Liquids Confined in Mesoscopic Pores

Abstract

Nuclear magnetic relaxation in polar liquids confined in mesoscopic pores of a solid matrix tends to be dominated by dynamic processes at the pore surfaces. In the adsorbed state, the motional degrees of freedom are restricted. If the liquid is of mesogenic nature, surface ordering is possible even above the bulk isotropization temperature. Based on the dipolar correlation effect, it is shown that the ordering is local and does not exhibit the features of macroscopic nematic domains. Field-cycling NMR relaxometry of both mesogenic and non-mesogenic liquids demonstrates that ‘reorientation mediated by translational displacements’ (RMTD) dominates the low-frequency spin–lattice relaxation dispersion. Specific sample preparations allow the experimental distinction of Gaussian and Cauchy propagators for ordinary surface diffusion and Lévy walk type displacements, respectively. The results are confirmed by Monte Carlo simulations.