Interaction Parameters of Anhydrous Cationic Surfactant Mixtures by Inverse Gas Chromatography

The miscibility of anhydrous cationic surfactant dodecylpyridinium chloride (DPC) and hexadecylpyridinium bromide (cetylpyridinium bromide (CPB)) mixtures has been studied by using them as stationary phases in Inverse Gas Chromatography (IGC). The temperature zone of work was determined by IGC and Differential Scanning Calorimetry (DSC) techniques. Values of the interaction parameter between the surfactants obtained at four different compositions and at four temperatures showed that the miscibility depends on the overall composition and suggested that the interactions are more favorable near the center of the composition range. Results are compared with other anhydrous cationic surfactant mixtures studied by IGC, the system didodecyldimethylammonium bromide (DDAB) and dioctadecyldimethylammonium bromide (DODAB), two twin-tailed surfactants, and are interpreted in terms of the structure of the anhydrous lamellar liquid crystals compared with that of aqueous lamellar mesophases.