Preparation,characterization and alkali metal ion permeation through cross-linked poly(styrene-co-maleic acid) membranes

Membranes were prepared from poly(styrene-co-maleic acid) under different conditions and characterized by measuring thickness, swelling, electrical resistance, membrane potential and permselectivity. Permeability coefficients of KCl, NaCl, Na₂SO₄, NaOH, urea and creatinine were evaluated from dialysis experiments. The charged membranes facilitated the active transport of alkali metal ions under a pH gradient. The energy for this movement comes from the simultaneous counter transport of protons.     

Polyether-segmented nylon hemodialysis membranes. I. Preparation and permeability characteristics of polyether-segmented nylon 610 hemodialysis membrane

The effect of the coagulation condition in the phase inversion method on the permeability characteristics of poly(propylene oxide) or poly(tetramethylene oxide)-segmented nylon 610 (PPO-Ny610 or PTMO-Ny610) hemodialysis membranes, the stability of the membrane performance, and the mechanical strength were investigated. The polymers were dissolved in a solvent such as formic acid and methanol saturated with calcium chloride, and thus PPO-Ny610 and PTMO-Ny610 membranes were prepared using formic acid and a calcium chloride/methanol/water mixture as a polymer solvent and a coagulant, respectively. It is concluded that PPO-Ny610 membrane has better permeability characteristics than PTMO-Ny610 membrane, and possesses additional properties for hemodialysis membranes such as mechanical properties and permeability stability in the drying and sterilizing processes. Furthermore, the blood compatibilities of PPO-Ny610 and PTMO-Ny610 membranes were superior to regenerated cellulose membranes on the basis of the result of platelet adhesion test. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1703–1711, 1997     

Polyether-segmented nylon hemodialysis membranes. II. Morphologies and permeability characteristics of polyether-segmented nylon 610 membrane prepared by the phase inversion method

The relationships between the morphologies and the permeability characteristics as dialysis membrane of polyether-segmented nylon 610 (PE-Ny610) have been investigated. PE-Ny610 used are poly(propylene oxide) (PPO)-segmented nylon 610 containing 25 wt % PPO (PPO-Ny610) and poly(ethylene oxide) (PEO)-segmented nylon 610 containing 15 wt % PEO (PEO-Ny610). The morphologies in the cross section of the membranes exhibit the cellular porous structures due to liquid-liquid phase separation. On the other hand, the structures of the surfaces are mainly composed of the crystalline spherulite due to liquid-solid phase separation. These morphologies are little affected by the composition ratio of the coagulant, calcium chloride/methanol/water mixture. PEO-Ny610 membranes have shown superior membrane performances to the PPO-Ny610 membrane. The effect of PEO content in PEO-Ny610 on the adhesion of platelet onto the PEO-Ny610 film surface was investigated and it is concluded that PEO-Ny610 having > 10 wt % PEO shows a good nonthrombogenicity equal to PPO-Ny610. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1713–1721, 1997     

Asymmetric cellulose acetate dialysis membranes: Synthesis,characterization, and performance

Cellulose acetate (CA) is highly comparable to other synthetic polymer materials and is effective in the hemodialysis process. In this work, asymmetric CA membranes were synthesized with the phase‐inversion method. CA with a molecular weight of 52,000, poly(ethylene glycol) (PEG) with a molecular weight of 400, and 1‐methyl‐2‐pyrrolidone (NMP) were used as the polymer, additive, and solvent, respectively. The effects of the CA and PEG concentrations and coagulation bath temperature (CBT) on the morphology, pure water permeability (PWP), insulin/human serum albumin (HSA) transmission, and finally thermal and chemical stability of the prepared membranes were determined and investigated. In general, increasing the PEG concentration and CBT and reducing the CA concentration resulted in increased PWP and insulin/HSA transmission. Also, these variations facilitated the formation of macrovoids in the membrane sublayer. On the other hand, increasing the PEG and CA concentrations and reducing CBT resulted in increased thermal and chemical stability of the prepared membranes. Also, ratios of 15.5/10/74.5 and 17.5/10/72.5 (w/w) for the CA/PEG/NMP casting solutions and their immersion into coagulation baths with CBTs of 0 and 25°C, respectively, resulted in the preparation of membranes that had not only optimum sieving properties and higher PWP but also thermal and chemical stability better than that of conventional CA hemodialysis membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of thermosensitive cellophane-graft-N-isopropylacrylamide copolymer membranes and permeation of solutes through the membranes

