INFLUENCE OF MEMBRANE MICROSTRUCTURE ON THE DIFFUSION BARRIER OF SUPPORTED LIQUID-CRYSTALLINE MEMBRANES

Several analytical techniques have been used to characterize the self- diffusion behavior of crown ether based cation carriers inside membran es. With pulsed field gradient nuclear magnetic resonance a significan t difference was found between the self-diffusion coefficient in the f ree solution and in the membrane pores. Furthermore, differences in th e pore geometry of different brands of polypropylene membranes could b e demonstrated. These results were verified with a combination of atom ic force microscopy and confocal scanning laser microscopy, which show ed characteristic differences in the morphology of the membranes. Thes e morphological variations may well explain differences in the transpo rt properties of the membranes when impregnated with liquid crystals.