Liquid-induced Phase Separation Research Articles

Simultaneous enhanced antibiotic pollutants removal and sustained permeability of the membrane involving CoFe2O4/MoS2 catalyst initiated with simple H2O2 backwashing

Membranes for wastewater treatment should ideally exhibit sustainable high permeate production, enhanced pollutant removal, and intrinsic physical rejection. In this study, CoFe2O4/MoS2 serves as a non-homogeneous phase catalyst; it is combined with polyether sulfone membranes via liquid-induced phase separation to simultaneously sustain membrane permeability and enhance antibiotic pollutant degradation. The prepared catalytic membranes have higher pure water flux (329.34 L m−2 h−1) than pristine polyethersulfone membranes (219.03 L m−2 h−1), as well as higher mean pore size, porosity, and hydrophilicity. Under a moderate transmembrane pressure (0.05 MPa), tetracycline (TC) in synthetic and real wastewater was degraded by the optimal catalytic membrane by 72.7 % and 91.2 %, respectively. Owing to the generation of the reactive oxygen species (ROS) during the Fenton-like reaction process, the catalytic membrane could exclude the natural organics during the H2O2 backwash step and selectively promote fouling degradation in the membrane channel. The irreversible fouling ratio of the catalyzed membrane was significantly reduced, and the flux recovery rate increased by up to 91.6 %. A potential catalytic mechanism and TC degradation pathways were proposed. This study offers valuable insights for designing catalytic membranes with enhanced filtration performance.

3 stage filtration system utilizing 3 distinct membranes derived from one single dope solution and finely-tuned phase inversion processes

Wastewater treatment by membrane processes requires at least 3 different membranes with performances falling in the microfiltration, ultrafiltration and nanofiltration ranges. Often, the composition of these membranes varies, and their preparation processes may involve several steps and lengthy or costly post-treatment procedures, for instance to endow the membrane with fouling-resistance property. Here, we intended to explore potential routes to simplify the treatment process. We solely used one single casting solution with the purpose of preparing 3 membranes without any post-treatment, that were then implemented in a 3-stage filtration process. This solution contains polyvinylidene fluoride (PVDF), a copolymer of styrene and polyethylene glycol methyl ether methacrylate (PS-r-PEGMA), and a solvent. 3 phase inversion processes: vapor-induced phase separation (VIPS), liquid-induced phase separation (LIPS) and evaporation-induced phase separation (EIPS) were executed to reach the desired membrane properties. Careful examination of the membrane structure, physical properties and permeability prove that the membranes prepared by VIPS (pore size: 0.4–0.8 µm), LIPS (pore size: 0.008–0.09 µm) and a combination of EIPS and LIPS (pore size: 3–6 nm) were suitable for the rejection of large biofoulants such as microalgae, large and small proteins, respectively, despite the presence of the antifouling copolymer that affected the membrane structure. Next, the 3 membranes were used to treat synthetic wastewater containing a mixture of microalgae, bovine serum albumin (BSA) and lysozyme. The first filtration stage permitted to reject almost entirely the Microalgae (99.3–99.5% rejection), the second filtration stage then removed larger proteins (cumulated “Microalgae/protein” rejection of about 93%) while the last stage rejected a large quantity of the smaller protein. The copolymer was also shown to reduce fouling by a 5-fold factor. Hence, this work demonstrates that a complete set of pressure-driven antifouling membranes for full wastewater treatment may be prepared from one single formulation and by phase inversion only.

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method.

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

Fine regulation on hour-glass like spongy structure of polyphenylsulfone (PPSU)/sulfonated polysulfone (SPSf) microfiltration membranes via a vapor-liquid induced phase separation (V-LIPS) technique

