorganic particles and are still beset by defects such as poor environmental performance, easy aging, and low mechanical strength. In this study, an aqueous mixture containing LNPs, cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVA) was sprayed onto wood surfaces and then modified by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS) to obtain a superhydrophobic surface. In the superhydrophobic surface, LNPs were used as the main structural materials instead of inorganic particles, CNC was used as a reinforcement material and PVA was used as an adhesive. The resulting superhydrophobic surface showed a water contact angle (WCA) of 162°, good robustness resistance and long UV resistance in which the superhydrophobicity was still retained after exposure to ultra-high UV light (power of 1000 W) for 7 h, providing more directions for high-value application of lignin.

Lignin nanospheres could be taken main structural materials and cellulose nanocrystals as a reinforcer for preparation of superhydrophobic surfaces with good robustness and long UV resistance.     

PVA and CS cross-linking combined with in situ chimeric SiO2 nanoparticle adhesion to enhance the hydrophilicity and antibacterial properties of PTFE flat membranes

Herein, a new hydrophilic and antibacterial polytetrafluoroethylene (PTFE) flat MF membrane was fabricated via a low-cost and simple preparation method in which chitosan (CS) was crosslinked with poly(vinyl alcohol) (PVA) using epichlorohydrin (ECH) as a cross-linker followed by in situ chimeric SiO₂ nanoparticle adhesion. The surface of the modified membrane had decreased C and F contents, and a large number of hydrophilic groups appeared. The treated membrane had good hydrophilicity and antibacterial properties. Moreover, the PTFE-modified membrane had high separation efficiency and antifouling property for oil-in-water emulsions. Finally, the hydrophilic stability of the PTFE membrane was studied by subjecting it to continuous water rinsing and soaking in solutions of different pH values. The present study demonstrates that this modified membrane has potential practical applications in industrial wastewater recovery.

Herein, a new hydrophilic and antibacterial PTFE flat MF membrane was fabricated via a low-cost and simple preparation method in which CS was crosslinked with PVA using ECH as a cross-linker followed by in situ chimeric SiO₂ nanoparticle adhesion.     

Synthesis and evaluation of eco-friendly carboxymethyl cellulose/polyvinyl alcohol/CuO bionanocomposites and their use in coating processed cheese

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese. Copper oxide nanoparticles (CuO-NPs) were prepared and added to a mixed solution of carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA) using compositions of 0.3, 0.6 and 0.9% (w/v). The CMC/PVA/CuO bionanocomposites were prepared by a solution casting method and used for coating processed cheese. The fabricated bionanocomposite films and CuO-NPs were characterized by TEM, SEM, EDEX, XRD, DLS, and FT-IR analysis. Inclusion of CuO-NPs decreased the gas transmission rate (GTR) and water vapor transmission rate (WVTR) of the prepared film. Also, the bionanocomposite suspensions exhibited high but variable inhibitory effects against several pathogenic bacteria and fungi. The impact of coating of processed cheese surfaces with the prepared bionanocomposite films on microbiological, physicochemical, textural and sensory properties of the processed cheese were assessed during 6 months of cold storage. Coating cheese with film containing CuO-NPs eliminated mould growth on the cheese surface and decreased significantly (P < 0.05) the total bacterial count of the cheese. Furthermore, coating of cheese decreased the moisture losses and retarded the increase in the cheese hardness during storage. The highest acceptability at the end of the storage period was given for processed cheese coated with the bionanocomposite containing 0.9% CuO-NPs. Thus, the obtained CMC/PVA/CuO bionanocomposite films could be a promising candidate for cheese packaging applications.

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese.     

