Developing homogeneous ion exchange membranes derived from sulfonated polyethersulfone/N-phthaloyl-chitosan for improved hydrophilic and controllable porosity

Ion exchange membranes (IEMs) composed of sulfonated poly (ether sulfone) (SPES) and N-phthaloyl chitosan (NPHCs) were synthesized. NPHCs was employed in membrane fabrication to improve the porosity and hydrophilicity of membranes. The effect of blend ratio of sulfonation (DS) and NPHCs content on physico-chemical characteristics of home-made membranes was investigated. The morphology of prepared membranes was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and scanning electron microscopy (SEM). SEM images revealed the formation of a more porous membrane structure and smoother surface. The electrochemical and physical properties of CEMs were characterized comprising water content, contact angle, ion exchange capacity (IEC) and thermal stability. Membrane water content, surface hydrophilicity and IEC were enhanced with increase of DS and NPHCs blend ratios in casting solution. Furthermore, the diffusion coefficient was also improved slightly with increase of DS and NPHCs blend ratios in prepared membranes. Membrane potential, permselectivity, transport number and areal membrane resistance all showed decreasing trends by the increase in NPHCs blend ratio in casting solution. These results indicated that the prepared membrane has good prospective and great potential for desalination in electrodialysis applications.     

聚偏氟乙烯/聚醚酰亚胺共混溶液的流变性能研究

采用二甲基乙酰胺(DMAc)为溶剂配制不同共混比的聚偏氟乙烯(PVDF)和聚醚酰亚胺(PEI)共混溶液,用锥板式黏度计研究了PVDF/PEI共混溶液的流变性能。结果表明:PVDF/PEI共混溶液表观黏度与剪切速率呈线性相关;当PVDF/PEI质量比为9/1时,共混溶液的零切黏度明显降低,非牛顿指数和黏流活化能出现极值;随着PEI含量的增加,黏流活化能急剧增大。     

Protein separation by cellulose acetate/sulfonated poly(ether imide) blend ultrafiltration membranes

A process for purifying aqueous solutions containing macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin, and trypsin has been investigated. Protein removal from food and biorelated industrial waste streams are gaining increased visibility due to environmental concern and saving precious materials. Ultrafiltration (UF) processes are largely being applied for protein separation from aqueous streams. In this work, an attempt has been made to separate the valuable proteins using cellulose acetate (CA)/sulfonated poly(ether imide) (SPEI) blend UF membranes prepared in the absence and presence of the additive, polyethyleneglycol (PEG600) in various compositions. The blend membranes were subjected to the determination of pore statistics and molecular weight cut‐off (MWCO). Porosity and pore size of the membranes increased with increasing concentrations of SPEI and PEG600 in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to greater than 69 kDa, depending on the various polymer blend compositions. Surface morphology of the blend membranes were analyzed using scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of proteins. On increasing the concentration of SPEI and PEG600, the rejection of proteins is decreasing, whereas the permeate flux has an increasing trend. The effect of hydrophilicity of SPEI on fouling of protein for CA/SPEI blend membranes was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and performance evaluation of poly (ether-imide) incorporated polysulfone hemodialysis membranes

Biocompatible Polysulfone (PSf) hemodialysis membranes were prepared by phase inversion technique using poly (ether-imide) (PEI) as the modification agent and Polyethylene glycol (PEG-200) as the pore former. The effect of PSf/PEI blend ratio on the morphology, hydrophilicity, water content, porosity, glass transition temperature, mechanical strength, biocompatibility and permeation rate of the prepared membranes were studied and were found to be improved significantly by the incorporation of PEI in the dope solution. The scanning electron microscopy (SEM) studies revealed that, incorporation of PEI resulted in the formation of spongy sub-layer and increased the connectivity of pores between sub-layer and bottom layer. The water content and permeation rate of the membranes of PSf/PEI blend membranes were increased considerably indicating the enhancement of hydrophilicity and it was supported by lower contact angle values of the blend membranes. The existence of single well defined Tg over entire composition established the compatibility between the components in blend membranes. The biocompatibility of membranes was investigated through protein adsorption, platelet adhesion and thrombus formation on the membrane surface. Anticoagulant activity of PSf/PEI blend membranes was evaluated by measuring the activated partial thrombin time (APTT), prothrombin time (PT), thrombin time (TT) and fibrinogen time (FT). The results revealed that antithrombogenicity of PSf/PEI blend membranes was increased significantly. The efficiency of these membranes in removal of urea, creatinine and vitamin B₁₂ were studied and found to be improved for blend membranes. Thus, it is worth mentioning to note that, the biocompatible PSf/PEI blend membranes prepared in this study would offer immense potential in hemodialysis.     

