Increasing Oxide Content Research Articles

The anti-inflammatory and antinociceptive effects of NF-κB inhibitory guanidine derivative ME10092

The guanidine compound ME10092 (1-(3,4-dimethoxy-2-chlorobenzylideneamino)-guanidine) is known to possess anti-radical and anti-ischemic activity but its molecular targets have not been identified. This study investigated whether ME10092 regulates the nuclear factor kappa B (NF-κB)-mediated signal transduction in vivo. The effect of ME10092 treatment (1–100 pmol/mouse) on nuclear translocation of NF-κB, activation of expression of inflammatory mediators and production of nitric oxide were measured in the lipopolysaccharide (LPS)-induced brain inflammation model in mice in vivo. The antinociceptive activity of ME10092 was tested in the formalin-induced paw licking test. ME10092 dose-dependently inhibited LPS-induced nuclear translocation of NF-κB, transcription of tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Electron paramagnetic resonance measurements showed that ME10092 inhibited the LPS-induced increase in nitric oxide content in mouse brain tissue in a dose-dependent manner. In the formalin-induced paw licking test, ME10092 (at the dose of 3 mg/kg, p.o. twice daily for eight days) significantly reduced nociceptive response. In conclusion, above results indicate that ME10092 inhibits NF-κB activation and suppresses the up-regulation of inflammatory mediators in experimental models in vivo.

Structural special features in nanodispersed Ni-SiO2 composite materials produced by method of chemical dispersion

The method of chemical dispersion with the use of inexpensive and available initial components is applied to obtain nanodispersed composite powders based on nickel and silicon oxide of various compositions. The methods of X-ray diffraction, electron microscopy, thermogravimetry, and low-temperature adsorption are used to determine the optimum modes of obtaining nanopowders as well as the dependence of their structure and dispersion ability on composition and conditions of metallization. It is shown that the increase in silicon oxide content in samples up to 30 wt % leads to almost complete suppression of the process of sintering and recrystallization of nickel particles at temperatures of 500–600°C. The microscopic studies make it possible to establish that temperature stability of the material is provided by the presence of a gaspermeable envelope of silicon oxide nanoparticles on the surface of nickel particles. The results show that these materials are promising for use as catalysts in various fields, including the processes of synthesis of carbon nanomaterials by the method of catalytic pyrolysis of methane.

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass–ceramics having iron oxide

The effect of ZnO on phase emergence and microstructure properties of glass and glass–ceramics with composition 25SiO 2–50CaO–15P 2O 5–(10 − x)Fe 2O 3– xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass–ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass–ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 °C calcium phosphate, hematite and magnetite are developed as major phases in the glass–ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca 3Si 2O 7) phase is also observed when glass is heat treated at 1000 °C. The microstructure of the glass–ceramics heat treated at 800 °C exhibits the formation of nano-size (40–50 nm) grains. On heat treatment at 1000 °C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration ( x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca–P-rich layer on the glass–ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

Surface and Bulk Aspects of Mixed Oxide Catalytic Nanoparticles: Oxidation and Dehydration of CH3OH by Polyoxometallates

