Influence of alkoxy chain length and fluorosubstitution on mesogenic and spectral properties of high tilted antiferroelectric esters

Abstract

The synthesis and properties of a few dozen highly evolved analogues of (S)-MHPOBC are reported. The liquid crystal phases, and phase transition temperatures and enthalpies, as evidenced by polarized optical microscopy and differential scanning calorimetry, respectively, are given. The helical pitch in pure compounds and some mixtures is estimated using the selective reflection method. All of the compounds show antiferroelectric phases, and some key structure–property relationships for the new materials are reported. Specifically, it is found that the length of the oligomethylene segment of a novel partially fluorinated alkoxy ether tail incorporated into the structures strongly influences the stability of the antiferroelectric phase and the observed phase sequences, as well as the values of the helical pitch and its temperature dependence. The formulation of a family of broad temperature range eutectic mixtures possessing the highly desirable orthoconic antiferroelectric phases with long helical pitch is described.