Dielectric Relaxation in Liquid Crystals with the Nematic and Smectic A Polymorphism

Abstract
Dielectric relaxation studies are reported of several substances exhibiting the nematic (N) and smectic A (Sm A) polymorphism. From the relaxation times times τ characterizing molecular reorientations around the short axes the activation enthalpies ΔH for both phases were calculated. It was found that ΔH(N) is markedly larger than ΔH(SmA). The effect is interpreted on the basis of existing models of Sm A phase.