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We have recently developed the Zs (Zetta spinning) system, which is composed of two high speed nanofiber manufacturing methods, and it is applicable for both polymer solutions and polymer melts. The Zs–solvent system can be used for a polymer solution, its flow rate from a nozzle is a maximum of 2 mL/min to produce nonwoven fabrics, the Zs–melt can be used for polymer melts, and the maximum production rate of the molten polymer is about 1–2 kg/h to produce nanofiber wadding, which was fabricated during the Zs–solvent development. The development of the Zs system to produce mass nanofibers has expanded their potential applications, which include filters for air pollution, water and oil treatment, battery separators, medical separation, desert greening, building materials, etc.

This paper reports the facile and high-throughput fabrication method of anisotropic Au nanoparticles with a highly sensitive local surface plasmon resonance (LPR) using cylindrical nanofibers as substrates. The substrates consisting of nanofibers were prepared by the electrospinning of poly(vinylidene fluoride) (PVDF). The Au nanoparticles were deposited on the surface of electrospun nanofibers by vacuum evaporation. Scanning electron microscopy revealed the formation of a curved Au island structure on the surface of cylindrical nanofibers. Polarized UV-visible extinction spectroscopy showed anisotropy in their LPR arising from the high surface curvature of the nanofiber. The LPR of the Au nanoparticles on the thinnest nanofiber with a diameter of ~100 nm showed maximum refractive index (RI) sensitivity over 500 nm/RI unit (RIU). The close correlation between the fiber diameter dependence of the RI sensitivity and polarization dependence of the LPR suggests that anisotropic Au nanoparticles improve RI sensitivity.

Liquid crystal polymer (LCP) nanofibers were prepared by electrospinning from isotropic and biphasic poly(γ-benzyl-L-glutamate) (PBLG)/dichloromethane-pyridine solutions. The as-spun PBLG fiber from the isotropic solutions had an undulating orientation of closed packed α-helices like a serpentine trajectory. The as-spun fibers from the biphasic solutions containing the LC phase, on the other hand, had uniaxially oriented hexagonal lattices of α-helices along the fiber axis. These results indicated that the orientation of the ordered structure of the electrospun lyotropic LCP fibers can be controlled by the initial microstructure of the spinning solution.

In the present paper, we report a novel ion-exchange carbon nanomaterial, surface sulfonated carbon nanofiber (S-CNF) fabrics, with a high surface area and high ion-exchange and adsorption capacities. S-CNF fabrics bearing SO3H groups were prepared by electrospinning, successive carbonization and sulfonation. We observed a nanosize effect, in which the surface area, and ion-exchange and adsorption capacities significantly increase with a decrease in the fiber diameter. The prepared fabrics with a diameter of 80 nm had the maximum values for the total pore surface area of 32.2 m2 g−1, the ion-exchange capacity of 2.94 mmol g−1, and an adsorption capacity of 943.1 mg g−1 for methylene blue (MB). The MB adsorption capacity is two times higher than that of commercial activated carbons. These results highlight the fact that the surface functionalized CNF fabrics with ionic groups are promising materials for high-capacity ion-exchangers.

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50 °C )= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.

In membrane separation, the incorporation of a given target molecule into a membrane is an important process to express permselectivity. Molecular imprinting method is an easy way to introduce molecular recognition sites into synthetic membranes. Applying an alternative molecular imprinting, various polymeric materials can be converted into membranes with molecular recognition sites toward a given target molecule. In membrane separation, flux values, and permselectivities, which often show a trade-off relationship, are important membrane performances. In a sense, the enhancement of flux is more important than that of permselectivity. Molecularly imprinted nanofiber membranes, which are fabricated by simultaneously applying an alternative molecular imprinting and an electrospray deposition, have potential that both flux and permselectivity can be simultaneously enhanced.

