Characterization of Surface Modification of Polyethersulfone Membrane

Surface modification of polyethersulfone (PES) membrane surfaces using UV/ozone pretreatment with subsequent grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. The surface modifications were evaluated in terms of hydrophilicity, chemical composition of the surface and static protein adsorption. In both methods, poly(vinyl alcohol) (PVA), poly(ethylene glycol) (PEG) and chitosan were chosen as hydrophilic polymers to chemically modify the commercial virgin PES membrane to render it more hydrophilic as these materials have excellent hydrophilic property. Modified PES membranes were characterized by contact angle and XPS. Contact angles of modified PES membranes were reduced by 19 to 58% of that of the virgin PES membrane. PES membrane modified with PEG shows higher wettability than other hydrophilic materials with the highest contact angle reduction shown for UV/ozone pretreated, PEG grafted PES membrane surface. In general, XPS spectra supported that the PES membranes were successfully modified by both grafting with UV/ozone pretreatment and interfacial polymerization methods. The results of the static protein adsorption experiments showed all surface modifications led to reduction in protein adsorption on PES membranes; the highest protein adsorption reduction occurred with membrane modified by UV/ozone pretreatment followed by PES grafting, which corresponded to the highest contact angle reduction. However, there seems to be no clear correlation between contact angle reduction and reduction in protein adsorption in the case that involved chitosan. Nevertheless, membranes modified with chitosan do show higher reduction in protein adsorption than membranes modified with other materials under the same conditions.     

Surface modification of poly(ether sulfone) ultrafiltration membranes by low‐temperature plasma‐induced graft polymerization

Low‐temperature helium plasma treatment followed by grafting of N‐vinyl‐2‐pyrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membranes was used to modify commercial PES membranes. Helium plasma treatment alone and post‐NVP grafting substantially increased the surface hydrophilicity compared with the unmodified virgin PES membranes. The degree of modification was adjusted by plasma treatment time and polymerization conditions (temperature, NVP concentration, and graft density). The NVP‐grafted PES surfaces were characterized by Fourier transform infrared attenuated total reflection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic‐force microscopy. Also, using a filtration protocol to simulate protein fouling and cleaning potential, the surface modified membranes were notably less susceptible to BSA fouling than the virgin PES membrane or a commercial low‐protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relative permeation flux values were quite similar for the plasma‐treated and NVP‐grafted membranes and notably higher than the virgin membrane. The main difference being the expected long‐term instability of the plasma treated as compared with the NVP‐grafted membranes. These results provide a foundation for using low‐temperature plasma‐induced grafting on PES with a variety of other molecules, including other hydrophilic monomers besides NVP, charged or hydrophobic molecules, binding domains, and biologically active molecules such as enzymes and ribozymes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1699–1711, 1999     

Chemical modification of polyethersulfone nanofiltration membranes: A review

Polysulfone (PS) and poly(ether)sulfone (PES) are often used for synthesis of nanofiltration membranes, due to their chemical, thermal, and mechanical stability. The disadvantage for applying PS/PES is their high hydrophobicity, which increases membrane fouling. To optimize the performance of PS/PES nanofiltration membranes, membranes can be modified. An increase in membrane hydrophilicity is a good method to improve membrane performance. This article reviews chemical (and physicochemical) modification methods applied to increase the hydrophilicity of PS/PES nanofiltration membranes. Modification of poly(ether)sulfone membranes in view of increasing hydrophilicity can be carried out in several ways. Physical or chemical membrane modification processes after formation of the membrane create more hydrophilic surfaces. Such modification processes are (1) graft polymerization that chemically attaches hydrophilic monomers to the membrane surface; (2) plasma treatment, that introduces different functional groups to the membrane surface; and (3) physical preadsorption of hydrophilic components to the membrane surface. Surfactant modification, self‐assembly of hydrophilic nanoparticles and membrane nitrification are also such membrane modification processes. Another approach is based on modification of polymers before membrane formation. This bulk modification implies the modification of membrane materials before membrane synthesis of the incorporation of hydrophilic additives in the membrane matrix during membrane synthesis. Sulfonation, carboxylation, and nitration are such techniques. To conclude, polymer blending also results in membranes with improved surface characteristics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyethersulfone-polyvinylpyrrolidone composite membranes:Effects of polyvinylpyrrolidone content and polydopamine coating on membrane morphology,structure and performances

