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Tungsten trioxide (WO3) is a well-known electroactive substance that stores electrochemical energy and changes color reversibly due to redox events triggered by a certain voltage and has a wide range of uses. In this research work, thin films of WO3 were prepared using spin-coating of additive free WO3 sols. The sols were prepared from tungstic acid precursor, purified through ion-exchange method, under hydrothermal conditions. Particle size of the suspensions and phase of the thin films prepared from suspensions, were evaluated using laser particle analyzer and XRD, respectively. Cyclic voltammetry was used to conduct electrochemical behavior of the synthesized material. Thin films obtained under hydrothermal temperature of 120 ℃ possessed the optimum particle size distribution centered around 80 nm, optimum crystallite size and superior electrochemical performance. [ABSTRACT FROM AUTHOR]

Lyophilic microgels based on Gum Acacia (GAC) were synthesized at room temperature and normal pressure. Briefly, high yield of the spherical shaped microgels of size ≤ 50 µm was obtained via introducing linear GAC and divinyl sulfone (DS) in the reverse micelle cores of NBSS in the stirring gasoline. The GAC microgels were then utilized as synthetic micro-templates for fabricating their nanocomposites with Cobalt (Co), to subsequently produce GAC-Co nanocomposite microgels. The as synthesis GAC based microgels and the GAC-Co microgels were characterized through FTIR, TGA, DSC, SEM, EDS, and TEM. Different amounts of GAC-Co microgels were used as nano-catalyst for the degradation of poisonous aromatic compounds and an Azo dye in aqueous medium. Briefly, 1 g GAC-Co microgels degraded 100 mL (250 ppm solution) of each the aforementioned compounds in ≤ 25 min at neutral pH. The increase in the kinetic parameter i.e., rate constant (kapp) value with increase in the GAC-Co nanocomposite microgels amounts manifests the positive impact of the fabricated nano-catalyst on these compounds degradation at room temperature. [ABSTRACT FROM AUTHOR]

Hydrogels of Acacia gum (AG) were synthesized in the reverse micelle core of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in gasoline medium. The as synthesized hydrogels were used as template to prepare Silver nanoparticle (AgNPs) in situ via the reduction mechanism of NaBH4. The successful synthesis of bare hydrogels and AgNPs loaded nanocomposite hydrogels (AG–Ag hydrogels) were characterized through Fourier Transform Infrared spectroscopy, Thermal gravimetric analysis, Differential Scanning Calorimetry, Scanning Electron Microscopy, energy dispersive X-ray spectroscopy and Transmission Electron Microscopy, and Atomic Absorption Spectroscopy (AAS). Different feeds of the as fabricated GA-Ag hydrogels were used to catalyze the well-known reactions of 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and Methyl Orange (MO) reduction in aqueous medium at ambient physical conditions. Remarkably, 1000 mg/L of AG–Ag hydrogels with reduced 4-NP and 2-NP into its counterparts, 4-aminophenol and 2-aminophenol in 24 min and 15 min, respectively at room temperature. Similarly, 1000 mg/L of AG–Ag hydrogels reduced MO completely within 25 min. The aforementioned catalytic reactions followed pseudo first order rate kinetics, and it was found that the value of rate constant (kapp) increased by increasing the catalyst amount which, thereby confirms the high conversion rate of the reactants. Schematic illustration of fabrication and catalytic action of AgNPs grown inside the pre-synthesized AG Hydrogel matrices. [ABSTRACT FROM AUTHOR]

Herein, accelerated photo-oxidation under UV light of polyimide (PI) films filled with functionalized vermiculite (VMT) clay (i.e., 1–7 wt %.) were examined from 0 to 600 h. Thick films (⁓ 60 µm) were fabricated and exposed to accelerated UV light (λ > 295 nm). The as-synthesized PI-reinforced clay nanocomposites were examined by Fourier transform infrared (FT-IR), scanning surface micrograph (SEM), yellowing index, and thermogravimetric analysis (TGA), respectively. The surface morphology examined by SEM exhibits well exfoliation of VMT clay in the PI matrix. The change in internal chemistry on a higher temperature and clay composition is found to be the result of the aggregation of clay. The yellowing index determined by UV–Vis spectroscopy followed a similar tendency as the carbonyl index. TGA analysis revealed good heat resistance in clay-based PI due to the lower thermal expansion of clay reinforcement. Overall, the data clearly showed a better photo-stability of the developed clay/PI composites over the pristine polymer. It is concluded that clay-based PI could be a better alternative in applications requiring harsh conditions, as clay has improved the oxidative, thermal, and insulation properties of the PI matrix. [ABSTRACT FROM AUTHOR]

