FT-IR STUDY OF MICELLE FORMATION OF IONIC SURFACTANTS AND WATER SOLUBILIZATION IN NONPOLAR ORGANIC SOLVENTS.

Abstract

The infrared spectra of the solutions of dodecylammonium propionate (DAP), hexadecyltrimethylammonium bromide (HTAB), and sodium bis(2-ethylhexyl) 2-sulfonatosuccinate (SBSS) in organic solvents were recorded in Fourier transform mode. Difference concentration spectra of DAP in dichloromethane exhibited the change in the stretching bands of the carboxylate ions, which was attributed to the formation of micellar aggregates. Difference hydration spectra were also obtained for water-containing DAP-CH//2Cl//2, HTAB-CH//2Cl//2, and SBSS-benzene systems, and the spectra in the region of 3000-3700 cm** minus **1 and 1600-1650 cm** minus **1 revealed the existence of free water dispersed in the organic phase and water bound to the micelles. The difference spectra also revealed the change in the bands of DAP and SBSS due to hydration of the ionic head groups. The absorption frequency of the O-H stretching bands was discussed in terms of the water-surfactant-interaction.