INFLUENCE OF OPTICAL PURITY ON THE SMECTIC-C-BETA(ASTERISK) PHASE OF ANTIFERROELECTRIC LIQUID-CRYSTALS

The Smectic-C-beta (SmCbeta*) phase, which appears between the SmA an d SmCA phases in an optically pure liquid crystal of MHPOBC, has been studied by means of simultaneous measurements of the dielectric const ant epsilon and the electroclinic coefficient kappa under a dc bias el ectric field. The result of electroclinic coefficient measurement show s that the SmCbeta phase is obviously different from the SmC* phase a nd can be considered as a ferrielectric phase. From the simultaneous m easurement of epsilon and kappa, we can observe the difference in the phase transition behaviors between pure and slightly racemized MHPOBC samples and confirm that the decrease of optical purity causes the cha nge from the SmCbeta phase to the SmC* phase.