Fluorinated and semi-fluorinated surfactants

Abstract

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

Fluorosurfactants at Structural Extremes: Adsorption and Aggregation

“…Altering the position and number of surfactant headgroup(s) had significant effects on both the adsorption and aggregation properties. The γ cmc values of both the L and Y surfactants were typical of nonionic fluorinated surfactants in water (∼20 mN m -1 ). ,− However, interestingly, the limiting surface tension of bolaform B was in the range of a typical hydrocarbon bolaform (30−40 mN m -1 ). , This result agrees with previous literature in that a bolaform structure is much less efficient at reducing tension than a corresponding conventional linear surfactant. , The cmc of B is ∼21 lower than that of L and ∼ 3 lower than that of Y, showing a strong dependence of the cmc on the number of headgroups rather than the actual molecular architecture. The difference depends on the hydrophile−lipophile balance of the headgroup and can be very large, the more so the more hydrophilic the group.…”

Per- and polyfluorinated substances (PFASs): Environmental challenges

“…Long-F-chain surfactants and polymers can indeed simultaneously provide utmost hydrophobicity and lipophobicity, extreme surface activity (effectiveness and efficiency), phase-separation and compartmentation ability, highly stable and thin self-assembled condensed film-forming capacity, tunable wetting properties, ultimate thermal stability and chemical inertness, excellent sun light resistance, water refractivity matching, at reasonable cost, generating innumerable industrial and every-day uses [2, [403][404][405]. The present (hopefully temporary) alternatives are merely variants of established commercial products.…”

Lack of Association between a Cationic Protein and a Cationic Fluorosurfactant

“…For comparison, we also performed NMR experiments in mixtures of lysozyme and hexadecyltrimethylammonium bromide (CTAB), which is a cationic surfactant with the same headgroup as FC134 and has been shown to interact with lysozyme. 15,16,32,33 In Figure 6, we can clearly observe chemical shift changes (see also Table 1) for all 1 H signals in CTAB when added to a lysozyme solution. The chemical shift may alter as a consequence of changes in the intermolecular environment and/or molecular conformation and, hence, is an indicator of interaction with the protein.…”

“…Since the integral intensity is directly proportional to the number of nuclear spins within the probe coil volume, 18 the surfactant concentration corresponding to the different CF 3 signals can be obtained. 1 H NMR spectra were recorded in samples with D 2 O solvent for solutions of pure protein, pure surfactant, and a mixture of the two.…”