Dynamics of water and amphiphile molecules in lamellar liquid crystalline phases

Abstract

Thin layers of water of controlled thickness may be prepared between the fluorocarbon sheets in the ammonium perfluoro-octanoate/water system at 23°C. Neutron scattering in this system is almost exclusively from the inter lamellar water due to the low scattering cross-section of fluorine and carbon. In a first series of experiments, the modification of water diffusion as a function of layer thickness has been studied and the anisotropy of this effect determined by using oriented samples. The results are compared with nuclear magnetic resonance spin-echo measurements, which measure the same phenomenon but on a timescale approximately 10⁶ times longer. The difference between these two types of measurements allows some tentative conclusions to be made about the presence of cracks and holes in the lamellae.

In the second series of experiments the motion of probe molecules (for example octanol) has been studied in the fluorocarbon layer to determine diffusion kinetics in this region.