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Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density

In this work, Langmuir films of two highly fluorinated fatty alcohols, CF(3)(CF(2))(12)CH(2)OH (F14OH) and CF(3)(CF(2))(16)CH(2)OH (F18OH), were studied. Atomic Force Microscopy (AFM) images of the films transferred at zero surface pressure and low surface density onto the surface of silicon wafers...

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Autores principales: Silva, Pedro, Nova, Duarte, Teixeira, Miguel, Cardoso, Vitória, Morgado, Pedro, Nunes, Bruno, Colaço, Rogério, Fauré, Marie-Claude, Fontaine, Philippe, Goldmann, Michel, Filipe, Eduardo J. M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697836/
https://www.ncbi.nlm.nih.gov/pubmed/33202626
http://dx.doi.org/10.3390/nano10112257
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author Silva, Pedro
Nova, Duarte
Teixeira, Miguel
Cardoso, Vitória
Morgado, Pedro
Nunes, Bruno
Colaço, Rogério
Fauré, Marie-Claude
Fontaine, Philippe
Goldmann, Michel
Filipe, Eduardo J. M.
author_facet Silva, Pedro
Nova, Duarte
Teixeira, Miguel
Cardoso, Vitória
Morgado, Pedro
Nunes, Bruno
Colaço, Rogério
Fauré, Marie-Claude
Fontaine, Philippe
Goldmann, Michel
Filipe, Eduardo J. M.
author_sort Silva, Pedro
collection PubMed
description In this work, Langmuir films of two highly fluorinated fatty alcohols, CF(3)(CF(2))(12)CH(2)OH (F14OH) and CF(3)(CF(2))(16)CH(2)OH (F18OH), were studied. Atomic Force Microscopy (AFM) images of the films transferred at zero surface pressure and low surface density onto the surface of silicon wafers by the Langmuir-Blodgett technique revealed, for the first time, the existence of solid-like domains with well-defined mostly hexagonal (starry) shapes in the case of F18OH, and with an entangled structure of threads in the case of F14OH. A (20:80) molar mixture of the two alcohols displayed a surprising combination of the two patterns: hexagonal domains surrounded by zigzagging threads, clearly demonstrating that the two alcohols segregate during the 2D crystallization process. Grazing Incidence X-ray Diffraction (GIXD) measurements confirmed that the molecules of both alcohols organize in 2D hexagonal lattices. Atomistic Molecular Dynamics (MD) simulations provide a visualization of the structure of the domains and allow a molecular-level interpretation of the experimental observations. The simulation results clearly showed that perfluorinated alcohols have an intrinsic tendency to aggregate, even at very low surface density. The formed domains are highly organized compared to those of hydrogenated alcohols with similar chain length. Very probably, this tendency is a consequence of the characteristic stiffness of the perfluorinated chains. The diffraction spectrum calculated from the simulation trajectories compares favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The present results highlight for the first time an inherent tendency of perfluorinated chains to aggregate, even at very low surface density, forming highly organized 2D structures. We believe these findings are important to fully understand related phenomena, such as the formation of hemi-micelles of semifluorinated alkanes at the surface of water and the 2D segregation in mixed Langmuir films of hydrogenated and fluorinated fatty acids.
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spelling pubmed-76978362020-11-29 Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density Silva, Pedro Nova, Duarte Teixeira, Miguel Cardoso, Vitória Morgado, Pedro Nunes, Bruno Colaço, Rogério Fauré, Marie-Claude Fontaine, Philippe Goldmann, Michel Filipe, Eduardo J. M. Nanomaterials (Basel) Article In this work, Langmuir films of two highly fluorinated fatty alcohols, CF(3)(CF(2))(12)CH(2)OH (F14OH) and CF(3)(CF(2))(16)CH(2)OH (F18OH), were studied. Atomic Force Microscopy (AFM) images of the films transferred at zero surface pressure and low surface density onto the surface of silicon wafers by the Langmuir-Blodgett technique revealed, for the first time, the existence of solid-like domains with well-defined mostly hexagonal (starry) shapes in the case of F18OH, and with an entangled structure of threads in the case of F14OH. A (20:80) molar mixture of the two alcohols displayed a surprising combination of the two patterns: hexagonal domains surrounded by zigzagging threads, clearly demonstrating that the two alcohols segregate during the 2D crystallization process. Grazing Incidence X-ray Diffraction (GIXD) measurements confirmed that the molecules of both alcohols organize in 2D hexagonal lattices. Atomistic Molecular Dynamics (MD) simulations provide a visualization of the structure of the domains and allow a molecular-level interpretation of the experimental observations. The simulation results clearly showed that perfluorinated alcohols have an intrinsic tendency to aggregate, even at very low surface density. The formed domains are highly organized compared to those of hydrogenated alcohols with similar chain length. Very probably, this tendency is a consequence of the characteristic stiffness of the perfluorinated chains. The diffraction spectrum calculated from the simulation trajectories compares favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The present results highlight for the first time an inherent tendency of perfluorinated chains to aggregate, even at very low surface density, forming highly organized 2D structures. We believe these findings are important to fully understand related phenomena, such as the formation of hemi-micelles of semifluorinated alkanes at the surface of water and the 2D segregation in mixed Langmuir films of hydrogenated and fluorinated fatty acids. MDPI 2020-11-14 /pmc/articles/PMC7697836/ /pubmed/33202626 http://dx.doi.org/10.3390/nano10112257 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Silva, Pedro
Nova, Duarte
Teixeira, Miguel
Cardoso, Vitória
Morgado, Pedro
Nunes, Bruno
Colaço, Rogério
Fauré, Marie-Claude
Fontaine, Philippe
Goldmann, Michel
Filipe, Eduardo J. M.
Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title_full Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title_fullStr Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title_full_unstemmed Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title_short Langmuir Films of Perfluorinated Fatty Alcohols: Evidence of Spontaneous Formation of Solid Aggregates at Zero Surface Pressure and Very Low Surface Density
title_sort langmuir films of perfluorinated fatty alcohols: evidence of spontaneous formation of solid aggregates at zero surface pressure and very low surface density
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697836/
https://www.ncbi.nlm.nih.gov/pubmed/33202626
http://dx.doi.org/10.3390/nano10112257
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