Hydrophilic modification is a promising method to inhibit fouling formation on ultrafiltration membrane.In this work,different mass concentrations (1％-16％) of hydrophilic polyvinylpyrrolidone were incorpo-rated into polyethersulfone (PES) membranes fabricated by none-solvent induced phase separation.Then,polydopamine (PDA) coating on the surface of prepared membrane was carried out at pH 8.5.The mor-phology and structure,surface hydrophilicity,permeation flux,BSA rejection,antifouling and stability performances of PES and PDA/PES modified membranes were investigated in detail.The results indicated that PDA was successfully attached onto the membranes.Membrane hydrophilicity was evaluated by water contact angle measurement.The contact angles of modified membranes reduced remarkably,sug-gesting that the membrane hydrophilicities were significantly increased.The results of filtration tests,which were done by dead-end filtration of bovine serum albumin solution,showed that the properties of permeability and fouling resistance were obviously improved by PDA modification.When polyvinylpyrrolidone mass content reached 10％,flux recovery ratio of modified membrane was up to 91.23％,and its BSA rejection were over 70％.The results of stability tests showed that the modified mem-branes had good mechanical stability and chemical stability.This facile fabrication procedure and out-standing performances suggested that the modified membranes had a potential in treating fouling.     

Novel thin-film composite forward osmosis membrane using polyethylenimine and its impact on membrane performance

ABSTRACT

Polyethylenimine (PEI), a cationic, hydrophilic flexible polymer has been incorporated into the polyamide (PA) skin layer through an interfacial polymerization (IP) reaction. The modified thin-film composite (TFC) membranes display improved forward osmosis performance: enhancement in water permeability and antifouling characteristics. The incorporation of PEI into the skin layer has been evidenced by different characterization techniques; FTIR for modification of surface functionalities, zeta potential for surface charge, water contact angle for hydrophilicity of the surface, SEM and AFM for surface morphologies including surface roughness, XPS for surface attachment of heteroatoms and their relative composition. PEI was found to induce a positive zeta potential, high degree of hydrophilicity and high factional free volume into the active skin layer. The increase in the relative composition of PEI in the active skin layer was found to decrease the surface roughness and the skin layer thickness. An optimized PEI composition showed significantly enhanced water permeability, salt rejection and fouling resistance in FO and pressure-retarded osmosis (PRO) mode.     

Hydrophilic Modification of PVDF Microfiltration Membrane with Poly (Ethylene Glycol) Dimethacrylate through Surface Polymerization

The hydrophilic modification of poly (vinylidene fluoride) (PVDF) membrane with poly (ethylene glycol) dimethacrylate (PEGDMA) through grafting reaction for antifouling was reported. The influence of PEGDMA content, reaction temperature and time, on the structure, morphology, antifouling, and hydrophilicity of PVDF-g-PEGDMA membrane has been investigated. The PEGDMA monomers that were grafted on the surface of PVDF microfiltration membrane were confirmed by Attenuation total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and morphology study conducted by SEM revealed the changes before and after modification. The protein adsorption, filtration performance, water content, and dynamic contact angle were used to characterize the antifouling and hydrophilicity of the modified PVDF membranes. Compared with the pristine PVDF membrane, the bovine serum albumin (BSA) adsorption on the PVDF-g-PEGDMA membrane decreased about 80%, and the water contact angle of the membrane dropped to 0°. Besides, the experimental results revealed no significant differences between the membrane samples with respect to pore size.     

聚丙烯膜表面磷脂自组装/交联改性及其表面性能

发展了一种基于分子自组装/交联的聚丙烯微孔膜(PPMM)表面改性方法,以含不饱和长烷基链的两亲性天然卵磷脂为改性剂,首先通过分子自组装在PPMM表面形成类磷脂组装层,再采用紫外线原位聚合交联方法在PPMM表面构建稳定的类磷脂仿生修饰层,进而赋予PPMM表面优异的亲水性和生物相容性。分别采用FTIR/ATR和XPS分析确证了改性前后膜表面基团及化学成分的变化。通过水接触角测定、荧光标记蛋白质吸附和酶联免疫吸附(ELISA)实验,考察了类磷脂仿生修饰前后膜表面亲水性和抗蛋白质吸附性能,发现类磷脂仿生修饰后PPMM表面水接触角由130°下降至30°,抗蛋白质吸附性能也得到明显改善;自组装/交联改性PPMM经多次水洗后仍能保持良好的亲水性和抗蛋白质吸附性能,表明膜表面所形成的类磷脂仿生修饰层具有良好的稳定性。     

Surface modification and preparation of nanofiltration membrane from polyethersulfone/polyimide blend—Use of a new material (polyethyleneglycol‐triazine)

