Investigation of high Δε derivatives of the [closo-1- CB_9H_10] anion for liquid crystal display applications

Abstract

Two series of polar compounds 3[n] and 4[n] with longitudinal dipole moments ranging from 10 to 17 D were synthesized and investigated as additives to two nematic hosts, ClEster and CinnCN. Compounds 3[n] do not exhibit liquid crystalline behavior and have limited compatibility with nematic hosts, but still are effective additives for increasing dielectric anisotropy, Δε, of liquid crystalline host materials. On the other hand, esters 4[n] typically exhibit nematic behavior and form stable solutions in ClEster up to 5 mol%. In this concentration range, the binary solutions exhibit a linear dependence of dielectric parameters and the extrapolated Δε values range from <18 (4[3]l, μ = 11.3 D) to 70 (4[3]c, μ = 14.1 D and 4[3]k, μ = 17.2 D). Analysis of the dielectric data with the Maier–Meier formalism using DFT-calculated α and μ parameters gave apparent order parameter values Sapp in a range of 0.51–0.68 and Kirkwood parameters g in a range 0.55–0.78 for esters 4[n].