The molecular structures and surface chemistry of mixed metal oxide heteropolyoxo vanadium tungstate (H(3+x)PW(12-x)V(x)O(40) with x = 0, 1, 2, and 3) Keggin nanoparticles (NPs), where vanadium is incorporated into the primary Keggin structure, and supported VO(x) on tungstophosphoric acid (TPA, H(3)PW(12)O(40)), where vanadium is present on the surface of the Keggin unit, were investigated with solid-state magic angle spinning (51)V NMR, FT-IR, in situ Raman, in situ UV-vis, CH(3)OH temperature-programmed surface reaction (TPSR), and steady-state methanol oxidation. The incorporated VO(x) unit possesses one terminal V horizontal lineO bond, four bridging V-O-W/V bonds, and one long V-O-P bond in the primary Keggin structure, and the supported VO(x) unit possesses a similar coordination in the secondary structure under ambient conditions. The specific redox reaction rate for VO(x) in the Keggin primary structure is comparable to that of bulk V(2)O(5) and the more active supported vanadium oxide catalysts. The specific acidic reaction rate for the WO(x) in the TPA Keggin, however, is orders of magnitude greater than found for bulk WO(3), supported tungsten oxide catalysts, and even the highly acidic WO(3)-ZrO(2) catalyst synthesized by coprecipitation of ammonium metatungstate and ZrO(OH)(2). From CH(3)OH-TPSR and in situ Raman spectroscopy it was found that incorporation of vanadium oxide into the primary Keggin structure is also accompanied by the formation of surface VO(x) species at secondary sites on the Keggin outer surface. Both CH(3)OH-TPSR and steady-state methanol oxidation studies demonstrated that the surface VO(x) species on the Keggin outer surface are significantly less active than the VO(x) species incorporated into the primary Keggin structure. The presence of the less active surface VO(x) sites in the Keggins, thus, decreases the specific reaction rates for both methanol oxidation and methanol dehydration. During methanol oxidation/dehydration (O(2)/CH(3)OH = 2.17, T = 225 degrees C), in situ UV-vis diffuse reflectance spectroscopy revealed that vanadium oxide is primarily present as the V(+5) cation, which reflects the Mars-van Krevelen redox mechanism and rapid reoxidation by molecular O(2). The bulk TPA Keggin structure becomes more disordered and less thermally stable as the vanadium content increases. Although surface polyaromatic carbon forms during methanol oxidation on the Keggin surfaces, its influence on the reaction kinetics seems minimal as the carbon content diminishes as the vanadium oxide content increases and the reaction temperature is raised. No relationships were found between the electronic structure (UV-vis E(g) values) and TOF(redox) and TOF(acid) (TOF = turnover frequency) kinetics, which reflect the complexity of H(3+x)PW(12-x)V(x)O(40) Keggins. The overall catalytic performance of the H(3+x)PW(12-x)V(x)O(40) Keggin materials results from a complex interplay among the presence of redox vanadium (as secondary surface VO(x) species and substituted VO(x) sites in the primary Keggin NP structure), structural disorder of the Keggin NPs, exposed surface acid and redox sites, and coke deposition. These new insights reveal that the Keggin heteropolyoxometallates are much more complex than originally thought and that care must be taken in using Keggins as model mixed metal oxide NPs in catalytic kinetic and theoretical studies because their surface and bulk structures are dynamic under the reaction conditions.

Preparation and study of magnetic properties of silico phosphate glass and glass-ceramics having iron and zinc oxide

The magnetic properties of 25SiO 2–50CaO–15P 2O 5–(10− x)Fe 2O 3− xZnO (where x=0, 2, 5 mol%) glass and glass-ceramics have been studied. These glasses are prepared by melt quench technique and heat treated at 800 °C for 6 h. Electron Spectroscopy for Chemical Analysis (ESCA) revealed that the fraction of non-bridging oxygen decreases with the increase in zinc oxide content. Evolution of crystalline phases in glass-ceramics has been studied by X-ray diffraction (XRD). The microstructure as seen by scanning electron microscopy (SEM) exhibits formation of nanosize particles. Effect of controlled heat treatment on magnetic properties was studied by means of a Superconducting Quantum Interference Device (SQUID) magnetometer. Mössbauer spectroscopy at room temperature was also carried out to determine the state of iron ions in glasses and glass-ceramics. Isomer shift values of the glasses suggest that Fe 3+ and Fe 2+ are in tetrahedral coordination. The analysis of the glass without ZnO shows about 58 wt% of total iron ions is in the Fe 3+ state. The samples on heat treatment show improved magnetic properties due to the formation of magnetic nanoparticles. Magnetic studies revealed the relaxation of magnetic particles and the increase in saturation magnetization with addition of 2 mol% ZnO. Increase in ZnO content results in decrease in the strength of dipolar interactions.

Effect of physical exercise on tumor growth regulating factors of tumor microenvironment: Implications in exercise-dependent tumor growth retardation