Thermosensitive membranes with high mechanical strength were prepared by heterogeneous graft copolymerization of N-isopropylacrylamide (NIPAAm) onto cellophane in a nitric acid solution using cerium ammonium nitrate as an initiator, and the permeation behavior of solutes such as lithium chloride and poly(ethylene glycol)s (PEGs) through the membranes at various temperatures was investigated. The degree of graft copolymerization of NIPAAm on cellophane depended on temperature, time, initiator concentration, and so on. The copolymer membranes having a high content of the NIPAAm moiety could be obtained at 25°C for 24 h. The permeation of Li⁺ through the membranes was affected by temperature, i.e., the permeation rate of Li⁺ increased with increasing temperature up to 32°C and then decreased rapidly above 35°C. The permeation rate of Li⁺ through the copolymer membranes at 40°C decreased considerably, but that at 20°C decreased slightly with an increasing amount of the NIPAAm moiety in the membranes. The permeation rate of PEGs with a molecular weight more than 1000 through the cellophane-g-NIPPAm copolymer membranes was considerably suppressed and only the permeation rate of PEG300 increased with increasing temperature up to 35°C and then decreased at 40°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 209–216, 1997     

Polyether-segmented nylon hemodialysis membranes. IV. Membrane morphologies and permeability characteristics of dialysis membrane composed of poly(ethylene oxide)-segmented Ny69/M10

Dialysis membrane was prepared by a phase inversion method using a new polyether-segmented nylon which dissolves in common organic solvents such as dimethylsulfoxide. The polyether-segmented nylon contained poly(ethylene oxide) block and nylon block (random copolyamide: Ny69/M10) prepared by sebacic acid, azelaic acid, m-xylenediamine, and hexamethylenediamine. The morphologies and permeability characteristics of the membranes were investigated. It was shown by scanning electron microscope observation that the membrane had a fingerlike structure when dimethylsulfoxide was used as a polymer solvent, and a spongelike structure when an additive such as calcium chloride was added to the polymer solution. The high permeability for the solutes such as urea and vitamin B₁₂ were observed in comparison with the polyether-segmented Ny610 membranes prepared by a phase inversion method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1731–1737, 1997     

Microporous carbon membranes from sulfonated poly(phthalazinone ether sulfone ketone): Preparation,characterization, and gas permeation

Microporous carbon membranes (MCM) were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) through stabilization and pyrolysis processes. The effects of sulfonation degree (SD) of SPPESK and the stabilization temperature on the structure and gas permeation of MCM were investigated. The thermal decomposition behavior of SPPESK was studied by thermogravimetric analysis‐mass spectrometry. The evolution of functional groups on membrane surface was detected by Fourier transform infrared spectroscopy during heat treatment. The resultant MCM was characterized by X‐ray diffraction, Raman spectroscopy, nitrogen adsorption technique and pure gas permeation test (including the gases of H₂, CO₂, O₂, and N₂), respectively. The results have shown that the removal of sulfonic acid groups in SPPESK leads to a weight loss stage in the temperature range of 250–450°C. The surface area, maximum pore volume, and gas permeability of MCM increase with the SD increasing from 59 to 75%, together with the reduction of selectivity. Similarly, the gas permeability of MCM also increases with elevating the stabilization temperature from 350 to 400°C at the loss of selectivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Membrane transport of organics. I. Sorption and permeation of carboxylic acids in perfluorosulfonic and perfluorocarboxylic polymer membranes

Experimental studies have been made on the sorption and permeation of propionic (PA), acetic (AA), and formic (FA) acid in perfluorosulfonic Nafion, and perfluorocarboxylic Flemion membranes. The sorption isotherms show the increase of distribution coefficients K_d = C_m/C_e with the pK of acids, i.e., K_d,PA > K_d,AA > K_d,FA. The transmembrane fluxes (J) and permeabilities (P) change their values in the same order for C_e < 0.1M and in the order J_PA > J_FA > J_AA for higher concentrations. The differentiation of fluxes in single-component dialyses does not result in the effective separation of AA and PA during their competitive permeation through the Nafion-120 membrane. Under the same conditions, the Flemion membrane exhibits the preference toward propionic acid and transports PA and AA with the selectivity coefficient a_AA^PA equal to 1.5. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 355–362, 1997     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, Polysulfone was functionalized by sulfonation and ultrafiltration membranes were prepared based on sulfonated polysulfone and cellulose acetate in various blend compositions. Polyethyleneglycol 600 was employed as a nonsolvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The total polymer concentration, cellulose acetate, and sulfonated polysulfone polymer blend composition, additive concentration, and its compatibility with polymer blends were optimized. The membranes prepared were characterized in terms of compaction, pure water flux, membrane resistance, and water content. The compaction takes place within 3–4 h for all the membranes. The pure water flux is determined largely by the composition of sulfonated polysulfone and concentration of additive. Membrane resistance is inversely proportional to pure water flux, and water content is proportional to pure water flux for all the membranes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1749–1761, 2002     

