ON THE NEMATIC-NEMATIC PHASE-TRANSITION IN MIXTURES COMPOSED OF SHEET-SHAPED PALLADIUM ORGANYLS AND APOLAR ORGANIC-SOLVENTS

The three sheet-shaped palladium organyls la-e exhibit lyotropic nemat ic properties in apolar organic solvents. The occurrence of two nemati c lyomesophases was verified by the investigation of the orientational properties of these liquid crystalline systems. In cells with oblique ly deposited SiOx layers, the director of the high temperature phase N -2 is aligned in a homogeneous, planar manner. In the low temperature phase N-1, a different orientational pattern is observed. The specific pattern type depends on the deposition conditions of the SiOx layers. In samples homeotropically aligned in the N-2 phase, the director is tilted away from the cell normal after the transition into the N-1 pha se. These changes of orientation are reversible. The experimental obse rvations presented here support our proposed model for the structural change at the nematic-nematic phase transition.