The fine micro-structure regulation of polymeric membranes is crucial to the separation performances. Herein, we prepared a novel Polyphenylsulfone (PPSU)/sulfonated polysulfone (SPSf) microfiltration membrane with ‘hour-glass’ like spongy micropore-structure via vapor and liquid induced phase separation (V-LIPS) technique. A precritical casting solution was prepared by adding a certain amount of H2O using N, N-dimethylacetamide (DMAc) as the solvent and Polyvinyl Pyrrolidone (PVP) as the pore-forming agent. The effect of residence time in vapor on membrane structures is extensively evaluated. Results revealed that the resultant membranes evolved from finger-like to bicontinuous structure with extending the exposure time (>5s) in vapor. The pure water flux of the membrane with the vapor time (30s) under the pressure of 0.2 bar reached a high value of 3045.7 ± 42.7 L/(m2∙h). Moreover, the obtained membrane M3 showed excellent separation properties for surfactant-stabilized n-hexane-in-water, isooctane-in-water and decamethylcyclopentasiloxane (D5)-in-water emulsions with rejection coefficient up to >99%, >99% and >98% and high rejection of 99.0% to SiO2 nanoparticles. Therefore, PPSU/SPSf membrane with controlled ‘hour-glass’ like spongy micro-pore structure showed high permeability with high rejection coefficient for both inorganic nanoparticles and oily water.

About a Membrane with Microfluidic Porous-Wall Channels of Cylindrical Shape for Droplet Formation.

A low-energy emulsification process is hollow-fiber emulsification. In this process, the lumen diameter of the membrane mostly determines the droplet size. To gain smaller droplets, approaches for downsizing the inner diameter of membranes have to be carried out. In this work, we describe a new method for the fabrication of parallel microfluidic porous-wall channels of a homogeneous cylindrical shape with lumen diameters down to 7 μm. Parallel and symmetric porous-wall channels are induced into polyvinylidene fluoride membranes during the casting process. The technique comprises liquid-induced phase separation and phase-separation micromolding using thin glass and carbon fibers as molds and an in-house designed tool to position the fibers. The channel positioning and alignment are verified within this work. We show and investigate the droplet formation in these porous-wall channels via hollow-fiber emulsification. The formed droplets are very small in diameter and size distribution. The droplet formation at varying flow rates and channel diameters is examined in detail. Moreover, an area of sufficient operating conditions is given using Weber and capillary numbers. As a numbering-up approach, we show the simultaneous formation of spherical droplets in two parallel channels. With the proposed membrane fabrication using micromolding, we push the downscaling approach of hollow-fiber emulsification to lower micron ranges of the channel diameter. With these small channels, droplets with a diameter down to 25 μm were produced, which are more attractive for most applications.

Novel composite membranes for simultaneous catalytic degradation of organic contaminants and adsorption of heavy metal ions

Novel composite membranes are successfully developed for simultaneous adsorption of heavy metal ions and catalytic degradation of organic contaminants by blending polydopamine-coated ferroferric oxide (Fe3O4@PDA) nanoparticles in polyethersulfone (PES) matrix via liquid-induced phase separation (LIPS) method. The permeabilities of the as-fabricated composite membranes are significantly improved by introducing Fe3O4@PDA nanoparticles, because the hydrophilic coating on the surface of Fe3O4@PDA nanoparticles enables to generate more microporous structures between the PES matrix and nanoparticles during the LIPS process. The composite membrane containing 20 wt% Fe3O4@PDA nanoparticles shows water flux as high as 2640 L∙m−2∙h−1∙bar−1, which is six times larger than that of PES blank membrane. The composite membranes exhibit efficient and repeatable performances for simultaneous adsorptive removal of heavy metal ions and catalytic degradation of organic contaminants based on the mechanism of Fenton-like reaction. The proposed composite membranes with multifunction of simultaneous catalytic degradation of organic contaminants and adsorption of heavy metal ions provide a new pathway to deal with some hard-to-be-treated wastewaters from papermaking, leather, textile printing-dyeing industries, and so on. Furthermore, the proposed one-step strategy for fabricating composite membranes with both large permeability and high separation efficiency in this work is easy to be scaled up.

High-flux efficient catalytic membranes incorporated with iron-based Fenton-like catalysts for degradation of organic pollutants

A novel composite catalytic membrane is developed by blending silicon oxide coated ferroferric oxide (Fe3O4@SiO2) nanoparticles in polyether sulfone (PES) membrane as Fenton-like catalysts via liquid-induced phase separation (LIPS) method. By introducing Fe3O4@SiO2 nanoparticles in PES membrane matrix, the surface hydrophilicity, porosity and mean pore diameter of as-prepared composite catalytic membranes are improved due to the hydrophilic nature of the SiO2 coating layer on the Fe3O4@SiO2 nanoparticles. The as-fabricated catalytic membrane can filter large particles above ~100 nm and shows a high water flux of 2084 kg m−2 h−1 under 0.1 MPa. Importantly, the composite catalytic membrane shows efficient catalytic performance and satisfactory stability in the degradation of organic pollutants based on the Fenton-like reaction mechanism. The proposed strategy for membrane fabrication and the experimental results in this study provide valuable guidance for developing high-flux catalytic membranes with efficient catalytic performances for treatment of industrial and municipal wastewater.

