Two-step electrical percolation in nematic liquid crystal filled by multiwalled carbon nanotubes

TL;DR

This study reveals a two-step electrical percolation process in nematic liquid crystal composites filled with multiwalled carbon nanotubes, characterized by distinct percolation thresholds and explained via core-shell structure modeling.

Contribution

It demonstrates the existence of a two-step percolation process in CNT-LC composites and provides a theoretical explanation based on core-shell structures.

Findings

First percolation threshold at ~0.0002 wt.% CNTs.

Second percolation threshold at ~0.5 wt.% CNTs.

Two-stage percolation explained by core-shell model.

Abstract

Percolation of carbon nanotubes (CNTs) in liquid crystals (LCs) opens way for a unique class of anisotropic hybrid materials with a complex dielectric constant widely controlled by CNT concentration. Percolation in such systems is commonly described as a one-step process starting at a very low loading of CNTs. In the present study the two-step percolation was observed in the samples of thickness 250 $\mu$m obtained by pressing the suspension between two substrates. The percolation concentrations for the first and second percolation processes were $C_n^{p_1}\approx 0.0002$ wt. \% and $C_n^{p_2}\approx 0.5$ wt. \%, respectively. The two-stage nature of percolation was explained on a base of mean field theory assuming core-shell structure of CNTs.