Fluorinated surfactants chemical stability

The high thermal and chemical stability of fluorocarbons, combined with their very weak intermolecular interactions, makes them ideal stationary phases for the separation of a wide variety of organic compounds, including both hydrocarbons and fluorine-containing molecules Fluonnated stationary phases include per-fluoroalkanes, fluorocarbon surfactants, poly(chlorotrifluoroethylene), polyfper-fluoroalkyl) ethers, and other functionalized perfluoro compounds The applications of fluonnated compounds as stationary phases in gas-liquid chroma... 

Partly fluorinated or perfluorinated sulfonic and carboxylic acids are compounds with excellent surface activity combined with an extreme stability against chemical or physico-chemical attacks as also described for non-ionic fluorine containing surfactant compounds. The anionic surfactants are shown with their structural formulae in Fig. 2.11.24(1)—(III). A selected ESI-FIA-MS(-) spectrum of a partly fluorinated surfactant (CF3-(CF2)4-(CH2)8-S03H, m/z 461) is presented in Fig. 2.11.25. The FIA spectrum also contains ions of the by-products CF3-(CF2)2-(CH2)8-S03H (m/z 361) and CF3-(CF2)3-(CH2)8-S03H (m/z 411). 

Abstract Fluorinated surfactants have been conunercially available since the 1950s. The first available were perfluoroalkyl sulfonic acids. The unique properties e.g., surface tension lowering in aqueous systems, high chemical and thermal stability of these acids and their derivatives when used at low concentrations resulted in their widespread use in industrial processes and consumer uses. The most common commercially produced peifluorinated surfactants are the perfluoroalkyl acids. 

The outstanding chemical stability of fluorinated surfactants to strong acids and alkali permits their use under conditions in which conventional surfactants would decompose. Certain fluorinated surfactants can be used in the presence of strong oxidants, acids, or alkalies even at elevated temperatures. 

Fluorinated surfactants are unique. The stability of fluorinated surfactants to heat or chemical attack is advantageous when preparing emulsions containing corrosive chemicals. The fluorocarbon part of the molecule is not only hydrophobic but also oleophobic and contributes to a very low free-surface energy of the ad-... 

A unique characteristic of fluorinated surfactants is the chemical stability of the fluorocarbon chain to strong acids, oxidizing agents, and concentrated alkalis. Hence, fluorinated surfactants can be used in media where hydrocarbon-based surfactants would decompose. 

The excellent chemical stability permits fluorinated surfactants to be used in electroplating baths where hydrocarbon-type surfactants would not survive [1,8,9,87-93]. Fluorinated surfactants are remarkably stable in a solution of chromic oxide in sulfuric acid at 50°C [94,95]. (See Section 3.1.)... 

A range of fluorinated anionic surfactants, which are structural relatives of Aerosol-OT, were synthesized and characterized, with the aim of investigating the effects of chemistry on the structure and stability of water-in-carbon dioxide microemulsions. The dilute aqueous phase behavior was studied to check for chemical purity and fuUy characterize the compounds. Once appropriate measures were taken to achieve sufficient purity, the surface excesses measured by both tensiometry and neutron reflection measurements agreed well, and the surface tensions were consistent with a prefactor of 2 in the Gibbs equation. 

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