The influence of surfactant head group on miscibility in mixed hydrocarbon-perfluorocarbon monolayers

Sowah-Kuma, David; Paige, Matthew F.

doi:10.1016/j.colsurfa.2018.08.025

Cited by 6 publications

(12 citation statements)

References 17 publications

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“…The height profiles illustrate that, in both alcohols, the height of the visible domains is comparable to the length of the fully extended molecules (~1.8 nm for F14OH [ 44 ] and ~2.5 nm for F18OH [ 37 ]) within the experimental error. This is an indication that the molecules within the aggregates are perpendicular to the underlying substrate in agreement with the GIXD results.…”

Section: Resultsmentioning

confidence: 63%

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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

et al. 2020

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In this work, Langmuir films of two highly fluorinated fatty alcohols, CF3(CF2)12CH2OH (F14OH) and CF3(CF2)16CH2OH (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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Section: Resultsmentioning

confidence: 63%

“…This intrinsic “antipathy” between hydrogenated and perfluorinated substances has been the basis for a number of studies on the segregation and 2D phase-separation in Langmuir films of mixtures of hydrogenated and perfluorinated carboxylic acids [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ] and alcohols [ 43 , 44 ].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…The majority of our works to date have emphasized the impact of tail length on pattern formation, but we have just recently begun to investigate the effects of surfactant headgroups. We have started by examining the behavior of a mixed monolayer consists of nonadecanol (C18H-ol) and our benchmark C13F and compared results with the fatty acid analogue of the hydrocarbon component (nonadecanoic acid, C18H) . Although the thermodynamic differences in mixing behavior attributed to headgroup interactions between these two systems were minimal, there were notable differences in film morphology.…”

Section: Morphology Study Of Hydrocarbon–fluorocarbon Mixed Monolayersmentioning

confidence: 99%

“…(A) Pure C18H-ol, (B) pure C18H, (C) C18H-ol-C13F (H:F = 4:1), (D) C18H–C13F (H:F = 4:1), and (E) pure C13F, deposited at π = 30 mN m –1 and T = 22 ± 1 °C. Reprinted with permission from ref . Copyright 2018 Elsevier.…”

Section: Morphology Study Of Hydrocarbon–fluorocarbon Mixed Monolayersmentioning

confidence: 99%

Pattern Formation in Phase-Separated Langmuir and Langmuir Monolayer Films

Yan

Paige

2021

Langmuir

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Mixed monolayer films comprising hydrogenated and fluorinated surfactants can undergo phase separation to produce interfaces with diverse structures at the micrometer and nanometer scales. This review discusses our progress over the past decade to probe the relationship that exists between the molecular structure of the surfactants that comprise the films and the overall patterns formed in the monolayers. We review two main classes of mixed perfluorocarbon–hydrocarbon surfactant systems, including fatty acids and a recently developed family of EDTA-based gemini surfactants. In addition to summarizing the state-of-the-art of this field, the key scientific questions and relationships that require further elucidation are discussed, along with directions for continuing research into this fascinating area of research.

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“…Examinations of the π-A isotherms of single and mixed SA/PFTA and C18OH/PFTA monolayers ( Figure 2) are helpful for studying their phase behaviors on aqueous subphases. At the air-pure water interface (Figure 2a), compression of the SA monolayer exhibited typical phase behavior of fatty acids (Griffith et al, 2012;Sowah-Kuma & Paige, 2018). The isotherm started with a gaseous-tilted condensed (G-TC) coexistence phase and entered a tilted condensed (TC) phase after being compressed to the lift-off area of 32.8 Å 2 /molecule.…”

Section: Surface Pressure-area (π-A) Isothermmentioning

confidence: 99%

Understanding the Interfacial Behavior of Typical Perfluorocarboxylic Acids at Surfactant‐Coated Aqueous Interfaces

Cheng

George

2020

JGR Atmospheres

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Sea surface microlayers (SMLs) play an important role in the transport and fate of surfactants from both anthropogenic and biogenic sources. The formation of sea spray aerosols (SSAs) at the SML has been recognized as a critical pathway for the entry of surfactants into the atmosphere. Perfluorocarboxylic acids (PFCAs) have become increasingly concerning as a class of emerging organic pollutants, having high enrichment in surface seawaters due to their remarkable surface activity. Using artificial seawater coated by extensively existed surfactants, including stearyl alcohol (C18OH) and stearic acid (SA) as simplified models of the SML and fresh SSAs, the interfacial behaviors of soluble and insoluble PFCAs were examined. Information about lateral packing and chain conformation of films was obtained by means of Langmuir trough and infrared reflection‐absorption spectroscopy (IRRAS). Perfluorooctanoic acid (PFOA) dissolved in aqueous subphases was found to be incorporated into lipid monolayers via alterations in surface pressure‐area (π‐A) isotherms. With negligible solubility, perfluorotetradecanoic acid (PFTA) formed condensed mixed monolayers with other lipids at the air‐water interface. The mixed monolayers of C18OH/PFTA and SA/PFTA were expanded by the addition of sea salts into the pure water subphase. Compared with the π‐A isotherms of SA/PFTA, decreased molecular areas were observed for those of C18OH/PFTA. This research suggests that PFCAs can be incorporated into air‐water interfaces by acting as film‐forming materials. The introduction of PFCAs will alter the surface properties and thus the atmospheric fate and behavior of SSAs and SMLs.

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The influence of surfactant head group on miscibility in mixed hydrocarbon-perfluorocarbon monolayers

Cited by 6 publications

References 17 publications

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

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

Pattern Formation in Phase-Separated Langmuir and Langmuir Monolayer Films

Understanding the Interfacial Behavior of Typical Perfluorocarboxylic Acids at Surfactant‐Coated Aqueous Interfaces

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