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

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.