Abstract
Novel discotic liquid crystals possessing two triphenylene (TP) mesogenic cores covalently connected via a rigid spacer, i.e., π-conjugated ethynyl- or butadiynyl-bridge, (TP twins) are reported. The TP twins are categorized by the lengths of β-substituted chains (R2 and R3) and peripheral alkoxy or branched aliphatic chains (R1 and R4). Three varieties of TP twins are prepared: A) TP twins having identical β-substituted and peripheral chains (R1 = R2 = R3 = R4), B) equivalent TP entities having a β-substituted chain (R2 = R3) and peripheral chains (R1 = R4) of different length from the β substitution, and C) TP twins with different TP entities having the same β-substituted and peripheral alkoxy chains (R1 = R2, R3 = R4). The phase behavior is characterized by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. These TP twins exhibit a discotic nematic (N) and/or columnar rectangular (Colr) mesophases over a wide temperature range. We found that the relative length of rigid spacer and β-substituted alkoxy chains play an important role in the creation of the molecular self-assembly and formation of the mesophases. To the best of our knowledge, this is the first report of TP twins exhibiting polymesomorphism.
ACKNOWLEDGMENT
SKV is very grateful to Prof. K. A. Suresh for his sustaining support for the research work and thankful to Dr. S. Krishna Prasad for helpful discussion. A fellowship by Japan Society for Promoting Science (JSPS), Japan is gratefully acknowledged.
Notes
*Data from ref. [Citation33].