A functional PES membrane for hemodialysis-Preparation,characterization and biocompatibility

In this work, we evaluate the properties of solution casted polysulfone (PSf)/sulfonated polyethersulfone (SPES) blend membranes prepared by non-solvent induced phase inversion technique. The morphologies of these blend membranes, observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging, indicated a smoother skin layer and an increased number of highly interconnected pores in the sub layer. The efficacy of the prepared membranes was evaluated in terms of porosity, ultrafiltration rate (UFR), molecular weight cut-off (MWCO) and mean pore size. The hydrophilicity of these membranes was in consonance with contact angle values. It was observed that the selectivity and the UFR of the blend membranes were higher when compared to pristine membranes. Furthermore, these blend membranes demonstrated an increase in bio-compatibility—prolonged blood clotting time, suppressed platelet adhesion, reduced protein adsorption and lower complement activation. These membranes were also investigated for uremic solute removal. Diffusive permeability of middle molecular weight cytochrome-c revealed an increase from 8 × 10?4 cm·s?1 to 18 × 10?4 cm·s?1 and illustrates the possibility that these sulfonated PES/PSf blend membranes can be used to prepare membrane modules for hemodialysis applications.     

Proton conducting blend membranes: physical,morphological and electronic properties

Blend membranes of sulfonated poly(ether ether ketone) (SPEEK) and sulfonated polyetherimide (SPEI) have been prepared and investigated as a potential polymer electrolyte membrane (PEM) for direct methanol fuel cell (DMFC). Polymers were dissolved in N-methyl-2-pyrrolidone (NMP) in different mixing ratios and membranes were casted using a semi-automatic casting machine on a pre-cleaned glass plate. The influence of SPEI percentage on ion exchange capacity (IEC), water uptake, methanol permeability and proton exchange capacity have been investigated. Blend membranes showed slightly better IEC, water uptake and methanol crossover properties as compare to pure SPEEK; but proton conductivity was slightly lower than that of pure SPEEK membrane. Membrane morphology was investigated by FESEM, TGA and AFM. Overall, a homogeneous surface was observed for most of the blend membranes, with minor phase separation at higher SPEI contents samples. AFM image of the membrane surface shows nanoscale surface roughness.     

Formation of integrally skinned asymmetric polyetherimide nanofiltration membranes by phase inversion process

Integrally skinned asymmetric polyetherimide (PEI) membranes were prepared by the phase inversion process from casting solution containing dimethylformamide (DMF) as a solvent and 1,4‐dioxane as a cosolvent. Deionized water was used as a coagulation medium in preparing asymmetric membranes. The effect of 1,4‐dioxane was investigated by measuring casting solution properties, permeation properties, and membrane structures. Various effects of polymer concentration, evaporation time, and coagulation bath temperature were also studied. Low miscibility of 1,4‐dioxane with coagulant (water) resulted in reducing membrane pore size. The molecular weight cutoff values of asymmetric membranes could be controlled by changing the amount of 1,4‐dioxane in the casting solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1300–1307, 2002; DOI 10.1002/app.10452     

Effect of polyvinylpyrrolidone molecular weights on morphology,oil/water separation,mechanical and thermal properties of polyetherimide/polyvinylpyrrolidone hollow fiber membranes

