Alkanoic acids, perfluorinated

Recently fluorinated chains were also attached to amine based dendrimers, like PPI and poly(amido amine) (PAMAM), by means of ionic self assembly with semiperfluorinated alkanoic acids (Fig. 71, 216, 217). All dendrimer complexes 216 with perfluorinated alkanoic acids show SmA phases except the fifth generation dendrimer which shows a Colrec phase [378]. Also semiperfluorinated 4-alkoxybenzoic acids 217 [379] and mixed systems combining fluorinated and nonfluorinated alkanoic or benzoic acids (216, 217) have been reported [379-381]. In most cases layer structures (SmA) and for higher generation dendrimers also modulated SmA phases (Colrec phases) were observed. The layer thickness of the SmA phases of the mixed complexes 216 depends on the ratio of fluorinated and non-fluorinated acids, where smaller d values were observed for dendrimers with low Rp-content for Rp-rich dendrimers the more rigid Rp-chains provide... 

The use of ultrasounds to aid the extraction is another possibility. Phthalates (Abb et al. 2009) and perfluorinated alkanoic acid (PEA) (Kato et al. 2009) determinations have been reported. Ethyl acetate (phthalates) or formic acid with methanol (perfluoroalkyl chemicals) was added to the dust sample, and extraction was performed in an ultrasonic bath at room temperature for 10 min. In the case of phthalates an enrichment step was not carried out to avoid the risk of contamination. Pyrethroids and their metabolites can also been extracted from indoor dust samples by adding methylene chloride followed by sonication for 10 min (Starr et al. 2008). Another option is the combination of Soxhlet extraction with an ultrasonic treatment (Schecter et al. 2009). 

A series of N-alkyl perfluoroalkanamides were recently prepared by the Weiss group [6]. Perfluorinated alkanoic acids were transformed into acid chlorides by oxalyl chloride in benzene, and subsequent amidation with alky-lamine in benzene gave N-alkyl perfluoroalkanamides (Scheme 1). The amide derivative 3 exhibited efficient gelation (mgc < 2.5 wt %) of various organic solvents including EtOH, 1-butanol, 1-octanol, hexane, -octane, benzyl alcohol, toluene, and CCI4. 

Fluoropolymers, such as poly(tetrafluoroethylene) (PTFE), and SAM-forming molecules, such as perfluorinated thiols, silanes, and n-alkanoic acids, are widely used for surface fluorina-tion in academia and industry (e.g., as easy-to-clean surfaces). The modification of surfaces with PTFE is chemically challenging because of its low reactivity and solubility. Thiols, on the other hand, generally form stable layers on (noble) metals only and are thus not applicable to the functionalization of most materials. Utilizing catechol derivatives to fluorinate a wide variety of surfaces in order to render them hydrophobic or nonadhesive is therefore a promising alternative. 

Branching of the fluorocarbon chain decreases the efficiency of a fluorinated surfactant in surface tension reduction [57,58]. In analogy, a condensed (spread) monolayer of a perfluorinated n-alkanoic acid has a lower critical surface tension than its terminally branched isomer. Bemett and Zisman [59] attributed the effect of branching to different molecular packing and carbon chain adlineation. 

Fig. 5.2 Contact angles observed for n-alkanes on monolayers of perfluorinated alkanoic acid homologs. (From Ref. 26. Reproduced by permission of the American Chemical Society.)...

The excellent chemical stability of perfluorinated alkanoic and alkanesul-fonic acids to acids, oxidants, and alkali [5,13,17] allows their application under conditions too severe for hydrocarbon-based surfactants. Gramstad and Haszel-dine [14] did not detect fluoride when they heated potassium perfluorooctanesulfonate (0.9 g) in water (5 mL) at 300°C for 8 h. However, when potassium perfluorooctanesulfonate was heated in 10% aqueous potassium hydroxide for 8 h at 270°C, 8% of the theoretical amount of fluoride was liberated. Perfluorooctane-... 

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