Article

Nano-segregation in mixtures of hydrogenated and fluorinated alcohols: Using 129Xe NMR spectroscopy to measure local composition

Journal of Molecular Liquids

Tiago M. Eusébio; Pedro Silva; Eduardo J. M. Filipe — 2025 — Elsevier

Key information

Authors:

Tiago M. Eusébio (Tiago Mendonça Eusébio); Pedro Silva (Pedro Manuel Ribeiro Silva); Miguel Guedes (Rúben Miguel Guedes Monteiro); Diogo Machacaz (Diogo Nuno Rodrigues Marques Torcato Machacaz); Pedro Morgado (Pedro Jorge Rodrigues Morgado); Luís F. G. Martins; Eduardo J. M. Filipe (Eduardo Jorge Morilla Filipe)

Published in

January 15, 2025

Abstract

Binary liquid mixtures of n-alkanols and 1H,1H-perfluoroalcohols were investigated, combining 129Xe NMR spectroscopy, atomistic molecular dynamics (MD) simulations and the measurement of excess molar volumes. All mixtures display very large and positive excess molar volumes, which are accurately reproduced by the MD simulation results. The 129Xe NMR spectra confirm the existence of segregation between hydrogenated and fluorinated chains and thus the existence of hydrogenated-rich and fluorinated-rich nanodomains. The degree of segregation gradually increases with the chain length of both alcohols but is lower than that observed in equivalent mixtures of alkanes + perfluoroalkanes. The average local composition within xenon’s coordination sphere was calculated from the 129Xe NMR spectra and found to differ up to ±0.03 mol fraction from the nominal composition of the mixtures. For all mixtures, the xenon’s enrichment curves are S-shaped: at low concentration of the fluorinated alcohol, xenon atoms are located predominantly in more fluorinated environments (than the nominal concentration of the mixture), while at higher concentrations, they are found in environments that are more hydrogenated. MD simulations confirm the existence of segregation between hydrogenated and fluorinated chains and the tendency of xenon atoms to locate near end groups, CH3 and particularly CF3, but not OH. Local compositions computed from the simulation runs reproduce the experimental S-shaped curves with remarkable accuracy, validating the used molecular models and methodology and adding enhanced consistency to the whole study. The MD simulations were further used to analyse the interstitial space in the mixtures, in particular the existence of voids with the adequate volume to accommodate xenon atoms and its dependence on the mixture composition. The results indicate that the location of xenon atoms results from a balance between the degree of segregation between hydrogenated and fluorinated chains and the existence of voids with the adequate volume.

Publication details

Authors in the community:

Publication version

VoR - Version of Record

Publisher

Elsevier

Link to the publisher's version

https://www.sciencedirect.com/science/article/pii/S0167732224027582

Title of the publication container

Journal of Molecular Liquids

First page or article number

126697

Volume

418

ISSN

0167-7322

DOI

10.1016/j.molliq.2024.126697

Fields of Science and Technology (FOS)

physical-sciences - Physical sciences

Keywords

  • Fluorinated alcohols
  • Xe NMR spectroscopy
  • Nano-segregation
  • Local concentration
  • Void analysis

Publication language (ISO code)

eng - English

Rights type:

Only metadata available

Creative Commons license

CC-BY - Attribution

Financing entity

Fundação para a Ciência e a Tecnologia

Title of the project, award or grant: Doctoral Grant

Visit project

Identifier for the funding entity: https://doi.org/10.13039/501100001871

Type of identifier of the funding entity: Crossref Funder

Number for the project, award or grant: SFRH/BD/149192/2019