Improved liquid phase separation processes for generating biodegradable microspheres loaded with high concentrations of drugs for tumor embolization

ABSTRACTDrug-eluting microspheres are the most commonly used particulate embolic agents for transarterial chemoembolization of liver tumors. However, drug loading of degradable embolic particles is often insufficient. In the current study, microspheres prepared from poly(D,L-lactic-co-glycolic acid) were investigated as a biodegradable embolic agent for arterial embolization applications. Through modified solvent evaporation and liquid-induced phase separation, high drug loading (as high as 32%) and low solvent residue (as low as 0.03%) was achieved. Degradation performance, 1H NMR, and the nonsolvent’s influence on solvent residue content were assessed. These drug-loading microspheres with biodegradability hold promise for embolization therapies.

Tailoring PVDF Membranes Surface Topography and Hydrophobicity by a Sustainable Two-Steps Phase Separation Process

This work validates a sustainable way to produce customized PVDF membranes, suitable for contactors applications, in which DMSO is employed as nonhazardous solvent, in place of substances of very high concern (SVHC), by a combination of vapor-induced and liquid-induced phase separation (VIPS and LIPS) stages, and without using any chemical additive as pore forming. The experimental results highlight the key role of the kinetic and thermodynamic parameters of the phase separation processes involved in the control of the surface and transport properties of the PVDF membranes. Namely, combining VIPS and LIPS techniques in a controlled way, allowed to produce symmetric porous membranes with customized rough surface topography (root-mean-square roughness up to 0.67 μm) and hydrophobicity (water contact angle up to 140°) according to a biomimetic behavior as that of lotus leaves surfaces, through an environmental friendly fabrication process. The resulting membranes are characterized by a high porosity (total p...

Dual pH-responsive smart gating membranes

A novel dual pH-responsive smart gating membrane is proposed for the first time by skillfully blending poly(N,N′-dimethylamino-2-ethyl methacrylate) (PDMAEMA) microgels into poly(ether sulfone) membrane as functional gates via liquid-induced phase separation method. The as-prepared membrane exhibits dual pH-responsive characteristics, i.e., this novel membrane is featured with both positively pH-responsive characteristics in acidic environment and negatively pH-responsive characteristics in basic environment. The mechanism of the positively pH-responsive performance is attributed to the pH-responsive volume change of PDMAEMA microgels embedded in the membrane, while that of the negatively pH-responsive performance is originated from the pH-responsive hydrophobicity and stiffness of the microgels. As a result, the permeability of this novel membrane is increased at first and then decreased with increasing the environmental pH value. The dual pH-responsive property of the prepared membrane is reversible and repeatable. The dual pH-responsive membrane proposed in this study provides a novel gating mode for design and development of pH-responsive smart membranes, which is highly potential for myriad applications, such as sewage treatments, sensors, controlled release of drugs and so on.

Effect of stereoisomerism of poly(lactic acid) during neural guide conduit membrane synthesis

ABSTRACTPoly(lactic acid) membranes are being developed as biomaterials for several purposes such as artificial implants for peripheral nerve injury, also known as neural guide conduits (NGC). These membranes need to meet standards of mechanical, degradability, and permeability properties, besides dimensional and structural requirements. Among the stereoisomers of polylactides, poly(l‐lactic acid), and poly(d,l‐lactic acid) are the most used as biomaterials, having significant differences in solubility, crystallinity thermal, and mechanical properties. In this work, PLLA and PDLLA were compared for hollow fiber membrane synthesis by liquid induced phase separation. PLLA samples presented 18% of crystallinity, while PDLLA is amorphous. PDLLA and PLLA polymer solutions on N‐methyl‐pyrrolidone presented values of 3428 and 320.2 cP, respectively. In immersion of PLA‐NMP solutions in water, PLLA solution presented instantaneous demixing, while PDLLA showed a 28 s delay on precipitation. The PLLA–NMP–water has a larger demixing region compared to PDLLA–NMP–water system. Hollow fibers of both polymers presented closed external surface with finger‐like macropores morphology in their cross‐sections. PDLLA presented typical liquid–liquid demixing pores while PLLA presented spherulitical crystalline solid–liquid separation structures, which deeply compromised its mechanical properties. PDLLA presented as a good candidate for hollow fiber NGC material, as presented good mechanical resistance in tensile and suture simulating tests. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46190.

