Slow Molecular Processes in a Liquid Crystal Embedded in Aerosil Matrix: Nuclear Magnetic Relaxometric Study

Frequency dispersion studies on proton spin-lattice relaxation rates of a liquid crysal (4’-octyloxy-4-cyanobiphenyl) embedded in Aerosil matrix show significant increase at low frequencies (sub-MHz regime) relative to the bulk sample, and are interpreted as primarily due to slow reorientations near the surface ordered layers mediated by translation displacements. The computed exponent in the power law behavior of the dispersion profiles at different temperatures in the isotropic phase indicates an enhanced role of the low-wavelength diffusion modes during this process. The data also show critical contribution near the isotropic-nematic transition to the length scales relevant to adsorption kinetics.