Synthesis of poly(styrene sulfonate) brushes.

Dense poly(styrene sulfonate sodium salt) brushes were prepared on silicone wafers using a two-step procedure: polystyrene (PS) chains, terminated by a reactive trichlorosilane group, were first covalently grafted, and then the PS brush was converted to a poly(styrene sulfonate) brush by a soft sulfonation reaction. Ellipsometry and infrared spectroscopy in ATR were used to characterize the samples and to optimize the procedure: in particular, the sulfonation was shown to be homogeneous along the chain backbone and the neutralization complete. In some cases, the polymer layer revealed to be quite fragile: the chains were pulled out of the brush. A consolidation treatment which consisted in grafting oligomers inbetween the long PS chains significantly increased the robustness of the layer. This might be relevant for industrial applications.     

Performance evaluation of the different nano-enhanced polysulfone membranes via membrane distillation for produced water desalination in Sert Basin-Libya

A Polysulfone-Polyethylene glycol (PS/PEG) flat sheet membrane was prepared by phase inversion technique. Dimethyl Formamide (DMF) was utilized as a solvent and deionized water was utilized as the coagulant. Polyethylene glycol (PEG) of a various dose of PEG 2000 was utilized as the polymeric improvers and as a pore-forming agent in the casting mixture. The single-walled carbon nanotube (SWCNTs), multi-walled carbon nanotube (MWCNTs), aluminum oxide (Al₂O₃) and copper oxide (CuO) nanoparticles (NPs) were utilized to improve the PS/PEG membrane performances. The characterizations of the neat PS, PS/PEG, PS/PEG/Al2O3 (M1) PS-PEG/CuO (M2), PS-PEG/SWCNTs (M3) and PS/PEG/MWCNTs (M14) nanocomposite (NC) modified membranes were acquired via Fourier-transform infrared analysis (FTIR), water contact angle estimation (WCA), scanning electron microscope (SEM), dynamic mechanical analyzer (DMA) and thermogravimetric analysis (TGA). Enhanced Direct contact membrane distillation (EDCMD) unit was used for estimating the efficiency of the performance of the synthesized NC membranes via 60 °C feed synthetic water and/or saline oil field produced water samples containing salinities 123,14 mg/L. Adjusting the operational procedures and water characteristics confirmed a high salt rejection of 99.99% by the synthesized NC membranes. The maximum permeate flux achieved in the order of SWCNTs (20.91) > Al₂O₃ (19.92) > CuO (18.92) > MWCNT (18.20) (L/m².h) with adjusted concentration of 0.5, 0.75, 0.75, 0.1 wt% compared with PS weight, i.e. 16%. The optimum operational circumstances comprised feed and permeate temperatures 60 °C and 20 °C, respectively. The achieved flux was 5.97 L/m².h, using brine oil field produced water, via PS/PEG/SWCNTs membrane with 0.5 wt% of SWCNTs. Moreover, the membrane indicated sustaining performance stability in the 480 min continuous desalination testing, showing that the synthesized PS/PEG/SWCNTs NC modified membrane may be of magnificent potential to be activated in EDCMD procedure for water desalination.     

Solvent dependent friction force response of polystyrene brushes prepared by surface initiated polymerization

Polystyrene (PS) brushes were prepared on oxide passivated silicon by the surface initiated polymerization (SIP) technique. From an AIBN-type free radical initiator, which was silanized and immobilized on silicon wafers, styrene brushes were directly polymerized and grafted from the surface. The formation of the initiator monolayer and, subsequently, the polymer brush on the surface were monitored by X-ray photoelectron spectroscopy (XPS) and ellipsometry. Friction force measurements were performed by atomic force microscopy (AFM), using a 5 microm SiO2 colloidal sphere tip and under systematically varied solvent environments (nonpolar to polar), to demonstrate the dependence of brush lubricity on solvation. The relative uptake of solvents in the PS brush was determined by quartz crystal microbalance (QCM), and it correlates well with friction data. It is surmised that, in poor solvent environments, the polymer brush exists in a collapsed conformation, giving rise to the higher observed friction response.     

