ABSTRACT
In this paper we report the use of dynamic light scattering, in the presence of electric fields, as a means of studying pretransitional phenomena in the nematic phase of a mesogen undergoing a nematic to smectic A phase transition. We have measured the splay and twist elastic constants (k11, and k22) and the splay and twist viscosities (ηSplay and γ1,) as a function of temperature over the entire nematic range of 4-cyano-4′-octyl-biphenyl. Near to the SA phase a strong critical divergence has been observed for k22 and γ1, whilst k11 and ηSplay show an unexpected weak divergence but are finite at the transition. For comparison data are also presented for the purely nematic pentyl homologue which does not exhibit a smectic A phase.