EVIDENCE OF ELECTROCLINIC EFFECT IN SOME TGBA MESOPHASES

Two members of a chiral tolane series exhibiting a new TGBA phase and a S(C) ferroelectric phase have been investigated by means of electro -optical measurements. These materials belong to the optically active series of nyl)-4'-(4''-alkyloxy-3''-fluorobenzoyloxy)tolanes and are t he tetra- and octa-decyloxy derivatives. Due to the large pitch values in these TGBA mesophases, complete unwinding of the helix is found to be possible in thick cells. This also allows measurements of the elec troclinic properties, such as the electric field induced tilt angle, r esponse time, and the ferroelectric properties in the S(C) phase.