Patterning nanocluster polystyrene brushes grafted from initiator cores on silicon surfaces by lithography processing

In this study, we formed grafted polystyrene (PS) brushes possessing nanocluster structures through atom transfer radical polymerization from initiator cores presented on Si surfaces that had been generated using reactive ion etching (RIE). We established the surface grafting polymerization kinetics of the nanoclustered PS chains on the Si surfaces to fit their experimentally determined thickness (ellipsometry) and number-average molecular weight (M _n) of “free” PS (gel permeation chromatography). The propagation rate (k _p) and active grafting species deactivation rate (k _d) were obtained from reactions involving styrene concentrations from 0.2 to 2 M. We also used scanning electron microscopy to observe the morphologies of the PS grafted to the surfaces after various reaction times at various styrene concentrations. The PS brushes grafted onto the Si surfaces under styrene concentrations of 0.2, 0.5, 1, and 2 M exhibited clustered structures having cluster diameters of 12, 28, 42, and 45 nm, respectively; from these observations, we calculated the critical grafting density. In addition, we generated highly dense, well-defined patterns of PS on patterned Si(100) surfaces through the use of a very-large-scale integration process involving electron beam lithography and RIE. We employed the RIE system to generate a high density of reactive species at the bottom of the trenches for graft polymerization. After 21 h of grafting, AFM imaging revealed dense line patterns of nanoclustered PS.     

Performance improvement of polysulfone ultrafiltration membrane by blending with polyaniline nanofibers

Polyaniline (PANI) nanofibers were used to improve hydrophilic property and permeability of polysulfone (PS) membrane. PS membrane and PS/PANI nanofibers blended membranes with different PANI–PS mass ratios (1, 5, 10, and 15 wt.%) were prepared by phase inversion process. The blended membranes showed similar bovine serum albumin (BSA) and albumin egg (AE) rejections to PS membrane. The blended membranes had larger porosity and better hydrophilic property than PS membrane, which caused the improvement of their permeability. Pure water fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 1.6 and 2.4 times that of PS membrane, respectively. During the filtration of BSA solution, the blended membranes had slower flux decline rate than PS membrane. Moreover, stable permeate fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 2.0 and 2.5 times that of PS membrane, respectively. Compared with PS membrane, mechanical property and thermal stability of the blended membranes with less PANI–PS mass ratio, e.g. 1 wt.%, had no obvious change. For the blended membrane with PANI–PS mass ratio of 15 wt.%, breaking strength increased 28% and elongation at break decreased 30.6%.     

Environmentally responsive "hairy" nanoparticles: mixed homopolymer brushes on silica nanoparticles synthesized by living radical polymerization techniques

This article reports on the preparation of environmentally responsive "hairy" nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stober process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M(n) of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and (1)H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl(3), a selective solvent for PS, and also in CH(3)OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.     

Influence of graft interface polarity on hydration/dehydration of grafted thermoresponsive polymer brushes and steroid separation using all-aqueous chromatography

We have prepared poly( N-isopropylacrylamide) (PIPAAm) brush-grafted surfaces with varied temperature-responsive hydrophobic properties through surface-initiated atom transfer radical polymerization (ATRP). These temperature-responsive surfaces were characterized by chromatographic analysis using modified silica beads as a chromatographic stationary phase in aqueous mobile phase. Mixed silane self-assembled monolayers (SAMs) comprising ATRP initiator and silanes with various terminal functional groups were formed on the silica bead surfaces. IPAAm was then polymerized by ATRP using the CuCl/CuCl2/Me6TREN catalyst system in 2-propanol at 25 degrees C for 16 h. The chromatographic retention behavior of steroids on the resulting PIPAAm brushes made on more polar silane components was distinct from that on more apolar silane interfaces. Retention times for steroids on PIPAAm mixed apolar silane graft interfaces were significantly longer than those on analogous polar silane interfaces due to enhanced dehydration of PIPAAm brushes on apolar silane-grafted surfaces. Changes in retention factor, k', on polar silane PIPAAm-grafted interfaces were relatively large compared to that on apolar PIPAAm grafted interfaces due to larger hydration/dehydration alterations of grafted PIPAAm brushes on the former surfaces. Applied step-temperature gradients from 50 to 10 degrees C show that PIPAAm brushes on polar silane interfaces tend to hydrate more, leading to shorter retention times. In conclusion, the polarity of the grafted interface significantly influences the grafted PIPAAm brush hydration/dehydration characteristics and subsequently also the temperature-modulated separation of bioactive compounds in all-aqueous chromatography.     

