Nuclear magnetic and dielectric relaxation of a homologous series

Abstract

Nuclear magnetic and dielectric relaxation behavior of an asymmetric homologous series of the nematic liquid crystalline compound p-alkoxybenzal-p′-ethoxyaniline and of p-octylbenzal-p′propylaniline have been investigated. The nuclear T1 measurements indicate to consider the different molecules of the series in the nematic phase as ellipsoids with dissimilar lengths of the long axis. Applying a 90°–τ–90°90° pulse different decays were observed for the even and the odd members of the series, the differences vanishing below the clear point. They were interpreted by a different chain configuration for the odd and the even members. The dielectric measurements in the microwave range show a strong dependence of the Debye relaxation time on the chain length. The role of the oxygen atom in the chain became evident.