Magnetic separation accompanied by the phase transition for the purification of nematic liquid crystal

Abstract Free ions are generally unfavorable in liquid crystal (LC) displays, and LC purification technologies are critically important. The colloidal γ-Fe2O3 magnetic nanoparticles (MNPs) have a high ratio of surface to volume, which may adsorb more free ions and are uniform in the LC at room temperature. The precipitation and separation of the doped colloidal γ-Fe2O3 MNPs resulting from the magnetic field accompanied by an isotropic-nematic phase transition are more efficient than in the single case of the phase transition or the magnetic field. The residual ion concentrations have decreased distinctly using the low gradient magnetic field (∇B ~ 2 T/m) with the phase transition. In addition, the higher the concentration of the doped colloidal γ-Fe2O3 MNPs, the lower the concentrations of the residual ions and γ-Fe2O3 MNPs. As a result, the commercial nematic LC can be purified by this approach based on nanotechnology in our study.