TEMPERATURE-DEPENDENCE OF TILT, PITCH AND POLARIZATION IN FERROELECTRIC LIQUID-CRYSTALS

Present temperature measurements of the important parameters defining the properties of the smectic C* phase in a series of schiff bases. The pitch of the helical texture is measured optically. The molecular tilt is deduced from optical observations and from X-ray measurements of the smectic layer thickness. The critical electric field for unwinding of the helical texture is measured in the homeotropic and planar geometries. With these data, the spontaneous polarization is estimated to be in the range of 10** minus **3 Debye/molecule/radian, excepted for HOBACPC, a compound with a chlorine directly fixed on the asymmetric carbon, where it is one order of magnitude larger. Intramolecular rotations appear as an important factor to decrease the spontaneous polarization.