Orientational order and enthalpic measurements on binary mixtures at the N–S A transition: Comparison with McMillan’s models

Abstract

We have studied binary mixtures which present a nematic to smectic A transition leading continuously from a first order transition to a second order transition. The evolution of the order parameter, close to the N–S_A transition is observed by using diamagnetic susceptibility measurements. In addition, the transitional enthalpies were determined. A correlation between those different data is shown. We discuss the results with respect to the rigid molecule model proposed by McMillan to describe the N–S_A transition.