MCR-Raman spectroscopy of sodium octanoate micelles in aqueous solutions

Abstract

Development of nanotechnologies and the active use of self-organization processes of amphiphilic compounds in them require fast and accurate diagnostics of these processes. Active use of sodium octanoate in medicine, pharmaceuticals and nanotechnologies necessitates the elimination of existing contradictions in scientific studies of the surfactants self-organization in water and conducting diagnostics of NaС8 solutions at a higher quality level. In this study, self-organization of micelle-forming compounds in water was studied on the example of sodium octanoate by combining laser Raman spectroscopy and MCR-ALS analysis. As a result of the analysis of the OH- and CH-groups stretching bands structure using the MCR method, the spectral components were identified as the stretching bands of water molecules that are not in contact with surfactants, and molecules formed monomers, dimers and micelles surrounded by hydration shells during the surfactants self-organization. Comparative analysis of the dependences of the water stretching band characteristics and characteristics of the obtained components of the OH-groups stretching bands decomposition on the NaC8 concentration showed that the most bound water molecules are in the aqueous shell of dimers, and the weakliest bound are in the aqueous shell of micelles. It was found that the formation of dimers and micelles increases the fraction of hydrocarbon surfactant chains in the trans-conformation. It is shown that using Raman spectroscopy in combination with the MCR method, it is possible not only qualitatively, but also quantitatively to estimate the ratio of monomers, dimers and micelles in solution and fraction of surfactant ions present in micelles.