Acrylonitrile-based copolymer membranes containing reactive groups: effects of surface-immobilized poly(ethylene glycol)s on anti-fouling properties and blood compatibility

The anti-fouling properties and blood compatibility of poly(acrylonitrile-co-maleic acid) (PANCMA) membranes were improved by the immobilization of poly(ethylene glycol)s (PEG) on membrane surface. It was found that the reactive carboxyl groups on PANCMA membrane surface could be conveniently conversed into anhydride groups and then esterified with PEG. Chemical and morphological changes as well as biocompatibility on membrane surface were analyzed by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, water contact angle, protein adsorption, and platelet adhesion. Results revealed that, with the immobilization of PEG, the hydrophilicity and blood compatibility of the acrylonitrile-based copolymer membranes were improved obviously. The molecular weight of PEG had an obvious influence on the properties of the PEG-immobilized membranes. Permeation behaviors for the studied membranes were investigated by water and bovine serum albumin (BSA) filtration experiments. Compared with the original PANCMA membrane, the membrane immobilized with PEG 400 (M_w=400 g/mol) showed a three-fold increase in a BSA solution flux, a 40.4% reduction in total fouling, and a 57.9% decrease in BSA adsorption.     

类肝素聚乳酸微孔膜的血液相容性

通过在生物基聚乳酸(PLA)膜表面进行类肝素化修饰,得到了具有良好血液相容性的生物基聚合物膜。首先通过自由基聚合合成了聚(乙烯基吡咯烷酮–乙烯基三乙氧基硅烷)[P(VP–VTES)]预聚物,进一步通过其界面交联,将高含量的聚乙烯基吡咯烷酮固化到PLA膜表面,提高膜表面的亲水性和抗污性能。其次通过自由基聚合合成类肝素预聚物苯乙烯磺酸钠–乙烯基三乙氧基硅烷–丙烯酸三元共聚物[P(SSNa–VTES–AAH)],并利用预聚物中VTES链段的水解缩合反应将类肝素共聚物固定在PLA膜表面,从而提高膜的血液相容性。通过红外光谱确定了PLA膜表面亲水层P(VP–VTES)和P(SSNa–VTES–AAH)的分子结构。通过接触角测试表明类肝素分子修饰的PLA膜具有良好的亲水性,并可以抑制膜表面血小板的吸附和聚集。同时,凝血测试结果表明类肝素分子修饰的PLA膜表面具有良好的血液相容性。     

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...     

紫外光诱导接枝共聚制备离子识别性聚丙烯微孔膜

以聚丙烯微孔膜(MPPM)为支撑,采用物理包埋和紫外光诱导共价键合组合法固定光引发剂,再通过紫外光诱导接枝共聚制得离子印迹复合膜。考察了制备条件对离子印迹聚合物接枝量的影响,并用扫描电子显微镜(SEM)-能量色散X射线光谱仪(EDX)对复合膜表面及截面离子印迹聚合物的分布进行了分析。静态水接触角和纯水通量实验结果显示,离子印迹复合膜具有良好的表面亲水性和渗透性,纯水通量可达(2 077±77)L/(m2.h)。再生性研究表明,离子印迹复合膜具有良好的再生性能,10次吸附-脱吸附循环后,膜对Pb(Ⅱ)的吸附量和选择性系数分别能维持在90%和80%以上。     

Biomimetic surface modification on polyacrylonitrile-based asymmetric membranes via direct formation of phospholipid moieties

To improve the antifouling property and biocompatibility for polyacrylonitrile-based asymmetric membranes, phospholipid moieties were directly anchored on the poly(acrylonitrile-co-2-hydroxyethyl methacrylate) (PANCHEMA) membrane surface through the reaction of hydroxyl groups and 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) followed by the ring-opening of COP with trimethylamine. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurement were employed to confirm the conducted surface modification. Water and protein solution filtration tests plus cell adhesion measurement were used to evaluate the antifouling property and the biocompatibility of the membranes. It was found that the content of the phospholipid moieties on the membrane surface, which can be mainly modulated by the content of reactive hydroxyl groups in PANCHEMA, has a great influence on the performances of the studied membranes. With the increase in the phospholipid moieties content at the modified membrane surface, the hydrophilicity and biocompatibility on the basis of water contact angle and macrophage adhesion can be improved significantly. Furthermore, the modified membranes show higher water and protein solution fluxes, and better flux recovery after cleaning than those of the original PANCHEMA membranes. All these results reveal that the antifouling property and biocompatibility of PANCHEMA membrane could be enhanced obviously by the introduction of phospholipid moieties on the membrane surface.     