Elucidating the mechanism behind the laccase-mediated modification of poly(ethersulfone)

Laccase-mediated oligomerisation of 4-hydroxybenzoic acid (4-HBA) derivatives and simultaneous in situ surface modification has proven to be a cost-effective, easily applicable and eco-friendly strategy for preventing biofouling of poly(ethersulfone) (PES) water filtration membranes. Modification of the membrane surface has previously been hypothesised to occur through covalent bonding of enzymatically generated phenolic radicals to the polymeric membrane. The current study shows, however, that in situ formation of soluble phenolic oligomers does not result in covalent membrane modification. We studied in situ laccase-mediated oligomerisation of custom-synthesised positively charged and commercially available negatively charged monomeric phenols, and demonstrated that their mode of binding to PES is not covalent. In addition, soluble, non-soluble and on-resin PES model compounds were synthesised and used in the laccase-mediated oligomerisation of 4-HBA. Covalent bond formation between these model compounds and (oligomeric) 4-HBA could not be observed either. Furthermore, extensive washing of PES membranes modified through laccase-mediated oligomerisation of 4-HBA resulted in substantial discolouration of the membrane surface, showing that the layer of oligomerised phenolics could easily be removed. Altogether, it was concluded that laccase-assisted modification of PES membranes resulted from strong physical adsorption of phenolic oligomers and polymers rather than from covalent bonding of those.

The mechanism behind the laccase-mediated functionalisation of poly(ethersulfone) was studied using a multifaceted approach, which revealed that surface modification had occurred through strong physical adsorption, rather than through grafting of phenolic oligomers.     

Preparation and characterization of an amphiphilic polyamide nanofiltration membrane with improved antifouling properties by two-step surface modification method

Membrane fouling is an urgent problem needing to be solved for practical application of nanofiltration membranes. In this study, an amphiphilic nanofiltration membrane with hydrophilic domains as well as low surface energy domains was developed, to integrate a fouling-resistant defense mechanism and a fouling-release defense mechanism. A simple and effective two-step surface modification of a polyamide NF membrane was applied. Firstly, triethanolamine (TEOA) with abundant hydrophilic functional groups was grafted to the membrane surface via reacting with the residual acyl chloride group of the nanofiltration membrane, making the nanofiltration membranes more hydrophilic; secondly, the 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS), well-known as a low surface energy material, was covalently grafted on the hydroxyl functional groups through hydrogen bonding. Filtration experiments with model foulants (bovine serum albumin (BSA) protein solution, humic acid solution (HA) and sodium alginate solution (SA)) were performed to estimate the antifouling properties of the newly developed nanofiltration membranes. As a result of surface modification proposed in this study the antifouling properties of an amphiphilic modified F-PA/PSF membrane were enhanced more than 10% compared to the PA/PSF specimen in terms of flux recovery ratio.

Schematic diagram of amphiphilic NF membrane by a two-step modification.     

Novel cross-linked poly(vinyl alcohol)-based electrolyte membranes for fuel cell applications

Herein, a new series of polymer electrolyte membranes was prepared by chemically cross-linked poly(vinyl alcohol) (PVA) and sulfonated poly(ether sulfone) (SPES). A typical polymerization reaction was conducted using three different monomers i.e. bisphenol A, phenolphthalein, and 4,4′-dichlorodiphenyl sulfone. The SPES polymer was obtained by the post-sulfonation technique using chlorosulfonic acid as a sulfonating agent. The resultant SPES polymer at different concentrations was blended with cross-linked poly(vinyl alcohol). Structural analysis of the samples was conducted by FTIR, SEM, and XRD. Among the prepared PEM materials, PVA–SPES-20 blend membranes exhibited higher ion-exchange capacity and % water uptake values than those of the other membranes. In addition, the PVA–SPES-20 membrane exhibits the proton conductivity of 0.0367 S cm⁻¹ at 30 °C, whereas pristine PVA shows the proton conductivity of 0.0259 S cm⁻¹. The overall experimental results revealed that the PVA–SPES blend membranes are promising candidates for fuel cell applications.

A series of cross-linked poly(vinyl alcohol)-sulfonated poly(ether sulfone) blend membranes were prepared. The studies of physico-chemical properties revealed that the reported membranes are promising candidate for PEMFC applications.     