Symmetrical polysulfone/poly(acrylic acid) porous membranes with uniform wormlike morphology and pH responsibility: Preparation, characterization and application in water purification

Well defined porous membranes have been fabricated from polystyrene based block copolymers by self-assembly and non-solvent induced phase separation. However, simplifying the time-consuming preparation steps and overcome the limitation in materials remain challenging. Here, symmetrical polysulfone/poly(acrylic acid) (PSf/PAA) membranes with uniform wormlike morphology were fabricated by a two-stage phase inversion strategy combining a vapor-induced phase separation (VIPS) with a liquid-induced phase separation (LIPS) for the first time. The casting solutions were synthesized via in situ cross-linking polymerization of AA in PSf solution and spread into films without any treatment. After exposing in humid air for a certain time, the films were soaked in a water bath. It was confirmed that the wormlike networks covered the membrane surfaces by tuning the exposure time and AA concentration. The membranes exhibited pH-dependent permselectivity. When the solution pH was varied from 1.3 to 12.5, water flux ranged from ~ 334.1 to ~ 55.4Lm−2h−1bar−1, and molecular weight cutoff of the membrane decreased from 2000 to 600kg/mol. Moreover, the membranes were able to remove copper ions from water with a maximum static adsorption capacity of ~ 235mg/g at pH 6, and reused as reusable adsorbents. The present work opens a new path for fabricating symmetrical porous membranes with uniform wormlike morphology and pH responsibility in up-scale for application in water purification, especially the removal of heavy metal anions.

Preparation of Poly(lactic acid) Flat Sheet Membranes by Liquid Induced Phase Separation

SummaryBiodegradable and biocompatible polymers have been evaluated as materials for membrane separation based processes due to their flexibility and highly aggregated value in biomedical, food and packaging applications. Polylactides is a promising class of biodegradable polymers mostly due to its mechanical properties and ease in processing. In this work, flat sheet Poly(L‐lactic acid) (PLLA) membranes were made by liquid induced phase separation (LIPS) technique using water as non‐solvent and N‐methyl‐2‐pyrrolidone (NMP) as solvent. Processing conditions as polymer concentration of the casting solution, time of exposure in humid atmosphere and composition of coagulation bath were evaluated. The effects of these variables were analyzed in the performance, morphology and mechanism of phase separation during membrane formation. The PLLA‐water‐NMP system miscibility gap was estimated by cloud points and viscosity of polymer solutions were measured. Membranes were characterized by precipitation kinetics by light transmission, hydraulic permeability and scanning electron microscopy. Porous microfiltration membranes could be formed with permeabilities of 62.87 L m−2 h−1. It could be concluded that the morphology of PLLA membranes is a result of a complex interplay between solid‐liquid and liquid‐liquid demixing during phase separation.

Effects of fabrication conditions on the microstructures and performances of smart gating membranes with in situ assembled nanogels as gates

Smart gating membranes with in situ assembled poly(N-isopropylacrylamide) (PNIPAM) nanogels as gates are successfully prepared via vapor-induced phase separation (VIPS) with different exposure time periods, temperatures and relative humidities of the water vapor. Effects of the fabrication conditions on microstructures as well as thermo-responsive and mechanical performances of the membranes are investigated. Both the membrane microstructure and the movement of blended PNIPAM nanogels in the membrane forming solution can be controlled by adjusting the fabrication conditions. With increasing the exposure time, the membrane microstructure undergoes a transition from typical liquid-induced phase separation (LIPS) structure (unsymmetrical finger-like porous structure) to typical VIPS structure (symmetric cellular-like porous structure). The critical time periods for the microstructure transition of membranes prepared with vapor temperature and relative humidity of 25°C/90%, 25°C/70% and15 °C/70% are about 1.5min, 2min and 10min respectively. The performances of membranes are heavily dependent on the microstructures. The membranes with unsymmetrical finger-like porous structures show large thermo-responsive factor (R39/20, the ratio of water flux at 39°C to that at 20°C), with the maximum R39/20 value being 43.2. All the membranes with symmetric cellular-like porous structures exhibit strong mechanical property and large water flux at 39°C, which is higher than the volume phase transition temperature (VPTT) of PNIPAM nanogels. The results provide valuable guidance for rational design and fabrication of smart gating membranes with desirable performances.

