One-dimensional electronic conductivity in discotic liquid crystals

The discotic mesogen 2,3,6,7,10,11-hexa-hexyloxytriphenylene (HAT6) forms a columnar hexagonal phase which is an electrical insulator. Doping with 1 mol% of the Lewis acid AlCl3 converts it to a p-type semiconductor with the preferred direction of conduction being along the axes of the columns. The electrical conductivity is envisaged to arise from the migration of positive holes created in the π-electron band of the triphenylene stack. The behaviour is established by electrical conductivity measurements, which show anisotropy, and ESR lineshapes which are consistent with Dyson's theory of resonance absorption by conduction electrons.