Calamitic and discotic liquid crystalline phases for mesogens based on triangular core
Mesogenic compounds having new triangular mesogenic cores containing salicylaldimine and enaminocarbonyl or barbituric moieties have been synthesized and their liquid crystalline, dielectric and optical properties have been studied. Proper substitution of such cores with various number of latteral chains (alkoxy, perfluorinated or polyether) leads to mesogens forming either lamellar (SmC), nematic or columnar (Colhd, Colho) phases. Some of the materials show an unusual phase sequence with re-entrant isotropic phase appearing below columnar (Colhd) phase; other form two columnar hexagonal phases with weakly first order transtion between them. Also a new columnar superstructure with p2gg symmetry (Colros) was found, which crystallographic lattice is decorated by two-molecule motive.