Features of self-organization of sodium dodecyl sulfate in water-ethanol solutions: Theory and vibrational spectroscopy

In this work, experimental and theoretical studies of the micelle formation processes of sodium dodecyl sulfate in water-ethanol solutions with different ethanol content - 0% by volume, 8% by volume, 15% by volume, 30% by volume were carried out. For the first time, the manifestation in the vibrational spectra of the features of self-organization of sodium dodecyl sulfate (SDS) molecules in water-ethanol solutions was found. In the studied concentration ranges of ethanol and SDS it was found that in the presence of SDS, the strengthening of hydrogen bonds in solutions is observed in a wider range of changes in the concentration of ethanol than in the absence of SDS. The behavior of the band at 1060 cm(-1) at low concentrations of ethanol (8%) indicates the dual behavior of ethanol molecules as a co-surfactant and co-solvent in the process of micelle formation. The obtained experimental data are confirmed by theoretical calculations. For the first time, a contactless express method was proposed for determining the critical micelle concentration of SDS in water-ethanol solutions with different ethanol content from Raman spectra. The measured values of SDS critical micelle concentration are in good agreement with the literature data. (C) 2019 Elsevier B.V. All rights reserved.