Measurements of the Bend and Splay Elastic Constants of Octyl-Cyanobiphenyl

Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB–N phase transition

“…Ultimately, values of the K 1 and K 3 elastic constants are extracted by fitting the entire voltage dependence of the capacitance to the theory. 41 A more detailed description of the technique can be found elsewhere. 42 …”

Lehmann effect in compensated cholesteric liquid crystals

“…From this experiment (and capacity measurements of homeotropic samples) we deduced the dielectric constants (ε =9.4 ± 0.5a n dε ⊥ =4.5 ± 0.2) and the ratios K1 ε0εa = 0.076 ± 0.006 V 2 (with ε a = ε − ε ⊥ )a n d K3 K1 =1.7 ± 0.1. The latter was deduced from the fit of the whole capacity vs. voltage curve according to the procedure given in [15] by neglecting flexoelectric effects [16] (this point will be justified in a forthcoming article). Second, we measured the Fréedériks transition in a π/2-twisted planar cell (thickness 6.8 μm, from Instec, Inc) close to the compensation point.…”

Lehmann effect in a compensated cholesteric liquid crystal: Experimental evidence with fixed and gliding boundary conditions

“…Note that K 1 was obtained from the direct measurement of the critical voltage given by V c = π K1 ε0εa , while the ratio K 3 /K 1 was deduced from the fit of the whole capacitance-vs.-voltage curve according to the procedure given in [18]. We emphasize that we neglected the flexoelectric effects in the fitting procedure, which is justified as long as the flexoelectric coefficient difference e 3 − e 1 is smaller than 10 −11 Cm −1 [19].…”