Carbon nanotube-induced macroscopic helical twist in an achiral nematic liquid crystal

An achiral nematic liquid crystal was doped with a small quantity of carbon nanotubes, and the mixture was found to induce an average mechanical twist over macroscopic dimensions. The nanotube-induced chiral pitch length P was determined as a function of average nanotube concentration by measuring the radii of curvature of reverse twist disclination lines in 90° twisted nematic cells. The results reveal information about the nanotubes’ spatial distribution inside the cells. A concentration for the onset of significant aggregation of the nanotubes can be quantified from the apparent saturation of P at higher concentrations. The macroscopic helical twisting power of the nanotubes has been estimated from the results.