Observation of Three Subphases in Smectic C* of MHPOBC by Dielectric Measurements

In the phase transition from the paraelectric smectic A to the antiferroelectric SmC A * phase via the ferroelectric SmC * phase in MHPOBC, the existence of a subphase, SmC α * , between SmA and the normal SmC * (SmC β * ) was confirmed in addition to that of another subphase, SmC γ * , between SmC * and SmC A * by means of dielectric measurements. It was also confirmed that these subphases, SmC α * and SmC γ * , disappear in the same compound of lower optical purity as observed by DSC. The model structure of the SmC α * phase is speculated on the basis of the dielectric measurements.