Blends of polyethersulfone/polyimide (PES/PI) were prepared by dissolving in dimethylformamide/dioxane (DMF/DO) to manufacture nanofiltration membranes by using polyvinylpirrolidone (PVP) as a pore former. The membrane modification was carried out by adding ethylenediamine (EDA) to open the imide group ring of PI and by using polyethyleneglycol (PEG)‐triazine, as a new modifier material, that was produced in the laboratory. This modification involves the formation of a covalence ‐C‐N‐ bound between PEG‐triazine and amine groups (according to addition‐elimination reactions) at different temperatures. After functionalizing the membranes, diethanolamine (DA) was utilized as a hydrophilic modifier to change the membranes properties. SEM, AFM, FTIR‐ATR, EDS (X‐ray analysis) and contact angle tests were carried out to characterize modified membranes. The hydrophilicity of PES/PI membranes was improved by modification. An increase in pure water flux (up to 195 kg/m² h) and a decline in NaCl rejection (from 25 to 16%) are largely influenced by diminishing the PES/PI ratio in L₁‐L₅ membranes (Category 1). In L₆, L₇, and L₈ membranes (Category 2), by introducing PEG‐triazine into the membrane recipe, salt rejection increased from 75 to 80%. Addition of DA further enhances the salt rejection up to 93%. Fluxes were approximately similar for membranes in Category 2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Improvement of performance of polyamide reverse osmosis membranes using dielectric barrier discharge plasma treatment as a novel surface modification method

In this research, surface modification of aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes was carried out using dielectric barrier discharge (DBD) plasma treatment to improve the performance and fouling resistance of prepared RO membranes. First, polyamide TFC RO membranes were synthesized via interfacial polymerization of m‐phenylenediamine and trimesoyl chloride monomers over microporous polysulfone support membrane. Next, the DBD plasma treatment with 15 s, 30 s, 60 s, and 90 s duration was used for surface modification. The surface properties of RO membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), SEM, AFM, and contact angle measurements. The ATR‐FTIR results indicated that DBD plasma treatment caused hydrogen bonding on the surface of RO membranes. Also, the contact angle measurement showed that the hydrophilicity of the membranes was increased due to DBD plasma treatment. The changes in the membranes surface morphology indicated that the surface roughness of the membranes was increased after surface modification. In addition, it was found that the DBD plasma treatment increased the water permeation flux significantly and enhanced sodium chloride (NaCl) salt rejection slightly. Moreover, the filtration of bovine serum albumin revealed that the antifouling properties of the modified membranes had been improved. POLYM. ENG. SCI., 59:E468–E475, 2019. © 2018 Society of Plastics Engineers     

Surface Modification of Polyamide 6 Immobilized with Collagen: Characterization and Cytocompatibility

Polyamide 6 (PA6) membranes were exposed to Ar plasma to produce peroxides on their surfaces, followed by grafting polymerization of methacrylic acid (MAA) introducing -COOH on surfaces. PA6 membranes immobilized with collagen I were obtained by coupling collagen to the MAA graft chains. The physicochemical properties were characterized by contact angle measurement, ATR-FTIR, XPS, and AFM. The results showed that the hydrophilicity of the surface improved after surface modification. The surface topography of the original and the modified PA 6 membranes showed an increase in roughness. Moreover, collagen immobilized onto PA 6 membranes showed enhanced growth in ROB culture tests.     

Fabrication and performance of a polyethersulfone nanofiltration membrane impregnated with a mesoporous silica–poly(1‐VInylpyrrolidone) nanocomposite

Fouling is a serious problem in the membrane formation process. Adding hydrophilic polymers or inorganic particles into the membrane is an effective way for improving the antifouling performance. However, most of the water‐soluble polymeric additives leach out during the phase inversion process, and the inorganic particles are prone to agglomerate in the membrane, which decreases the antifouling property of the membrane. In this study, poly(1‐vinylpyrrolidone) (PVP) was grafted onto mesoporous silica (MS) nanoparticle surface, and polyethersulfone (PES)/MS–PVP nanocomposite membranes were fabricated by the phase inversion method. MS–PVP dispersed well on the membrane surface, and the hydrophilicity of the PES/MS–PVP membranes increased with increasing content of MS–PVP. PES/MS–PVP membranes exhibited higher water flux than that of the bare PES membrane without any loss in NaCl rejection, and water flux of 25 L/m²h could be achieved by the membrane containing 3% of MS–PVP, which is almost 1.5 times as high as that of bare PES membrane at 0.6 MPa. The protein adsorption onto the membrane surface declined significantly from 49 to 25 mg/cm² when the MS–PVP loading increased from 0% to 3%. POLYM. COMPOS., 38:908–917, 2017. © 2015 Society of Plastics Engineers     

