Sabir S. Guseynov

Correlation of enthalpic and volume characteristics of 15-crown-5 in solution with molecular parameters and physical properties of solvents

Abstract The solution and solvation enthalpies at infinite dilution of 15-crown-5 in different organic solvents and water were measured. The limiting partial molar volumes of the crown ether in a series of solvents studied were determined using experimental density data. On the basis of the scaled particle theory the satisfactory multiparameter correlation of the quantities measured with properties of solvents was obtained. The known equations as modified by the introduction of more accurate radial distribution function g 12 ( r ) were used.

Thermal behaviour of polystyrene/silica composites

ABSTRACT The particle-size distribution in silica powder prepared by the sol–gel method has been determined by dynamic light scattering analysis. The average diameter of the particles was found to be 250 nm. Using a low-temperature nitrogen adsorption–desorption technique, it was found that the synthesised powder may be referred to as mesoporous materials. Polystyrene/silica composite films were fabricated by casting from o-xylene solutions. It was found, using thermogravimetry, that incorporation of silica leads to an increase in both the onset temperature of polymer degradation and in the temperature at which the maximum rate of weight loss occurs. Using differential scanning calorimetry, the phase transitions from the glassy state to the elastic one were studied for the polymeric materials. New data relating to the effect of silica on the glass-transition temperature, Tg, of composites with a low weight fraction of SiO2 were found. Specifically, we found a non-monotonic concentration dependence of the value of Tg. The present results advocate for employing silica as an effective filler for producing polymer composites with enhanced thermal properties.

Kinetics of Thermal Degradation of Polystyrene/Silica Film Composites

Using thermogravimetry, the thermal stability of polymeric polystyrene/silica composites containing 0–5 wt % of filler is studied. It is found that, the higher the concentration of SiO2, the higher the characteristic temperatures of thermal destruction of the composite. Using the van Krevelen method, kinetic analysis of the obtained thermogravimetric curves was carried out. An increase in the activation energy of the process of thermal destruction is revealed with increasing silica concentration in the composite.

Features of the thermal behavior of PMMA/C60 film composites

Polymethylmethacrylate-based film composites containing small additives of fullerenes (up to 3 wt %) are obtained. The thermal behavior of the obtained materials is studied by DSC in the temperature range from 25 to 130°C. It is found that the character of the DSC curve depends on the composite composition. For films containing up to 0.1 wt % C60, one glass transition temperature (Tgsoft) is observed, while in the case of films with a higher concentration of the filler, two glass transition temperatures (Tgsoft and Tgsolid) are observed. It is found that the dependence of Tgsoft value on the content of fullerenes is nonmonotonic with a minimum at 0.5 wt % of C60.