Amides cubic phases

Guo et al. [25] studied fluorinated surfactants (perfluoroheptanoic acid, its salts, and ethoxylated amide of perfluoroheptanoic acid). The characteristics of F-NIVIR spectra and optical isotropy suggested that the aggregates of nonionic fluorinated surfactants (ethoxylated amides) may exist in a cubic phase. The formation of a cubic phase by a fluorinated surfactant has been reported also by Caboi et al. [179]. 

Figure 23. Phase diagram of 18 with acryl amide (k = crystalline, s = smectic, cub = bicontinuous cubic, col = hexagonal columnar, i = isotropic).

The phase behavior of fatty amide ethoxylates is compared with that of alcohol ethoxylates [19]. At low surfactant concentrations micellar isotropic phases are formed for both surfactant types. At higher concentrations, hexagonal phases are formed when 10 oxyethylene units are present. For surfactants with longer head groups a cubic region appears between the micellar and the hexagonal region. When double bonds are present in the hydrophobe an isotropic melt is formed while the saturated amide and alcohol ethoxylates form crystals for 100% surfactant. 

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