The polydopamine-assisted heparin anchor enhances the hydrophilicity,hemocompatibility, and biocompatibility of polyurethane

Surface heparinization is an effective solution to resolve low endothelialization, poor anticoagulation, and hemocompatibility of polyurethane (PU) used as materials of small-diameter vascular grafts. Here, the effects of polydopamine (PDA) and poly (acrylic acid) (PAA) as crosslinking agents on the surface heparinization were explored. The PU membranes grafted with heparin (Hep) via dopamine (PU/PDA-Hep) showed better hydrophilicity and stability, compared to heparinized PU membranes via acrylic acid (PU/PAA-Hep). The results of X-ray photoelectron spectroscopy demonstrated that heparin was successfully grafted onto the PU surface and the grafting efficiency was high when PDA as a cross-linking agent. The grafted heparin aggregated and formed nanoparticles, and increased the surface roughness of PU membranes. The heparinized membranes demonstrated good anti-adhesion of bovine serum albumin and fibrin protein. In addition, no activated platelets or educts on heparinized PU were found by platelet adhesion tests, implying that heparin-immobilized surfaces had good hemocompatibility. Moreover, the in vitro cytocompatibility assessment showed that the PU/PDA-Hep significantly improved the proliferation of L929 cells and was superior to PU/AA-Hep. These results demonstrated that PDA-assisted surface heparinization was an effective method to improve the anticoagulant and biocompatibility of PU small-diameter vascular materials and could be extended to other implantable materials.     

Preparation of blend polyethersulfone/cellulose acetate/polyethylene glycol asymmetric membranes for oil–water separation

Blend PES/CA hydrophilic membranes were prepared via a phase-inversion process for oil–water separation. PEG-400 was introduced into the polymer solution in order to enhance phase-inversion and produce high permeability membranes. A gas permeation test was conducted to estimate mean pore size and surface porosity of the membranes. The membranes were characterized in terms of morphology, overall porosity, water contact angle, water flux and hydraulic resistance. A cross-flow separation system was used to evaluate oil–water separation performance of the membranes. From FESEM examination, the prepared PES/CA membrane presented thinner outer skin layer, higher surface porosity with larger pore sizes. The outer surface water contact angle of the prepared membrane significantly decreased when CA was added into the polymer solution. The higher water flux of the PES/CA membrane was related to the higher hydrophilicity and larger pore sizes of the membrane. From oil–water separation test, the PES/CA membrane showed stable oil rejection of 88 % and water flux of 27 l/m² s after 150 min of the operation. In conclusion, by controlling fabrication parameters a developed membrane structure with high hydrophilicity, high surface porosity and low resistance can be achieved to improve oil rejection and water productivity.     

Plasma‐induced solid‐state polymerization modified poly(tetrafluoroethylene) membrane for pervaporation separation of aqueous alcohol mixtures

Acrylamide (AAm) solid state polymerization was induced using argon plasma to improve the pervaporation performance of poly(tetrafluoroethylene) (PTFE) membranes (PTFE‐g‐PAAm) in aqueous alcohol mixtures. The surface morphology, chemical composition, and hydrophilicity changes in the PTFE and PTFE‐g‐PAAm membranes were investigated using ATR‐FTIR, SEM, AFM, X‐ray photoelectron spectroscopy, and water contact angle measurements. The surface hydrophilicity rapidly increased with increasing Ar exposure time, but decreased after longer Ar exposure time because of the degradation in the PTFE‐g‐PAAm membrane grafted layer. Compared with the hydrophilicity of the pristine PTFE membrane (water contact angle = 120°), the argon plasma induced acrylamide (AAm) solid‐state polymerization onto the PTFE surface (water contact angle = 43.3°) and effectively improved the hydrophilicity of the PTFE membrane. This value increases slowly with increasing aging time and then reaches a plateau value of about 50° after 10 days of storage under air. The pervaporation separation performances of the PTFE‐g‐PAAm membranes were higher than that of the pristine PTFE membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:909–919, 2006     

