Variation of supramolecular structure of heat-resistant polyimide films during thermal treatment

Variation of the supramolecular structure of heat-resistant polymide films in the course of high-temperature treatment was studied by X-ray diffraction analysis and NMR spectroscopy in solids.     

Changes in the supramolecular structure of heat-resistant polyimide fibers in the course of thermal treatment

Changes in the supramolecular structure of heat-resistant fibers based on polyimide PM were studied by X-ray diffraction analysis and NMR spectroscopy.     

Specific features of chitosan-montmorillonite interaction in an aqueous acid solution and properties of related composite films

The rheological properties of chitosan solutions in a 2% aqueous solution of acetic acid with added montmorillonite nanoparticles and the mechanical properties and structural organization of chitosan-based composite films are studied. The interaction between the polymer functional groups and surface charges of nanoplatelets is confirmed by conductometric and potentiometric measurements. With the use of a X-ray diffraction analysis, it is shown that the nanoparticles in films are in the exfoliated and intercalated states. The incorporation of up to 10 wt % modified montmorillonite nanoparticles into the chitosan matrix results in a successive increase in rigidity and a decrease in the elongation at break.     

Effect of cerium oxide on the activity of platinum catalysts of hydrogen and CO oxidation

Effective catalytic systems based on Pt/CeO₂-C were prepared. The use of a cerium oxide addition in the substrate stabilized the platinum catalysts against their poisoning with carbon monoxide at room temperature.     

Proton conductivity of benzoic and 2-sulfobenzoic acids

The dependence of proton conductivity of 2-sulfobenzoic acid trihydrate on the environmental humidity and temperature is studied. It is shown that trihydrate remains solid when exposed to atmosphere with humidity of up to 65 rel. %. The comparison of 2-sulfobenzoic acid trihydrate with bezoic acid shows that the absence of sulfo group in the benzene ring sharply lowers down the hydrophilic properties of the compound and, correspondingly, its hydration and conductivity.     

Thermal Polymerization of Styrene Sorbed from the Gas Phase into Polymer Films as a Method for Synthesizing Precursors of Ion-Exchange Membranes

Russian Journal of Electrochemistry - Abstract—The thermal polymerization of styrene sorbed from the gas-phase into polymer films of polyvinylidene fluoride (PVDF) is carried out at...     

Activation energy of hydrogen migration by relay in the O2/Pt19/SnO2/H2 + n H2O system

In the framework of investigation of active and stable electrocatalysts for fuel cells, the hydrogen migration by relay with the consecutive formation of H₂O molecules in the O₂/Pt₁₉/SnO₂/H₂·nH₂O → O/Pt₁₉/SnO₂·nH₂O + H₂O system was simulated. The simulations were performed by the density functional theory (DFT) method with the generalized gradient adjustment (GGA=PBE) under periodic boundary conditions in the projector augmented plane wave (PAW) basis set with a pseudo-potential using the VASP program package. At the cathode on the platinum cluster surface, the oxygen molecules without a barrier form peroxide complexes that dissociate with an energy decrease. The protons transferred via the proton-conducting channels from the anode to cathode form first OH groups bound to the platinum cluster and then H₂O molecules that are easily separated from the cluster (～0.2 eV). The proton transfer process proceeds by relay and involves several water molecules.     

Proton conductivity of calix[4]arene-para-sulfonic acids

The proton conductivity of hydrates of calix[4]arene-para-sulfonic acids is studied. The high proton conductivity is observed at ambient temperatures in the wide ranges of environmental humidity and, correspondingly, water content in the hydrate. For the air humidity of 10 rel. %, the conductivity of compounds is 10^?4-10^?3 S cm^?1 and approaches 10^?2-10^?1 S cm^?1 as the humidity increases up to 70 rel. %.     

A new method for the synthesis of sulfonated polynaphthylimides

A new method for the synthesis of sulfonated polynaphthylimides has been developed on the basis of the postsulfonation of high-molecular-mass polynaphthylimides with a sulfuric acid-oleum mixture. Sulfonated polymers of this type have been obtained from the polycondensation products of 5-phenylthiophenylene-1,3-diamine with dianhydrides of 1,4,5,8-naphthalenetetracarboxylic acid and 4,4′-(1,4-phenylenedicarbonyl)-bis-naphthalene-1,8-dicarboxylic acid. It has been shown that hydrogen peroxide oxidation of sulfide bridge groups of these polymers in an acidic medium yields high-molecular-mass compounds that contain sulfonic bridge fragments and, therefore, have increased thermal stabilities and enhanced proton conductivities.     

Platinum nanoparticles on the antimony-doped tin dioxide surface: Quantum-chemical modeling

The interaction of Pt₂₉ nanoparticles with pristine and reduced (110) and (100) SnO₂ surfaces doped with Sb has been modeled using the density functional theory method within the generalized gradient approximation (GGA). It has been demonstrated that the introduction of antimony contributes to dispersion of substrate particles and, in some cases, leads to an increase in the energy of interaction with platinum and to the fixation of platinum nanoparticles on the surface.