INDICATION OF FERROELECTRICITY IN COLUMNAR MESOPHASES OF PYRAMIDIC MOLECULES

We have synthesized and studied trisbenzocyclononenes carrying six chi ral side chains. They are pyramidic shaped molecules exhibiting column ar mesophases. The optical and electro-optical effects of this chiral pyramidic compound have been studied. A homeotropic alignment of the c olumnar phase was achieved by cooling the film between plates treated with octadecyltriethoxysilane in the presence of a d.c. field. A trans ient optical effect was observed with these films on electric field re versal. Simultaneously there was a peak in the time dependence of the electric current flowing through the sample. The observations indicate that the columnar phase is ferroelectric with the polarization parall el to the optical axis. A few degrees below the clearing point, the ti me for polarization reversal is in the range of seconds and the magnit ude of the polarization is 10 mC m(-2). An electroclinic effect was ob served for films with fan textures.