Thermosensitive water-dispersible hairy particle-supported pd nanoparticles for catalysis of hydrogenation in an aqueous/organic biphasic system

We report in this article the use of thermosensitive water-dispersible polymer brush-grafted polymeric particles as carriers for Pd nanoparticles for the catalysis of hydrogenation of styrene in an aqueous/organic biphasic system. Thermoresponsive poly(methoxytri(ethylene glycol) methacrylate) brushes were grown from initiator-functionalized core-shell cross-linked poly( t-butyl acrylate) (P tBA) particles via surface-initiated atom-transfer radical polymerization. The t-butyl group of P tBA in the core was removed with trifluoroacetic acid, followed by loading of Pd2+ cations through ion exchange. Pd nanoparticles were prepared by reduction of Pd2+ ions with ethanol at 70 degrees C. Dynamic light scattering studies showed that the Pd nanoparticle-loaded thermosensitive hairy particles in water began to shrink when the temperature was above 30 degrees C. The supported Pd nanoparticles efficiently catalyzed hydrogenation of styrene in an aqueous/octane biphasic system and were reused five times with no changes in the yields in the first three cycles and slight decreases in the fourth and fifth cycles after the same period of time. Kinetics studies showed that the catalytic activity of Pd nanoparticles was modulated by the phase transition of the thermosensitive brush layer, resulting in a non-Arrhenius dependence of apparent initial rate constant, k app, on temperature.     

Effect of temperature on the frictional forces between polystyrene brushes

Normal and shear forces between opposing polystyrene (PS) brushes made from preferentially assembled PS–polyvinylpyridine diblock copolymers were measured in toluene and in near‐theta cyclohexane at 32, 40, and 50 °C, using a modified surface forces apparatus. In cyclohexane, over the temperature window probed, the normal forces of interaction are repulsive and the range of those force profiles changes only slightly; however, for both of the PS brushes studied, the onset of shear forces in near‐theta cyclohexane is strongly influenced by changes in temperature: As the temperature is increased, the onset of the frictional interactions between the brushes in cyclohexane shifts to smaller distances, approaching the distances where frictional forces are observed for brushes in the good solvent toluene. The pattern of behavior seen in the frictional response between the limits of good and theta condition is attributed to composition fluctuations, which increase near the theta condition because of the decrease in excluded volume interactions. These fluctuations may give rise to increased drag during shearing motion because of interfacial roughness or interchain coupling across the brush–brush interface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 649–655, 2006     

Effects of dip coating parameters on the morphology and transport properties of cellulose acetate–ceramic composite membranes

This work presents the fabrication of cellulose acetate (CA)–ceramic composite membranes using dip coating technique. Ceramic supports used in this work were prepared from kaolin with an average pore size of 560 nm and total porosity of 33%. The dip coating parameters studied experimentally were the concentration of CA solution (varying from 2 wt% to 8 wt%) in acetone and dipping time (varying from 30 s to 150 s). The fabricated composite membranes were characterized using scanning electron microscope, gas permeation, pure water flux and ultrafiltration (UF) experiments using bovine serum albumin (BSA). It was observed that the membrane prepared with 2 wt% and 4 wt% CA were suitable for microfiltration applications and those with 6 wt% and 8 wt% were for ultrafiltration applications. Theoretical investigation was conducted to know the macroporous and mesoporous structure of the prepared membranes using Knudsen and viscous permeability analysis of air. A resistance in series model was applied to identify different resistances responsible for the flux decline. Phenomenological models were proposed to illustrate the dependency of hydraulic resistance of membrane on the structural parameters such as average pore size, effective porosity as well as dip coating parameters like dipping time and concentration of CA. It was found that, the growth rate of CA film on the ceramic support followed exponential growth law with respect to dipping time. The total hydraulic resistance of the membrane was evaluated to be inversely proportional to the ratio of pore sizes of top layer and ceramic support. The resistance due to the CA film was found to be depended to the order of 1.73 with respect to concentration of CA. An increase in the concentration of CA was found to be more effective than dipping time to reduce the membrane pore size.     

