The influence of structure and concentration of cyano-terminated and terphenyl dopants on helical pitch and helical twist sense in orthoconic antiferroelectric mixtures

A bicomponent mixture in the orthoconic aniferroelectric phase, based on three-ring esters with fluorine atoms and ether group in a nonchiral chain, was doped with a variety of cyano-terminated compounds containing different numbers of phenyl rings in a rigid core and a terminal chain of different chirality. Compounds with two chiral chains were added to the basic mixture. The influence of the structure and concentration of dopant on the temperature-dependence of helical parameters, such as helical pitch and twist sense, were assessed by spectrophotometric and polarimetric methods. Long cyano-terminated compounds were found to be better than the other dopants tested for improving the usable properties of the antiferroelectric mixtures.