The pressure effect on the thermodynamic properties of polystyrene—trans-decalin solution

Abstract

The viscosity of a solution of polystyrene in trans-decalin was measured over pressure and temperature ranges from atmospheric pressure to 400 kg/cm 2 and 20° to 40°C. The viscosity measurements at elevated pressure were made by the use of a rolling-ball type viscometer, and the validity of this method was confirmed by comparing with the calibrated Ubbelohde viscometer at atmospheric pressure. Values of the interaction parameter, χ, were obtained from the coil expansion coefficients on the assumption of the fifth-power rule of the Flory theory for the expansion of the polymer molecules in the solution. χ 1 increases with increasing pressure. The pressure coefficient of the theta-temperature calculated from the pressure and the temperature derivatives of χ 1 is in good agreement with the result of Schulz et al. The values of χ 1 were compared with those calculated from the new Flory theory and the Patterson theory for polymer solutions. At lower pressure these theories predict the behaviour of χ 1 well, but at higher pressure the prediction becomes inaccurate.