Recently, we reported that treadmill exercise renders survival benefits in a murine tumor model of a transplantable lymphoma of spontaneous origin, designated as Dalton’s lymphoma (DL), owing to an augmented apoptosis of tumor cells. However, the underlying the mechanisms of the same remained unclear with respect to the role alterations if any in the components of tumor microenvironment following physical exercise. Therefore, in the present we investigated the role of oxygen, pH, lactate and cytokines of tumor micro-environment associated with physical exercise-dependent alteration in the growth properties of tumor cells to explore their contribution in modulation of tumor. Physical exercise of tumor-bearing host resulted in a decreased angiogenesis in the vicinity of tumor. This was also found to be accompanied by a decrease in erythrocyte count and increase in the level of oxygen while the content of lactate showed a concomitant decrease in the tumor microenvironment along with normalization of pH. Moreover, physical exercise also resulted in an inhibition of VEGF expression which was correlated to an altered expression of cytokines: IL-1, IL-4, IL-10, TGF-β and IFN-γ. Ascitic fluid of tumor-bearing host subjected to physical exercise showed an increase in nitric oxide content along with an increase in the expression of inducible nitric oxide synthase (iNOS). The study discusses the possible role of the aforesaid alterations in constituents of tumor microenvironment of tumor-bearing host following physical exercise in retardation of tumor growth.

Nitric oxide signals ROS scavenger-mediated enhancement of PAL activity in nitrogen-deficient Matricaria chamomilla roots: side effects of scavengers

Owing to the abundance of phenolic metabolites in plant tissue, their accumulation represents an important tool for stress protection. However, the regulation of phenolic metabolism is still poorly known. The regulatory role of reactive oxygen species (ROS) in the activity of phenylalanine ammonia-lyase (PAL) in nitrogen (N)-deficient chamomile roots treated for 24 h was studied using three ROS scavengers [dithiothreitol (DTT), salicylhydroxamic acid, and sodium benzoate]. Scavengers decreased the level of hydrogen peroxide and/or superoxide (and up-regulated ascorbate/guaiacol peroxidase and glutathione reductase), but, surprisingly, stimulated PAL activity. This up-regulation was correlated with increases in nitric oxide (NO) content, total soluble phenols, selected phenolic acids, and, partially, lignin (being expressed the most in DTT-exposed roots). We therefore tested the hypothesis that NO may be involved in these changes. Application of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) decreased PAL activity and the accumulation of soluble phenols in all treatments. Exogenous H 2O 2 and NO also stimulated PAL activity and the accumulation of phenols. We conclude that NO, in addition to hydrogen peroxide, may regulate PAL activity during N deficiency. The anomalous effect of PTIO on NO content and possible mechanism of ROS scavenger-evoked NO increases in light of the current knowledge are also discussed.

Effect of feldspar concentrate on the chemical resistance of acid-resistant materials prepared on the basis of argillaceous materials of different chemical and mineral composition

Research shows that introduction of feldspar concentrate into the composition of ceramic mixes improves mullite crystallization, and this promotes an increase in the acid resistance of refractory materials. An increase in iron oxide content reduces the acid resistance of refractory materials since it does not promote an improvement in mullite lattice crystallization.

Optical and structural properties ofZnO–PbO–B2O3 and ZnO–PbO–B2O3–SiO2 glasses

Borate and borosilicate glasses with compositions ofxZnO–2xPbO–(1−3x)B2O3 and xZnO–2xPbO–1/2(1−3x)B2O3–1/2(1−3x)SiO2 with x varying from 0.1 to 0.26 mole fraction were prepared by the conventional meltquench technique. Optical and structural properties have been determined by usingultraviolet–visible (UV/vis) and Fourier transform infrared (FTIR) spectroscopictechniques. Decreases in the band gap from 3.57 to 2.62 eV for borate glasses and from 3.00to 2.35 eV for borosilicate glasses with an increase in the metal oxide content is observed.The density and molar volume has also been measured. Increases in density from 3.994 to6.339 g cm−3 for borate andfrom 4.221 to 6.548 g cm−3 for borosilicate glasses are observed with an increase in metal oxide (PbO, ZnO orPbO+ZnO)content. Changes in the atomic structure with composition are observed due to the formation ofBO4− units.

A pulsing electric field (PEF) increases human chondrocyte proliferation through a transduction pathway involving nitric oxide signaling

