Fast and Slow Dynamics in a Discotic Liquid Crystal with Regions of Columnar Order and Disorder

Aromatic disk-shaped molecules tend to self-organize into a herringbone packing where the disks are inclined at angles +/-theta with respect to the axis of the column. In discotic liquid crystals this can introduce defects between stacks of limited length. In a C(3)-symmetric hexa-peri-hexabenzocoronene, solid-state NMR, x-ray scattering, and rheology identifies such a packing with theta = 43 degrees and stacks of about seven disks. Disordered regions containing defects fill the space in between the ordered stacks. Biaxial intra-and intercolumnar dynamics differing by eight decades are identified.