Critical Behavior at the SmC*_α−SmC* Phase Transition Studied by High Sensitivity DSC

High-resolution calorimetric study of critical behaviour at the smectic-C*–smectic- phase transition

“…Although the present α value for the narrower data range seems to approach 0.11 expected theoretically for three-dimensional Ising model, the critical amplitude ratio, close to unity, is rather far from the theoretical value A − /A + = 1.85 [11,12]. On the other hand, the present α value as well as the critical amplitude ratio almost agree with those for LN36 [5]. These facts suggest that the present group of phase transitions belong to a new universality class, as expected theoretically in layered systems [13].…”

“…Recently, the present authors constructed a highsensitivity differential scanning calorimeter (DSC) [5,6]. This high-sensitivity DSC successfully revealed detailed features of heat anomalies accompanying phase transitions between SmC * subphases and the SmA phase in the case of several antiferroelectric liquid crystals.…”

Effect of Enantiomeric Excess on the Smectic- – Smectic-C* Phase Transition

“…This is also strongly supported by the reduction of the thermal hysteresis. Recently, the corresponding behavior changing from a first-order to a continuous transition is also measured in pure enantiomers of the different compounds as shown in Figures in ref [4]. This can also be explained by taking the chiral strength of the compounds into account, which is expected to give rise to the different behavior.…”

“…However, since the thermal relaxation process due to the helical modulation is thought to be very sluggish, the frequency-domain measurement by an ac calorimetry at a low-frequency operation (0.03125 Hz) could not detect noticeable heat capacity response even close to the critical point [3]. To overcome this problem, recently, calorimetric studies have been performed using a high-sensitivity differential scanning calorimetry (DSC) for several liquid crystalline samples exhibiting the SmC Ã a -SmC Ã phase transition [4]. In that work, the obtained heat anomalies clearly exhibited different types of behavior, which agrees with the results of the earlier RXRD measurements.…”