Abstract:
The acoustic and structure-dynamic properties of decylpyridinechloride (DPCI) aqueous solutions at concentrations of 0.06--2.0 mol/l were investigated using acoustic and rheologic methods. Sound spreading rate and absorption in the frequency range from 5 to 2500 MHz as well as density and shear viscosity coefficients in the temperature range of 283--353 K were measured. Based on experimental data obtained, a number of acoustic parameters for aqueous solutions, such as bulk to shear viscosity ratio and classical sound attenuation, were calculated. It was shown that in the solutions studied (as in the case with water) additional, in relation to classical, sound absorption is caused by structure reorganization (i.e., changes in arrangement of molecules, molecular associations, and surfactant-water complexes). The kinetic compensation effect was observed for reactions of intermolecular bond tearing. The mechanism for micellar formation is proposed. For the DPCI aqueous solutions at concentrations lower than 0.2 mol/l acoustic relaxation is not observed, whereas in the case of more concentrated solutions the predominant mechanisms for acoustic relaxation are intermicellar interaction and micellar aggregates formation. The lack of a hydrocarbon conformational transition region in the acoustic spectra gives one grounds to assume that the micellar core is structurized and possesses the properties inherent to crystalline hydrocarbons.