The crystallization of poly(vinylidene fluoride) (PVDF) was observed after the poly(methyl methacrylate) (PMMA) component was extracted from the PVDF/PMMA (50/50) composite nanofiber fabricated by electrospray deposition, even though the original composite showed a completely amorphous pattern in the wide-angle X-ray diffraction. The content of the β-crystal form in the crystalline region depended on the PVDF/PMMA composite ratios and the type of solvents used for the extraction of the PMMA component, e.g., chloroform and toluene. Thus, the content of the β-crystal form can be controlled by selecting the original PVDF/PMMA composition and the solvent used to extract the PMMA component. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Phenolic resin-based carbon nanofibers with a diameter of about 110 nm, the highest electrical conductivity of 5.29 S/cm and highest BET specific surface area of 792.7 m2/g were prepared by electrospinning, followed by successive carbonization. The addition of a high-molecular-weight polymer, poly(vinyl butyral) (Mw = 340,000), and electrolytes, pyridine and sodium carbonate, to the phenolic resin/MeOH solution can effectively form a thinner smooth fiber by electrospinning, and then the as-spun fabrics were successfully carbonized at 900 °C for 2h. Thus the prepared carbonized fabrics are very flexible and showed a thinner diameter, a higher conductivity and a higher specific surface area as already described.

Nanotextured polymer coatings were prepared on aluminum substrates by electrospray deposition (ESD) from poly(ethylene oxide) (PEO) solution. By controlling the size of deposits on the substrate, it is possible to change coloring of coatings — red, orange, yellow, green, and blue, — due to thin-film interference. These results indicate that the ESD method is a useful option for preparing optical coatings.

In the present study, composite polyelectrolyte membranes were prepared from sulfonated polystyrene and fullerene. The additive effect of the fullerene on the membrane properties – electric resistance, mechanical strength, oxidation resistance, and methanol permeability – were measured. The addition of fullerene improved the oxidation resistance, and reduced the methanol crossover. The mechanical strength of the fullerene-composite membrane, on the other hand, was not improved. The direct methanol fuel cell (DMFC) based on a 1.4 wt% fullerene-composite membrane showed the highest power density of 47 mW cm −2 at the current density of 200 mA cm −2 (this value is 60% of the Nafion-based DMFC). The transmission electron microscopy (TEM) observations suggest that the improved dispersity of the fullerene and the reduced number of micropores in the membranes would improve its performance in the fuel cell.

Nanofiber with porous structures were prepared by electrospray deposition (ESD) from poly(vinylidene fluoride) (PVDF)/poly(vinylpyrrolidone) (PVP) blend and subsequent selective removal of PVP. In the present work, the effect of blending ratio of PVDF/PVP on formation of the pore and crystal structure of residual PVDF fiber was investigated. The residual PVDF nanofiber showed a higher specific surface area (the highest specific surface area was 28.54 m2/g from PVDF/PVP = 67/33 w/w). The Fourier transform infrared spectroscopy and wide angle X-ray diffraction measurement also showed that selective removal of PVP enhanced the formation of β-phase crystal structure in PVDF nanofiber (β-phase content > 90%).

Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). In the present work, the additive effect of ionic fluorinated surfactants—anionic and cationic surfactants —on the diameter, morphology, and crystalline structure of PVDF nanofiber was investigated. The addition of ionic fluorinated surfactants is useful for the formation of bead-free homogeneous fiber. At a higher concentration of the ionic surfactants, thicker fiber was formed. In addition, the Fourier transform infrared spectroscopy and the wide angle X-ray diffraction measurements showed that the addition of both ionic fluorinated surfactants causes a complete change in conformation from the initial α-phase of to the β-phase of PVDF during ESD. A possible mechanism based on the interaction between the polymer and surfactant molecules during ESD is discussed.

Carbon nanotubes/polyamide (PA) nanocomposite thin films have become very attractive as reverse osmosis (RO) membranes. In this work, we used molecular dynamics to simulate the influence of single walled carbon nanotubes (SWCNTs) in the polyamide molecular structure as a model case of a carbon nanotubes/polyamide nanocomposite RO membrane. It was found that the addition of SWCNTs decreases the pore size of the composite membrane and increases the Na and Cl ion rejection. Analysis of the radial distribution function of water confined in the pores of the membranes shows that SWCNT+PA nanocomposite membranes also exhibit smaller clusters of water molecules within the membrane, thus suggesting a dense membrane structure (SWCNT+PA composite membranes were 3.9% denser than bare PA). The results provide new insights into the fabrication of novel membranes reinforced with tubular structures for enhanced desalination performance.