Surface immobilization of polymer brushes onto porous poly(vinylidene fluoride) membrane by electron beam to improve the hydrophilicity and fouling resistance

Poly(vinylidene fluoride) (PVDF) membrane was pre-irradiated by electron beam, and then poly(ethylene glycol) methyl ether methacrylate (PEGMA) was grafted onto the membrane surface in the aqueous solution. The degree of grafting was significantly influenced by the pH value of the reaction solution. The surface chemical changes were characterized by the Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Combining with the analysis of the nuclear magnetic resonance proton and carbon spectra (¹H NMR and ¹³C NMR), PEGMA was mainly grafted onto the membrane surface. Morphological changes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The porosity and bulk mean pore size changes were determined by a mercury porosimeter. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle, dynamic water contact angle and the dynamic adsorption process. Furthermore, relative high permeation fluxes of pure water and protein solution were obtained. All these results demonstrate that both hydrophilicity and fouling resistance of the PVDF membrane can be improved by the immobilization of hydrophilic comb-like polymer brushes on the membrane surface.     

Hydrophilic modification of polyacrylonitrile membranes by oxyfluorination

The surface of polyacrylonitrile (PAN) membranes was modified by oxyfluorination with various conditions to improve its wettability. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. The properties and functional groups on the surface of PAN membranes were investigated by contact angle, SEM, ATR-IR and XPS. And permeability of PAN membranes was compared by permeating pure water flux through membrane surface under 100, 150 and 200 kPa pressure. Oxyfluorination introduced oxygen contained functional groups such as the carboxylic acid groups that help increment of wettability on the surface of PAN membrane. Water flux of oxyfluorinated PAN UF membrane increased 20% at pure water permeation pressure 200 kPa compared to that of untreated PAN UF membrane.     

Microwave-assisted functionalization of polyurethane surface for improving blood compatibility

In order to improve the hemocompatibility of polyurethane (PU), we report a rapid and efficient two-step approach to graft poly(ethylene glycol) (PEG) onto PU surface by a microwave-assisted method, involving diphenylmethane diisocyanate (MDI) – functionalization and subsequent PEG coupling. Compared with conventional heating, the effects of solvent, time and MDI concentrations on the microwave-assisted MDI-functionalization, and the effect of time on the microwave-assisted PEG coupling were studied. PEGs with different molecular weights were successfully grafted onto PU surface under the optimum microwave-assisted conditions within only 20 min, and characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and chemical titration. The hydrophilicity and in vitro blood compatibility of the surfaces were evaluated by water contact angle measurements, blood coagulation time (whole blood clotting time and prothrombin time) and platelet adhesion tests, respectively. All the PU-PEG surfaces had improved surface wettability and hemocompatibility. The results suggested that microwave-assisted functionalization may be a promising method for rapidly and effectively decorating polyurethane surfaces.     

Surface Modification of Commercial Aromatic Polyamide Reverse Osmosis Membranes by Crosslinking Treatments

Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance. The crosslinking agents including 1,6-hexanediol diglycidyl ether, adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments. Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments. It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide II groups, which is confirmed by surface charge measurements. Based on contact angle measurements, crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface. With increasing amount of crosslinking agent molecules connected to membrane surface, the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity. The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane. Since the active sites (N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments, the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.     

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     

The Grafting of Chitosan Oligomer to Polysulfone Membrane via Ozone-Treatment and its Effect on Anti-Bacterial Activity

Polysulfone (PSF) membranes were treated with ozone to introduce peroxides, and then grafted with acrylic acid, followed by the coupling of chitosan oligomer. Water soluble chitooligosaccharides (COS) was prepared to induce antimicrobial activities. The surface densities of the carboxylic and amino groups on the PSF membranes were characterized by dyeing determination and the hydrophilicity was evaluated by the contact angle. The antibacterial activities on the PSF membrane were evaluated based on a viable cell counting method. The results show that COS can be covalently bound to the surface of PAA-grafted PSF membrane via the activation of 1-ethyl-3-dimethylaminopropyl carbodiimide (EDC). The water contact angle was lower for the PAA-grafted and COS-coupled PSF, indicating that they were more hydrophilic than the untreated PSF membrane. Only COS-coupled PSF membrane showed a strong biocidal effect for bacteria, including E. coli and S. aureus.     

