Thermomechanical effect in a hybrid-oriented nematic liquid crystal

10.1007/s11451-008-3031-7

“…The values of six Leslie coefficients and two elastic coefficients K 1 (T) and K 3 (T) were estimated from the experimental data taken from [8,10]. The thermomechanical coefficient was estimated to be ξ ~ 10 -12 J/m K [6]. Correspondingly, the two dimensionless parameters were estimated to be δ 1 ~ 30 and δ 2 ~ 10 -5 .…”

“…DISCUSSION AND CONCLUSIONS SInce there are only few experimental investigations of hydrodynamic flows that arise in hybrid liquid-crystal cells due to the transverse temperature gradients [6], we cannot reliably evaluate both the behavior and magnitude of these flows and the relaxation times of other dynamic processes, for example, the relaxation times of components of the tensor of the stresses induced in hybrid liquid-crystal cells. Estimation of the thermomechanical coefficient ξ ~ 10 -12 J/m K is the maximum information that could be obtained from these experiments.…”

“…The presence of the temperature gradient -T ( t , r ) leads to the appearance of tangential thermomechanical stresses [5] in addition to the existing hydrodynamic stresses, an additional contribution to the torque balance, and the necessity of accounting for the heat conduction equation for the liquid-crystal phase with two thermal conductivity coefficients parallel and perpendicular to the director ( t , r ). Akopyan et al [6] experimentally demonstrated that the presence of the temperature gradient in a hybrid liquid-crystal cell leads to the appearance of a hydrodynamic flow directed parallel to the horizontal bounding surfaces. However, no satisfactory description has so far been proposed for the processes of formation and evolution of these flows and director field deformations under different conditions caused by different temperature ZAKHAROV, VAKULENKO regimes and anchoring of liquid-crystal molecules to the bounding surfaces.…”

Thermomechanical effects in uniformly aligned dye-doped nematic liquid crystals

“…Indeed, it is hardly possible to find a setup which leads to the contribution of one of the coefficients only. Since for uniformly aligned nematics no thermomechanical effects are expected, the hybrid-oriented nematics were used in the experiments [5,6]. There, the hydrodynamic flow appeared as a result of the applied temperature gradient, which allowed to find the magnitude for the thermomechanical coefficients.…”