title: Generation of liquid crystallinity from a Td-symmetry central unit.
abstract: A series of new columnar liquid crystals containing an adamantane central unit with its four bridgehead positions partially or fully decorated with different numbers (1-4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups were designed and investigated carefully to explore the structure-property correlations. The molecular structures and mesomorphic properties of the DLCs were characterized by (1)H-NMR, (13)C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives. No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited a rectangular columnar phase, which switched to a square columnar phase possessing a wide temperature range. Similarly, a hexagonal columnar mesophase was observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized 1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.
authors.affiliation: School of Chemistry and Chemical Engineering, Jiangsu Province Hi-Tech Key Laboratory for Bio-medical Research, Jiangsu Optoelectronic Functional Materials and Engineering Laboratory, Southeast University, Nanjing, 211189, China. yangh@seu.edu.cn.
authors.forename: Sayed Mir
authors.initials: SM
authors.lastname: Sayed
authors.affiliation: School of Chemistry and Chemical Engineering, Jiangsu Province Hi-Tech Key Laboratory for Bio-medical Research, Jiangsu Optoelectronic Functional Materials and Engineering Laboratory, Southeast University, Nanjing, 211189, China. yangh@seu.edu.cn.
authors.forename: Bao-Ping
authors.initials: BP
authors.lastname: Lin
authors.affiliation: School of Chemistry and Chemical Engineering, Jiangsu Province Hi-Tech Key Laboratory for Bio-medical Research, Jiangsu Optoelectronic Functional Materials and Engineering Laboratory, Southeast University, Nanjing, 211189, China. yangh@seu.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang