Antiferroelectric phase and tristable-switching in MHPOBC

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Abstract
Antiferroelectric phases of MHPOBC were studied by means of thermal analysis, electrooptic measurements and conoscopy. It was found that the phase transitions are seriously influenced by the optical purity of the material. Subphases in the transition region of SmA (paraelectric) -SmC (ferroelectric)-SmCA(antiferroelectric) are distinguished only in compounds with high optical purity. One of them are clearly recognized by conoscopy under an electric field as well as pitch and optical rotation measurements. Threshold behavior in the tristable switching was also studied as functions of temperature and cell thickness. It was found that the hysteresis in the apparent tilt angle tends to disappear with increasing the cell thickness, while the dc threshold is an inherent property of the antiferroelectric phase. The dc threshold behavior was also confirmed in a homeotropic cell using conoscopy.