Self-assembling of tetradecylammonium chain on swelling high charge micas (na-mica-3 and na-mica-2): Effect of alkylammonium concentration and mica layer charge

Abstract

A family of tetradecylammonium micas is synthesized using synthetic swelling micas with high layer charge (NanSi8–nAlnMg6F4O20·XH2O, where n = 2 and 3) exchanged with tetradecylammonium cations. The molecular arrangement of the surfactant is elucidated on the basis of XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas is investigated by IR/FT, 13C, 27Al, and 29Si MAS NMR. The structural arrangement of the tetradecylammonium cation in the interlayer space of high-charge micas is more sensitive to the effect of the mica layer charge at high concentration. The surfactant arrangement is found to follow the bilayer-paraffin model for all values of layer charge and surfactant concentration. However, at initial concentration below the mica CEC, a lateral monolayer is also observed. The amount of ordered conformation all-trans is directly proportional to the layer charge and surfactant concentration