Volume properties of some linear and ring oligomer solutions

Abstract

Volume investigations have been carried out on the solutions of two pairs of linear and cyclic (ring) oligomers in chloroform and in p-dioxane. For both pairs, the linear and cyclic oligomers had similar molar masses (244 and 384 g mol^–1). The densities of pure liquid components and solutions were determined using a vibrating tube densitometer (Sodev) at 25, 30, 35 and 40 °C; the concentrations of the solutions varied by up to 20% in mass/volume of solvent. The densities of three solid oligomers were measured with a pycnometer using water as the reference liquid over the same temperature range. Partial molar volumes of the components, excess molar volumes of the solutions and thermal expansion coefficients of components were all deduced from the density data. The negative departure from the ideal mixing law of most linear and cyclic oligomer solutions is attributed to specific intermolecular interactions between the solvent and the oligomer as well as to the free-volume effect related to the molecular configuration of each compound. There is a clear difference in volume properties between linear and cyclic oligomers of the same molar mass.