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Ion-exchange Capacity (ion-exchange + capacity)
Selected AbstractsEffect of molecular structure of hybrid precursors on the performances of novel hybrid zwitterionic membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Junsheng Liu Abstract Three types of novel hybrid zwitterionic membranes were prepared via a coupling reaction between two silane-coupling agents in a nonaqueous system and a subsequent reaction with 1,4-butyrolactone to create ion pairs in the hybrid precursors. FT-IR spectra corroborated the corresponding reactions. The synthesized membranes were characterized by thermal analyses, ion-exchange capacities, streaming potentials, and pure water flux. Thermal analyses exhibited that the degradation temperature of the hybrid precursors decreased with an increase in zwitterionic extent because of the introduction of ion pairs. Ion-exchange capacity measurements revealed that the anion-exchange capacities and cation-exchange capacities were in the range of 0.023,0.05 and 0.32,0.58 mmol g,1, respectively. Streaming potentials displayed that when the membranes coated for one or three times, the isoelectric points were in the pH range of 6.6,7.58 and 6.58,7.7, respectively. The pure water flux showed that it could be affected by the coating times and the ingredients of these zwitterionic membranes. This difference in membrane's characteristics can be ascribed to the effect of molecular structure of the hybrid precursors. Both the Coulombic interactions of ion pairs between the polymer chains and the hydrophilicity of these membranes were proposed to clarify the above phenomena. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Highly Stable Nickel Hexacyanoferrate Nanotubes for Electrically Switched Ion Exchange,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007W. Chen Abstract Nickel hexacyanoferrate (NiHCF) nanotubes are fabricated by an electrokinetic method based on the distinct surface properties of porous anodic alumina. By this method, nanotubes can be formed rapidly with the morphologies faithfully replicating the nanopores in the template. The prepared nanotubes were carefully characterized using SEM and TEM. Results from IR, UV, EDX, and electrochemical measurements show that the NiHCF nanotubes exist only in the form of K2Ni[Fe(CN)6]. Because of this single composition and unique nanostructure, NiHCF nanotubes show excellently stable cesium-selective ion-exchange ability. The capacity for electrodes modified with NiHCF nanotubes after 500,potential cycles retains 95.3,% of its initial value. Even after 1500 and 3000 cycles, the NiHCF nanotubes still retain 92.2,% and 82.9,%, respectively, of their ion-exchange capacity. [source] Effect of addition of organic microspheres on proton conductivity property of sulfonated poly(arylene ether sulfone) membraneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Cui Liang Abstract Sulfonated poly(arylene ether sulfone) (SPAES)/polystyrene(PS) and SPAES/polystyrene sulfonic acid (PSSA) composite membranes were studied for a proton-exchange membrane used in a fuel cell. PS microspheres were synthesized by emulsion polymerization. PSSA microspheres with 5.3 mmol/g ion-exchange capacity (IEC) were prepared by sulfonation of PS microspheres. The composite membranes were prepared by solution casting. SPAES/PSSA composite membranes showed higher proton conductivity than a SPAES membrane because of the IEC improved by adding PSSA. Although the addition of PSSA also brought about the increase of a methanol permeability, the proton/methanol selectivity defined as the ratio of the proton conductivity to the methanol permeability was improved at low humidity by adding 5 wt % of PSSA microspheres. Differential scanning calorimetry results indicated that the amount of free water varied in the cases of the addition of the two kinds of organic microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation and characterization of UV-grafted ion-exchange textiles in continuous electrodeionizationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2004Kyeong-Ho Yeon Abstract Ion-exchange textiles (IETs) suitable for use in continuous electrodeionization (CEDI) stacks were prepared using the ultraviolet (UV)-induced grafting of acrylic acid and sodium styrene sulfonate for cation-exchange textiles, or 2-hydroxyethyl methacrylate and vinylbenzyl trimethyl ammonium chloride for anion-exchange textiles, onto nonwoven polypropylene fabric using benzophenone as photoinitiator. Although the ion-exchange capacity (2.2 meq g,1) of the prepared strong acid cation-exchange textile was lower than that of IRN77 strong acid cation-exchange resin (4.2 meq g,1), the overall rate constant of IET was very high due to its low crosslinking and high specific surface area. There was no significant difference between the two different media in terms of the Co(II) removal rate. Furthermore, the current efficiency for IETs was higher than that of IRN77 cation-exchange resin during a CEDI operation, with efficiencies of 60% and 20%, respectively. The IET also showed the faster exchange kinetics. Therefore, IETs prepared in this study proved to have desirable ion-conducting characteristics within the CEDI systems. Also this study revealed that the primary removal mechanism in CEDI is the transport of ions through a medium and not the ionic capacity of a medium. Copyright © 2004 Society of Chemical Industry [source] Effect of ion-exchange fiber structure on the binding and release of model salicylatesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2005Kaisa R. Hänninen Abstract Salicylates were used as model anions to evaluate the effect of the structure (framework and ion-exchange groups) of fibrous anion-exchangers on the extent and mechanism(s) of compound binding and release. Binding was affected by the physicochemical properties of both the salicylates and the ion-exchange fibers. The highest molar amount of binding was obtained with the most lipophilic salicylate (5-chlorosalicylic acid) and the weak base (vinylpyridine) anion-exchange fibers. However, when the ion-exchange