Pressure-Temperature Phase Diagrams of Ferroelectric Liquid Crystals

The pressure-temperature phase diagrams of the ferroelectric liquid crystals FLC-031 and FLC-032 were obtained from the complex dielectric constant. As the pressure increases, all the transition temperatures increase. On heating, the temperature width of the smectic phase is almost independent of the pressure, while the width of the ferroelectric chiral smectic C (SmC*) phases reduces with pressure and disappears at 300 MPa and 125degreesC for FLC-031 and 160 MPa and 102'C for FLC-032. On the other hand, the width of the paraelectric smectic A (SmA) phase increases with increasing pressure. Therefore, this indicates that, for FLC-031 and FLC-032, the application of pressure reduces the stability of the SmC* phase, while the stability of the SmA phase increases. Moreover, there is no systematic relation between the length of the non-chiral alkyl chain in molecules and the decreasing rate of the width of the SmC* phase with pressure.