Modified melamine-formaldehyde resins improve tensile strength along with antifouling and flame retardancy in impregnation of cellulose paper

In this study, polyvinyl alcohol (PVA) and benzoguanamine (BG) modified melamine-formaldehyde (MF) resins were used to prepare two high-pressure laminates (HPLs) as well as a pure cellulose paper laminate and core sandwich laminates with the core material of aramid paper (AP) or polypropylene non-woven fabric (PPNF). The tensile strength, flame retardancy and antifouling properties of the modified MF resin laminates were studied and compared with the MF resin laminate. The tensile test results showed that the MF resins modified with BG and PVA improved the tensile strength of the impregnated paper. In comparison with pure kraft cellulose paper laminates, the aramid paper core laminates displayed comparatively higher tensile strength. Antifouling test results indicated that modified MF resin laminates had no obvious change while the MF resin laminate was stained. Thermal stability of the modified resins was investigated by thermogravimetric (TG) analysis and the results showed that the char yield of modified MF resin was higher than that of the unmodified MF resin due to the addition of BG. The modified MF resin laminates exhibited better flame retardancy properties through the analysis of limiting oxygen index (LOI), vertical burning and cone calorimetry (CONE) compared to the MF resin laminate. In addition, the flame retardancy of laminates was further enhanced when prepared with core materials of aramid paper. Scanning electron microscopy analysis of residue char after CONE tests showed that the AP-core laminate formed a dense and stable char layer compared with the loose char layer of the PPNF-core laminate. This study shows a new direction to develop sustainable high-performance flame retardant laminates for commercial decoration application.

Polyvinyl alcohol (PVA) and benzoguanamine (BG) modified melamine-formaldehyde (MF) resins were used to prepare high-pressure laminates (HPLs) and the improved tensile strength, flame retardancy and antifouling properties were investigated.     

In situ nanoarchitectonics of magnesium hydroxide particles for property regulation of carboxymethyl cellulose/poly(vinyl alcohol) aerogels

Carboxymethyl cellulose (CMC)-based aerogels with low density, low thermal conductivity, and biodegradability are promising candidates for environmentally friendly heat-insulating materials. However, the application of CMC-based aerogels as insulation materials in building exterior walls is limited by the high water sensitivity, poor mechanical properties and high flammability of these aerogels. In this work, a simple hydration method was used to generate magnesium hydroxide (MH) directly from CMC/polyvinyl alcohol (PVA) mixed sol with active MgO obtained by calcined magnesite as the raw material. A series of composite aerogels with different MH contents were prepared through the freeze-drying method. Scanning electron microscopy showed that nanoflower-like MH was successfully synthesised in situ in the 3D porous polymer aerogel matrix. Compared with the mechanical properties and water resistance of the original CMC/PVA composite aerogels, those of the composite aerogels were significantly improved. In addition, the flame retardancy of the CMC/PVA composite aerogels was greatly enhanced by the introduction of MH into the polymer matrix, and the limiting oxygen index reached 35.5% when the MH loading was 60%.

Flame retardant efficiency of magnesium hydroxide in cellulose aerogels improved by in situ formation.     

Fabrication and evaluation of melamine-formaldehyde resin crosslinked PVA composite coating membranes with enhanced oxygen barrier properties for food packaging

