The influence of temperature on the rheology of systems containing alkyltrimethylammonium bromides/cetostearyl alcohol: Variation with quaternary chain length

Abstract

Gel networks formed in the continuous phases of oil-in-water emulsions stabilized by cetostearyl alcohol combined with alkyltrimethylammonium bromides (of C 12C 18 chain lengths) have similar mechanical properties to those of ternary systems formed by dispersing the appropriate quaternary bromide and alcohol in water. The rheological changes with temperature of such emulsions and ternary systems were examined by continuous shear and creep experiments. Variations in the viscosities and compliances were correlated with thermal phase transitions determined microscopically. The C 12 quaternary networks were tenuous. Continuous shear results were uninterpretable, and in creep the networks became nonlinear viscoelastic as the temperature rose. The consistency of each ternary system and emulsion prepared from higher quaternary surfactants increased to a maximum as the temperature rose. These temperatures of maximum consistency were close to the transition temperature at which each network melted from frozen smectic to liquid crystalline phase. They correlated well with penetration temperatures of approximately 1% w/w aqueous solutions of the appropriate alkyltrimethylammonium bromide into cetostearyl alcohol. The transition temperatures of the emulsions were lower than those of the corresponding ternary systems, owing to the presence of solubilized liquid paraffin in the networks. Above the transition temperatures the consistencies of the ternary systems and emulsions decreased as the networks weakened and finally dissolved to form isotropic solutions.