Herein, the electrochemical and structural properties of sulfonated polyimide (SPI) clay-based composite films have been investigated. SPI reinforced with grafted sonicated clay (GSC) was fabricated via a solution casting method in the form of thin films. The as-synthesized thin films were light brown, tough, flexible and transparent. The thickness of the films were 0.109 mm and 0.056 for pristine SPI and GSC-SPI, respectively. The fabricated composite was fully investigated via Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), carbon (13C) NMR and impedance spectroscopy. The completion of the proton exchange reaction was confirmed by 1H NMR. The electrical properties of the SPI-clay based composite film were investigated by impedance spectroscopy. The conductivity was measured in a wide frequency range from room temperature to 363 K by applying an ac signal of 0.5 V. The appearance of two semicircular arcs at low and high frequency shows two conduction mechanisms with different relaxation times at the exterior and interior of the system. Bode plot also confirms the presence of two electro-active regions. The shift in the position of tanδ peaks to lower frequency region with increasing temperature shows that these relaxations are thermally deactivated. The ac conductivity of the system increased from 6.02E−10 for neat SPI to 6.61E−6 Ω−1 cm−1 for SPI-GSC composite. In conclusion, these layered silicates based conductive films have the potential to act as a polyelectrolyte membrane for fuel cell energy devices. [ABSTRACT FROM AUTHOR]

Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic applications. The work presented here details the preparation of ultra-lightweight aerogel materials with tailored properties through the appropriate combination of silica and methacrylate polymer using laser-induced rapid photogelation fabrication technique. For fabrication, an ethanolic solution of hexanediol diacrylate, tetraorthosilicate, Eosin Y and a tertiary amine was prepared. The amounts of reactants were varied to prepare different compositions of aerogel monoliths. The solution was irradiated with a green beam from a low power laser source. The samples, after drying in supercritical ethanol, were characterized using FTIR, BET, SEM, TGA, and a mechanical testing instrument. FTIR data suggests that neither low nor high silica content has an effect on the reactivity of acrylate functionalities during polymer formation. SEM micrographs reveal that variation in silica or polymer content does not produce any phase-separated structures. Instead, uniformly distributed nano-sized polymer-silica structures were obtained for all compositions. Our results suggest that a variety of combinations of mechanical and other properties (such as densities, surface areas, pore sizes, and pore volumes) can be produced through appropriate combination for diverse applications. All these findings provide convincing evidence that the variation of silica and/or polymer content can be used to fabricate aerogels with a variety of properties, which have the depth needed for use in laser-based 3D printing technology of simple or complex structures with nearly any dimensions. [ABSTRACT FROM AUTHOR]

In this study, blends of alginic acid (AA) and chitosan (Cs) cross-linked with bis phenol-F-diglycidyl ether (BPFDGE) were prepared by solvent evaporation method. Chemical structure was analyzed by FTIR showing the existence of interaction between chitosan and sodium alginate. Three transition temperatures were observed for the AA/Cs/BPFDGE blend system in differential thermo-gravimetric analysis thermograms. The first transition showed weight loss due to elimination of absorbed moisture and second transition was due to cleavage of glycosidic linkage of chitosan and decarboxylation from polysaccharide backbone of alginic acid. In the third transition, decomposition temperature of blends (769 °C) was higher as compared to chitosan (580 °C) and alginic acid (620 °C). Investigation on mechanical properties of blends revealed a decreasing trend due to alginate addition that alters crystallization as well as molecular orientation in AA/Cs blend. Increased water uptake was observed owing to interaction between cationic (chitosan) and anionic (alginic acid) groups. [ABSTRACT FROM AUTHOR]

A series of novel coatable polyimide silica (PI-SiO) nanocomposites have been synthesized. A new PI matrix, containing pendant hydroxyl groups, was prepared reacting diamine monomers (4,4'-diamino-4'-hydroxytriphenylmethane, and 4,4'-oxydianiline) and pyromellitic dianhydride (PMDA). Whereas, silica reinforcement was generated using TEOS. A coupling oligomeric species 2,6- bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (APA) was used to furnish silica nanoparticles with imide linkages and hydroxyl groups. As these groups are already present in PI matrix, so their presence in nanoparticles brought structural similarity, and hence enhanced phase connectivity among two phases. The resulting PI-SiO hybrids, with improved interfacial interactions through hydrogen bonding and like-like chemical interactions, displayed much enhanced morphological, thermomechanical, and thermal properties. The properties of resulting hybrids were studied by various advanced techniques and compared with PI-SiO hybrid system which was prepared from same polyimide and unmodified silica network. [ABSTRACT FROM AUTHOR]

