Induced blue phase of cholesteric-nematic mixtures under the action of acetone vapors

Abstract

Liquid crystals can exhibit structural orientational order. The creation of a mixture with the addition of chiral molecules to the nematic liquid crystal induces helical twisting, the axis of which is directed perpendicular to the cell surfaces. When some cholesteric mixtures with a sufficiently short spiral pitch (up to 400-500 nm) are heated to a temperature close to, but still lower than, the temperature of the main transition to the isotropic state, in some cases the so-called blue phases can be formed. We carried out a study on the detection of structural manifestations of the blue phase under the action of vapors of chemical substances, in particular acetone. The main dependences of effect of acetone on the liquid crystal mixture depending on the concentration were also revealed. The two-stage phase transformation from cholesteric liquid crystal to the isotropic liquid via the intermediary blue phase could be clearly recorded by changes in optical transmission. Possible applications are discussed.

Keywords

• liquid crystal
• e7
• gas sensor
• blue phase
• optical sensor