PHASE SEQUENCE IN SMECTIC LIQUID-CRYSTALS HAVING FLUOROPHENYL GROUP IN THE CORE

The phase sequence of a new family of chiral smectic liquid crystals, represented by 4-(1-methylhepthyl-oxycarbonyl) 3-fluorophenyl 4'-dodec ylbiphenyl-4-carboxylate (MHFPDBC), were investigated by measurements of dielectric dispersion under various bias field strengths. Three pha ses, ferrielectric smectic C-gamma() phase (Sm-gamma(*)), antiferroel ectric phase (AF) and ferrielectric phase (FI), were confirmed between ferroelectric SmC phase and antiferroelectric SmCA* phase. In the di electric measurements around the ferrielectric phases, an opposite bia s treatment prior to the application of the target bias field strength is important. Observed dielectric relaxation modes were discussed tog ether with the results of electrooptical and conoscopic observations.