We report synthesis of a novel diamine 1,2-bis(4-(Hydrazonomethyl)phenoxy)ethane ( bis- HPE) and a derived novel polyimide. The diamine was reacted with PMDA and ODA to synthesize copolyimide. Unmodified and modified silica particles were dispersed in the polyimide to prepare polyimide-silica hybrids: (a) unmodified (PSH-UM), and (b) modified (PSH-M). The PSH-UM were prepared by generating silica particles in situ in PI. In PSH-M, structural group identical to PI, 2,6- bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone was introduced into silica nano-particles. The structural similarity enhanced compatibility between organic-inorganic components by like-like chemical interactions as both contain flexible alkyl groups. PSH-M have shown improved surface smoothness, hydrophobicity and thermal stability. Such properties are mandatory for stable coatings. The structure of silica and PI was affirmed by FTIR, EDX, and solid-state 29Si NMR spectroscopy. Morphological and thermal properties of the prepared PI-SiO nano-composites were investigated by field emission scanning electron microscopy, atomic force microscopy, contact angle measurement and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Silica packed epoxy networks are prepared in two steps via in situ, solvent free sol-gel processing of tetraethoxysilane in liquid epoxy monomer and curing the mixture with a flexible diamine afterwards. The influence of filler content and processing conditions on the mechanical properties and the fracture behavior is studied by means of the static mechanical analysis and AFM characterization of the pristine and the fractured polymer surfaces, and a mechanism to enhance polymer strength and toughness is proposed. The in-situ evolution and packing of silica nanostructures into epoxy networks influences the overall morphology and performance of polymers under high stress. It is found that smaller silica domains distributed at the molecular level cause efficient crack distribution by absorbing energy and thus improve the strength and toughness of silica packed epoxy polymers. [ABSTRACT FROM AUTHOR]

A series of silica-epoxy nanocomposites were prepared by hydrolysis of tetraethoxysilane within the organic matrix at different processing temperatures, i.e., 25 and 60 °C. Epoxy matrices reinforced with 2.0-10.0 wt% silica were subsequently crosslinked with an aliphatic diamine hardener to give optically transparent nanocomposite films. Interphase connections between silica networks and organic matrix were established by in situ functionalization of silica with 2.0 wt% γ-aminopropyltriethoxysilane (APTS). The microstructure of silica-epoxy nanocomposites as studied by transmission electron microscopy indicated the formation of very well-matched nanocomposites with homogeneous distribution of silica at relatively higher temperatures and in the presence of APTS. Thermogravimetric and static mechanical analyses confirmed considerable increase in thermal stability, stiffness, and toughness of the modified composite materials as compared to neat epoxy polymer and unmodified silica-epoxy nanocomposites. A slight improvement in the glass transition temperatures was also recorded by differential scanning calorimetry measurements. High temperature of hydrolysis during the in situ sol-gel process not only improved reaction kinetics but also promoted mutual solubility of the two phases, and consequently enhanced the interface strength. In addition, APTS influenced the size and distribution of the inorganic domain and resulted in better performance of the modified silica-epoxy nanocomposites. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrids based on a triblock copolymer [polystyrene-b-poly (ethylene-ran-butylene)-b-polystyrene-g-maleic anhydride] (SEBS-g-MA) with silica and clay were prepared using sol-gel and solution intercalation methods respectively. Reinforcement in the first system was achieved by the in-situ hydrolysis/condensation of tetraethoxysilane in the copolymer matrix yielding hybrid materials. The interaction between organic and inorganic phases was developed through a coupling agent. In another system, copolymer was reinforced by organoclay and compatibility between copolymer and hydrophilic montmorillonite was achieved by intercalation of clay with dodecylamine which increased the organophilicity of the clay. Thin transparent films of these hybrids materials were characterized for their mechanical, thermal and thermomechanical behavior. The tensile strength of hybrids improved relative to the pure copolymer in all the systems. Dynamic mechanical thermal analysis carried out gave α-relaxation temperature associated with glass transition temperature (Tg). The results indicate a shift in Tg values with the addition of silica in the matrix, which suggests an increased interfacial interaction between organic and inorganic phases while this effect is less pronounced in polymer–clay system. Thermal decomposition temperatures of the hybrids were found in the range of 450–500 °C. The weights of the residues left at 700 °C were nearly proportional to the inorganic contents in the original hybrids. [ABSTRACT FROM AUTHOR]

Novel sulfonated diamine (NSDA) having pendant sulfonic acid group was synthesized. Polycondensation reaction of this NSDA, dianhydride, and graphene oxide (GO) yielded sulfonated imidized graphene oxide (SIGO). Sulfonated imidized graphene oxide(SIGO) along with NSDA, 4,4′-oxydianiline (ODA) and 1,4,5,8-naphthalene tetracarboxylic dianhydride dianhydride(NTDA) were used for the preparation of polymer electrolyte membranes (PEMs). High temperature proton conduction due to the hydrophobic- hydrophilic phase separation resulted from the incorporation of SIGO. 2.28 meq/g of ion exchange capacity (IEC), 11.18 × 10−2 S/cm of proton conductivity at room temperature and bound water of worth 5.1% between temperature ranges of 100 °C to 150 °C were exhibited by NSPI/3 wt%SIGO composite membrane. Maximum power density of 74.9 mWcm−2 was achieved at 70 °C by NSPI/ 3% SIGO in single cell direct methanol fuel cell test. All these results make these composite membranes suitable candidate to be used as PEM. [ABSTRACT FROM AUTHOR]