Surfactants perfluoroalkyl-based

Despite their intrinsically higher costs perfluoroalkyl surfactants have unique advantages over conventional hydrocarbon-based surfactants, including ... 

Perfluoroalkyl or Polysiloxane Group The presence of either of these groups as the hydrophobic group in the surfactant permits reduction of the surface tension of water to lower values that those attainable with a hydrocarbon-based hydrophobic group. Perfluoroalkyl surfaces are both water- and hydrocarbon-repellent. 

A very different kind of surfactant molecule obtains if the carboxylate head group of an alkanoic acid is replaced by one that is both hydrophobic and lipophobic, like a perfluoroalkyl group. Such diblock molecules, F(CF2) (CH2) H(FmHn), have been shown to form normal and reverse micelles in perfluoroalkanes and alkanes, respectively [68,69]. On the bases of the well-known antipathy between hydrocarbons and perfluorocarbons, the disparity between cross-sectional areas and volumes of CH (18.5 and 10.22 A ) [70, 71] and CF (28.3 A and 16.04 A ) [70, 71] groups, and the tendency of long perfluoroalkyl chains to adopt helical conformations, it is expected and found that organized assemblies of FmH/i molecules exhibit some strange properties. For instance, the alkyl portions of many of these molecules melt before their perfluoroalkyl portions [72], and the allowed motions resemble closely those of -alkanes in their rotator phases [73, 74]. 

The free-radical addition of TFE to pentafluoroethyl iodide yields a mixture of perfluoroalkyl iodides with even-numbered fluorinated carbon chains. This is the process used to commercially manufacture the initial raw material for the fluorotelomer -based family of fluorinated substances (Fig. 3) [2, 17]. Telomeri-zation may also be used to make terminal iso- or methyl branched and/or odd number fluorinated carbon perfluoroalkyl iodides as well [2]. The process of TFE telomerization can be manipulated by controlling the process variables, reactant ratios, catalysts, etc. to obtain the desired mixture of perfluoroalkyl iodides, which can be further purified by distillation. While perfluoroalkyl iodides can be directly hydrolyzed to perfluoroalkyl carboxylate salts [29, 30], the addition of ethylene gives a more versatile synthesis intermediate, fluorotelomer iodides. These primary alkyl iodides can be transformed to alcohols, sulfonyl chlorides, olefins, thiols, (meth)acrylates, and from these into many types of fluorinated surfactants [3] (Fig. 3). The fluorotelomer-based fluorinated surfactants range includes noiuonics, anionics, cationics, amphoterics, and polymeric amphophiles. 

Many compounds containing a perfluorinated or hydrogenated hydrophobic chain and an amino acid as either polar head or junction modulus have been synthesized. Among the different structures that have been prepared, a variety of amino acids are encountered, but a-amino acids are the most common however, P-alanine or its derivatives play an important role, too. Moreover, molecules based on perfluoroalkyl-amino acids, prepared from different functionalized perfluoroalkyl starting compounds, have been synthesized. It should be stressed that the different types of surfactants based on amino acids encountered in this family of products may be classified as ionic, nonionic, or zwitter-ionic. In all the structures obtained, the concept of modularity is important, since the amino acid—with or without prior chemical transformation—represents either the polar head group or a pivot modulus linking one or more lipophilic chains to different polar heads. 

Amino-acid-based amphoteric surfactants containing a hydroxyl group have been obtained by reacting an amino acid with a perfluoroalkylated epoxide [197] ... 

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