Thermodynamics of Mixtures Containing Alkoxyethanols. XXI. Application of the Flory Theory to the Study of Orientational Effects in Systems with Dibutyl Ether or 1-Butanol

The physical meaning of the energetic parameter, χ12, that is characteristic of Flory theory is explored in connection to the random mixing hypothesis. It is known that, if such a hypothesis is valid, χ12 is independent of the concentration (x1). Here, deviations from the random mixing hypothesis are attributed to an excess of interactions between like molecules (if χ12(x1) > χ12(x1 = 0.5)) or of interactions between unlike molecules (if χ12(x1) < χ12(x1 = 0.5)). Binary mixtures of the type hydroxyether + dibutyl ether, or + 1-alkanol, or + 2-methoxyethanol have been investigated studying the χ12 variation with x1. Toward this end, we provide a new expression for χ12 which makes possible the exact determination of this magnitude at any composition if the corresponding molar excess enthalpy, , is known. Orientational effects are present in the studied solutions, although the model can represent the for hydroxyether + 1-alkanol or + 2-methoxyethanol, where the mentioned effects are weaker. The excess molar ...