Since PVA membrane is of limited use for food packaging applications in moist conditions, polyvinyl alcohol/melamine-formaldehyde resin (PVA/MF) composite coating membranes with various contents of MF were fabricated by a chemical crosslinking method to reduce the sensitivity of PVA to moisture. The morphology, chemical structure, thermal and mechanical properties of the resultant PVA/MF composite coating membranes were characterized by scanning electron microscopy (SEM), FT-IR spectrometer, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC) and universal testing machine. In addition, their hazes and OTRs were also measured as a function of MF content. Experimental results showed that –OH in the molecular chain of MF and PVA could be crosslinked at room temperature to form a dense polymeric structure, resulting in the increase in viscosity and the decline in water absorption. The incorporation of MF into PVA gave rise to the enhancement of crosslinking through the C–O–C bonding and strong interface interaction between MF and PVA that was beneficial to improving its thermal stability, mechanical properties and barrier properties. Furthermore, the PVA/MF composite coating membranes exhibited superior transparency due to their good leveling and wettability on both BOPET and PLA substrates. The moisture resistance and barrier properties of the MF/PVA composite coated BOPET and PLA membranes under high humidity conditions have been greatly improved, and the oxygen transmission rates (OTRs) under 75% RH could still remain at about 1.0 cm³ per m² per day. These characteristics of the PVA/MF composite coating membranes have made them exhibit widespread application prospects for coating membranes in the food packaging field.

Since PVA membrane is limited use for food packaging applications in moist conditions, PVA/MF composite coating membranes with various contents of MF were fabricated by a chemical crosslinking method to reduce the sensitivity of PVA to moisture.     

Modification of a polyethersulfone membrane with a block copolymer brush of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate) and a branched polypeptide chain of Arg–Glu–Asp–Val

Polyethersulfone (PES) has good thermal stability, superior pH, chlorine tolerance, and excellent chemical resistance; however, the hydrophilicity and biocompatibility of PES need to be improved for its real applications. In this study, we report a surface modification method for the preparation of a functional PES membrane with hydrophilic polymer chains (MPC and GMA) via surface-initiated electrochemically-mediated atom-transfer radical polymerization (SI-eATRP) technology, and the Arg–Glu–Asp–Val polypeptide groups (REDV) were immobilized onto the modified membrane by a ring-opening reaction. XPS and SEM were used to analyze the chemical composition and morphology of the modified membrane surfaces, confirming that the hydrophilic polymer chains MPC and GMA and the polypeptide group REDV were successfully grafted onto the PES membrane surface. The static water contact angle decreased from 89° to 50–65°, and the hydrophilic property of the modified membrane was enhanced. The water flux increased from 4.29 L m⁻² h⁻¹ for the pristine PES membrane to 25 L m⁻² h⁻¹ for the modified membrane with PGMA chains grafted on it and REDV functional groups immobilized on it; note that the antifouling tests showed that all the modified membranes had the higher flux recovery ratio values (FRR) of above 80% than the pristine PES membrane (about 60%), and the APTT for the modified membrane increased from 46 s to 93 s, indicating that these modified membranes could be applied in the separation and blood purification fields.

A block copolymer involving chains of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate) and Arg–Glu–Asp–Val was designed and used for modification of polymer membrane for applications in separation and blood purification field.     

Fabrication of an antifouling PES ultrafiltration membrane via blending SPSF

Sulfonated polysulfone (SPSF) with different sulfonation degrees (10%, 30%, and 50%) was added to polyethersulfone (PES) to improve the separation and antifouling performance of polyethersulfone ultrafiltration membranes. The PES/SPSF blend ultrafiltration membrane was prepared by the non-solvent induced phase inversion method (NIPS), and the effect of sulfonation degree on the ultrafiltration performance was studied. The compatibility of SPSF and PES was calculated by the group contribution method, and confirmed by differential scanning calorimetry (DSC). The morphology and surface roughness of the membrane were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the chemical composition of the membrane was analyzed by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR), and the permeability and anti-fouling performance of the blend membrane were studied through filtration experiments. The research shows that the flux and anti-fouling performance of the blend membrane have been improved after adding SPSF. When the sulfonation degree of the SPSF is 30%, the pure water flux of the blend membrane can reach 530 L m⁻² h⁻¹, the rejection rate of humic acid (HA) is 93%, the flux recovery rate of HA increases from 69.23% to 79.17%, and the flux recovery rate of BSA increases from 72.56% to 83%.

The chemical structures of (a) PES and (b) SPSF.