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Updated: Jul 28, 2025

Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
High unimer concentration and asymmetric bilayer observed in small unilamellar vesicles of mixed surfactants
Anja F Hörmann1, Artem Feoktystov2, Theyencheri Narayanan3
1Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, D-10623 Berlin, Germany.
Abstract:
The mixed surfactant system of tetradecyldimethylamine oxide (TDMAO) and lithium perfluorooctanoate (LiPFO) is known to spontaneously self-assemble into well-defined small unilamellar vesicles. For a quantitative analysis of small-angle x-ray scattering on this model system, we complemented the measurements with densitometry, conductimetry, and contrast-variation small-angle neutron scattering. The analysis points to two main findings: first, the vesicles formed to contain a much higher mole fraction (0.61-0.64) of TDMAO than the bulk sample (0.43) and predicted by Regular Solution Theory (RST, 0.46). In consequence, the unimer concentration of LiPFO is more than 5 times higher than predicted by RST. Second, the vesicle bilayer is asymmetric with a higher fraction of LiPFO on the outside. These findings on a model system should be of broader relevance for the understanding of similar mixed surfactant vesicle systems and thereby also be of importance for their use in a number of applications.
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