Synthesis and Characterization of a Novel Liquid Crystalline Polymer Showing a Nematic Columnar to Nematic Discotic Phase Transition

A novel liquid crystalline polyacrylate, exhibiting a nematic columnar and a nematic discotic phase, the latter not found in any polymer previously, has been synthesized using a polymer analogous reaction, substituting the discotic mesogens on a reactive polymer. The highly flexible concept of the polymer analogous reaction enables us to introduce structural variations and to create and control molecular architectures. The mesophases of polymer 1, bearing the pentakis(methylphenylethynyl)benzene mesogen via a flexible undecanoxy spacer, as well as its low molar weight homologue 2, were fully characterized by optical polarizing microscopy, differential scanning calorimetry and powder X-ray diffraction. The thermal behavior of both compounds is qualitatively similar. Both materials exhibit a nematic discotic phase (ND) at higher temperatures, which is unique for the polymer, as this phase has only been observed in low molar mass materials so far. At lower temperatures 2 crystallizes, whereas 1 undergoes a transition into the nematic columnar phase (Ncol).