Preparation of poly(vinyl alcohol)-graft-N-isopropylacrylamide copolymer membranes with triphenylmethane leucocyanide and permeation of solutes through the membranes

Thermo- and photosensitive hydrogel membranes were prepared by graft copolymerization of an N-isopropylacrylamide (NIPAAm) and triphenylmethane leucocyanide (LeCN) monomer onto poly(vinyl alcohol) (PVA). The yield of the graft copolymerization as well as the content of the poly(NIPAAm) segments grafted onto PVA was depressed by copolymerization of the LeCN monomer. The change in the permeation rate of poly(ethylene glycol)s through the hydrogel membranes was induced photochemically by dissociation of LeCN moieties in the membranes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1931–1937, 1998     

Preparation and characterization of polyacrylonitrile-based membranes: Effects of internal coagulant on poly(acrylonitrileco-malefic acid) ultrafiltration hollow fiber membranes

Ultrafiltration hollow-fiber membranes (UHFMs) ofpoly(acrylonitrile-co-malefic acid) (PANCMA) were prepared by a dry-wet phase inversion process. The morphologies of inner surface and cross section for these hollow fibers were inspected with scanning electron microscopy. It was found that, by increasing the amount of solvent DMSO in internal coagulant, the number and size of macrovoid underneath the inner surface decreased. The water flux of the UHFMs also decreased while the bovine serum albumin rejection increased minutely. These results were interpreted based on the ternary phase diagrams for the PANCMA/DMSO/(H₂O+DMSO) system, which was obtained from the experimental cloud point measurements and empirical linearized cloud point relation. It was envisaged that the membrane surface could be further modified by the reaction of acid groups with poly(ethylene glycol).     

Competitive transport of hydrochloric acid and zinc chloride through polymeric anion‐exchange membrane

Competitive transport of hydrochloric acid and zinc chloride has been investigated in a two‐compartment mixed cell with an anion‐exchange membrane Neosepta‐AFN developed and produced by Tokuyama Soda Co. These experiments have proved that hydrochloric acid permeates well through the membrane used but, on the other hand, zinc chloride is not effectively rejected. The flux of zinc chloride has been found to be increasing with increasing acid and salt concentrations. Furthermore, it has been found that it is approximately one order of magnitude higher than that found in the case of simultaneous transport of sulfuric acid and zinc sulfate through the same membrane. The further calculations concerning the ionic equilibria with sorption isotherms for the HCl? ZnCl₂ system, which have been measured experimentally, have revealed that high flux of ZnCl₂ is due to the fact that a considerable amount of zinc chloride in the membrane is in the form of ZnCl₃^? complex, which is relatively small and passes well through this membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1391–1397, 2006     

Preparation,characterization, and applicability of novel calix[4]arene‐based cellulose acetate membranes in gas permeation

Cellulose acetate (CA) is well known glassy polymer used in the fabrication of gas‐separation membranes. In this study, 5,11,17,23‐tetrakis(N‐morpholinomethyl)‐25,26,27,28‐tetrahydroxycalix[4]arene (CL) was blended with CA to study the gas‐permeation behavior for CO₂, N₂, and CH₄ gases. We prepared the pure CA and CA/CL blended membranes by following a diffusion‐induced phase‐separation method. Three different concentrations of CL (3, 10, and 30 wt %) were selected for membrane preparation. The CA/CL blended membranes were then characterized via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X‐ray diffraction analysis. The homogeneous blending of CL and CA was confirmed in the CA/CL blended membranes by both SEM and AFM analysis. In addition to this, the surface roughness of the CA/CL blended membranes also increased with increasing CL concentration. FTIR analysis described the structural modification in the CA polymer after it was blended with CL too. Furthermore, CL improved the tensile strength of the CA membrane appreciably from 0.160 to 1.28 MPa, but this trend was not linear with the increase in the CL concentration. CO₂, CH₄, and N₂ gases were used for gas‐permeation experiments at 4 bars. With the permeation experiments, we concluded that permeability of N₂ was higher in comparison to those of CO₂ and CH₄ through the CA/CL blended membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39985.     

