Experimental-Observation of a Transition Between 2 Uniaxial Nematic Liquid-Crystal Phases

The experimental observation of a phase transition between two uniaxial nematic liquid-crystalline phases is reported. High-resolution x-ray scattering and ac calorimetric studies on binary mixtures of octyl- and decyloxyphenyl-nitrobenzoyloxy benzoates show evidence of a first-order transition between two nematic phases with different types of short-range smectic order. This transition is observed in the vicinity of the termination of the smectic-Ad-smectic-A1 phase boundary, in accordance with theoretical predictions.