Influence of the molecular structure of compounds differing with terminal polar group on the induction of the smectic A phase. Part III

Abstract

ABSTRACT The aim of this work is to determine the influence of the terminal polar group of nematic compounds, namely -OCF3, -NCS, -CN, -F, on the induction of the SmA phase in their mixtures with compounds having terminal non-polar groups. The former group of compounds has positive dielectric anisotropy, and the latter negative. The phase transition temperatures of binary mixtures were measured using polarising thermomicroscopy, and phase diagrams for investigated systems were constructed. The strength of the SmA phase induction increases upon the increase of the polarity of compounds. The strongest induction is observed in systems with compounds having a terminal trifluoromethoxy group. Although compounds with the cyano group have the highest polarity, their ability for the SmA phase induction is smaller due to their dimerisation.