Excess molar volumes and excess molar heat capacities of (polyethylene glycols + water) at temperatures betweenT = 278 K andT = 328 K

Abstract

Densities of aqueous solutions of the following polyethylene glycols (PEGs) of average molar mass (300, 400, and 600) g·mol−1have been measured over the entire mass fraction range atT= 298.15 K, using a vibrating-tube densimeter. In the case of PEG 300, heat capacities have been determined atT= 298.15 K in dilute solutions with a flow microcalorimeter. In addition, densities and heat capacities of (PEG 300 + water) have been measured over the entire composition range using a differential scanning microcalorimeter in the temperature intervalT= (278 to 328) K. Excess molar volumes and excess molar heat capacities as functions of mole fraction have been deduced therefrom for the selected temperatures. Excess volumes are found to be negative, and become more negative as the molar mass of PEG increases and/or the temperature decreases. In contrast, excess heat capacities are always positive, and increase with temperature.