Abstract
The helical structure in an antiferroelectric liquid crystal (AFLC) phase may show a complicated temperature dependence such as the change in the helical handedness. However, the mechanism of the helical arrangement of molecules has not been clarified. In this study, we investigated the temperature dependence of the helical structure using several types of AFLC material and the effect of the optical purity on the helical structure in terms of optical rotatory power (ORP) and circular dichroism (CD). Results show that the increase in the helical pitch, which originates from a decline of the optical purity, is not due to the decrease in the macroscopic twisting power but the microscopic coexistence of both the helical handedness. Furthermore, it is clear that the change in the helical handedness is a premonitory phenomenon of the phase transition from the antiferroelectric smectic C (SmCA*) to the lower temperature phase such as the crystal phase. On the other hand, it is confirmed that the change in the helical handedness is not intrinsic to all AFLC media.