Thermodynamic Investigation (Volume and Compressibility) of the Systems β-Cyclodextrin + n-Alkyltrimethylammonium Bromides + Water

Abstract

Density and sound velocity data for aqueous solutions at 298 K containing a homologue series of alkyltrymethylammonium bromides (CnTAB, n = 10, 12, 14, 16) in the absence and presence of β-cyclodextrin were analyzed to calculate the molar apparent and partial volumes and adiabatic compressibilities. For the binary systems, the molar partial compressibilities and volumes of the pure surfactants in water have been obtained as a function of the concentration and compared with the literature data, and the methylene group contributions have been deduced. For the ternary systems, a remarkable increase of both the molar partial volume and compressibility of the surfactant at infinite dilution with respect to the value in water is observed. The large values of the transfer properties of the surfactants at infinite dilution, molar partial compressibilities and volumes, can be discussed in terms of a simple model in which the balance between the released water from the cavity and the methylene groups of the substra...