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Synthesis and liquid crystalline behavior of azulene-based liquid crystals with 6-hexadecyl substituents on each azulene ring |
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| Authors: | Kosuke Nakagawa Kozo Toyota Shunji Ito Shota Tahata Jun Kawakami Yoriko Kanai |
| Affiliation: | a Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan b Graduate School of Science and Technology, Hirosaki University, Hirosaki 036-8561, Japan c Smart Materials Science and Technology, Department of Bioscience and Textile Technology, Interdisciplinary Graduate School of Science and Technology, Shinshu University, Ueda 386-8567, Japan |
| Abstract: | Hexakis(6-hexadecyl-2-azulenyl)benzene (1b) has been synthesized by Co2(CO)8-catalyzed cyclotrimerization reaction of bis(6-hexadecyl-2-azulenyl)acetylene (2b). The mesomorphic behaviors of 1b, 2b, and 6-hexadecyl-2-phenylazulene (3b) were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques and their mesomorphic properties were compared with those of their 6-octyl derivatives 1a, 2a, and 3a. Increase of the number of carbon atoms in the peripheral side chains drops the isotropization temperatures of 1b, 2b, and 3b by 56.9 °C, 33 °C, and 23.6 °C, respectively. Additionally, the phase-transition behavior varied with increase of the number of the peripheral chains, as well as decrease of the crystalline-mesophase transition temperatures, except for compound 3b. As the results, spontaneous monodomain homeotropic molecular alignment was revealed by compound 1b in its Colhd mesophase on non-treated glass substrate, which would be attracted to the application for the device fabrication of molecular materials. |
| Keywords: | Discotic liquid crystals Homeotropic alignment Azulenes Cyclotrimerization |
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