First Fluorinated Zwitterionic Micelle with Unusually
Slow Exchange in an Ionic Liquid
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Abstract
The micellization of a fluorinated
zwitterionic surfactant in ethylammonium
nitrate (EAN) was investigated. The freeze-fracture transmission electron
microscope (FF-TEM) observations confirm the formation of spherical
micelles with the average diameter 25.45 ± 3.74 nm. The micellization
is an entropy-driven process at low temperature but an enthalpy-driven
process at high temperature. Two sets of <sup>19</sup>F NMR signals
above the critical micelle concentration (cmc) indicate that the unusually
slow exchange between micelles and monomers exists in ionic liquid;
meanwhile, surfactant molecules are more inclined to stay in micelle
states instead of monomer states at higher concentration. Through
the analysis of the half line width (Δν<sub>1/2</sub>),
we can obtain the kinetic information of fluorinated zwitterionic
micellization in an ionic liquid