Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles

The paper presents a study of the polymer dispersed liquid crystals that consist of liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT) microdroplets dispersed in polyvinyl alcohol and doped with various kinds of magnetic particles. As magnetic nanoparticles there were used single walled carbon nanotubes and magnetite labeled single walled carbon nanotubes. The volume concentration of the particles was 2 x 10(-3). Magnetic properties were investigated by a SQUID magnetometer. The higher saturation magnetization has been achieved in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes. The phase transition temperature from isotropic to nematic phase at the external magnetic field 0 T and 12 T was monitored by precise capacitance measurements in the capacitance cell filled with prepared sample. The significant shift of the phase transition temperature (0.2 degrees C) at the external magnetic field 12 T has been observed in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes.