Proton spin–lattice relaxation in smectic TBBA

Abstract

The angular, temperature, and frequency dependences of the proton spin–lattice relaxation rate T⁻¹₁ in the smectic A phase of TBBA have been determined. An analysis is made of the possible relaxation mechanisms in smectic A systems. The results seem to show that the angular dependence of T⁻¹₁ is produced by the modulation of the intramolecular dipolar interactions due to the coupling between self‐diffusion and local ’’director’’ fluctuations. The low temperature smectic phases of TBBA have been as well investigated. The decrease in the self‐diffusion constant due to two‐dimensional translational ordering at the smectic C→smectic H transition is shown to produce a dramatic increase in T₁ and decrease in T_1D. The rotation of the chain segments abruptly slows down on going from smectic H to smectic VI and discontinuously freezes out on going from smectic VI to smectic VII.