Synthesis and thermotropic properties of new mesogenic pyrazole and isoxazole derivatives

Abstract

The synthesis of new mesogenic alkyloxy pyrazole and isoxazole derivatives is reported. The mesogenic properties of these compounds were investigated by differential scanning calorimetry, polarizing microscopy and X-ray diffraction. Almost all compounds show preferred orientation in a magnetic field of about 1·5 T. Pyrazole derivatives show higher transition temperatures than the corresponding isoxazole derivatives. Small differences (1–3 Å) between the molecular lengths (as determined from models and the smectic layer thickness indicated by X-rays) are explained in terms of interdigitation or skewing of the alkyloxy chains.