Cationic fluorocarbon surfactant

In the coagulation of PTFE latices by cationic hydrocarbon surfactants> however, a dilTerent behavior is observed in that only very small differences are observed in the magnitude of the ccc with variation of chain length (Richardson, 1979). This effect is illustrated by the data in Table V. Again, it appears to demonstrate the lack of affinity of hydrocarbon chains for fluorocarbon surfaces. 

Fluorocarbon surfactants have been prepared with various structures, consisting of perfluoroalkyl chains and anionic, cationic, amphoteric and poly(ethylene oxide) polar groups. These surfactants have good thermal and chemical stability and they are excellent wetting agents for low energy surfaces. 

The interaction of cationic fluorocarbon and hydrocarbon surfactants was studied by Tamori et al. [145]. The mixed cmc of diethanolheptadecafluoro-2-2-undecanolammonium chloride and dodecyltrimethylammonium chloride was determined by electric conductivity measurements. Partition coefficients of alcohols (methanol and C4F7H2OH) and a fluorescent probe (pyrene-3-carboxaldehyde) between micelles and the bulk aqueous phase were determined. The data interpreted by a regular solution theory fitted an interaction parameter /3 = 1, indicating a much smaller repulsive interaction between the two cationic surfactants than that between an anionic fiuorinated surfactant and an anionic hydrocarbon-type surfactant. The weak repulsion between the two cationic surfactants was explained by a large difference in their cmc values. 

The water permeability of dialysis membranes containing fluorocarbon polymers can be increased by a surface treatment with a cationic fluorinated surfactant [281]. 

A special class of surfactant is the fluorocarbon type. Fluorocarbon surfactants, or fluorosurfactants, are very effective in lowering fluid surface tension. They are available in cationic, anionic, and nonionic forms. Nonionic fluorosurfactants are the most common. Fluorosurfactants are especially useful as flowback enhancement additives and for improving wettability (nonwetting). 

The process of adsorption of polyelectrolytes on solid surfaces has been intensively studied because of its importance in technology, including steric stabilization of colloid particles [3,4]. This process has attracted increasing attention because of the recently developed, sophisticated use of polyelectrolyte adsorption alternate layer-by-layer adsorption [7] and stabilization of surfactant monolayers at the air-water interface [26], Surface forces measurement has been performed to study the adsorption process of a negatively charged polymer, poly(styrene sulfonate) (PSS), on a cationic monolayer of fluorocarbon ammonium amphiphilic 1 (Fig. 7) [27],... 

Corresponding to the type of surfactant the hydrophobic group consists of an anion (anionics), a cation (cationics) or segment in nonionic or related polymer surfactants. Also, in amphoteric surfactants or betaine structures the fluorocarbon tail is extremely hydrophobic. 

Quaternary Ammonium Ions. In a recent study (17), 1200 EW Nafion has been used to construct a membrane ion selective electrode. The electrode was placed in both the tetrabutylammonium ion and cesium ion forms, and the response characteristics of each form were measured. These electrodes show Nernstian responses, and the tetrabutylammonium ion electrode has no interference from inorganic cations such as Na" ", K" ", and Ca2" ". However, this electrode shows a marked interference with decyltri-methylammonium ion. In addition the cesium ion electrode response is sensitive to the presence of tetrabutylammonium ion and especially dodecyltrimethylammonium ion. Although membrane electrode sensitivities are not in general proportional to thermodynamic selectivity coefficients, the results do indicate that these large, hydrophobic cations are preferred over smaller inorganic cations by the polymer. The authors suggest that the surfactant character of the two asymmetric tetraalkylammonium ions may lead to non-electrostatic interactions with the fluorocarbon regions of the polymer, which would enhance their affinities (17). 

Surfactants are amphiphilic compounds (Figures 5.1 and 5.2), consisting of a polar head (ionic -anionic-or cationic- or polar group) and a hydrophobic part. The hydrophobic part is typically a hydrocarbon chain of varying length it can be also a fluorocarbon or a dimethylsiloxane chain. 

Thoay [101] studied interfacial activity of partially fluorinated surfactants in an oil-water medium. The fluorocarbon group was located either at the end of the hydrocarbon tail, inserted in the middle of the hydrocarbon chain, or attached as a branch to a conventional hydrocarbon-type cationic surfactant. Three types of surfactants were used ... 

In the first type, a fluorocarbon branch was attached to a cationic surfactant. At low concentrations, these fluorinated surfactants lower the interfacial tension, 7, more than their hydrocarbon analogs, but the limiting value of 7, is much higher for the fluorinated surfactants than for the hydrocarbon analogs (Fig. 4.36). 

Zhao and Zhu (109] studied the interfacial tension and spreading properties of mixed solutions of anionic (cationic) and cationic (anionic) fluorocarbon and hydrocarbon surfactants. The anionic-cationic system exhibited much higher sur-... 

Esumi et al. [71] arrived at a similar conclusion when studying the adsorption of binary mixtures of cationic surfactants, bis(2-hydroxyethyl) (2-hydroxy-3-perfluorooctylpropyl)methylammonium chloride and hexadecylpyridinium chloride from their solution in water to negatively charged silica. The total adsorption of the mixture was found to be lower than that of single surfactants adsorbed separately, indicating a mutual phobicity between hydrocarbon and fluorocarbon chains. 

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