Insight into the Hydration of Cationic Surfactants: A Thermodynamic and Dielectric Study of Functionalized Quaternary Ammonium Chlorides

Žiga Medoš, Natalia V. Plechkova, Sergej Friesen, Richard Buchner*, Marija Bešter-Rogač

*Corresponding author for this work

Research output: Contribution to journalArticle

6 Citations (Scopus)
159 Downloads (Pure)

Abstract

Hydrophobic interactions are one of the main thermodynamic driving forces in self-assembly, folding, and association processes. To understand the dehydration-driven solvent exposure of hydrophobic surfaces, the micellization of functionalized decyldimethylammonium chlorides, XC 10 Me 2 N + Cl - , with a polar functional group, X = C 2 OH, C 2 OMe, C 2 OC 2 OMe, C 2 OOEt, together with the "reference" compound decyltrimethylammonium chloride, C 10 Me 3 N + Cl - , was investigated in aqueous solution by density measurements, isothermal titration calorimetry (ITC), and dielectric relaxation spectroscopy (DRS). From the density data, the apparent molar volumes of monomers and micelles were estimated, whereas the ITC data were analyzed with the help of a model equation, yielding the thermodynamic parameters and aggregation number. From the DRS spectra, effective hydration numbers of the free monomers and micelles were deduced. The comprehensive analysis of the obtained results shows that the thermodynamics of micellization are strongly affected by the nature of the functional group. Surprisingly, the hydration of micelles formed by surfactant cations with a single alkyl chain on quaternary ammonium is approximately the same, regardless of the alkyl chain length or functionalization of the headgroup. However, notable differences were found for the free monomers where increasing polarity lowers the effective hydration number.

Original languageEnglish
Pages (from-to)3759-3772
Number of pages14
JournalLangmuir
Volume35
Issue number10
Early online date12 Mar 2019
DOIs
Publication statusPublished - 12 Mar 2019

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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