We prepared polyetherimide (PEI) hollow fiber membranes using polyvinylpyrrolidones (PVP) with different molecular weights (PVP 10,000, PVP 40,000, and PVP 1,300,000) as additives for oil/water separation. Asymmetric hollow fiber membranes were fabricated by wet phase inversion technique from 25 wt % or 30 wt % solids of 20 : 5 : 75 or 20 : 10 : 70 (weight ratio) PEI/PVP/N‐metyl‐2‐pyrrolidone (NMP) solutions and a 95 : 5 NMP/water solution was used as bore fluid to eliminate resistance on the internal surface. Effects of PVP molecular weights on morphology, oil‐surfactant‐water separation characteristics, mechanical, and thermal properties of PEI/PVP hollow fiber membranes were investigated. It was found that an increase in PVP molecular weight and percentage in PEI/PVP dope solution resulted in the membrane morphology change from the finger‐like structure to the spongy structure. Without sodium hypochlorite posttreatment, hollow fiber membranes with higher PVP molecular weights had a higher rejection but with a lower water flux. For oil‐surfactant‐water emulsion systems (1600 ppm surfactant of sodium dodecylbenzenesulfonate and 2500 ppm oil of n‐decane), experimental results illustrated that the rejection rates for surfactant, total organic carbon, and oil were 76.1 ≈ 79.8%, 91.0 ≈ 93.0%, and more than 99%, respectively. Based on the glass transition temperature values, PVP existed in hollow fiber membranes and resulted in the hydrophilicity of membranes. In addition, using NaOCl as a posttreatment agent for membranes showed a significant improvement in membrane permeability for PVP with a molecular weight of 1300 K, whereas the elongation at break of the treated hollow fiber membranes decreased significantly. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2220–2233, 1999     

PEI/EVAL blend membranes for granule neuronal cell culture

Recently we developed a novel type of membrane, based on polyethylene vinyl alcohol (EVAL), for biomedical applications. To improve the physical and biological performance of this membrane, polyethylenimine (PEI) that has been widely used as a gene transfer vector was chosen to blend with EVAL in this study. The properties and in vitro neuronal interaction of the blend membranes were investigated. Scanning electron microscopic observations show that the membranes exhibited increasingly smoother surface morphologies as the PEI content increased. Differential scanning calorimetric analysis demonstrated that EVAL was compatible with PEI at the microscopic level and the crystallinity of EVAL membrane was reduced by amorphous PEI. The surface nitrogen to carbon ratios, surface positive charges, surface hydrophilicity and surface protein adsorption were found to increase with increasing PEI content in the blend membranes as evidenced by the evidences from electron spectroscopy for chemical analysis as well as measurements of zeta potential, water contact angle, and serum protein adsorption respectively. From the morphology and viability of neurons cultured on the surfaces, it was observed that the neurons adhered, spread, grew and differentiated more onto the moderately hydrophilic PEI-containing membranes than onto the unmodified and hydrophobic EVAL. These PEI/EVAL blend membranes, which displayed high compatibility, thermal stability, moderate hydrophilicity, improved serum protein adsorption and enhanced neuronal interaction, may offer the potential to improve the healing and axonal regeneration of injured neuronal tissues.     

Investigation on the effects of fabrication parameters on the structure and properties of surface‐modified membranes using response surface methodology

Surface Modifying Macromolecules (SMM) were used to alter the hydrophobicity of polyetherimide (PEI) hollow fiber membranes and the effects of three fabrication parameters, which are the mass fraction of PEI and SMM in the casting dope and air gap, on the properties of fabricated membranes were investigated by application of Response Surface Methodology (RSM). The fabricated membranes were characterized in terms of mean pore size (r_P,m), permeation rate of helium gas at 1 bar transmembrane pressure difference, membrane porosity, and contact angle of water with inner and outer surfaces of membrane. The regression models obtained for mean pore size and permeation rate have good statistical parameters and are accurate. The model for r_P,m predicts that plot of r_P,m versus air gap has a minimum point, whereas the plots of r_P,m versus PEI (wt %) and SMM (wt %) have maximum points. The regression model developed for membrane porosity predicts that membrane porosity decreases when air gap increases. Since water was used as bore fluid, the model developed for inner surface contact angle has low accuracy but the model developed for outer surface contact angle predicts that contact angle increases with SMM concentration in dope solution but there is a maximum point versus air gap. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influences of the chain structure of PE‐b‐PEG on the properties of PE/PE‐b‐PEG blend membranes prepared by TIPS

