Liquid crystalline blue phase in mixtures of fluorinated compounds with positive and negative dielectric anisotropy and its electro-optic performance

Abstract

Dependence of a blue phase temperature range on a chiral dopant and cyano compound addition as well as character of nematic base mixture was investigated. Base nematic mixtures of fluorinated compounds, one with positive and the other one with negative dielectric anisotropy, were chosen. Various fluoro compounds, chiral compounds and cyano compound were added in order to evaluate the relationship between blue phase stability and molecular structure of components. The stability of a blue phase in selected mixtures has been extended by polymer network formation. Fundamental electro-optic properties such as Kerr constant, operating time and switching voltage of a polymer-stabilised blue phase with positive and negative dielectric anisotropy are given, too. It has been confirmed that blue phase temperature range and its electro-optic performance strongly depends on molecular structure of mixture components as well as chiral dopants and their helical twisting power. Specifically, it was found that the cyano compound addition causes destabilisation of blue phase in mixtures consisted of fluorinated compounds.

Keywords:

• liquid crystal blue phase
• Kerr effect
• polymer network

Acknowledgement

This work was carried out under the project NATO PDD (TC)-(CBP.EAP.CLG 983701).