Pressure dependence of upper critical solution temperatures in the polystyrene - cyclohexane system

Abstract

The pressure dependence of the upper critical solution temperature ( dT dp ) c in the polystyrene-cyclohexane system has been measured over the pressure range of 1 to 50 atm. The value of ( dT dp ) c determined over the molecular weight ( M w ) range of 3.7 × 10 4 to ∼145 × 10 4 greatly depends on the molecular weight of polystyrene. The value of ( dT dp ) c for a polystyrene solution of low molecular weight ( M w = 3.7 × 10 4) is positive (3.14 × 10 −3 degree atm −1), while the values are negative (−0.52 × 10 −3∼−5.64 × 10 −3 degree atm −) for solutions of polystyrene over the high molecular weight range of 11 × 10 4 to ∼145 × 10 4. The Patterson-Delmas theory of the corresponding state and the newer Flory theory have been used to explain this behaviour.