(Soft Matter) Generation of Liquid Crystallinity from a Td-Symmetry Central Unit-Hong Yang

A series of new columnar liquid crystals containing an adamantane central unit with the 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 1H-NMR, 13C-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 rectangular columnar phase which switched to square columnar phase with a wide range of thermal stability. Similarly, 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.

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