Molecular disorder in columnar-phase discotic liquid-crystal strands

Abstract

We present x-ray diffraction measurements of freely suspended single-orientation columnar-phase strands of 2,3,7,8,12,13-hexa(-n-tetradecanoyloxy)truxene [(${\mathrm{C}}_{13}$ ${\mathrm{H}}_{27}$COO${)}_6$-TX] which show a dramatic difference between the ordering of the rigid, planar central cores and the flexible hydrocarbon chain tails of the molecules. Diffraction from the strands reveals two types of behavior: the tails are highly disordered, producing a nearly isotropic scattering pattern, whereas the rigid cores are orientationally ordered and translationally disordered within the columns. High-resolution diffraction measurements show that the hexagonal lattice correlation length is greater than 4000 Å, corresponding to more than 200 columns.