A potential treatment modality for joint pain due to cartilage degradation is electromagnetic fields (EMF) that can be delivered, noninvasively, to chondrocytes buried within cartilage. A pulsed EMF in clinical use for recalcitrant bone fracture healing has been modified to be delivered as a pulsed electric field (PEF) through capacitive coupling. It was the objective of this study to determine whether the PEF signal could have a direct effect on chondrocytes in vitro. This study shows that a 30-min PEF treatment can increase DNA content of chondrocyte monolayer by approximately 150% at 72 h poststimulus. Studies intended to explore the biological mechanism showed this PEF signal increased nitric oxide measured in culture medium and cGMP measured in cell extract within the 30-min exposure period. Increasing calcium in the culture media or adding the calcium ionophore A23187, without PEF treatment, also significantly increased short-term nitric oxide production. The inhibitor W7, which blocks calcium/calmodulin, prevented the PEF-stimulated increase in both nitric oxide and cGMP. The inhibitor L-NAME, which blocks nitric oxide synthase, prevented the PEF-stimulated increase in nitric oxide, cGMP, and DNA content. An inhibitor of guanylate cyclase (LY83583) blocked the PEF-stimulated increase in cGMP and DNA content. A nitric oxide donor, when present for only 30 min, increased DNA content 72 h later. Taken together, these results suggest the transduction pathway for PEF-stimulated chondrocyte proliferation involves nitric oxide and the production of nitric oxide may be the result of a cascade that involves calcium, calmodulin, and cGMP production.

Non-linear absorption and second harmonic imaging of Zn–BaTiO 3 thin films prepared by laser ablation

Zinc-doped barium titanate samples have been prepared on Corning glass as well as on silicon wafer by laser ablation. Samples on glass having different deposition time and varying zinc oxide content have been studied by Z-scan technique at a wavelength of 540 nm and laser intensity of 20 GW while samples on silicon have been characterized by second harmonic (SH) imaging as a function of zinc content. The result on Z-scan measurements shows that films doped with 1 wt.% ZnO and deposited for a period of 80, 100 and 180 min respectively exhibit non-linear absorption with the maximum non-linear absorption coefficient ( β max) of 800 cm/GW. The undoped as well as samples of BaTiO 3 doped with 3, 4 and 5 wt.% ZnO with deposition time of 60 min each exhibit non-linear saturation with the sample containing 5 wt.% ZnO having the lowest value of − 5.9 × 10 2 cm/GW, which signifies that an increase in zinc oxide content leads to a reduction in the observed bleaching effect. In addition, it is also suggested that switching from non-linear absorption to non-linear saturation is probably due to thickness effect. The SH imaging has shown the location dependence of the films, which we assume may be due to the geometry of the deposition module and crystal growth through the formation of small crystallites as the building block of the films.

Neuroprotective effects of cactus polysaccharide on oxygen and glucose deprivation induced damage in rat brain slices.

1. The neuroprotective effect of cactus polysaccharide (CP) on oxygen and glucose deprivation (OGD) and reoxygenation (REO)-induced damage in the cortical and hippocampal slices of rat brain was investigated. 2. Cell viability was evaluated by using the 2, 3, 5-triphenyl tetrazolium chloride (TTC) method. The fluorescence of propidium iodide (PI) staining was used for quantification of cellular survival, and lactate dehydrogenase (LDH) activity in incubation medium was assessed by LDH assay to evaluate the degree of injury. 3. The OGD ischemic condition significantly decreased cellular viability and increased LDH release in the incubation medium. CP (0.2 mg/l approximately 2 mg/l) protected brain slices from OGD injury in a dosage dependent manner as demonstrated by increased A 490 value of TTC, decreased PI intensity and LDH release. At the above concentration, CP also prevented the increase of nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity induced by OGD. 4. CP can protect the brain slices (cortical and hippocampus) against injury induced by OGD. Its neuroprotective effect may be partly mediated by the NO/iNOS system induced by OGD insult.

Surface structure and properties of mixed fumed oxides

A variety of fumed oxides such as silica, alumina, titania, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST) were characterized. These oxides have different specific surface areas and different primary particle composition in the bulk and at the surface. These materials were studied by FTIR, NMR, Auger electron spectroscopy, one-pass temperature-programmed desorption with mass spectrometry control (OP TPDMS), microcalorimetry, and nitrogen adsorption. Nonlinear changes in the surface content of alumina in SA and AST and titania in ST and AST samples with increasing oxide content along with simultaneous changes in their specific surface area cause complex dependencies of the heat of immersion in water and desorption of water on heating on the structural parameters. Simultaneous analysis of changes in the surface phase composition, in the concentration of hydroxyls, and in the structural characteristics reveals that at a low content of the second phase the structural characteristics (e.g., S BET ) are predominant; however, at a large content of these oxides the phase composition plays a more important role.

