Effects of pressure on the dielectric properties of ferroelectric smectic C* liquid crystal DOBAMBC

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Abstract
The dielectric properties of the ferroelectric chiral smectic C* liquid crystal DOBAMBC were measured under hydrostatic pressures up to 2 kbar. The complex permittivity epsilon and the spontaneous polarisation Ps versus temperature T curve shift towards higher temperatures with increasing pressure p. The isotropic to smectic A(SmA), T1, SmA to chiral smectic C*(SmC*), Tc, SmC* to SmG*, T3, and SmG* to solid, T4, transition temperatures increase with p with rates dT1/dp=17.9, dTc/dp=12.5, dT3/dp=21.3 and dT4/dp=16.1 degrees C kbar-1, respectively. The Ps in the temperature range (Tc-T) below about 5 degrees C increases with p at constant temperature. The saturated P2 and the maximum real part of epsilon in the temperature range removed from Tc decrease with p. The stability of the ferro-electric SmC* phase decreases with p. The dielectric properties associated with the ferroelectric SmA to SmC* transition are explained in terms of a phenomenological theory.