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 having a net chirality, and the mixture was found to exhibit an average mechanical twist over macroscopic dimensions. The nanotube-induced chiral pitch length P was determined as a function of the average nanotube concentration by measuring the radii of curvature of reverse twist disclination lines in 90 degrees nematic twist cells. The results suggest that the nanotubes' spatial concentration can vary significantly across the cell and that at high average concentration, the nanotubes undergo aggregation, resulting in an apparent saturation of P(-1) at high concentrations. The macroscopic helical twisting power of the nanotubes has been estimated from the results. (C) 2011 American Institute of Physics. [doi:10.1063/1.3576101]