Discotic Liquid Crystals

New radial polyalkynylbenzene derivatives, which consist of 4-phenylacetylene unit connected with a central phenyl or phenoxy or tolyl linking moiety, are presented. The mesomorphic properties of these compounds in their pure form and as donor-accepter (D-A) complexes with 2,4,7-trinitrofluoren-9-one (TNF) were investigated with polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies. The hexaalkynylbenzene derivatives in a pure form had a columnar mesophase texture, and pentaalkynylphenyl and pentaalkynyltoluene derivatives remained in a highly viscous liquid state even at room temperature, whereas D-A complexes showed a the columnar hexagonal (Colh) mesophase. The unexpected mesophase behavior of these radial polyalkynylbenzene derivatives comes from the molecular architecture arising from the branched aliphatic chain.