In this article, a series of diblock copolymer polyethylene‐b‐ poly(ethylene glycol)s (PE‐b‐PEGs) with various molecular weight of polyethylene segment was blended with linear low‐density PE. The PE/PE‐b‐PEG blend porous membranes with high porosity were obtained by thermally induced phase separation (TIPS) process. The isothermal crystallization kinetics of PE/LP/PE‐b‐PEG blends indicated that the introduction of PE‐b‐PEG could inhibit the growth rate of polyethylene crystals which could increase the pore size and porosity of the membranes. The PE/PE‐b‐PEG blend membranes with PE₁₃₀₀‐b‐PEG₂₂₀₀ showed the largest pore size and porosity due to its crystallization behavior during TIPS. The surface of the membranes became smoother and the morphology of the membranes could be effectively tuned by introducing PE‐b‐PEG. Compared with the PE membrane, the PE/PE‐b‐PEG blend membranes exhibited higher hydrophilicity (the water contact angle decreased from 112° to 84°), water permeability (the permeation flux increased from 80 to 440 L/m² h under 0.1 MPa), rejection performance (completely reject carbon particles in the filtration of carbon ink solution), and fouling resistance (the value of protein adsorption dropped from 0.25 to 0.05 mg/cm²). The hydrophilicity and fouling resistance of PE/PE‐b‐PEG blend membranes increased as the length of PE segment in PE‐b‐PEGs decreased. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46499.     

Highly methanol resistant and selective ternary blend membrane composed of sulfonated PVdF‐co‐HFP,sulfonated polyaniline and nafion

Partially sulfonated poly(vinylidene fluoride‐co‐hexafluoro propylene)/partially sulfonated polyaniline (SPVdF‐co‐HFP/SPAni) binary blend membranes have shown promising results in terms of low methanol permeability and high membrane selectivity compared to Nafion‐117 membrane. However, the proton conductivity and IEC of this binary blend membrane was much lower than Nafion‐117. It was found that incorporation of minimal quantity of Nafion within SPVdF‐co‐HFP/SPAni blend membrane at a constituent weight % ratio of SPVdF‐co‐HFP:SPAni:Nafion = 50:40:10 induced significant improvements in ion‐exchange capacity (IEC), proton conductivity and tensile strength over that of the binary blend membrane. In addition, the SPVdF‐co‐HFP/SPAni/Nafion ternary blend membrane exhibited much lower methanol permeability, higher membrane and relative selectivities and comparable IEC to Nafion‐117. In effect, presence of minimal quantity of Nafion induced significant positive attributes to the ternary blend membrane; and assisted in reaching a balance between material cost and properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43294.     

Fabrication and characterization of polyetherimide/polyvinyl acetate polymer blend membranes for CO2/CH4 separation

This article presents fabrication, characterization, and performance evaluation of polyetherimide (PEI)/polyvinyl acetate (PVAc) blend membranes. Polymer blend membranes with various blend ratios of PEI/PVAc were prepared by solution casting and evaporation technique. Morphology and miscibility of polymer blend membranes were characterized by field emission scanning electron microscope (FESEM) and differential scanning calorimetry (DSC), respectively. The interaction between blend polymers was analyzed by FTIR analysis. Gas separation performance was evaluated in terms of permeability and selectivity. FESEM results revealed that pure polymer and blend membranes were homogeneous and dense in structure. A single glass transition temperature of polymer blend membranes was found in DSC analysis which indicated the miscibility of PEI/PVAc blend. FTIR analysis confirmed the presence of molecular interaction between blend polymers. The permeation results showed that the presence of PVAc (3 wt%) in blend membranes has improved CO₂ permeability up to 95% compared to pure PEI membrane. In addition, CO₂/CH₄ selectivity was found to be 40% higher than pure PEI membrane. This study shows that blending a small fraction of PVAc can improve the gas separation performance of PEI/PVAc blend membranes. POLYM. ENG. SCI., 59:E293–E301, 2019. © 2018 Society of Plastics Engineers     