Preparation and characterization of V-shaped PS-b-PEO brushes anchored on planar gold substrate through the trithiocarbonate junction group

Trithiocarbonate group was introduced into the polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymers as the junction of the blocks through RAFT polymerization. Mixed PS and PEO brushes with a V-shape were prepared by anchoring the trithiocarbonate group on the planar gold substrate. The morphology of the V-shaped brushes was characterized by atomic force microscopy (AFM) and the surface composition responsive to solvent treatment was detected by X-ray photoelectron spectroscopy (XPS). Different morphologies were observed for the V-shaped PS-b-PEO brushes, depending on the chain structure and solvent treatment. The highly selective solvent for PEO, ethanol, can intensify or induce microphase separation of the V-shaped brushes, leading to vertical microphase separation. When the V-shaped brushes are treated with the co-solvent, THF, miscible morphology, lateral microphase separation, and vertical microphase separation are observed as the PS block length increases. After treatment with the non-selective poor solvent, cyclohexane, the V-shaped PS(106)-b-PEO(113) brush, exhibits a laterally microphase-separated morphology, but the V-shaped PS(52)-b-PEO(113) and PS(253)-b-PEO(113) brushes are vertically microphase-separated.     

Effect of separating layer in pervaporation composite membrane for MTBE/MeOH separation

The composite membranes with polyvinylalcohol (PVA) as separating layer material and polyacrylonitrile (PAN) or cellulose acetate (CA) as supporting layer material were prepared for separating methyl tert-butyl ether (MTBE)/MeOH mixture by pervaporation (PV). The results showed that PV performance of the composite membrane with PVA membrane as separating layer was superior to that with CA membrane as separating layer, and the PV performance of PVA/CA composite membrane with CA membrane as supporting layer was better. The parameters to prepare the composite membrane remarkably affected PV performance of the composite membrane. The permeate flux of both composite membranes of PVA/PAN and PVA/CA was over 400 g/m² h, and the concentration of MeOH in the permeate reached over 99.9 wt.% for separating MTBE/MeOH mixture.     

Functional colloidal particles stabilized by layered silicate with hydrophilic face and hydrophobic polymer brushes

In this study, we describe a new strategy for producing narrowly dispersed functional colloidal particles stabilized by a nanocomposite with hydrophilic clay faces and hydrophobic polystyrene (PS) brushes on the edges. This method involves preparation of polymer brushes on the edges of clay layers and Pickering suspension polymerization of styrene in the presence of the nanocomposites. PS brushes on the edges of clay layers were prepared by atom transfer radical polymerization. X‐ray diffraction and thermogravimetric analysis results indicated that PS chains were grafted to the edges of clay platelets. Transmission electron microscope results showed that different morphologies of clay‐PS particles could be obtained in different solvents. In water, clay‐PS particles aggregated together, in which PS chains collapsed forming nanosized hydrophobic domains and hydrophilic clay faces stayed in aqueous phase. In toluene, clay‐PS particles formed face‐to‐face structure. Narrowly dispersed PS colloidal particles stabilized by clay‐PS were prepared by suspension polymerization. Because of the negatively charged clay particles on the surface, the zeta potential of the PS colloidal particles was negative. Positively charged poly(2‐vinyl pyridine) (P2VP) chains were adsorbed to the surface of PS colloidal particles in aqueous solution at a low pH value, and gold nanoparticles were prepared in P2VP brushes. Such colloidal particles may find important applications in a variety of fields including waterborne adhesives, paints, catalysis of chemical reactions, and protein separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1535–1543, 2009     

