Absolute prediction of upper and lower critical solution temperatures in polymer/solvent systems based on corresponding state theory

Abstract

The upper critical solution temperature (UCST) and lower critical solution temperature (LCST) have been predicted for 45 polymer/solvent systems based on Patterson's theory. The configurational energy and configurational heat capacity used in the theory are determined by the following thermodynamic relations −U conf. =γ VTV C P, conf. =α PTγ VV where the thermal expansion coefficient and thermal pressure coefficient are obtained from our empirical equations ln(α PT) −1=1.1820+0.8425 ln T C −T T ln(γ V/γ V C )=0.8452+1.1324 ln(V/V C )+2.8940[ ln(V/V C )] 2 where T C, V C and γ V C are the critical temperature, critical volume and thermal pressure coefficient at the critical state. The deviations between predicted and experimental UCST and LCST are generally less than 20°C for 28 polymer/solvent systems. The molecular weight dependence of UCST and LCST is predicted for polystyrene (PS)/cyclohexane, PS/methyl cyclohexane and PS/toluene systems, and good agreement with experimental results is obtained.