Sulfonated poly(ether imide) and poly(ether sulfone) blends for direct methanol fuel cells. I. Sulfonation of PEI and characterization of the products

This investigation examines characteristics of sulfonated polyether imides (SPEI) with various ion exchange capacity values (IEC) and completes previous work to enable its blends to be adopted as polyelectrolyte in direct methanol fuel cells (DMFC). Polyether imides (PEI) were sulfonated by using chlorosulfonic acid as the sulfonating agent and chloroform as the solvent. The structure of SPEI was observed by FTIR and ¹H NMR. The sulfonate or sulfonic acid content of the polymers, expressed as a number per repeat unit of the polymer, was accurately determined by elemental analysis and conductometric titration. Physical properties such as solubility, intrinsic viscosities, thermal stability, and glass transition temperature (T_g) were studied for both PEI and SPEI. TGA‐FTIR verified that sulfonic groups, attached to the aromatic ring in the PEI backbone, are split at 230–350°C, but the main‐chain splitting temperature of SPEI is similar to that of pure polymer. The sulfonated samples exhibited good solubilities and increased glass transition temperatures (T_g values) as degree of sulfonation (DS) increased; two T_g values were detected when IEC was sufficiently high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of high‐flux ultrafiltration membranes by blending strongly charged polymer

Three kinds of high‐flux ultrafiltration membranes were fabricated by blending strongly charged polymer [sulfonated poly(phenylene oxide) (SPPO)] with neutral polymer [cellulose acetate (CA), polyethersulfone (PES), or polyvinylidene fluoride (PVDF)]. After blending with SPPO, the pure water flux of CA‐SPPO, PES‐SPPO, and PVDF‐SPPO membrane increase by 3, 76, and 30 times at a transmembrane pressure of 100 kPa. Compared with the unblended membranes, the pore radius of CA‐SPPO, PES‐SPPO, and PVDF‐SPPO membrane increased from 31.9 to 33.2 nm, 26.1 to 28.6 nm, and 19.8 to 25.7 nm, respectively. The addition of strongly charged polymer decreased the thermodynamic stability of casting solutions, promoting the phase inversion process and resulting in highly porous structure. The charged groups and hydrophilicity of the polymer facilitate the formation of an additive concentration gradient (more additive in the active layer), endowing the blend membrane with better hydrophilicity and greater wettability gradient. The high porosity, good hydrophilicity, and larger wettability gradient enable the high permeation of blend membranes. This work shows how the strongly charged polymer affects the formation and performance of blend membrane, which will be useful for designing high‐performance membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44570.     

Preparation and properties of PVDF/PVA hollow fiber membranes

On principle of polymer blend phase separation, PVDF/PVA hollow fiber membranes were prepared using phase inversion method. The membrane morphology and performance varied with the blending ratio. The PVDF/PVA blends showed incompatibility by the results of dynamic mechanical analysis (DMA) and infrared attenuated total reflection (FTIR-ATR) sampling technique. Based on bursting pressure and tensile strengths results, we suggest that the mechanical properties of PVDF/PVA blend membranes are worse than that of PVDF membrane. PVA can improve the hydrophilicity of PVDF/PVA hollow fiber membranes, which could be illuminated by the decrease in contact angle, the increase in equilibrium water content (EWC) and the variety in dynamic moisture regain. The pure water flux increases while the rejection ratio decreases with PVA content increasing. Moreover, PVA can improve the anti-fouling property of PVDF/PVA hollow fiber membranes, which could be illuminated by the result of increase coefficient of resistance.     