Polysaccharide—chitosan, sodium chondroitin sulfate, and pectin—nanofibrous fabrics were prepared from the respective polysaccharide/poly(ethylene oxide) (PEO) blend solutions by electrospray deposition (ESD). The surface morphologies of the electrosprayed fabrics were observed by scanning electron microscopy (SEM). Unblended polysaccharide solutions showed low ESD processability; viz., the solutions could not be electrosprayed, or provided a non-fibrous morphology composed of spherical entities when ESD was applicable. The addition of high-molecular-weight PEO (Mw=500,000) to chitosan solutions significantly enhanced the formation of a fibrous structure. Sodium chondroitin sulfate/PEO and pectin/PEO blend solutions were generally too viscous to be sprayed at 25 °C; at 70 °C, however, we succeeded in forming the fibrous structure from these solutions by ESD. The results indicate that adequate heating is effective to improve the processability of such highly viscous blend solutions into the electrostatic fiber formation.

Nanostructured thin films were prepared by electrospray deposition (ESD) from poly(ethylene oxide) (PEO) aqueous solution. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM). The SEM images revealed the correlations between the morphologies and the ESD conditions. By changing the applied voltage and solution properties such as viscosity, surface tension, conductivity, and molecular weight, PEO thin films with diverse nanostructures—from nanospheres to nanofibers —were fabricated. It was also revealed that the addition of alcohols to polymer solution, which enables simultaneously changing the viscosity, the surface tension, and the conductivity, enhanced the formation of the fibrous structure. These results indicate that the ESD method is potentially a useful option for producing nanoengineered polymer surface.

Protein thin films were prepared by the electrospray deposition (ESD) method from aqueous solutions of α -lactalbumin ( α -LA) at different concentrations, and their surface morphologies and biological activities were characterized. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM images showed that the film surfaces had a fine porous structure, in which the pore diameters ranged from 40 to 600 nm. The biological activities of the cross-linked protein films were tested by the mechanochemical method. The response to calcium ion (Ca 2+ ) demonstrated that the biological activity of the films was preserved. These results indicate that the ESD method is potentially useful for the fabrication of active protein thin films. The freestanding protein thin films prepared by ESD and postdeposition cross-linking provide novel options for protein-based biomaterials.

Weak amphoteric charged membranes were prepared by the radiation-induced graft copolymerization of the poly(ethylene glycol) (PEG) derivatives with pendant ionizable groups onto polyethylene (PE) porous membranes. In this study, two types of amphoteric charged membranes, which are the amphoteric ion-pair side chain (ASC) type and the mixed grafted chain (MGC) type, were prepared and then characterized by means of zeta (ζ)-potential measurements. The ζ-potential measurements were performed using streaming potential method over the pH range of 2–12. The ζ-potential/pH profiles for the amphoteric charged membranes showed their characteristic behavior. The pH dependence of the apparent surface charge density derived from the ζ-potential was compared with the calculated result from the theoretical model, site dissociation model (SDM), which was based on the dissociation of ionizable groups on the pore surface. Our analysis indicated that the interfacial charge of the ASC-type membrane was ascribed to the dipolar ion structure of cysteine residues. On the other hand, not only the charge groups but also the conformation of grafted polyelectrolyte chain affected the electrokinetic pore-surface charge of the MGC-type membrane.

Electromembranes refer to the membranes which are composed of polyelectrolytes with the positive or/and negative charge groups. The membrane which has positively charged groups is called as an anion-exchange membrane from which cations are excluded. On the other hand, the membrane which has negatively charged groups is called as a cation exchange membrane from which anions are excluded. Biological membranes are well known as typical electromembranes because they are composed of amino acids and show selectivity to the specific ions, that is, H+, Na+, K+, etc.. A synthetic electromembrane was firstly prepared by Juda et al. in 1950 (hydrocarbon-type cation exchange membrane) and applied to the salt industry in Japan to produce salt from sea water. In 1972 a fluorocarbon-type cation exchange membrane composed of polytetrafluoroethylene and perfluorosulfonyl-ethoxyvinylether copolymer was invented in USA and firstly applied to sodium hydroxide production by a Japanese chemical company. Recently, it is recognized that the fluorocarbon-type cation exchange membranes have exhibit performances as a solid state polyelectrolyte membrane for a fuel cell because the proton conductivity is higher and its resistance to acid and base is stronger than those of the hydrocarbon-type cation exchange membrane. We, however, have to solve many problems on charged membranes before general use. In this paper, recent problems which are laid in charged membrane are overviewed in order to develop the research activities of this field.

