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  • Author or Editor: Malgorzata Józwiak x
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Abstract  

Enthalpies of solution of 1,4-dioxane, 12-crown-4 ether (12C4), 15-crown-5 ether (15C5) and 18-crown-6 (18C6) have been analyzed from the point of view of preferential solvation of these cyclic ethers (crown ethers) by a molecule of acetone or dimethylsufoxide in the mixtures of water with acetone or dimethylsulfoxide. It has been observed that the carbonyl carbon atom replacement in acetone molecule by sulfur atom brings about completely different behavior of molecules of these solvents in relation to cyclic ethers dissolved in mixed solvents. Crown ethers are preferentially solvated by acetone (ACN) molecules, which is not observed in the case of dimethylsulfoxide (DMSO).

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The effect of carbonyl carbon atom replacement in acetone molecule (ACN) by sulfur atom (DMSO)

Part III. Effect of base–acid properties of the mixtures of water with acetone or dimethylsulfoxide on the solution enthalpy of cyclic ethers in mixed solvent

Journal of Thermal Analysis and Calorimetry
Author:
Małgorzata Jóźwiak

Abstract  

The enthalpies of solution of cyclic ethers: 1,4-dioxane, 12-crown-4 (12C4), and 18-crown-6 (18C6) in water–acetone mixtures have been measured within the whole mole fraction range at 298.15 K. Based on the obtained data, the effect of base–acid properties of water–acetone mixtures on the solution enthalpy of cyclic ethers in this mixed solvent has been analyzed. The strong dependence of the enthalpy of solution (solvation) of cyclic ethers on basic properties of mixed solvent has been observed. The effects of carbonyl atom replacement in acetone (ACN) molecule by sulfur atom (DMSO molecule) and base–acid properties of mixed solvent on the solvation process of cyclic ethers have been analyzed.

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Enthalpies of dissolution of benzo-15-crown-5 ether (B15C5) in mixtures of acetonitrile with water and in solutions of NaI and NaBPh4 (I=0.05 mol dm−3) in these mixtures were measured at 298.15 K. From the obtained results and appropriate literature data, the thermodynamic functions of B15C5/Na+ complex formation in acetonitrile-water mixtures were determined. The enthalpies of transfer of the complex B15C5/Na+ from pure acetonitrile to the examined mixtures were calculated and are discussed.

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Abstract  

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na+) in acetone–water mixtures at 298.15 K have been calculated. The equilibrium constants of B15C5/Na+ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of B15C5 by a molecule of water and acetone, respectively and the solvation of Na+ on the complex formation processes have been discussed. The calculated thermodynamic functions of B15C5/Na+ complex formation and the effect of benzene ring on the complex formation have been compared with analogous data obtained in dimethylsulfoxide–water mixtures. The effect of carbonyl atom replacement in acetone molecule by sulphur atom (DMSO molecule) on the thermodynamic functions of complex formation has been analysed.

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Abstract

This paper presents the effect of halloysite intercalated with a base or modified montmorillonite on the thermal properties and flammability of peroxide and sulfur vulcanizates of styrene–butadiene rubber (SBR). Based on the test results obtained by means of thermal analyses (DTA, TG, DTG, and DSC), oxygen index and microcalorimeter (FAA) it has been found that the thermal stability and flammability of the nanocomposites investigated depend on the spatial network structure as well as the content and type of nanoadditive in the vulcanizate obtained. The nanofillers used considerably reduce the flammability and fire hazard of the cross-linked SBR.

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Abstract

This article presents a procedure of the activation of halloysite and a method of the synthesis of nucleus-sheath type filler. The effects of the nanoadditives obtained on the thermal properties, flammabilities and fire hazards of peroxide and sulfur vulcanizates of NBR and SBR rubbers, are discussed. Based on the test results obtained by derivatography, oxygen index, FAA micro-calorimeter and cone calorimeter, the thermal stability, flammability, and fire hazard of the nanocomposites investigated were determined. The results obtained were interpreted from the point of view of the chemical structure of the diene elastomers investigated, their spatial network structure, and the method of halloysite modification.

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