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.     

Immobilization of tannery industrial sludge in ceramic membrane preparation and hydrophobic surface modification for application in atrazine remediation from water

Chromium laden waste produced from tannery industry was immobilized in ceramic matrix for fabrication of the tubular single channel microfiltration membranes by extrusion. The presence of chromia resulted in substitutional solid solution formation with alumina and catalyzed mullite phase growth, hence increasing the mechanical and chemical stability of the membranes. The structural, morphological and water permeation characteristics of the membranes were studied to analyze their formation mechanism and effect of different parameters, viz. the sintering temperature, amount of waste added, presence of organics and extent of chromium immobilization. The surface of the macroporous membrane was hydrophobically modified, by polydimethylsiloxane (PDMS), producing contact angle of 141°. The process efficiency of the hydrophobic membrane was assessed in terms of the removal of atrazine, a contaminant of emerging concern, following the principle of hydrophobic interaction. Effect of different operating parameters affecting atrazine removal, viz. transmembrane pressure, cross flow velocity and filtration time was studied in cross flow filtration mode. High atrazine removal of >95% was obtained along with the maintenance of high flux during the filtration operation. The prepared cost-effective microfiltration membranes can thus be further modified for efficient water treatment applications.     

Characterisation of the solvent stability of polymeric nanofiltration membranes by measurement of contact angles and swelling

This communication describes contact angle and swelling measurements for different (commercially available) polymeric nanofiltration membranes. Contact angle measurements and surface tension calculations on new and solvent-treated membranes confirm that organic solvents change the hydrophilicity of polymeric membrane surfaces, leading to different water permeability before and after solvent treatment. Swelling measurements confirm the assumption that a reorganisation of the membrane material takes place, leading to differences in porosity and changes in rejection.     

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.     

紫外键联马来酸酐表面改性聚丙烯腈超滤膜

采用紫外光法将马来酸酐（MAH）单体键联到聚丙烯腈（PAN）超滤膜表面,考察了紫外光强度、辐射时间、光敏剂浓度以及单体浓度对MAH反应率的影响。采用衰减全反射-傅里叶红外光谱（ATR /FT-IR）、扫描电镜（SEM）和水接触角（CA）对改性膜和原膜进行表征,结果表明单体MAH已成功键联到PAN膜表面,膜表面的亲水性得到提高。蛋白质静态污染以及超滤实验表明马来酸酐键联改性对PAN膜水通量影响不大,但抗污染性能得到明显提高,且由于MAH含有酸酐基团,使PAN膜的可反应性大大提高,使PAN膜易于进一步改性。     

Preparation and characterization of modified ultrafiltration nylon 6 membrane modified by poly (acrylamide-co-maleic anhydride)

In attempt to prepare modified ultrafiltration (UF) Nylon 6 membrane and improve its hydrophilicity and anti-fouling performance, poly (acrylamide-co-maleic anhydride)(AM-MA) was utilized as hydrophilic copolymer additive in the dope solution. The UF Nylon 6/AM-MA membranes were synthesized through blending Nylon 6 with poly(AM-MA) using a phase inversion process. Characterization of the prepared membranes for morphological studies and thermal behavior was carried out by SEM and DSC instruments respectively. The SEM photos demonstrated that by increasing the copolymer density in the dope solution, the morphology was changed from spongy to bi-continuous, composed of small interlocked and stick-like crystallites. FTIR/ATR and water contact angle data also confirmed the existence of AM-MA copolymer on the blend membranes surface. Furthermore, the effect of different molecular weights and concentration of hydrophilic copolymer on filtration performance and antifouling properties were experimentally studied. The results exhibited that the blend UF membranes possessed better water flux permeability than pure Nylon 6 membrane due to the increased surface hydrophilicity and porosity. Fouling resistance experiments revealed that the surface anti-fouling ability of the blend membranes was improved via the addition of AM-MA copolymer with lower MW (co1) to the cast solution, while this parameter was weakened in higher MW of copolymer (co2).