Sound Speed and Density Studies of Interactions Between Cationic Surfactants and Aqueous Gelatin Solution

Abstract

Studies on the interactions of surfactants with proteins can contribute to an understanding of the action of surfactants as denaturants and as solubilizing agents for membranes of proteins and lipids. Quantitative aspects of such studies may include direct measurements of properties, such as viscosity, density, sound speed, conductance, and elucidation of the often highly complex phase diagrams. In this study, sound speed and density studies of surfactants, viz., cetyltrimethyl ammonium bromide, cetyltrimethyl ammonium chloride, and di(dodecydimethyl ammonium bromide) (12-2-12) have been carried out in a 0.02 % w/v aqueous solution of gelatin at temperatures of 20 °C, 25 °C, 30 °C, and 35 °C. From the measured data, the parameters apparent molar volumes (\({(\phi_{v})}\)), adiabatic compressibility (β), and apparent molar compressibility \({(\phi_{k})}\) have been calculated to interpret the protein–surfactant interactions. The variations in these parameters with the concentration of the surfactant suggests the manifestation of hydrophobic interactions in the system.