Phase diagrams of water-alkyltrimethylammonium bromide systems

Phase diagrams of water-alkyltrimethylammonium bromide (C(n)TAB, n = 10, 12, 14 and 16) systems were measured as a function of the temperature and the total surfactant concentration. All C(n)TABs form an isotropic solution (L-1), a hexagonal liquid crystalline phase (H-1), a cubic phase (V-1) and a lamellar phase (L-alpha) with increasing surfactant concentration. The size of the alkyl chain length of the surfactant influences the extension of the liquid crystalline phases; the shorter the alkyl chain the smaller the extension of the liquid crystalline region. In the case of the pseudobinary system H2O-C(10)TAB/C(16)TAB a shrinking of the H-1 phase was observed. The structure of the H, phases was investigated by means of small angle X-ray scattering (SAXS) and polarizing microscopy. (c) 2007 Elsevier B.V. All rights reserved.