Langmuir, Vol.10, No.12, 4681-4687, 1994
Interlayer Dynamics of a Fatty-Acid Exchanged Lithium Aluminum Layered Double Hydroxide Monitored by Infrared-Spectroscopy and Pyrene Fluorescence
The interlayers of layered metal double hydroxides provide a novel environment for arrangement of molecular species as well as their reactions. In this study, we report on a system which has a dense packing of myristic acid molecules (CH3(CH2)(12)COOH) in a Li-Al layered double hydroxide (LiAl2(OH)(6)(+)), the acid chains being aligned perpendicular to the metal hydroxide layer. This hydrophobic interlayer space acts as a partition medium for molecules like pyrene, which retain enough mobility to form excimers. The interlayer space is also solvated with ethanol. Upon heating the myristic acid exchanged sample, the interlayers separate making room for the solvent to escape. This leads to realignment of the myristic acid chains. The chains become considerably more rigid in the absence of ethanol and this leads to the stabilization of the expanded interlayer. Resolvation makes the chains mobile and leads rapidly to recovery of the properties of the as-synthesized material.