Effect of surfactant on structure thermal behavior of cetyl stearyl alcohols

The thermal behaviors of cetyl (C16OH) and stearyl (C18OH) alcohols, alone or in mixture (C16/18OH), or flooded with water in the absence or presence of cetyl trimetyl ammonium chloride (CTAC), have been investigated using differential scanning calorimetry and X-ray scattering. Additional endothermic temperature transitions were observed at 16.9, 58.8, and 70.7 A degrees C and also an unusual exothermic transition at 63.5 A degrees C, when C16/18OH is in the presence of CTAC. The two first transitions at 16.9 and 58.8 A degrees C seems to be, respectively, linked to the hydration mechanism and the melting of long-chain alcohols, while the exothermic one at 63.5 A degrees C is corresponding to the crystallization of a swollen lamellar phase L (beta) . The crystallized swollen lamellar phase L (beta) melts at 70.7 A degrees C into a L (alpha) swollen liquid lamellar mesomorph phase, inducing an endothermic transition. This L (beta) -> L (alpha) transition is reversible upon cooling and reheating. Those data are key information to control the dispersion state of swollen lamellar crystals of long-chain alcohols.