Adsorption of Semifluorinated Alkanes at Hydrocarbon-Air Surfaces

Binks, Bernard P.; Fletcher, Paul D. I.; Sager, W.F.C.; Thompson, Richard L.

doi:10.1021/la00003a047

Cited by 45 publications

(71 citation statements)

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“…This has been verified in our laboratory [74]. The adsorption of a range of linear SF As at hydrocarbon-air surfaces has been investigated using surface tension methods [75][76][77].…”

Section: Fluorosurfactants Without a Hydrophilic Groupmentioning

confidence: 64%

“…In favourable cases, adsorbed SF A mono layers at the alkane-air surface are close packed. For example, F IlH14 at the dodecane-air interface at 20°C shows a limiting area per SF A molecule of 0.26 nm l [77], close to (or even slightly less than) the cross sectional area of an all-trans perftuorocarbon chain in a crystal phase (0.2S nm l ). 3.…”

Section: Fluorosurfactants Without a Hydrophilic Groupmentioning

confidence: 82%

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Fluorinated and semi-fluorinated surfactants

Fletcher¹

1997

Specialist Surfactants

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Surfactants which contain one or more fluorinated or partially fluorinated hydrophobic groups (fluorinated surfactants or 'fluorosurfactants') can show dramatically different properties to those of hydrocarbon surfactants. The special properties of fluorosurfactants, which result from the unique properties of fluorocarbon chains, makes them irreplaceable in a wide range of applications and justifies Kissa's claim in his 1994 text on the subject that fluorinated surfactants are truly 'super surfactants' [1]. Rather than exhaustively review the huge literature on fluorosurfactants, the main aim of this chapter is to give an account of the special surfactant properties of fluorinated surfactants and to relate these properties to the differences in physical properties between fluorocarbon and hydrocarbon chains.The chapter is organized as follows. The main structural types of common fluorosurfactants and some aspects of their synthesis are described briefly in sections 5.2 and 5.3. In section 5.4, the physical properties of fluorinated and partially fluorinated chains are discussed and compared with those of the corresponding hydrocarbons. As will be seen, the different properties of the two types of chain provide a good basis for the rationalization and interpretation of the special properties of fluorosurfactants. Adsorption and aggregation behavior of fluorosurfactants in water is discussed in section 5.5. Adsorption and aggregation in apolar oil solutions of fluorosurfactants is covered in section 5.6. Section 5.7 gives a description of their phase behavior in mixtures of oil and water. The wetting of solid surfaces by fluorosurfactant solutions is dealt with in section 5.8. Finally, section 5.9 gives a brief summary of the main applications of fluorosurfactants. Structures of fluorinated surfactantsLike conventional surfactants, fluorosurfactants generally contain a hydrophilic group and a hydrophobic group within the same molecule. A selection of the wide range of fluorosurfactant molecular structures are described here. A more exhaustive list is given in chapter 1 of Reference 1.The hydrophobic group of fluorinated or semifluorinated surfactants can I. D. Robb (ed.), Specialist Surfactants

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“…This has been verified in our laboratory [74]. The adsorption of a range of linear SF As at hydrocarbon-air surfaces has been investigated using surface tension methods [75][76][77].…”

Section: Fluorosurfactants Without a Hydrophilic Groupmentioning

confidence: 64%

Section: Fluorosurfactants Without a Hydrophilic Groupmentioning

confidence: 82%

Fluorinated and semi-fluorinated surfactants

Fletcher¹

1997

Specialist Surfactants

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“…[3,6,[9][10][11] Due to the lipophobic character of F-alkyl chains, fluorocarbon/hydrocarbon diblocks (C n F 2n + 1 C m H 2m + 1 , FnHm) display some amphiphilic behavior, despite the absence of a hydrophilic polar head group. [5,6,12,13] A distinctive feature of semifluorinated alkanes is indeed the fact that, although they are apolar in the sense that they do not dissolve in protic solvents, they possess a significant dipole moment that is located at the junction between the two blocks and reflects the strong electron-withdrawing character of the F-alkyl chain. These characteristics endow FnHm diblocks with specific properties in both the solid (liquid-crystal behavior) [14,15] and liquid states (surface freezing), [16] in solutions (micelle formation in both hydrocarbons and fluorocarbons), [17][18][19] and at interfaces (formation of stable Langmuir films).…”

Section: Introductionmentioning

confidence: 99%

Compression of Self‐Assembled Nano‐Objects: 2D/3D Transitions in Films of (Perfluoroalkyl)Alkanes—Persistence of an Organized Array of Surface Micelles

Lux

Gallani

Waton

et al. 2010

Chemistry A European J

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Understanding and controlling the molecular organization of amphiphilic molecules at interfaces is essential for materials and biological sciences. When spread on water, the model amphiphiles constituted by C(n)F(2n+1)C(m)H(2m+1) (FnHm) diblocks spontaneously self-assemble into surface hemimicelles. Therefore, compression of monolayers of FnHm diblocks is actually a compression of nanometric objects. Langmuir films of F8H16, F8H18, F8H20, and F10H16 can actually be compressed far beyond the "collapse" of their monolayers at approximately 30 A(2). For molecular areas A between 30 and 10 A(2), a partially reversible, 2D/3D transition occurs between a monolayer of surface micelles and a multilayer that coexist on a large plateau. For A<10 A(2), surface pressure increases again, reaching up to approximately 48 mN m(-1) before the film eventually collapses. Brewster angle microscopy and AFM indicate a several-fold increase in film thickness when scanning through the 2D/3D coexistence plateau. Compression beyond the plateau leads to a further increase in film thickness and, eventually, to film disruption. Reversibility was assessed by using compression-expansion cycles. AFM of F8H20 films shows that the initial monolayer of micelles is progressively covered by one (and eventually two) bilayers, which leads to a hitherto unknown organized composite arrangement. Compression of films of the more rigid F10H16 results in crystalline-like inflorescences. For both diblocks, a hexagonal array of surface micelles is consistently seen, even when the 3D structures eventually disrupt, which means that this monolayer persists throughout the compression experiments. Two examples of pressure-driven transformations of films of self-assembled objects are thus provided. These observations further illustrate the powerful self-assembling capacity of perfluoroalkyl chains.

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“…Despite numerous options for molecular structure and composition, the most investigated SFAs are those with long perfluorinated chains. They were characterized in solid state [8][9][10][11], in solutions [12][13][14][15][16], and as Langmuir monolayers [17][18][19].…”

Section: Introductionmentioning

confidence: 99%