Effects of Nitroglycerin on Erythrocyte Rheology and Oxygen Unloading

We hypothesized that nitroglycerin improves O2 delivery to ischemic tissue by altering erythrocyte rheology and O2 unloading through an increase in bioactive nitric oxide (NO) content. Twelve dogs with resting flow-reducing single-vessel stenosis were studied at rest and during intracoronary infusion of nitroglycerin (0.3 to 0.6 microg.kg(-1).min(-1)). Half the dogs also had occlusion of the remote coronary artery to remove any collateral effects. Systemic and coronary hemodynamics, myocardial blood flow (MBF), whole blood viscosity (WBeta), erythrocyte charge (EC) and mobility (EM), regional myocardial O2 delivery and consumption, and tissue O2 pressure (Po2) were measured. No changes in systemic hemodynamics were seen with nitroglycerin. Despite flow-limiting stenosis, MBF increased significantly in the central 25% of the ischemic bed, which was associated with an approximately 19% decrease in WBeta. There was a good correlation (r=0.87) between the two. The decrease in WBeta was associated with a decrease in EC and an increase in EM (r=0.83). The nitroglycerin-induced increase in tissue Po2 was disproportionate to the increase in MBF, indicating enhanced O2 unloading. Erythrocyte S-nitrosothiol content (reflecting mainly S-nitrosohemoglobin) was significantly higher for blood exposed in vitro to 0.1 micromol/L nitroglycerin or the NO donor SNAP, as compared with control (18.9+/-8.8 and 10.5+/-6.5 versus 2.6+/-0.5x10(-5), P<0.05). The augmented MBF in the ischemic microcirculation during nitroglycerin administration occurs in tandem with increased erythrocyte S-nitrosothiol content, EM, and O2 unloading. These additional microvascular mechanisms may contribute to the powerful antiischemic effects of nitroglycerin, especially during low-flow states.

Studies on lattice thermal expansion and XPS of ThO 2[sbnd]NdO 1.5 solid solutions

The lattice parameter changes with respect to temperature ( T) have been measured by high temperature X-ray diffraction (HTXRD) technique for ThO 2 NdO 1.5 solid solutions containing 23.8 and 42.5 mol% NdO 1.5 in the temperature range from 298 to 2000 K. The temperature versus lattice parameter data have been made use of in calculating the lattice thermal expansivity. The values of thermal expansion of the solid solutions were found to be increased with increase in neodymium oxide content and temperature. The mean linear thermal expansion coefficients in this temperature range for ThO 2 NdO 1.5 solid solutions are 12.28 × 10 −6 and 12.90 × 10 −6 K −1, respectively. The binding energies of Th 4f 7/2 and Nd 3d 5/2 energy levels of the solid solutions containing 13.1, 23.8, 31.9, 37.2 and 42.5 mol% NdO 1.5 and two-phase mixtures containing 47.6 and 51.8 mol% NdO 1.5 were experimentally determined by X-ray photoelectron spectroscopy (XPS).

Relationship between the Thermal Expansion Coefficient and the Composition for R&lt;sub&gt;2&lt;/sub&gt;O-MO-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; System Glass

The R2O-MO- Al2O3-SiO2 system glasses were prepared by conventional melt quenching technology. The composition mass fraction range of the glass is SiO2 (55%∼65%), MgO (0%∼15.2%), CaO (0%∼15.2%), SrO (0%∼15.2%), BaO (0%∼15.2%), Na2O (0%∼15.6%), K2O (0%∼15.6%). The relationship between the composition and the thermal expansion coefficient of the glass was investigated by comparing the thermal expansion coefficients of the glasses with different chemical composition. The results show that the thermal expansion coefficient of the glass increases sharply with the increase of alkali-metal oxide content and when K+, Na+ and Li+ exist simultaneously in the structure of the glass, the complex “mixed alkali effect” can be observed from the composition–thermal expansion coefficient curve. When introducing different kind but same quantity alkaline-earth metal oxide, the thermal expansion coefficient of the glasses increased obviously with the rising of the radius of alkaline-earth metal ions but the “mixed alkali effects” can also be observed for the glasses containing a few kinds of alkaline-earth metal oxides.

