Fluorocarbon surfactants characteristics

The size and shape of micelles also are affected by fluonnation Whereas hydrocarbon surfactants usually form spherical micelles, linear fluorocarbon surfactants tend to produce larger rodlike species [31, 32] This is attributed to two inherent characteristics of the (CFj), chain (1) it adopts a helical rather than a linear zigzag conformation [dd 34, 35,36], and (2) it is much suffer than the (CH2) chain J5 37, 38] The relatively stiff, helical (CF2) chains thus prefer cylindrical to spherical packing... 

The fluorocarbon surfactants, while expensive, have much greater surface activity than hydrocarbon analogues, produce greater surface tension reductions, and usually withstand harsher environmental conditions without significant degradation. They also sometimes exhibit other unusual and useful characteristics that justify their added expense. 

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). 

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. 

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