Micropatterned fabrication of chitosan-based thermoresponsive membranes for improving cell adhesion and gene expression

A simple, rapid, and economical method to fabricate micropatterned thermoresponsive chitosan membranes was developed. Porous polystyrene films were prepared by liquid-induced phase separation. The size of pores on polystyrene films could be regulated by adjusting the composition of coagulation bath and changing the solvent evaporation rate. Subsequently, chitosan-based thermoresponsive membranes with island protrusions were fabricated using porous polystyrene films as templates. The effects of the micropatterns on the behaviors of mouse fibroblast L929 were investigated. The presence of micropatterns altered the cell cycle distribution and enhanced the gene expression of cyclin D1 and integrin β1. The micro-convex surface could promote the adhesion and proliferation of L929 cells. These results provided valuable guidance to design appropriate topographic surfaces for tissue engineering applications.

Dry–wet phase inversion block copolymer membranes with a minimum evaporation step from NMP/THF mixtures

Block copolymer (BCP) membranes are a very promising new type of membranes, but often have a difficult fabrication method that involves a long evaporation step prior to phase inversion. In this work, we study new novel BCP phase inversion recipes for the fabrication of asymmetric membranes with a thin, ordered isoporous selective layer on top of a highly interconnected porous support layer. A key aim is to shorten the evaporation time while simultaneously allowing the formation of even thinner selective top layers. Asymmetric membranes were fabricated via the combination of polystyrene-block-poly(4-vinyl pyridine) self-assembly, solvent evaporation and liquid induced phase separation. Using a solvent mixture of THF and NMP, a selective top layer of just 60nm thick was formed with an ordered honeycomb-like pore structure. The formed structure depended on several parameters, such as THF/NMP ratio, polymer concentration of the polymer solution and the duration of solvent evaporation. When a high THF/NMP ratio was used (more THF than NMP) the solvent evaporation step could be reduced to only 1s, a clear advantage when considering scale up of this approach. The THF/NMP ratio also influenced the morphology of the support layer, which translated into a variety of permeabilities (270–1320Lm−2h−1bar−1). Filtration experiments showed that the different top layer structures result in different filtration performance, with more ordered pores resulting in more selective filtration.

Hemocompatibility of PVDF/PS-b-PEGMA membranes prepared by LIPS process

The lack of knowledge on the hemocompatibility of PVDF-based membranes suggested the need for a dedicated study. The present work lays the focus on the effect of polystyrene-b-poly (ethylene glycol) methacrylate (PS-b-PEGMA) on the blood compatibility of PVDF membranes prepared by liquid-induced phase separation. First, the adhesion behavior of three major blood plasma proteins – fibrinogen (FN), γ-globulin and human serum albumin (HSA) – onto the membranes is thoroughly discussed. PS-b-PEGMA acts as a protein repellent, favoring the formation of a hydration layer at the surface of the membranes. A similar result is obtained whether using pure proteins or proteins from a platelet-poor plasma solution. Next, our results suggest that interactions between thrombocytes, erythrocytes and leukocytes with PEGylated membranes are importantly reduced. The mechanism for cell repulsion is believed to be identical as that responsible for protein resistance: the formation of a hydration layer around the ethylene glycol groups minimizes (i) the interactions between the membrane and the proteins constituting the wall of blood cells and (ii) prevents mediation of cells attachment by plasma proteins. Also, the hemolytic activity and the plasma clotting time are reduced and delayed, respectively, supporting the improvement of membranes hemocompatibility with PS-b-PEGMA content. Finally, the copolymer contributes to the resistance of irreversible biofouling due to plasma proteins during filtration. A flux recovery ratio of 91% is obtained for modified membranes while it is only 17% for commercial hydrophobic PVDF membrane and 56% for commercial hydrophilic PVDF membrane, after applying a similar treatment involving the adsorption of plasma proteins. Therefore, PEGylated PVDF membranes presented in this work are hemocompatible and could be used in blood contacting devices.

