Dendritic morphology in homeotropically aligned discotic films

Abstract

A hexa-alkylether-substituted hexa-peri-hexabenzocoronene, as a discotic liquid crystal, spontaneously homeotropically self-orients when cooled from the isotropic phase. During this process, a dendritic morphology is formed in which a significant optical difference is observed between the dendritic shapes and their periphery. However, local structural analysis using microfocus synchrotron radiation experiments demonstrate that there is an identical supramolecular order in both areas. Three-dimensional confocal surface measurements reveal that these dendritic structures result from a dewetting process, which occurs during solidification. Thereby, the contact area between the organic material and the surface is reduced. These results are important for the design of organic electronics, since the reduction of the contact area in an electronic device might inhibit the charge transport between the discotic semiconductor and the electrode. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.