High resolution study of the compression modulus B in the vicinity of the nematic-smectic A transition in 60CB/80CB mixtures

The temperature dependence of the compression modulus B of the molecular layers in the smectic A phase has been studied in the vicinity of the nematic to smectic A transition by high-resolution light-scattering studies. Using mixtures of the liquid crystals 60CB and 80CB it is shown that B obeys a simple power law of the form B = B0(Tc-T)ϕ. The magnitude of a discontinuity jump of B at the transition temperature compared with values of Fisch et al. is found to be smaller by orders. The prefactor B0 appears to be independent of the concentration of the mixtures.