Facile surface modification of PVDF microfiltration membrane by strong physical adsorption of amphiphilic copolymers

To endow the surface of poly(vinylidene fluoride) (PVDF) microfiltration (MF) membranes with hydrophilicity and antifouling property, physical adsorption of amphiphilic random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and poly(methyl methacrylate) (PMMA) (P(PEGMA‐r‐MMA)) onto the PVDF membrane was performed. Scanning electron microscopy (SEM) images showed that the adsorption process had no influence on the membrane structure. Operation parameters including adsorption time, polymer concentration, and composition were explored in detail through X‐ray photoelectron spectroscopy (XPS), static water contact angle (CA), and water flux measurements. The results demonstrated that P(PEGMA‐r‐MMA) copolymers adsorbed successfully onto the membrane surface, and hydrophilicity of the PVDF MF membrane was greatly enhanced. The antifouling performance and adsorption stability were also characterized, respectively. It was notable that PVDF MF membranes modified by facile physical adsorption of P(PEGMA₅₈‐r‐MMA₃₃) even showed higher water flux and better antifouling property than the commercial hydrophilic PVDF MF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3112–3121, 2013     

聚丙烯微孔膜荷负电表面的构建与阻抗蛋白质吸附性能

报道一种有效构建聚丙烯微孔膜(PPMM)荷负电表面的新方法.组合大气压介质阻挡放电等离子体预处理和界面交联技术,制得表面荷正电的PPMM;通过动态静电自组装技术将阴离子聚电解质固定到膜表面,从而获得荷负电的PPMM,ATR-FTIR,XPS和FESEM分析确证了修饰过程中膜表面化学组成与形貌的变化.静态水接触角和纯水通...     

Surface modification of polysulfone membranes by low‐temperature plasma–graft poly(ethylene glycol) onto polysulfone membranes

A novel and general method of modifying hydrophobic polysulfone (PSF) to produce highly hydrophilic surfaces was developed. This method is the low‐temperature plasma technique. Graft polymer‐modified surfaces were characterized with the help of Fourier transform infrared attenuated total reflection (FTIR–ATR) and X‐ray photoelectron spectroscopy (XPS). Study results demonstrated that poly(ethylene glycol) (PEG) could be grafted onto the PSF membrane surface by low‐temperature plasma. The hydrophilic character of the modified surfaces was increased in comparison with that of the parent membrane. The contact angle for a modified PSF membrane was reduced apparently. We analyzed the effectiveness of this approach as a function of plasma operating variables including plasma treatment power and treatment time. Hence, plasma‐induced graft polymer modification of membranes can be used to adjust membrane performance by simultaneously controlling the surface hydrophilicity and hemocompatibility. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 979–985, 2000     

BWRO复合膜和SWRO复合膜的本质对比(英文)

采用均苯三甲酰氯和间苯二胺通过界面合法分别得到苦咸水反渗透复合膜和海水反渗透复合膜。两者在低盐浓度时,对氯化钠的脱除率相近;在高盐浓度时,苦咸水反渗透复合膜对氯化钠的脱除率明显低于海水反渗透复合膜。用扫描电镜、原子力显微镜分析两者表面形态发现海水反渗透复合膜表面粗糙度更小。X射线光电子能谱分析结果表明,海水反渗透复合膜表面的羧酸根含量更多。     

Improving the hydrophilicity of polyethersulfone membrane by the combination of grafting technology and reverse thermally induced phase separation method

In this work, surface grafting modification technology was combined with reverse thermally induced phase separation (RTIPS) method in order to improve the structure and permanent hydrophilicity of polyethersulfone (PES) membranes. Acrylic solution with different concentrations was grafted on the surface of PES membranes while grafting temperature and grafting time were also varied. The modified PES membranes were characterized in all aspects. Attenuated total reflectance Fourier transform-infrared confirmed successful modification of the PES membrane by grafting acrylic acid. Scanning electron microscopy revealed that homogeneous porous top surface as well as spongy-like cross-section structure appeared in the membrane by RTIPS procedure. Moreover, porosity was affected by changes of acrylic acid concentration, grafting temperature, and grafting time. Atomic force microscopy showed that grafting acrylic acid gave a reduction in roughness of PES membrane. Combined with the decreased values of contact angle, the hydrophilicity and antifouling performance of the PES membrane were improved. The pure water flux and BSA rejection rate of the grafted PES membranes were remarkably improved for pure PES membrane and attained a maximum, which was 1,646.24 L/(m²h) and 94.5%, respectively. The long-term test demonstrated that grafting membranes exhibited outstanding elevated water flux recovery ratio (>85%).     

