Молекулярна динамiка та фазовi перетворення у бiнарних сумiшах жирних кислот та гексадецилтриметiламонiумбромиду: дослiдження давидовського розщеплення молекулярних коливальних мод

• Date: 2018
• Main Authors: Gavrilko, T. A., Puchkovska, G. O., Styopkin, V. I., Bezrodna, T. V., Baran, J., Drozd, M.
• Format: Article
• Language: English
• Published: Publishing house "Academperiodika" 2018
• Online Access: https://ujp.bitp.kiev.ua/index.php/ujp/article/view/2018334
• Journal Title: Ukrainian Journal of Physics

The 1:1 solid phase complexes of stearic (SA) and behenic (BA) fatty acids (FA) with cationic surfactant cetyltrimethylammonium bromide (CTAB) are prepared from an equimolar ethanol solution of their binary mixtures. A supramolecular complexation between FA and CTAB molecules is proven with FTIR spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC). A single-phase layered crystalline structure of both CTAB:SA and CTAB:BA complexes is revealed by XRD. The greatly enhanced thermal stability of the CTAB:FA complexes over the pure FA (by about 40–50oC) is found with DSC along with a number of successive solid-solid phase transitions. The temperature-dependent FTIR study of the Davydov splitting for CH2 rocking (720–730 cm^-1) vibrations revealed a significant difference in the conformational disorder of methylene chains and the molecular packing in successive solid phases of CTAB:SA and CTAB:BA complexes. Our research provides a molecular basis for a prospective application of such class of binary mixtures of oppositely charged cationic and anionic surfactants in thermo-sensitive supramolecular systems.