Hexadecyltrimethylammonium alkyl sulfate

TABLE 1 Transition Temperatures (T) and Enthalpy Changes (AH) of Hexadecyltrimethylammonium Alkyl Sulfate... 

TABLE 2 The Long Spacing, D (A), of Hexadecyltrimethylammonium Alkyl Sulfates at Selected Temperatures... 

The constant increment of 0.1 nm in the long spacing of successive members of the homologous series corresponds to half the difference in chain length between C and C +2 and indicates that there is probably no trans conformation of alkyl sulfate chains in hexadecyltrimethylammonium alkyl sulfates. 

Additionally, X-ray diffraction patterns of hexadecyltrimethylammonium alkyl sulfates in the heating cycle display a superposition of rather sharp diffraction lines on diffuse amorphous maxima, indicating the presence of two phases. One phase is the three-dimensionally ordered crystalline phase, and the other is a disordered one, indicating some kind of a two-dimensionally ordered liquid crystalline phase. The presence of a disordered phase in addition to the ordered phase is not observed in the symmetrical catanionic surfactants [62]. 

Asymmetrical catanionic surfactants consist of anionic and cationic surfactants with different chain lengths. Similar to Eq. (1), the formation of asymmetrical catanionic surfactants from hexadecyltrimethylammonium bromide (CTAB) and an anionic surfactants such as sodium alkyl sulfate (the numbers of carbon atoms per chain being 10, 12, and 14) can be represented as... 

Surfactants are those molecules that comprise both hydrophilic and hydrophobic groups simultaneously. The hydrophilic groups can be either ionic (e.g., -SOj, -SO3, -COOH, and -N(CHsIj) or nonionic (e.g., -0-(CH2-CH2-0) -H). As to the hydrophobic groups, the most widely used ones are the alkyl chains (-C H2 +i) and arakyl chains (-C H2 +i-C6H4-). Representative surfactants include anionic sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), sodium bis(2-ethylhexyl) sulfosuccinate, sodium stearate, cationic hexadecyltrimethylammonium bromide, and nonionic i-octophenol polyethoxylate with an average of 40 monomeric units of ethylene oxide per molecule. Such amphoteric species tend to diffuse toward the interface between the oily and aqueous phases and reside therein. 

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