Investigating protein crossflow ultrafiltration mechanisms using interfacial phenomena

Protein separation mechanisms by a crossflow ultrafiltration membrane process are investigated using interfacial phenomena analysis of protein–protein and protein–membrane interactions. Varying operating conditions are used and membrane morphological parameters like hydrophilicity and hydrophobicity obtained from contact angle measurement. A single protein solution of bovine serum albumin (BSA) or ovalbumin (OV) or lysozyme (LY) is used in each filtration study case under various operating conditions, such as pH, ionic strength, and different polyethersulfone (PES) membranes with varying surface hydrophobicity and hydrophilicity. Under these conditions analyse of protein–membrane interfacial phenomena and protein separation filtration mechanisms are undertaken. Results indicate that electrostatic forces play an important role in protein deposition on the membrane surface and the rate of protein transmission across the membrane. Findings show that, at the proteins isoelectric point (pI), a hydrophobic membrane causes severe protein adsorption to the membrane surface, allowing a very small percentage of protein to be transported to the permeate side.     

Adsorption of blood proteins on glow‐discharge‐modified polyurethane membranes

Polyurethanes are a class of polymers that have a wide range of applications in the medical field although their blood compatibility still needs improvement. In order to obtain medical purity, this study prepared membrane‐form polyurethanes from toluene 2,4‐diisocyanate (TDI) and poly(propylene ethylene glycol) without the addition of any ingredients such as solvents, catalysts, or chain extenders. The aim was to increase surface hydrophilicity and improve blood compatibility. Therefore, the prepared membranes were modified by treatment with oxygen or argon plasmas. Characterizations of the samples were achieved by contact‐angle and water‐uptake studies as well as from atomic force microscope (AFM) pictures. It was found that oxygen‐modified samples were more hydrophilic than argon‐modified samples. The AFM images showed that surface roughness increased with plasma treatment. The protein adsorption experiments carried out with single protein solutions demonstrated that the adsorption of bovine serum albumin and fibrinogen decreased drastically by increasing the applied power and exposure time of the glow discharge. A similar decrease in the adsorption of protein was also observed for human blood proteins. The alterations of the conformational structures of the adsorbed proteins were examined by fluorescence spectrophotometry. Similar spectra with the same maximum wavelength were observed for native and desorbed proteins. These results showed that no denaturation of the proteins occurred upon adsorption on the surfaces of the prepared membranes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1322–1332, 2001     

Nanostructured β-Cyclodextrin-Hyperbranched Polyethyleneimine (β-CD-HPEI) Embedded in Polysulfone Membrane for the Removal of Humic Acid from Water

The synthesis of a new β-cyclodextrin-hyperbranched polyethyleneimine (β-CD-HPEI)/polysulfone (PSf) membranes via interfacial polymerization of trimesoyl chloride and β-CD-HPEI is described in this paper. The membranes were characterized by atomic force microscopy (AFM), high resolution scanning electron microscopy (HR-SEM) and contact-angle measurements. Water permeability and rejection data were obtained using a cross-flow filtration system at 0.69 MPa. The membranes were hydrophilic (25° to 63°), showed high humic acid rejection (>80%), and maintained a constant flux throughout the filtration. The modified membranes were rougher than the pristine PSf membranes but they exhibited better antifouling properties due to the hydrophilic surface which acted as a barrier against humic acid deposition. The modification of PSf with β-CD-HPEI resulted in enhanced hydrophilicity and water permeability while still maintaining high humic acid rejection. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

Hydrophilic modification of P(VDF-co-CTFE) porous membranes

This paper describes fabrication of a poly(vinylidene difluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) porous membrane via non-solvent induced phase inversion and subsequent hydrophilic modification using high efficient surface initiated atom transfer radical polymerization (ATRP). The effect of viscosities of casting solutions on microstructures of the P(VDF-co-CTFE) membrane was investigated. The surface chemistry, thermal stability, morphological structure, and hydrophilicity of the modified membranes were evaluated by Fourier Transform Infrared Attenuated Total Reflection (FTIR-ATR), Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM), and contact angle measurements, respectively. The degree of grafting and the degree of swelling were measured to analyze the effect of polymerization time on the wettability. The mechanical strength of the membranes after modification was also investigated. The permeability and fouling resistance were evaluated according to pure water flux and protein solution filtration measurements. The results demonstrate that the hydrophobic P(VDF-co-CTFE) membrane can be feasibly modified by immobilization of hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) brushes via surface initiated ATRP.