本研究では, 薄膜作製法の一つであるエレクトロスプレーデポジション (Elnctro-spray Deposition; ESD) 法を用いて, ポリエチレングリコール (分子量: 4.0×103; 2.0×104; 5.0×105) および, ポリアクリル酸 (分子量: 4.0×103; 2.5×104; 2.5×105) の薄膜作製を行い, 薄膜の表面構造に及ぼす分子量の影響を求めた. 走査型電子顕微鏡 (FE-SEM) 観察の結果によると, 本法で作製された薄膜の表面は主に球状の粒子が積み重なった構造を示すが, 分子量が大きくなると50～100nmの直径を有する繊維からなる網状構造を示すことが明らかとなった.

The transport mechanism of 1-butene and propylene through dry AgNO3-doped perfluorosulfonate ion-exchange membranes was investigated on the basis of the results obtained from sorption and permeation experiments. A derivation of a multilayer diffusion equation was carried out in order to interpret the transport mechanism of gases or vapors through microporous materials, assuming that the BET n-layer adsorption takes place and that the transport of the adsorbed molecules is controlled by the activated diffusion mechanism. The transport mechanism of 1-butene and propylene through dry AgNO3-doped PSM membranes can be explained by multilayer diffusion together with swelling of the surrounding polymer pendant side chains by the sorbed alkene molecules. The diffusion coefficients of the sorbed alkene molecules in the first adsorbed layer, D1, are always lower than those of the sorbed alkene molecules in the second and higher adsorbed layers, D2. This indicates that the interaction between the silver salts and th...

We have studied both theoretically and experimentally the passive transport of ionic drugs through membranes with pH-dependent fixed charge. The system considered constitutes a simplified model for pH-controlled drug delivery through membranes of biochemical and pharmaceutical interest. The theoretical approach employed is based on the Nernst-Planck flux equations and all of the species present in the system (the neutral or ionic drug and the hydrogen and hydroxide ions) have been taken into account together with a Langmuir-type isotherm for the adsorption of the ionic drug onto the membrane surface. The membrane permeabilities of cationic, anionic, and neutral drugs through porous membranes with graft-polymerized weak polyelectrolytes have been measured as a function of the external pH. According to the nature of the grafted polyelectrolyte, the ionized membrane fixed groups can be negative or positive. For the amphoteric membrane, both fixed charge groups are present in the grafted chains. In all cases, the ionization state of the weak polyelectrolyte fixed groups changes with the local pH within the membrane. A comparison of the theoretical results with the experimental data allows one to explain qualitatively the changes of the membrane flux with the external pH and gives new physical insights into the transport problem. Copyright 2000 Academic Press.

The current-voltage curves of a composite bipolar membrane (CBM) were experimentally measured by inserting the thin poly(acrylonitrile) (PAN) membrane between cation- and anion-exchange membranes for water and methanol solutions. In each solution system, 0.05 mol/L LiCl was used as the electrolyte. The measured results show that the thin PAN membranes enhanced the water- and methanol-splitting effect. This phenomenon can be explained by the protonation-deprotonation reactions occurring between the functional group of PAN (-C≡N, cyano) and the water or methanol molecules in the intermediate region of the CBM. The effect of niobium alloy (Nb 3 Ga), fullerene (C 60 ) and titanium oxide (TiO 2 ) existing in the intermediate region of the CBM was also experimentally examined in this study. It was found that the effect of these compounds on water or methanol-splitting was not obvious.

The transport of 5-fluorouracil (an anti-cancer medicine, 5FU) through a protein membrane was investigated. The membrane was prepared from silk fibroin. The permeability coefficients of 5FU were measured at different pH values ranging from 3.0 to 9.0. The protein membrane was composed of both weak acid and weak base groups—a so-called amphoteric membrane. The isoelectric point of this membrane is about pH 4.0. The measured results showed that the permeability coefficient of 5FU abruptly decreased above about pH 7 because 5FU became anionic in an alkaline solution and the membrane become a cation exchanger above pH 4.0. The abrupt decrease in permeation can be theoretically explained in terms of the Donnan equilibrium and the Nernst-Planck equation. Fibroin membranes are suggested to be potentially very useful in drug delivery systems.

