Light-Scattering Study of a Smectic-APhase near the Smectic-A- Nematic Transition

Mechanical instabilities of smectic-A liquid crystals under dilative or compressive stresses

“…In our case we would need a width of the order of 0.5 °C to find an exponent of 0.25 (classical). This is too high when compared with the results obtained on the same compound by P. E. Cladis [21], D. Salin et al [22] who observed a value for (T* -Tc) 20 [12] which has been observed under the microscope especially close to the A -C transition. This instability which appears as an undulation of small wavevector q (q -qcl50) seems to result from a coupling between the molecular orientation and the flow, and is under study at the present time.…”

“…15) (Fig.16b) [19], and in a light scattering experiment by thermal fluctuations [20]. Discussion : From the analogy with the A transition in Helium the penetration length variation should follow a law of the form A -(Tc -T) -0.33.…”

Defect model of the smectic A-nematic phase transition

“…Experimentally, some materials [11,14] were found to display second-order transitions within currently possible accuracy (ca. 3 [12] and a theoretical explanation was suggested [10].…”

Fluctuation Modes of a Twist-Bend Nematic Liquid Crystal

“…Finally, we note that numerous works [31][32][33][34][35][36] over the years have reported on the temperature dependence of the smectic-layer compression constant B as T → T NA (from below). However, to our knowledge, no data are yet available for the T dependence of the analogous quantity, B eff , as T → T TB [37] in the N TB phase.…”

“…However, this is not the case in the analogous smectic-A system near the transition to the nematic phase (temperature T NA ). Here, experiment indicates D ∝ ðT NA − TÞ x with x ≈ 0.5 [31][32][33], whereas mean-field theory predicts x ¼ 1, and a more sophisticated, anisotropic scaling analysis gives x ≈ 0.67 [28].…”