It is proposed to apply the direct measurement of spontaneous polarization using triangular waves to ferroelectric liquid crystals. The use of the triangular waves allows us to easily subtract the background contribution due to the conductive and the capacitive current and to accurately determine the spontaneous polarization, since a bump due to the polarization realignment appears on a straight base line. Moreover, the experiment with pulsed triangular waves clearly reveals no existence of the threshold voltage for deforming the helix and some characteristic properties of the dynamic reaction of the helix to the field applied.

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The helical pitches and the tilt angles are measured as a function of temperature for recently synthesized room temperature ferroelectric Sm C* liquid crystals to examine the possibility as materials for switching devices. The pitch of MBRA 8 is almost independent of temperature except in the range close to the Sm A to Sm C* phase transition, where it appears to decrease steeply as in nOBAMBC. In MORA 8 and 12, it gradually increases with temperature but does not decrease near the transition from Sm C* to isotropic. The tilt angle of MBRA 8 is relatively small as compared with the desired value of 22.5° for the best contrast. The tilt angle of MORA n could not be determined because the spontaneous polarization is too small to unwind the helix for the measurements. The present substances are not suitable for switching devices by themselves, but are pointed out to be useful as mixing components.