A partially bilayered smectic B (Bd) phase of a thermochromic mesogen

Abstract

N-hexadecyl-p-cyanopyridinium iodide was studied using X-ray scattering, differential scanning calorimetry and polarized light microscopy. Preliminary results reveal that the material is thermochromic, turning from yellow to red upon entering a liquid crystal phase at 104°C. The mesophase is of the smectic B type, where the lamellar spacing is between one and two molecular lengths. A structural model is proposed that can be described as a honeycomb arrangement of unpaired molecules with their dipolar moments alternating around the cells; a paired molecule lies in the center of each cell and two iodide ions are located axially at the cyano end of each unpaired molecule. It is noted, however, that the experimental data do not exclude the possibility of a model in which the paired and unpaired molecules are arranged randomly in the more usual hexagonal network