Application of the sCPA equation of state for polymer solutions

Abstract

Specific interactions, for example hydrogen bonding, dominate in numerous industrially important polymeric systems, both polymer solutions and blends. Typical cases are water-soluble polymers including biopolymers of special interest to biotechnology (e.g. the system polyethyleneglycol/dextran/water). Furthermore, most polymer blends are non-compatible and the requirement for compatible polymer pairs is often the presence of hydrogen-bonding interactions (e.g. polyvinylchloride/chlorinated polyethylene). In this work we give at first a short, comparative evaluation of existing thermodynamic models suitable for polymeric systems that take into account, explicitly, specific interactions like HB. The range of application of the models in terms of phase equilibria and their specific characteristics (accuracy of calculation, degree of complexity) are discussed. Finally, vapor–liquid equilibria (VLE) calculations for a number of polymer+solvent systems (including five different polymers) with a novel and very promising model are presented. This model is in the form of an equation of state that is (in its general formulation) non-cubic with respect to volume and has separate terms for physical and chemical interactions. The model has recently been proposed and has already been successfully applied to non-polymeric hydrogen-bonding systems (alcohol/water/hydrocarbons). This is the first time that it is extended to polymer solutions.