Sign-inversion of elastic anisotropy in a bent-core nematic liquid crystal doped with carbon nanodots

Abstract

In most bent-core nematic liquid crystals the bent elastic constant (K33) is usually lower than splay elastic constant (K11) owing to the presence of short range smectic-C like correlations in nematic phase. Thus the elastic anisotropy (K33−K11) is usually negative in bent-core nematics unlike rod-like nematic liquid crystals where K33 is always greater than K11. Here we report a short-core bent-shaped nematic liquid crystal whose negative elastic anisotropy was turned to positive by minute addition of carbon nanodots (C-dots). The experimental results demonstrate significant crossover of dielectric anisotropy and splay-bent elastic constant values at ~125°C. This effect is attributed to gradual formation of chain-like structures of C-dots as the mixture is cooled from isotropic temperature. Threshold voltage reduces significantly at high temperature region owing to higher local electric field and reduced viscosity. Dielectric relaxations of nano-sized clusters become faster in nano-dispersed liquid crystal.