Thieno[3, 2-b]thiophene-Based Discotic Liquid Crystal Mesogens: Rational Synthesis, Physical Properties and Self-Assembly

The straightforward synthesis of rigid fused thienoacenes through FeCl₃ mediated Scholl cylcodehydrogenation by utilizing thieno[3, 2-b]thiophene as core and alkylthiophenes (alkyloxylphenyls) as arms is described. Their thermal behaviours were studied by different techniques such as thermo-gravimetric analysis, differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. Their self-assembly properties were systematically investigated by variable concentration NMR, scanning electron microscopy and transmission electron microscopy. These new discotic mesogens have very good thermal stability and display thermo-tropic liquid crystalline behaviours. Ordered columnar liquid crystalline phases and crystalline phases were observed for these compounds with tunable phase transition temperatures and mesophase widths. Interestingly, these compounds could simultaneously generate micro-ribbons in various solvents due to strong π-π intermolecular interactions.