Correlation between dielectric properties and phase transitions of 8CB/Sn2P2S6 liquid crystal nanocolloids

The effect of Sn2P2S6 ferroelectric nanoparticles dispersed in 8CB liquid crystal on the dielectric properties of the nanocolloids is studied. The experimental results are discussed by taking into account different effects: the dielectric permittivity contribution of nanoparticles, the effect of permanent polarization of nanoparticles on the liquid crystal order and the anchoring interactions between nanoparticles and liquid crystal molecules. For a homogeneous nanoparticles dispersion, the doped liquid crystal shows an increase of the dielectric anisotropy which is more improved by increasing nanoparticles concentration. For high concentrations, the presence of aggregates decreases the dielectric anisotropy due to a decrease of polarization effect. Near the nematic-isotropic phase transition, the study evidences similar behavior between the shift of the dielectric anisotropy and that of the phase-transition temperature. Near the smectic-A-nematic phase transition, the results show that the shifts of the dielectric anisotropy and of the smectic-A-nematic phase-transition temperature present different behaviors. This difference is interpreted by the coupling between smectic and nematic ordering.