Diblock copolymer nanostructures

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) and poly(acrylic acid)-block-poly(2-cinnamoylethyl methacrylate) (PAA-b-PCEMA) were synthesized. These polymers formed micelles with PCEMA as the core in solvents poor for the PCEMA block but good for the other blocks. When the PS block was much longer than the PCEMA block, star micelles were prepared. The PCEMA cores of these micelles were then photo-crosslinked to yield PS star polymers. Nanospheres of PCEMA were obtained by photolyzing crew-cut micelles of PAA-b-PCEMA, in which the water-soluble PAA block was much shorter than the water-insoluble PCEMA block. PS-b-PCEMA self-assembled at silica and their THF/cyclopentane micellar solution interfaces to form diblock monolayers called polymer brushes, in which the insoluble PCEMA block spread like a melt on the silica surface and the chains of the soluble PS block stretched into the solution phase like bristles of a brush. By tuning the relative composition, PCEMA in bulk formed cylindrical micro-domains dispersed in the continuous PS matrix. Irradiation of the PS-b-PCEMA brushes enabled our preparation of crosslinked PS-b-PCEMA monolayers. Nanofibers were prepared by dissolving in THF the irradiated PS-b-PCEMA films with crosslinked cylindrical PCEMA micro-domains.     

Signal‐responsive gating of porous membranes by polymer brushes

Various types of signal‐responsive polymers were grafted on surfaces of porous membranes as polymer brushes. The grafted polymers shrank and extended in response to environmental signals, such as pH, ionic strength, temperature, redox reaction and photo‐irradiation. The pore size was regulated by the extent of the polymer brush. The phenomenon was observed in situ by atomic force microscopy. As a result, the substance permeation through the porous membrane was controlled in response to the signals. The permeation control was rapid in comparison with hygrogel‐type membranes, and was reversibly performed. Copyright © 2000 John Wiley & Sons, Ltd.     

A biomimetic approach to enhance selectivity of direct dyes using VGCNF in polysulphone based nanofiltration membranes

Mussel inspired chemistry has gain tremendous interest in the field of membrane science and technology. Inspired by the adhesive proteins present in mussels, approaches involving the dopamine to modify the surfaces have become the predominantly striking strategy. In this work, an effective strategy is proposed to improve the selectivity of vapour grown carbon nanofibers (VGCNF) via the bio inspired polydopamine (PDA) functionalization approach. The varying concentration of modified VGCNF (D-A-VGCNFs) were employed in polysulphone (PS) membrane. The morphological characteristics of membranes were evaluated by SEM and AFM. Data depicted the uniform distribution of nanofibers (NFs) in the media and amended microstructure of the membranes. Modified membrane having the maximum amount of D-A-VGCNFs (DM5) proved to be more hydrophilic in nature with contact angle value of 57° whereas the CA value of pure PS membrane (DM0) was 76°. The performance test confirmed that the DM5 has enhanced dye rejection ratios which are 95%, 97% and 96% with improved permeate fluxes (like 56 L/m².h, 40 L/m².h and 53 L/m².h for Direct Red 31, Direct Blue 86 and Direct Yellow 4 dyes respectively. Furthermore, DM5 showed much better anti-fouling properties after several cycles as compared to DM0. So, this work proved to be a milestone in the applications of nanofiltration (NF) membranes to remove the dyes from the textile wastewater.     

Synthesis of naringin‐based polymer brushes via seATRP

The flavonoid‐based macromolecule initiator was prepared for the first time by the transesterification reaction of naringin with 2‐bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naringin‐based copolymer brush with a polar naringenine‐7‐rhamnosidoglucoside core and an amphiphilic poly(methyl methacrylate)‐block‐poly(N‐isopropylacrylamide) (PMMA‐b‐PNIPAM) side chains was synthesized for the first time via a simplified electrochemically mediated ATRP (seATRP), utilizing only 40 ppm of catalytic complex. The rate of the polymerizations was controlled by applying optimal potential or current values during preparative electrolysis to prevent the possibility of intermolecular coupling of the growing polymer brushes. Naturally derived polymer brushes showed narrow molecular weight distributions (Đ = 1.06−1.08). ¹H NMR spectral results confirm the formation of citrus‐based polymer brushes. These new naringin‐based polymer materials may find biomedical applications as thermo‐sensitive drug delivery systems, membranes, and biologically active thin films in tissue engineering.     