Pore-surface characteristics of poly(acrylonitrile)-based porous membranes having amphoteric charge groups were investigated by zeta potential obtained from streaming potential measurements. The amphoteric-charged pore surface was theoretically examined by a single-acid, single-base site dissociation model, whose model is based on the assumption that the surface charge arises only from the protonation and deprotonation of the charged surface groups. From the theoretical approach, some characteristic parameters of the amphoteric pore surface such as the isoelectric point, dissociation constant, apparent site density of each acidic and basic group, and acid-to-base ratio were successfully determined. These parameters were changed in response to the variation of the feed monomer ratio. This approach can be expected to provide useful information concerning the pore-surface charge of an amphoteric-charged membrane.

The transport mechanism was investigated for n-butane, 1-butene, ethane, and ethene through anhydrous Ag+-doped PSM at various upstream gas pressures. 1-Butene and ethene molecules can be adsorbed and form multilayers on the Ag+ sites in the membrane. Their adsorption behavior can be described by the BET n-layer adsorption theory. These adsorbed alkene molecules can also swell the surrounding polymer chains to a certain extent, causing resistance to the migration of these alkene multilayer molecules to decrease as the concentration of the adsorbed alkenes increases. The permeation behavior of 1-butene and ethene is mainly controlled by the hydrodynamic surface flow mechanism, and their fluxes are much higher than those of alkanes, especially at high upstream gas pressures. This leads to the high ideal selectivity of 1-butene/n-butane and ethene/ethane at relatively high pressure. It is also shown that the more C atoms present in the hydrocarbon molecules, the higher will be the permselectivity of alkenes relative to their corresponding saturated alkanes, which will be expected in the anhydrous Ag+-doped PSM. Copyright 1999 Academic Press.

Transport of amino acids and other organic molecules through synthetic polymer and liquid membranes is of interest not only for devising efficient separation processes in biotechnology but also for a better understanding of a variety of metabolic processes concerning their permeability through biological membranes. Amino acids can be considered as amphoteric compounds having more than one ionizable group. They can exist in cationic, anionic and neutral form depending upon the solution pH. Previous studies on organic acid and amino acid permeation through ion exchange membranes have shown that the transport is pH dependent and that interfacial transport can be the rate-limiting step in the permeation process. We have addressed these questions here both theoretically and experimentally. Firstly, we describe a series of experiments especially designed to show the effects of pH on the interfacial transport of the amino acid (glycine in this case) through a cation exchange membrane. Secondly, we explain the experimental results by using a simple theoretical model based on the equilibrium dissociation equations for the fraction of amino acid forms at different pH values, a rate equation for the interfacial transport based on the interfacial chemical reaction (or alternatively, the Donnan equilibrium relationship) and the Nernst-Planck flux equations for the ion transport through the cation exchange membrane. The results presented show that the rate-limiting step in the transport process is the rate at which amino acid exits the membrane, and constitute a step further in the basic understanding of amino acid permeation across charged membranes.

Porous membranes having amphoteric charge groups were prepared by heterogeneous graft polymerization from aqueous solution containing acrylic acid and (N,N-dimethylamino)propyl acrylamide. The charging properties of the amphoteric charge groups grafted to the pore surface were investigated by ζ potentials obtained from streaming potential measurements. Theoretical development in terms of the amphoteric pore surface was attempted by introducing a site dissociation model of pH-dependent ζ potentials. The theoretical model is based on the assumption that the surface charge arises only from the protonation and deprotonation of the charged surface groups exposed to electrolyte solution. Good fits between experimental results and theoretical equations were attained, and thereby the isoelectric point, dissociation constant, apparent surface site density, and acid-to-base ratio of the amphoteric pore surface were determined. Depending on the variation in the feed monomer ratio for graft polymerization, these para...

