Synthesis and comparative structural investigation of crystalline and liquid-crystalline phases of low molecular mass compounds and side group polymers I. Low molecular mass compounds

Low molecular mass compounds and analogous side group polymers with a thermotropic phase behaviour crystalline-smectic liquid-crystalline-isotropic have been synthesized for a comparative structural study. As characteristic features of the compounds a biphenyl group has been chosen for the mesogenic core and alkoxy parts of various lengths as terminal and spacer groups. The phase behaviour has been studied with differential calorimetric (DSC) measurements and polarization microscopic observations. The low molecular mass compounds form crystalline phases at room temperature and exhibit predominantly mosaic textures in the polarization microscope at elevated temperatures indicating high order of the packing of the molecules. The arrangements of the molecules in the crystalline and liquid-crystalline phase can best be described as layered structures according to X-ray diffraction measurements. A structural analysis of a solution grown single crystal provides valuable information on the conformation and packing of the compounds investigated in this study.