Anomalous rotational diffusion in the vicinity of the isotropic to nematic phasetransition

Abstract

Dielectric relaxation measurements are performed with very high accuracy on a liquid crystalline compoundn-octylcyanobiphenyl (8CB) in the isotropic (I), nematic (N) and smectic A(SA) phases. The data obtained display an essential difference in the rotational diffusion process inthe vicinity of the I–N phase transition in comparison to that taking place in the vicinity of theN–SA phase transition. Thus, for the I–N transition, anomalously slowdiffusion (subdiffusion), characterized by an anomalous coefficientα<1, is observed, while normal Brownian rotational diffusion with is found for the N–SA transition. It is also shown how the fractal parameterα is temperature dependent with an extremely sharp variation at the I–N transition point inthe form of a lambda-like profile.