The relationship between the water splitting effects and the chemical composition of the intermediate layer has been studied. Firstly, the membrane resistance decreases if a quaternary ammonium group or a carboxyl group is inserted in the intermediate layer instead of a secondary or tertiary amino group, which implies that the water dissociation occurs not only due to the catalytic effect of the secondary or tertiary amino group but also to the electrical field. Secondly, it is proved that the current efficiency is determined by the ion exchange capacity in the anion and cation exchange layers, but not by the chemical structure of intermediate layer. Thirdly, it is also evidenced that the membrane which has a thick intermediate layer showed a high conductivity before the critical point of thickness of the intermediate layer, which means an increase in the reactive region of the water. In this study, we could not find evidence that the chemical reaction model is superior.

The permeability coefficients across cation- and anion-exchange membranes were measured for LiCl methanol−water solutions. The experimental data were analyzed on the basis of the Donnan equilibrium...

Lysozyme, albumin, and PAS-H (poly diallyl dimethyl ammonium chloride), which are positively and negatively charged proteins, and cationic polysulfones, respectively, were adsorbed by a cellulose triacetate (CTA) membrane to investigate their effects on ionic transport through the membrane. The interface states between the membrane and the adsorption layer are discussed based on the measurements of contact angle and membrane potential and atomic force microscopy (AFM). The contact angle shows that the membrane changed from hydrophobic to hydrophilic due to adsorption of the above substances. AFM imaged the aggregates on the surface and showed that lysozyme, in particular, penetrates the membrane pores, making them shallower and decreasing their porosity. The results of membrane potential measurements showed that lysozyme and albumin did not change the membrane charge state, but PAS-H changed it from negative to positive. The permeability coefficients of KCl and K2HPO4varied significantly with the adsorption of each polyelectrolyte. In particular, the permeability coefficient of phosphate through the lysozyme-adsorbed membrane increased to twice that of the nonadsorbed membrane. Such polyelectrolyte adsorption on the membrane surface can be used for the modification of commercial artificial kidney phosphate extraction.

The membrane potential of a bipolar membrane prepared by plasma-induced grafted polymerization on porous polypropylene was measured. The membrane potentials were plotted as a function of the logarithmic or reciprocal solution concentration on the low concentration side of the cells. If the high concentration side is against the positively charged surface, the membrane potential monotonically decreases with a concentration increase. On the other hand, the membrane potential has a maximum if the high concentration side is against the negatively charged surface. As the concentration increases, both membrane potentials gradually approach each other. These are theoretically explained using the Donnan potentials of both surfaces and diffusion potential in the membrane where the intermediate part between the two surfaces is supposed to be neutral. The calculated result is in good agreement with the experimental one.

Model calculations concerning the membrane potential and ionic fluxes in weak amphoteric polymer membranes have been presented and the results were compared with recent experimental data obtained with a membrane which contains succinyl chitosan as ampholyte and poly(vinyl alcohol) as supporting matrix. The ion transport through the membrane has been described with the aid of the Nernst—Planck equations, and the results obtained explain satisfactorily the observed experimental trends in broad ranges of pH and electrolyte concentration. Also, the model predictions concerning the membrane isoelectric point may be useful for the analysis of future experiments.

Piezodialysis in weakly amphoteric polymer membranes is discussed from the viewpoint of non-equilibrium thermodynamics. Succinyl chitosans were used as the weak polyampholytes. With varying pH in the outer solution, the apparent isoelectric point of the membrane was defined as the point of zero membrane potential, where solute permeation is much enhanced. Piezodialysis was confirmed from the phenomenological hydraulic permeability coefficients, reflection coefficients and solute permeability coefficients of the membrane, which were based on non-equilibrium thermodynamics. Permeation experiments with mixed ion systems were also performed. The permeation behaviour was in accordance with that expected for the interactions of ions with polyampholytes in aqueous solutions.

It has been suggested that positively charged membranes are very effective to eliminate phosphate from blood in dialysis for patients. However, this type of hollow fiber membranes have been pointed out to bring about several problems, such as thrombus formation or hemolysis. In this paper, the ion transport across a membrane was computationally examined in the system of multicomponent dialyzer. In this calculation, partition and diffusion coefficients of phosphate ion were used as parameters. The efficiency of phosphate elimination could be increased even for membranes with negative charges.

Ultrathin, flexible and highly water-permeable nanostructured carbon (NC)-based membranes are formed on porous polymer supports by plasma high-power impulse magnetron sputtering in order to fabricate carbon-based membranes for water desalination. The carbon membranes are produced at room temperature using mixtures of argon (Ar), nitrogen (N2) and methane (CH4) as precursors, and this procedure constitutes a simple solvent-free, waste-free scalable process. Structural characterization, molecular simulation, water permeation and salt rejection assessments are used to correlate the performance and membrane structure. Molecular simulations indicate that nitrogen doping on the carbon-based membranes drastically modifies the pore distribution and avoids the formation of clustered regions of high-density carbons. The optimum NC-based membrane has up to 96% salt rejection rate for 0.2 wt% NaCl saline water, with high water permeability ca. 25 l m−2 h−1 MPa−1. The NC-based membranes as active layers for desalination membranes exhibit attractive characteristics which render them a potential alternative to current polymeric technology used in reverse osmosis processes. An ultrathin and flexible carbon-based membrane for desalination can reject up to 96% of salt impurities with high flow rates. Amorphous carbon thin films have a mix of diamond-like and graphite-like chemical bonds that give rise to intriguing applications in semiconductors and designer coatings. Now, Morinobu Endo of Shinshu University in Japan and colleagues has developed a procedure to induce special nanostructure into amorphous carbon membranes for use in water treatment. The team formed sputtered carbon layers by using a mixture of argon, nitrogen and methane gases onto a porous ultrafiltration polymer film using a rapid, high-powered plasma technique. Desalination tests showed that this simple and scalable technique produced robust membranes with high salt rejection rates, particularly when nitrogen dopants were incorporated into the amorphous carbon structure. Nitrogen doping of nanostructured carbon-based membranes allows to produce ultrathin reverse osmosis membranes, which exhibit high robustness for water desalination applications. Structural and chemical characterization, water permeation and salt rejection tests, and computational modeling of these carbon-based membranes is discussed. Their salt rejection performance and degradation resistance reveal a strong dependency on the amount of nitrogen doping within the carbon structure. The properties shown by our nanostructured carbon membranes render them a potential alternative to current polymer-based membranes.

A study of the effective charge density of a charged membrane composed of poly(vinyl alcohol) and poly(sulfonate) was carried out. The ratio of the effective charge density obtained from the membrane potential to the net charge density from pH titration was shown to be a function of degree of hydration (H). In order to explain the decrement of the ratio cited above as H increased, a model that includes two kinds of ionic fluxes within the membrane was introduced. This model was found to be able to give a qualitative explanation for the behaviour of the effective charge density of a charged membrane.

薄膜・チップ作製技術の一つであるエレクトロスプレーデポジション法 (Electro-spray Deposition; ESD) を用いてα-ラクトアルブミン, およびインベルターゼのチップを作製した. 電子顕微鏡観察の結果から, 溶質・スプレー時間・濃度の各因子は, チップ表面の構造に大きく影響することが明らかになった. チップ表面は主に粒子の積み重なりによりできており, 多孔質であった. 粒子の形状は溶質により異なり, α-ラクトアルブミンは不定形状, インベルターゼは球状であった.

Synthetic polymer membranes for gas separation continue to be the object of intensive research in the fields of physical and polymer chemistry, and chemical engineering. Investigation of separation coefficients of various gases is the most primitive method of evaluating membrane properties. However, the ratios of permeability coefficients of different gases are used for separation coefficients, since other measurements are so complicated. The gas permeability coefficients of dense membranes are functions of solubility and diffusion coefficients. Therefore measurements of sorption isotherm, diffusion and permeability coefficients are important in the understanding of the fundamentally properties of polymer membranes for gas separation.

The membrane potential and the permeability coefficient of ions in various kinds of electrolyte systems are investigated as a function of membrane charge density. The theoretical predictions in the previous paper [J. Membrane Sci., 49 (1990) 145] agree with the experimental data using membranes made from poly(vinyl alcohol) (PVA) and poly(styrenesulfuric acid) (PSSA) mixtures, and PVA and poly(allylamine) (PAAM) mixtures. The results show that the counterion with the highest valence is the most important for ion permeation phenomena in a multicomponent ion system ion system and that uphill transport of a bivalent counterion occurs because its concentration gradient in a charged membrane is in the opposite direction to its external concentration gradient.