Electrokinetic characterization of poly(acrylic acid) and poly(ethylene oxide) brushes in aqueous electrolyte solutions

Surfaces carrying hydrophilic polymer brushes were prepared from poly(styrene)-poly(acrylic acid) and poly(styrene)-poly(ethylene oxide) diblock copolymers, respectively, using a Langmuir-Blodgett technique and employing poly(styrene)-coated planar glass as substrates. The electrical properties of these surfaces in aqueous electrolyte were analyzed as a function of pH and KCl concentration using streaming potential/streaming current measurements. From these data, both the zeta potential and the surface conductivity could be obtained. The poly(acrylic acid) brushes are charged due to the dissociation of carboxylic acid groups and give theoretical surface potentials of -160 mV at full dissociation in 10(-)(3) M solutions. The surface conductivity of these brushes is enormous under these conditions, accounting for more than 93% of the total measured surface conductivity. However, the mobility of the ions within the brush was estimated from the density of the carboxylic acid groups and the surface conductivity data to be only about 14% of that of free ions. The poly(ethylene oxide) (PEO) brushes effectively screen the charge of the underlying substrate, giving a very low zeta potential except when the ionic strength is very low. From the data, a hydrodynamic layer thickness of the PEO brushes could be estimated which is in good agreement with independent experiments (neutron reflectivity) and theoretical estimates. The surface conductivity in this system was slightly lower than that of the polystyren substrate. This also indicates that no significant amount of preferentially, i.e., nonelectrostatically attracted, ions taken up in the brush.     

Comparative evaluation of organic contamination sources from roller and pencil type PVA brushes during the Post-CMP cleaning process

In post-CMP (chemical mechanical polishing) processing, the use of poly vinyl acetal (PVA) brushes to clean the wafer surface is one of the most effective and prominent techniques applied for the removal of CMP contaminants. Recently, organic contaminants induced in different types of PVA brushes during brush manufacturing have been drawing substantial research interest in CMP communities. In this study, investigated the root cause of these residual organic impurities in two different types of PVA brushes was investigated: roller and pencil type brushes. PVA roller brushes have a skin layer due to the brush molding process, but pencil-type PVA brushes do not have the skin layer. Extraction of organic impurities from both types of brushes was accomplished using an ultrasound-assisted technique at a sonication frequency of 40 kHz, and input power of 600 W. Further evaluation of these organic impurities using Field Emission Scanning Electron Microscopy (FE-SEM) revealed a large number of organic impurities in roller brushes and negligible impurities in pencil brushes. Time of flight secondary ion mass spectrometry (TOF-SIMS) analysis confirmed polydimethylsiloxane (PDMS) as the organic impurities extracted from PVA roller brushes, which were generated during the brush manufacturing process. The PDMS content in PVA roller brushes was further analyzed using FE-SEM micrographs via dissolving the organic impurities in tetramethylammonium hydroxide solution (TMAH). During brush fabrication, the high content of PDMS organic impurities in roller PVA brushes is essentially attributed to the presence of the additional skin layer formed by the mold releasing agent at the mold-cavity interface.     

Surface modification of PVDF porous membranes

A novel method for the surface modification of PVDF porous membranes was introduced. Styrene-(N-(4-hydroxyphenyl) maleimide) alternating copolymer SHMI-Br was blended with PVDF to fabricate SHMI-Br/PVDF membranes. The C-Br bond on the SHMI-Br/PVDF membrane was served as initial site of ATRP, and P(PEGMA) brush was grafted on the PVDF membrane. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR/FTIR) was used to prove the P(PEGMA) brushes were successfully grafted onto the SHMI-Br/PVDF membrane surface. Introduction of P(PEGMA) brushes on the PVDF membrane surface enhanced the hydrophilicity effectively. When the PEGMA degree of grafting was 16.7 wt%, the initial contact angle of PVDF membrane decreased from 98° to 42°. The anti-fouling ability of PVDF membrane was improved significantly after P(PEGMA) brush was grafted. Taking the PEGMA degree of grafting 16.7 wt% as an example, the flux of protein solution was about 151.21 L/(m² h) when the pH value of the BSA solution was 4.9. As the pH value was increased to 7.4, the flux was changed to 180.06 L/(m² h). However, the protein solution flux of membrane M3 (PEGMA: 0 wt%) was only 73.84 L/(m² h) and 113.52 L/(m² h) at pH 4.9 and 7.4, respectively.