Preparation,characterization, and permeation property of a liquid crystal/PDMS membrane material

By introducing the ordered and flowing liquid crystalline groups into polymeric membranes, a novel liquid crystal/polydimethylsiloxane (LC/PDMS) membrane material is synthesized with PDMS containing vinyl group, polymethylhydrosiloxane and cholesteric LC as matrix materials. The chemical structure, LC behaviors and mechanical performance of the LC/PDMS crosslinked membranes are characterized by using FTIR, differential scanning calorimetry (DSC), and polarized light microscopy with a hot stage. Some factors on permeability and permselectivity for carbon dioxide and nitrogen gas are also examined. These results suggest that the membrane‐forming property and permeation properties of the crosslinked membranes are obviously enhanced due to the introduction of the LC groups into PDMS and crosslinking reaction in the preparation process. At pressure difference of 0.1 MPa and testing temperature of 40°C, the permeability coefficient for carbon dioxide and ideal separation factor for carbon dioxide and nitrogen are up to 4667 Barrer and 24.0, respectively. In addition, the incorporation of LC containing unsaturated linkage has the potential for further modification reactions such as grafting and crosslinking. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of PVDF/silica hybrid membranes containing sulfonic acid groups

Organic–inorganic hybrid membranes of poly(vinylidene fluoride)‐cohexafluoropropylene (PVDF‐HFP) and silica composites containing sulfonic acid groups were prepared via in situ polymerization of tetraethoxysilane (TEOS) and sulfosuccinic acid (SSA) using the sol‐gel process. The membranes containing more sulfonic acid groups showed a higher vapor sorption and greater swelling behavior. The bound and free water content of the membrane is proportional to the SSA concentration. However, the hybrid membranes without SSA do not have free water. The ion conductivity of the membranes is proportional to the SSA concentration. Silica content in the hybrid membrane without SSA had great effect on their mechanical properties. Tensile modulus and yield stress increased and yield strain and elongation at break decreased with increased silica content. However, in the case of the hybrid membrane containing SSA modulus, yield stress decreased and yield strain and elongation at break increased with increased silica content due to the weak interactions between the hydrophobic polymer chain and the hydrophilic group of SSA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 209–218, 2004     

Preparation and characterization of PVDF-PFSA flat sheet ultrafiltration membranes

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (M_w = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400+ 5 wt-% PFSA) had a pure water flux of 141.7 L/m²·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m²·h, BSA rejection of 96.3% and RFR of 42.86%).     

Perfluorinated sulfonic acid ionomer/poly(N-vinylpyrrolidone) nanofiber membranes: Electrospinning fabrication, water stability, and metal ion removal applications

Perfluorinated sulfonic acid ionomer/poly(N-vinylpyrrolidone) (PFSA/PVP) fibrous membranes with varying compositions were prepared by electrospinning. The morphology, physicochemical structure and water stability of these membranes were investigated by SEM, XRD, and FTIR. The crosslinking agent 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt (DAS) was added to the spinning solutions, and its effect on electrospinning behavior and PFSA/PVP membrane morphology was investigated. Thermal annealing of the DAS-containing PFSA/PVP fibrous membranes resulted in improved water stability due to PVP crosslinking. The adsorption properties of the nanofiber membranes were measured by the ability to remove Cu²⁺ and Ca²⁺ ions from water. Nanofiber membranes with higher surface area provide more exposed functional groups and thus better ion removal capability. These functional PFSA/PVP nanofiber membranes show applicability in water treatment and may find potential applications in sensors and drug delivery or as components of the catalytic layer of proton-exchange membrane fuel cells.     

Preparation,characterization, and adsorption properties of cellulose acetate‐polyaniline membranes

Four lots of cellulose acetate (CA) membranes, modified with polyacrylic acid, using various plasticizers, and coated with polyaniline (PANI) were prepared. The morphology of the membranes was evaluated by using scanning electron microscopy, and the membranes showed larger pore size when the plasticizers were used. The electrical conductivity of the modified membranes and coated with PANI increased by two orders of magnitude when the plasticizer triphenyl phosphate was used. The strain at break improved by an order of magnitude and the glass transition temperature (T_g) showed an average decrease of 36°C when the membranes were plasticized. Finally, these membranes were tested as ion‐exchange materials of a gold‐iodide complex. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

磷钨酸/二氧化硅/磺化聚醚醚酮复合膜的制备、表征与性能

以二氧化硅和磷钨酸改性磺化聚醚醚酮制得一种新型磺化聚醚醚酮复合膜。复合膜中杂多酸仍然保持着Keggin型PW12O430-阴离子的特征结构,二氧化硅和磷钨酸以无定形状态均匀分散于复合膜中。磷钨酸/二氧化硅/磺化聚醚醚酮复合膜的阻醇性能优于Nafion115;质子导电性能随着温度的提高有所增加。复合膜在磷钨酸中具有良好的稳定性。