Semifluorinated alkanes

More recently, other heavier than water products have been developed for temporary internal tamponade. These are fluorosilicones [46,47], semifluorinated alkanes [1,7], heavy fluorocarbon liquid (HFCL) oligomers [5,7] and solutions of fluorine-containing compound and silicone oil [8-10,47],... 

J. Roider, FI. Floerauf, K. Kobuch, V.P. Gabel, Clinical findings on the use of long-term heavy tamponades (semifluorinated alkanes and their oligomers) in complicated retinal detachment surgery, Graefes Arch. Clin. Exp. Ophthalmol. 240 (2002) 965-971. 

M. Maaloum, P. Muller, M.P. Krafft, Lateral and vertical nanophase separation in Langmuir-Blodgett films of phospholipids and semifluorinated alkanes, Langmuir 20 (2004) 2261-2264. 

Fig. 10.6.4. AFM images (non-contact) for FsHis (semifluorinated alkane) /S-CyD inclusion complex scale bar — 200 nm.

FIGURE 11.5 Synthesis of semifluorinated alkanes by radical addition of perfluoroalkyl iodides to olefins, derived from Reference 51 (a) initiation (b) iodine abstraction from Rj (c) addition of Rf radical to the double bond (d) chain propagation. 

FIGURE 11.12 Structural model for semifluorinated alkanes following Russell et al. [21], showing the interdigitated structure of the alkane molecules. 

Guenther, B. Theisinger, B. Theisinger, S. Scherer, D. Topical Pharmaceutical Composition Based on Semifluorinated Alkanes. PCT Int. Appl. WO 2012160179 A2 20121129 2012. 

Bulk-phase self-assembly of a series of semifluorinated alkanes with hydrocarbon chains of varying length has been investigated by F NMR spectroscopy. At room temperature, a single resonance for the terminal -CF3 group was observed at 81.7 ppm for perfluorododecylhexane... 

The investigated semifluorinated alkanes exhibit smectic phases, mainly of the hexagonal ordered type. However, a smectic A phase in an iodine derivative has also been reported [170]. 

Genzer, J., Sivaniah, E., Kramer, E.J. et al. (2000b) The orientation of semifluorinated alkanes attached to polymers at the surface of polymer films. Macromolecules, 33,1882-1887. 

Semifluorinated alkanes are low-molecular-weight block copolymers of nonnal perfluorocarbons and hydrocarbons [160-171]. Their structure formula F(CF2) (CH2) H is usually abbreviated to F ,H [164] or F H , [163]. The semifluorinated alkanes so far reported have 6 to 32 carbon atoms m -f- n). 

The compounds w = 12 and n = 8, 14, or 18 lower the surface tension of n-dodecane [164]. The adsorption of the semifluorinated alkane at hydrocarbon-air surfaces increases with increasing length of its fluorocarbon chain [172], increasing chain length of the alkane solvent and decreasing temperature [169]. 

The semifluorinated alkanes, such as FeHio, stabilize aqueous perfluoro emulsions by forming an interface between the fluorocarbon phase and the phospholipid emulsifier [174]. The stabilizing effect is attributed to a more favorable structure of the interfacial film [175]. 

Oleophilic/oleophobic fluorinated surfactants without a hydrophile, designed for use in hydrocarbon systems, are in a structural sense also nonionic fluorinated surfactants (see Section 1.8) for example, the semifluorinated alkanes [266-270], block polyethylene-polypropylene glycol ethers prepared with perfluoroalkene trimers [271], surfactants featuring an oligo(hexafluoropropene oxide) chain [272], and carboxamides and sulfonamides derived from A -(perfluorooctanesul-fonyl)piperazine [273]. 

Semifluorinated alkanes are prepared by a free-radical-initiated addition of perfluoroalkyl iodide to a terminal olefin [141,274,275]. Oil-soluble surfactants, CF3CF2CF20[CF(CF3)CF20] -2CF(CF3)C0R (R = phenyl or p-tolyl), are obtained by arylating hexafluoropropylene oxide oligomeric acid halides [272]. Carboxamides and sulfonamides are prepared by conventional reactions using N-(per-fluorooctanesulfonyl)piperazine as the intermediate [273]. 

The development of fluorinated surfactants for organic solvents is still ongoing. The structural design is limited by (1) the dependence of surface activity on the solubility of the surfactant in the solvent and (2) the initial surface tension of the solvent. Hence, a fluorinated surfactant cannot have the same optimum structure for all organic solvents [92]. For semifluorinated alkanes see Section 1.8. 

Supercritical fluid chromatography, with CO2 as the mobile phase, can determine the telomer and homolog distribution in nonionic fluorinated surfactants (Fig. 9.3). Supercritical fluid chromatography with an octadecylsilane-bonded stationary phase has been utilized in studies of semifluorinated alkanes [51]. 

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