DMFC용 PVDF/SPEEK/TiO2하이브리드 막의 수분함량과 메탄올 전이현상

유 무기 혼성 막의 계열은 티타니움 디옥사이드 나노파티클 함량의 체계적인 변화에 의해 조제된다. 유 무기 혼성 막의 수분함량, 메탄올 투과도와 전자 전도 특성은 무기 산화물의 함량의 기능에 따라 연구된다. 그 결과 망상구조의 무기 산화물은 전자 전도 특성과 수분함량의 감소를 보였다. 또한 무기 산화물의 함량이 증가할수록 메탄올 투과도도 감소함을 나타내었다. 형태학적인 관점에서 막은 폴리머 기반과 무기영역 사이에 균일하고 잘 점착됨을 보여준다. 혼성막의 특성은 나피온막과 비교 실험되었다. A series of inorganic-organic hybrid membranes were prepared with a systematic variation of titanium dioxide nano particles content. Their liquid uptake, methanol permeability and proton conductivity as a function of inorganic oxide content were investigated. The results obtained show that the inorganic oxide network decreases the proton conductivity and liquid uptake. It is also found that increase in inorganic oxide content leads to decrease of methanol permeability. In terms of the morphology, membranes are homogeneous and exhibit a good adhesion between inorganic domains and the polymer matrix. The properties of the composite membranes are compared with the standard nafion membrane.

Microstructure, mechanical properties, and adhesion in IN625 air plasma sprayed coatings

The effects of feed stock particle size on the microstructure and the mechanical properties of IN625 air plasma sprayed coatings were investigated. It was found that the porosity increases with the particles size while the oxide content rises with decreasing particle size. Because of the lower velocity of large particles, these produce weakly bonded splats resulting in coatings with low elastic modulus, low residual stresses, small oxide content, and low hardness. The porosity is high and it is largely comprised of surface connected pores. Small particles produce splats that are bonded through oxide layers. Due to higher particle speed the porosity and the fraction of connected pores are low. The small porosity produces a relatively large value of Young's modulus and high residual stresses. The hardness increases as the porosity decreases and the oxide content increases. The coating adhesion exhibits a maximum at intermediate particle sizes. This is caused by the limiting effect of the oxide content for small particles and the limiting effect of low particle velocities for large particles.

Nanosized TiO2‐filled sulfonated polyethersulfone proton conducting membranes for direct methanol fuel cells

AbstractThis paper presents an evaluation of the effect of titanium dioxide nanoparticles in sulfonated polyethersulfone with sulfonation degree of 70%. A series of inorganic–organic hybrid membranes was prepared with a systematic variation of titanium dioxide nanoparticles content. Their water uptake, methanol permeability, and proton conductivity as a function of temperature were investigated. The results show that the inorganic oxide network decreases the proton conductivity and water swelling. Increase in inorganic oxide content leads to decrease of methanol permeability. In terms of morphology, membranes are homogeneous and exhibit good adhesion between inorganic domains and the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1875–1878, 2005

Dielectric enhancement in polymer-nanoparticle composites through interphase polarizability

Dielectric measurements on polyimide-oxide nanoparticle composite thin films show a composite dielectric constant (εcomposite) that increased monotonically with increasing oxide content well above the value predicted by Maxwell’s rule for dielectric mixtures below the percolation threshold. Above certain volume fractions, the measured εcomposite values were found to exceed the corresponding nanoparticle ε such that εpolymer&amp;lt;εparticle&amp;lt;εcomposite contrasted to conventional composites where εpolymer&amp;lt;εcomposite&amp;lt;εparticle. The εcomposite was independent of frequency to 10MHz with dielectric loss of &amp;lt;0.005 throughout this range, indicating that the observed enhancement in ε does not originate from space-charge related contributions and hence should be due to dipolar contributions. The observed ε enhancement (εcomposite−εMaxwell) showed a correlation with the total surface area of the nanoparticles. The dielectric model of Vo and Shi [Microelectron. J. 33, 409 (2002), and references therein] showed that the enhanced dielectric behavior originates from significant interfacial nanoparticle-polymer interactions and the critical role of additional contributions to polarizability through specific physicochemical interactions within the interphase region. An interphase εint considerably higher than that of the nanoparticle and a high interface interaction constant of 3.24 for the nanocomposite suggest a strong interaction between the functional groups of the polymer and the nanoparticle surface. Although modeling suggests a maximum of ε∼65vol%, loss in micromechanical stability occurred above 20% due to incomplete polymer wetting films arising from the high nanoparticle surface areas.