INTERACTIONS OF ALUMINUM IONS IN MIXED AMPHIPHILIC LIQUID-CRYSTALLINE BILAYER SYSTEMS

Aluminum-27 NMR spectroscopy has been used to investigate phenomenological aspects of the binding of the aluminum ions Al(OH)4- and Al(H2O)6(3+) in a variety of amphiphilic liquid crystalline bilayer systems. Information has been obtained through utilization of the Al-27 quadrupole coupling. Studies of the mixed cationic/anionic system of potassium dodecanoate/alkyltrimethylammonium indicated the presence of binding interactions between Al(OH)4- and the carboxylate headgroups. In contrast to this, only weak interactions between the aluminum hydroxide and the trimethylammonium headgroup were indicated. These results were contrary to what might have been expected from simple electrostatic considerations. The results also were consistent with the presence of attractive interactions between Al(OH)4- and the anionic headgroup of decyl sulfate. Results from studies of the mixed nematic dodecanoate/decyl sulfate system indicate that the binding of Al(OH)4- in these anionic systems may be mediated by the water present in the mesophases. In the contrasting situation, little evidence was found for the occurrence of any significant specific interactions between the hydrate, Al(H2O)6(3+), and cationic amphiphiles such as alkyltrimethylammonium, alkylpyridinium, or alkylammonium.