Influence of crystal morphology of 1H-1,2,4-triazole on anhydrous state proton conductivity of sulfonated bisphenol A polyetherimide based polyelectrolytes

In this study, new anhydrous proton conducting polyelectrolytes were prepared based on sulfonated bisphenol A polyetherimide (SPEI) and 1H-1,2,4-triazole (Taz) as a solid state proton solvent. The effect of degree of sulfonation and triazole concentration on size, shape and dispersibility (crystal morphology) of triazole crystals in sulfonated polyetherimide were examined and correlated with proton conduction. At a constant triazole weight percent, increased sulfonation level caused enhanced nucleation density, reduction of crystallite size and their uniform distribution throughout SPEI matrix. The decrease in size was responsible for the depression of triazole melting temperature. Proton conduction through structure diffusion occurred effectively within the smaller size crystals due to the improved molecular mobility.     

磺化聚醚砜提高聚醚砜膜亲水性和血液相容性研究

Polyethersulfone (PES) is widely used as biomaterials due to its thermal stability, mechanical strength, and chemical inertness. Nevertheless, their blood compatibility is still not adequate for hemodialysis and blood pu-rification. In this study, the sulfonated polyethersulfone (SPES) was synthesized through an electrophilic substitu-tion reaction, and PES/SPES blending membranes were prepared. The characterization of the SPES was studied by FTIR. The water adsorption and water contact angle experiments show that the hydrophilicity of PES/SPES blend membrane was improved as for the sulfonate group existing in the SPES. Moreover, PES/SPES blend membrane could effectively reduce bovine serum albumin adsorption and prolong the blood coagulation time compared with the PES membrane, thereby improving blood compatibility.     

Sulfonated poly(styrene)s‐PBIOO® blend membranes: Thermo‐oxidative stability and conductivity

Low‐cost polymers poly(styrene) and poly(α‐methylstyrene) have been sulfonated followed by blending with PBIOO® (30 wt % sulfonated ionomer, 70 wt % PBIOO). At this polymer ratio the sulfonated ionomer served as the macromolecular acidic cross‐linker which led to enhancement of the PBIOO stability. Both membrane types were treated with Fenton's Reagent to investigate their resistance to oxidation and radical attack. Indeed, the blend membranes showed enhanced stability in oxidative conditions compared to the pure PBIOO membranes. Furthermore, the sulfonated poly(α‐methylstyrene)‐PBIOO blend membrane showed less weight loss during and after Fenton's Test than the corresponding poly(styrene sulfonic acid)‐PBIOO membrane. Assuming all the characteristics of the blend membrane before and after the Fenton's Test, we concluded for a partial degradation of both sulfonated poly(styrene)s, whereas they remain in the blend membrane matrix due to the acid‐base crosslinking. Thus, since the sulfonated poly((α‐methyl)styrene)‐PBIOO blend membranes conserved their integrity even after Fenton's Test they can be regarded as potential low‐cost high‐T fuel cell membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39889.     

Fabrication and characterization of silk fibroin powder/polyurethane fibrous membrane

The blend fibrous membranes with the different mass ratio of silk fibroin (SF) powder to polyurethane (PU) were fabricated by electrospinning. The structure, morphology, mechanical properties, and surface wettabilities of the blend fibrous membrane are characterized by field‐emission scanning electron microscope, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry, dynamic mechanical thermal analysis, tensile testing, and contact angle measurements. The results show that the SF was uniformly distributed in the blend fibers. The mass ratio of SF to PU played an important role in influencing the structure and morphology of the blend fibers, and the optimum mass ratio was 5/5. With the increase in SF content in fibers, the fraction of SF in the surface of the SF/PU blend fibers and the crystallinity degree of PU increased, and the molecular orientation of PU along the fiber axis took place. The SF content regulated the hydrophilicity property of the membrane. The thermal stability and the dynamic storage modulus of the fibrous membrane decreased, and the phase separation between soft and hard segments of PU increased. Similarly, the stress at peak and Young's modulus of the fibrous membrane decreased gradually; the strain at peak first increased and then decreased. POLYM. ENG. SCI., 52:2025–2032, 2012. © 2012 Society of Plastics Engineers