DIFFUSIVITY MEASUREMENTS USING HOLOGRAPHIC LASER INTERFEROMETRY IN A CUBIC LIPID-WATER PHASE

The diffusion of glucose in a cubic lipid-water phase was studied with holographic laser interferometry. The X-ray diffraction data showed t hat the structure of the cubic phase could be described as a primitive cubic lattice under the experimental conditions used. The present stu dy shows that holographic laser interferometry is suitable for determi ning the concentration profile due to diffusion, even for such intrigu ing structures as cubic lipid-water phases. The concentration profile obtained revealed that the diffusion process can be described by Fick' s Second Law, and the effective diffusion coefficient was obtained by fitting a theoretical concentration profile to the experimental data. The diffusion coefficient obtained for glucose was four times smaller than the corresponding coefficient in aqueous bulk solution. The effec tive diffusion coefficient in the cubic phase is greater than that pre dicted by models developed for polymer gels.