Phase behavior of aqueous two-polymer systems

Abstract

In this work we consider the thermodynamic description of the liquid-liquid phase behavior of dextran-polyethylene glycol-water systems which are of interest for biological separations. In this effort, we use the Flory-Huggins and UNIQUAC models, and develop a new numerical procedure to estimate the interaction parameters.Also, when using interaction parameters for the Flory-Huggins model obtained from osmotic pressure and plait point data, qualitatively reasonable binodal curves were obtained. Due to the asymmetry in the experimental binodal curves for these polymer systems, there is a small difference between the calculated interaction parameters for each of the polymers with water. The location of a binodal curve is found to be sensitively dependent on the interactions between the unlike polymers.Multiple sets of interaction parameters were found for the UNIQUAC model which could describe liquid-liquid phase splitting in a reasonable manner. In particular, an intercorrelation was found in which any set of parameters in a broad range could predict the phase behavior equally well. Also, the volume and surface area parameters of the polymers were found to play an important role in determining phase behavior of these polymer systems. The shift of the binodal curve with molecular weight of the polymers was also investigated.