Effect of oxyethylene groups on the behaviour of thermodynamic properties of pyrrolidin-2-one and poly(ethylene glycols)

Dilatometric measurements of excess volume VE and ultrasonic speed u have been carried out for mixtures of mono-, di-, tri- and tetra(ethylene glycol)s in pyrrolidin-2-one (PY) over the whole mole fraction range at 303.15 K. In the mixture of PY and monoethylene glycol, the VE is positive except for slight negative variation at the high mole fraction of PY. The other three mixtures PY+di-, + tri- and + tetra(ethylene glycol)s show negative VE over the entire composition range in the order di-<tri-<tetra-. There is a decrease in the values of ultrasonic speed u with increase in the mole fraction of PY in the case of monoethylene glycol while for other three systems u rises. From these measurements, partial molar quantities ViE and KS,iE have been calculated and analysed. Estimates of isentropic molar quantity KS equal to −(∂V/∂p)S and its excess counterpart KSE have also been computed. The KSE is positive for mono-, and negative for all the other mixtures over the whole composition range.