Origin of the central pit in hemimicelles of semifluorinated alkanes: How molecular dipoles and substrate deformation can determine supra-molecular morphology.

Autor: Silva P; Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Sorbonne Université, Institut des NanoSciences de Paris, CNRS-UMR 7588, 4 place Jussieu, 75005 Paris, France., Silva GMC; Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal., Morgado P; Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal., Fauré MC; Sorbonne Université, Institut des NanoSciences de Paris, CNRS-UMR 7588, 4 place Jussieu, 75005 Paris, France; Université Paris Cité, UFR des Sciences Fondamentales et Biomédicales, 45 Rue de Saints-Pères, 75006 Paris, France., Goldmann M; Sorbonne Université, Institut des NanoSciences de Paris, CNRS-UMR 7588, 4 place Jussieu, 75005 Paris, France; Université Paris Cité, UFR des Sciences Fondamentales et Biomédicales, 45 Rue de Saints-Pères, 75006 Paris, France; Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-Sur-Yvette, France., Filipe EJM; Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal. Electronic address: efilipe@tecnico.ulisboa.pt.
Jazyk: angličtina
Zdroj: Journal of colloid and interface science [J Colloid Interface Sci] 2024 Feb; Vol. 655, pp. 576-583. Date of Electronic Publication: 2023 Nov 08.
DOI: 10.1016/j.jcis.2023.11.007
Abstrakt: Hypothesis: Semifluorinated alkanes amphiphiles spontaneously form highly monodispersed hemimicelles at the surface of water. The origin of the formation and complex structure of these surprising supramolecular aggregates were only recently clarified using molecular dynamics simulations (MD). The existence of a pit at the center of these aggregates made up of almost 3000 molecules was indeed reproduced by the MD simulations, but not understood.
Method: A careful strategy of atomistic MD simulations comparing non-electrostatic force fields with force fields that include electrostatic forces, thus bearing an implicit or explicit dipole, allowed demonstrating the roles of dipolar interactions and interactions with the liquid subphase on the morphology of the aggregates.
Findings: The simulation results clearly show that within the hemimicelles the strong molecular dipoles located at the CH 2 -CF 2 junctions tend to align, leading to a collective shift of the PFAA molecules relatively to each other. This shift is responsible for the curvature of the hemimicelles and originates the central pit, provided the possibility of deforming the surface of the water sub-phase. Comparisons with non-electrostatic force field results further contribute to understand the origin of the self-assembling process. The results directly connect for the first time a molecular property with a mesoscopic structural feature. Given the molecular simplicity of these "primitive" amphiphiles compared to the common hydrophilic/hydrophobic surfactants, the results contribute to understand self-assembly in general.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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