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Meq G (meq + g)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Original Fuel-Cell Membranes from Crosslinked Terpolymers via a "Sol,gel" Strategy

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
Ozlem Sel
Abstract Hybrid organic/inorganic membranes that include a functionalized (-SO3H), interconnected silica network, a non-porogenic organic matrix, and a -SO3H-functionalized terpolymer are synthesized through a sol,gel-based strategy. The use of a novel crosslinkable poly(vinylidene fluoride- ter -perfluoro(4-methyl-3,6-dioxaoct-7-ene sulfonyl fluoride)- ter -vinyltriethoxysilane) (poly(VDF- ter -PFSVE- ter -VTEOS)) terpolymer allows a multiple tuning of the different interfaces to produce original hybrid membranes with improved properties. The synthesized terpolymer and the composite membranes are characterized, and the proton conductivity of a hybrid membrane in the absence of the terpolymer is promising, since 8,mS cm,1 is reached at room temperature, immersed in water, with an experimental ion-exchange-capacity (IECexp) value of 0.4,meq g,1. Furthermore, when the composite membranes contain the interfaced terpolymer, they exhibit both a higher proton conductivity (43,mS cm,1 at 65 °C under 100% relative humidity) and better stability than the standard hybrid membrane, arising from the occurrence of a better interface between the inorganic silica and the poly[(vinylidene fluoride)- co -hexafluoropropylene] (poly(VDF- co -HFP)) copolymer network. Accordingly, the hybrid SiO2 -SO3H/terpolymer/poly(VDF- co -HFP) copolymer membrane has potential use as an electrolyte in a polymer-electrolyte-membrane fuel cell operating at intermediate temperatures. [source]

Preparation and characterization of UV-grafted ion-exchange textiles in continuous electrodeionization

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2004
Kyeong-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]

Preparation of highly H+ permeable sulfonated poly(ether ether ketone) cation exchange membranes and their applications in electro-generation of thioglycolic acid

POLYMER INTERNATIONAL, Issue 7 2009
Xuehong Huang
Abstract BACKGROUND: Sulfonated poly(ether ether ketone) (SPEEK) was successfully synthesized from sulfonated 4,4,-difluorobenzophenone, 4,4,-difluorobenzophenone and bisphenol A. SPEEK cation exchange membranes were prepared by the casting method. The composition and morphology of SPEEK were characterized using Fourier transform infrared and 1H NMR spectroscopies, respectively. The ion exchange capacity (IEC), water uptake and degree of swelling of the membranes were also investigated. SPEEK120 was used as a separator in an electrolysis cell to produce thioglycolic acid (TGA). RESULTS: SPEEK polymerization was carried out at 145 and 175 °C for 10 h. The IEC of the SPEEK membranes was measured as 0.24,2.02 meq g,1 and the water uptake as 2.26,26.45%. The degree of swelling of the membranes was 1.71,15.28%. TGA was effectively prepared by electro-reduction of dithioglycolic acid. The current efficiency peaked at 58.31% at room temperature with a current density of 15 mA cm,2. CONCLUSION: SPEEK120 membrane shows good dimensional stability and H+ permeability. Compared to the traditional metal-reduction method, the current electro-reduction technique avoids the use of zinc powder and so reduces environmental pollution. Copyright © 2009 Society of Chemical Industry [source]

Polystyrene/Montmorillonite Nanocomposites Prepared by In Situ Intercalative Polymerization: Influence of the Surfactant Type

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2004
Hisham A. Essawy
Abstract Summary: Na-montmorillonite (MMT) with a cation exchange capacity (CEC) of 90 meq/100 g was converted to MMT-CTAB and MMT-CPC by the intercalation of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), respectively. The intercalation of CPC onto the basal space of the montmorillonite expanded the basal space from 12.19 to 21.47 Å, whereas in the case of CTAB, the spacing was only expanded to 19.35 Å. The MMT-CPC and MMT-CTAB forms were subsequently used as hosts for the preparation of polystyrene nanocomposites via intercalative free-radical polymerization of styrene. Different structures were obtained by varying the preparation conditions; the exfoliated and intercalated nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and differential scanning calorimeter (DSC). The produced nanocomposites exhibited improved thermal stability in comparison with that of pure polystyrene above 400,°C especially in the case of the nanocomposites based on the MMT-CPC, in which intercalation exists. A glass transition temperature (Tg) could not be detected for the prepared nanocomposites using DSC; this was assumed to result from the restricted molecular motion of the polymer chains. XRD pattern of PS nanocomposites prepared by intercalative polymerization. [source]