Glass-forming discotic liquid-crystalline oligomers

Isomerically pure dimers and trimers containing, two and three triphenylene hexaether mesogenic units, respectively, have been prepared. The key step of the synthesis was an oxidative coupling of a 1,2-dialkoxybenzene and a 3,4,3′,4′-tetraalkoxybiphenyl to give an unsymmetrically substituted triphenylene. The mesophase behaviour of these liquid crystals shows that there is surprisingly little difference between the clearing temperatures of the equivalent monomer, ‘dimer’, ‘trimer’ and polymer and that, like the polymer, these new oligomers supercool into ordered glassy films.