Low-biofouling membranes prepared by liquid-induced phase separation of the PVDF/polystyrene-b-poly (ethylene glycol) methacrylate blend

In the present work, the focus is laid on the formation, and low-biofouling properties of polyvinylidene fluoride (PVDF) membranes modified using an amphiphilic copolymer additive: polystyrene-b-poly (ethylene glycol) methacrylate (PS-b-PEGMA). PVDF was blended with PS-b-PEGMA and membranes were prepared by liquid-induced phase separation. The additive played a significant role on membrane formation, slightly decreasing surface porosity, reducing the shrinkage during phase separation, and increasing both the size and porosity of macrovoids. Owing to its numerous hydrophilic moieties, the copolymer was believed to promote solvent and nonsolvent exchanges during phase inversion. In addition, it significantly enhanced surface hydrophilicity and matrix hydration capability. Indeed, water was easily trapped by the PEGylated chains spread onto the surface and within the matrix, and then stored in the larger macrovoids. It led to an important reduction of protein adsorption, including bovine serum albumin (65%) and lysozyme (89%). Bacterial attachment tests revealed that adhesion of Escherichia coli and Staphylococcus epidermidis was almost totally prevented (over 99% reduction of attachment), which demonstrates the excellent efficiency of PS-b-PEGMA copolymer to provide PVDF membranes with low-biofouling properties.

Sol–gel preparation of PAA-g-PVDF/TiO2 nanocomposite hollow fiber membranes with extremely high water flux and improved antifouling property

High permeability and antifouling property are important performance of filtration membranes for reaching the requirement of real application. In this work, poly(acrylic acid) grafted PVDF (G-PVDF)/TiO2 nanocomposite hollow fiber ultrafiltration membranes were fabricated by combining tetrabutyl titanate in-situ sol–gel process with liquid-induced phase separation. Energy dispersive X-ray (EDX) and EDX mapping scanning spectra confirmed the formation of TiO2 component and uniformly dispersion of TiO2 nanoparticles in nanocomposite membranes with ultrafine size when the TiO2 content was less than 3wt%. The effect of TiO2 on the membrane performance was systematically investigated. The G-PVDF/TiO2 nanocomposite membranes exhibited extremely high water permeation, improved antifouling property and rejection efficiency as compared to PVDF and G-PVDF membranes. In case of ∼1wt% TiO2 content, the water flux of G-PVDF/TiO2 nanocomposite membranes reached 974L/m2h under 0.1MPa, which was more than four times of that of PVDF membranes. Simultaneously, G-PVDF/TiO2 nanocomposite membranes displayed greatly reduced amount of protein adsorption to be 24μg/cm2, which is a seventh of that of PVDF membranes. Two cycles of flux recovery test also indicated that G-PVDF/TiO2 nanocomposite membranes possessed better antifouling property and stability. More important is that the incorporation of TiO2 nanoparticles did not weaken the mechanical strength of the membranes. The superior performance of our G-PVDF/TiO2 nanocomposite hollow fiber ultrafiltration membranes offers a great potential for practical application.

PEGylation of anti-biofouling polysulfone membranes via liquid- and vapor-induced phase separation processing

Abstract This work describes the PEGylation of a polysulfone (PSf) membrane incorporated with poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO, Pluronic F108) via two different approaches for PEGylated membrane formation, including liquid-induced phase separation (LIPS) and vapor-induced phase separation (VIPS). Segregated and dispersed PEGylated domains on PSf membrane surfaces were achieved by LIPS and VIPS. The chemical composition and physical microstructure of the various PEGylated PSf membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), contact angle measurements, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements. The results show that the amount of adsorbed proteins and attached bacteria on the modified PSf membranes not only depends on the surface hydrophilicity and hydration capacity but also on the phase separation structures of PEGylated domains distributed on the PSf membrane surface. By controlling the surface uniformity of PEGylated domains, it is possible to highly regulate the PSf membrane to resist the adsorption of proteins and the attachment of bacteria. It was found that the PSf membranes prepared by the VIPS process present a higher polymer chain mobility of PEO–PPO–PEO than those prepared during the LIPS process, resulting in nano-structured phase separation during membrane formation. Consequently, the membranes prepared by VIPS have a better anti-biofouling character with respect to bacterial resistance. This work suggests that membrane formation by controlling PEO–PPO–PEO copolymer structures in nano-scale blending using the VIPS process shows great potential in the molecular design of anti-biofouling membranes for use in ultrafiltration applications.