Helical pitch parameters of ferroelectric phase in bi- and multicomponent mixtures

Abstrakt:

The list of required parameters for ferroelectric multicomponent mixtures suitable for applications is long. Properties such as: low melting temperature, low viscosity and broad temperature range of liquid crystalline phase existence as well as parameters important for electrooptic modes like tilt angle or helical pitch can be easily optimized. However preparation of multicomponent mixture should be preceded by miscibility studies in bicomponent systems, in order to select appropriate components. The compounds used for preparation of application mixture can differ in phase sequence and it is not necessary that all of them form ferroelectric phase or even liquid crystalline one [1, 2]. The most favourable are mixtures formed by optimization of eutectic composition. In order to prepare multicomponent mixture non-chiral compounds can also be used [3].

The aim of this work was to check how the structure of dopants (from non-chiral pyrimidines and terphenyls through chiral biphenyls to chiral quterphenyls) and their amount influence the phase situation and helical pitch of ferroelectric phase in binary mixtures. As base compounds three ring esters 6F2OBi and 1H6Bi(3F), differing in the type of terminal non-chiral chain and substitution in rigid core, were selected. Base compounds differ also in the dependence of helical pitch upon temperature: 6F2OBi forms only right-handed helix whereas 1H6Bi(3F) forms both left- and right-handed helix. Results of miscibility and helical pitch studies will be presented.

[1] K. Kurp, M. Czerwiński, M. Tykarska, Liquid Crystals 42, 248 (2015)

[2] A. Bubnov, M. Tykarska, V. Hamplova, K. Kurp, Phase Transitions 2016; DOI:10.1080/01411594.2015.1087523

[3] K. Kurp, M. Tykarska, Liquid Crystals 43, 1359 (2016)

This work was supported by the COST Action IC1208.