Liquid Crystal 6CHBT Research Articles

Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles

In this work the 4-(trans- 4'-n -hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) liquid crystal was doped with differently shaped magnetite nanoparticles. The structural changes were observed by capacitance measurements and showed significant influence of the shape and size of the magnetic particles on the magnetic Fréedericksz transition. For the volume concentration phi= 2 x 10(-4) of the magnetic particles, the critical magnetic field was established for the pure liquid crystal, and for liquid crystals doped with spherical, chainlike, and rodlike magnetic particles. The influence of the magnetic field depends on the type of anchoring, which is characterized by the density of anchoring energy and by the initial orientation between the liquid crystal molecules and the magnetic moment of the magnetic particles. The experimental results indicated soft anchoring in the case of spherical magnetic particles and rigid anchoring in the case of rodlike and chainlike magnetic particles, with parallel initial orientation between the magnetic moments of the magnetic particles and director.

Influence of electric field on photoluminescence of lanthanide-doped nematic liquid crystal

Highly resolved luminescence and luminescence excitation spectra of recently synthesized LnL 3bpy complexes, where Ln=Eu 3+, Tb 3+, bpy=2,2′- bipyridyne and L=phosphoroazo derivative of β-diketone: CCl 3C(O)NP(O)(OCH 3) 2, in solid state and dissolved in nematic liquid crystal 6CHBT [4-(isothiocyanatophenyl)-1-( trans-4-hexyl)cyclohexane] were measured. The photoluminescence intensity of the complexes dissolved in 6CHBT was found to exhibit a strong dependence on the electric field. The mechanism of the effect and reason of its asymmetry with respect to the sign of electric field are discussed in the paper. Luminescence decay time in various environments and experimental quantum yields of the luminescence of these compounds in CDCl 3 and CHCl 3 solutions were measured.

The study of structural transitions in liquid crystal droplets doped with magnetic particles

AbstractThe magnetically active ferronematic droplets were prepared in solutions of nematic liquid crystal 6CHBT with fine magnetic particles, dissolved in phenyl isocyanate. The phase diagram of the transitions between isotropic, droplet and nematic phases in prepared sample was found. The structural transitions in 6CHBT‐based ferronematic and in 6CHBT ferronematic droplets, exposed to external fields, were investigated. The possibility to use the observations of structural transitions for the determination of the type of anchoring of nematic molecules on magnetic particles surfaces was demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Guest Effect on Nematic-Isotropic Phase Transition Temperature of Liquid Crystal 6CHBT

The polarized absorption spectra of seven dichroic azo dyes dissolved in the nematogenic liquid crystal host 6CHBT have been recorded as a function of temperature. On the basis of these spectra, the guest order parameter has been determined. Moreover, the influence of the dye addition on the behaviour of the guest-host mixture in the vicinity of the nematic-isotropic phase transition has been examined. The experimental results have been compared in some details with the calculations done on the basis of the mean field theory for binary mixtures. PACS numbers: 61.30.Gd, 64.70.Md