capacity was taken into account, higher binding was obtained in fibers of poly(ethylene) framework compared to the viscose-based fibers. The extent of salicylate release into NaCl solution(s) was dependent on the physicochemical characteristics of both the fiber and the bound model salicylate as well as on the amount of extracting ions. With strong base fibers (trimethylammonium), the viscose framework released the salicylates more efficiently than the poly(ethylene) framework. In the case of weak base fibers, the poly(ethylene) framework released the salicylates to a higher extent than the viscose framework. Calculated equilibrium constants (K) of the ion-exchange reactions illustrated that in addition to electrostatic interactions (pure ion-exchange mechanism), non-electrostatic interactions (hydrophobic interactions and/or hydrogen bonding) were also involved. However, the release of the salicylates was efficiently modified by the amount of extracting electrolyte, demonstrating that ion-exchange was the prevalent release mechanism. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1772,1781, 2005 [source] Sulfonated naphthalene dianhydride based polyimide copolymers for proton-exchange-membrane fuel cells.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Abstract A novel sulfonated diamine, 3,3,-disulfonic acid-bis[4-(3-aminophenoxy)phenyl]sulfone (SA-DADPS), was prepared from m -aminophenol and disodium-3,3,-disulfonate-4,4,-dichlorodiphenylsulfone. The conditions necessary to synthesize and purify SA-DADPS in high yields were investigated in some detail. This disulfonated aromatic diamine, containing ether and sulfone linkages, was used to prepare N -methyl-2-pyrrolidinone-soluble, six-membered ring polyimide copolymers containing pendent sulfonic acid groups by a catalyzed one-step high-temperature polycondensation in m -cresol. These materials showed much improved hydrolytic stability with respect to phthalimides. High-molecular-weight film-forming statistical copolymers with controlled degrees of disulfonation were prepared through variations in the stoichiometric ratio of disulfonated diamine (SA-DADPS) in its soluble triethylamine salt form to several unsulfonated diamines. Three unsulfonated diamines, bis[4-(3-aminophenoxy)phenyl] sulfone, 4,4,-oxydianiline, and 1,3-phenylenediamine, were used to prepare the copolymers. The characterization of the copolymers by 1H NMR, Fourier transform infrared, ion-exchange capacity, and thermogravimetric analysis demonstrated that SA-DADPS was quantitatively incorporated into the copolymers. Solution-cast films of the sulfonated copolymers were prepared and afforded tough, ductile membranes with high glass-transition temperatures. Methods were developed to acidify the triethylammonium salt membranes into their disulfonic acid form, this being necessary for proton conduction in a fuel cell. The synthesis and characterization of these materials are described in this article. Future articles will describe the performance of these copolymers as proton-exchange membranes in hydrogen/air and direct methanol fuel cells. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 862,874, 2004 [source] Mixed-mode ion-exchangers and their comparative chromatographic characterization in reversed-phase and hydrophilic interaction chromatography elution modesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2008Michael Lämmerhofer Abstract A set of particulate silica-supported mixed-mode RP/weak anion-exchangers (RP/WAX) (obtained by bonding of N -undecenoylated 3-aminoquinuclidine, 3-aminotropane and 2-dimethylaminoethylamine as well as of N -butenoyl-(2S,4S,5R)-2-aminomethyl-5-[(2-octylthio)ethyl]-quinuclidine to thiol-modified silica) were chromatographically characterized in comparison to selected commercially available columns using two distinct isocratic elution modes, viz. an aqueous-rich RP-type elution mode (with 40% ACN and 60% buffer) as well as an organic solvent-rich hydrophilic interaction chromatography (HILIC)-type elution mode (95 and 90% ACN). The mixed-mode RP/WAX phases showed multimodal applicability, unlike a polar embedded RP material (Synergi Fusion RP), amino phases (Luna NH2, BioBasic AX) or typical HILIC packings (ZIC-HILIC, TSKGel Amide-80). Principal component analysis (PCA) of the RP test data confirmed that the in-house developed RP/WAX columns as well as the Acclaim Mixed-Mode WAX-1 phase resemble each other in their chromatographic characteristics having slightly lower hydrophobic selectivity (,CH2 of 1.5) than the tested Synergi Fusion RP (,CH2 ,1.8). In contrast, a decrease in mixed-mode character due to lowered ion-exchange capacity and concomitantly increased RP-like behavior could be identified for other mixed-mode phases in the order of Obelisc R > Primesep B2 > Uptisphere MM3. PCA on HILIC data revealed that the RP/WAX phases behave dissimilar to TSKGel Amide-80, ZIC-HILIC and polysulfoethyl A under the chosen elution conditions. Hence, they may be regarded as complementary to these commercial stationary phases with applicability profiles for hydrophilic but also hydrophobic solutes. [source] Ionic Polymer-Metal Composite Actuators Employing Radiation-Grafted Fluoropolymers as Ion-Exchange MembranesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2006Man Jae Han Abstract Summary: To develop ionic polymer-metal composites (IPMC) with improved performance, three new ion-exchange membranes were prepared and employed in IPMC construction. The membranes were prepared by radiation-grafting of polystyrene sulfonic acid onto three fluoropolymers; poly(vinylidenefluoride- co -hexafluoropropylene), poly(ethylene- co -tetrafluoroethylene), and poly(tetrafluoroethylene- co -hexafluoropropylene). The bending displacements of the IPMCs constructed with these membranes were at least several times larger than that of Nafion IPMC of similar thickness without straightening-back. The larger displacement was considered to be due to the higher concentration of ionic groups and consequent larger ion-exchange capacity. Actuation of (a) Nafion IPMC and (b) IPMC prepared in this study. [source] | |||||||||||||