Translational mobility in surface induced liquid layers investigated by NMR diffusometry

The self-diffusion properties of plastic succinonitrile and cyclohexane confined in nanoporous glass were investigated by means of NMR field-gradient diffusometry. The results are compared to diffusion measurements in the bulk as well as to the relaxational behaviour of other confined plastically crystalline substances. For all adsorbates, bed low the freezing point a thin layer near the glass surface is found to retain a high translational mobility as compared to the plastic phase in the center of the pore. The behaviour of the unfrozen layer can be described by liquid-like diffusion inside a network of channels with temperature-dependent width assuming fast molecular exchange with the plastic phase.