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The osmotic coefficient measurements for binary aqueous solutions of 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8] hexacosane) in the concentration range of ~0.009 to ~0.24 mol·kg(-1) and in ternary aqueous solutions containing a fixed concentration of 2,2,2-cryptand of ~0.1 mol·kg(-1) with varying concentration of KBr (~0.06 to ~0.16 mol·kg(-1)) have been reported at 298.15 K. The diamine gets hydrolyzed in aqueous solutions and needs proper approach to obtain meaningful thermodynamic properties. The measured osmotic coefficient values are corrected for hydrolysis and are used to determine the solvent activity and mean ionic activity coefficients of solute as a function of concentration. Strong ion-pair formation is observed, and the ion-pair dissociation constant for the species [CrptH](+)[OH(-)] is reported. The excess and mixing thermodynamic properties (Gibbs free energy, enthalpy, and entropy changes) have been obtained using the activity data from this study and the heat data reported in the literature. Further, the data are utilized to compute the partial molal entropies of solvent and solute at finite as well as infinite dilution of 2,2,2-cryptand in water. The concentration dependent non-linear enthalpy-entropy compensation effect has been observed for the studied system, and the compensation temperature along with entropic parameter are reported. Using solute activity coefficient data in ternary solutions, the transfer Gibbs free energies for transfer of the cryptand from water to aqueous KBr as well as transfer of KBr from water to aqueous cryptand were obtained and utilized to obtain the salting constant (ks) and thermodynamic equilibrium constant (log K) values for the complex (2,2,2-cryptand:K(+)) at 298.15 K. The value of log K = 5.8 ± 0.1 obtained in this work is found to be in good agreement with that reported by Lehn and Sauvage. The standard molar entropy for complexation is also estimated for the 2,2,2-cryptand-KBr complex in aqueous medium.

Synergistic stabilizing effect of layered double hydroxides (LDHs) with micro-as well as nano-sized calcium carbonate (CaCO 3 ) on thermal stability of polyvinyl chloride (PVC) was studied and evaluated. Nano-sized CaCO 3 was prepared in the laboratory by matrix-mediated growth and controlled (in situ deposition) technique. Crystal size of nano-CaCO 3 was estimated by studying x-ray diffraction pattern. The PVC composites were prepared using Brabender Plastograph instrument. Various formulations were prepared by taking fixed amount of LDH and varying the concentration of micro-/nano-sized CaCO 3 . PVC sheets of 1 mm thickness were prepared on compression molding machine. Thermal stability in terms of thermal degradation was studied by thermogravimetric analyzer. Surface morphology and mechanical property were studied using scanning electron microscopy and universal tensile machine. Increase in the onset temperature of the PVC sheets was considered as imparting a better thermal stability to PVC. Better synergistic effect on the stabilization of PVC was observed in case of LDH with nano-sized CaCO 3 and compared with micro-sized CaCO 3.

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Ethylene vinyl acetate copolymer (EVA) nanocomposites were prepared by melt blending of EVA with nano-sized magnesium hydroxide [Mg(OH)2] and modified montmorilonite clay. Nano Mg(OH)2 was synthesized in the laboratory by matrix-mediated growth and controlled technique. Particle size of Mg(OH)2 crystals was performed using X-ray diffraction technique and was found to be in nanometer range. Ternary EVA, clay and Mg(OH)2 nanocomposites were prepared by melt blending using Brabender Plastograph EC. The prepared samples were characterized by flame test, tensile tests and thermogravimetric analysis (TGA). Morphological study of the composites was studied by scanning electron microscopy (SEM). Flame retardant properties of samples were significantly improved in the EVA/clay/Mg(OH)2 nanocomposites without losing its mechanical properties. Ternary system showed better thermal, flame retardant and mechanical properties compared with nanocomposites of EVA filled only with the nano Mg(OH)2.

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