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Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase

Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, in this...

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Autores principales: Fontaine, Philippe, Filipe, Eduardo J. M., Fauré, Marie-Claude, Rego, Tomas, Taßler, Stephanie, Alves, Ana Carolina, Silva, Gonçalo M. C., Morgado, Pedro, Goldmann, Michel
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804139/
https://www.ncbi.nlm.nih.gov/pubmed/31590402
http://dx.doi.org/10.3390/molecules24193590
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author Fontaine, Philippe
Filipe, Eduardo J. M.
Fauré, Marie-Claude
Rego, Tomas
Taßler, Stephanie
Alves, Ana Carolina
Silva, Gonçalo M. C.
Morgado, Pedro
Goldmann, Michel
author_facet Fontaine, Philippe
Filipe, Eduardo J. M.
Fauré, Marie-Claude
Rego, Tomas
Taßler, Stephanie
Alves, Ana Carolina
Silva, Gonçalo M. C.
Morgado, Pedro
Goldmann, Michel
author_sort Fontaine, Philippe
collection PubMed
description Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, in this work, we presented Grazing Incidence X-ray Diffraction measurements, which exhibit two diffraction peaks on the transition plateau: One is the signature of the hexagonal structure of the LC phase, the second one is associated to the low-density fluid phase and is thus more ordered than expected for a 2D gas or a typical fluid phase. Atomistic molecular dynamics simulations, performed on the transition plateau, revealed the existence of clusters in which domains of vertical molecules organized in a hexagonal lattice coexist with domains of parallel lines formed by tilted molecules, a new structure that could be described as a “2D smectic C” phase. Moreover, the diffraction spectrum calculated from the simulation trajectories compared favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The results were also in agreement with the thermodynamic analysis of the fluid phase and X-ray Reflectivity experiments performed before and after the transition between these two phases.
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spelling pubmed-68041392019-11-18 Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase Fontaine, Philippe Filipe, Eduardo J. M. Fauré, Marie-Claude Rego, Tomas Taßler, Stephanie Alves, Ana Carolina Silva, Gonçalo M. C. Morgado, Pedro Goldmann, Michel Molecules Article Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, in this work, we presented Grazing Incidence X-ray Diffraction measurements, which exhibit two diffraction peaks on the transition plateau: One is the signature of the hexagonal structure of the LC phase, the second one is associated to the low-density fluid phase and is thus more ordered than expected for a 2D gas or a typical fluid phase. Atomistic molecular dynamics simulations, performed on the transition plateau, revealed the existence of clusters in which domains of vertical molecules organized in a hexagonal lattice coexist with domains of parallel lines formed by tilted molecules, a new structure that could be described as a “2D smectic C” phase. Moreover, the diffraction spectrum calculated from the simulation trajectories compared favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The results were also in agreement with the thermodynamic analysis of the fluid phase and X-ray Reflectivity experiments performed before and after the transition between these two phases. MDPI 2019-10-05 /pmc/articles/PMC6804139/ /pubmed/31590402 http://dx.doi.org/10.3390/molecules24193590 Text en © 2019 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
Fontaine, Philippe
Filipe, Eduardo J. M.
Fauré, Marie-Claude
Rego, Tomas
Taßler, Stephanie
Alves, Ana Carolina
Silva, Gonçalo M. C.
Morgado, Pedro
Goldmann, Michel
Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title_full Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title_fullStr Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title_full_unstemmed Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title_short Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase
title_sort structure of langmuir monolayers of perfluorinated fatty acids: evidence of a new 2d smectic c phase
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804139/
https://www.ncbi.nlm.nih.gov/pubmed/31590402
http://dx.doi.org/10.3390/molecules24193590
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