Viscometric and Densimetric Study of Water–PEG–KBr Systems

The dynamic viscosity and density of a water–PEG–KBr system are measured in the ranges of 293.15–323.15 K and 0–0.001 mol parts. Polyethylene glycol samples with average molecular weights of 1000, 1500, 3000, 4000, and 6000 g/mol are used. The concentration of KBr is 0.01 mol parts. The activation parameters of viscous flow (Gibbs energy, enthalpy, and entropy) and the partial molar volume of PEG in a solution are calculated using experimental data in the specified range of temperatures and concentrations. It is shown that the activation parameters of viscous flow grow along with concentration and molar weight. It is found that the partial molar volume of PEG in a solution falls as the concentration rises, and the partial molar volume per monomer does not change, depending on the average molecular weight of PEG. A simple way of determining the hydration number of a polymer molecule is described, based on which the hydration number of a PEG macromolecule in a solution is calculated. It is found that the hydration number of a PEG macromolecule falls as the temperature rises and grows along with the molecular weight.