The alignment of the lyotropic discotic liquid crystal 2, 3,6,7,10,11-hexa-(1,4,7-trioxaoctyl)-triphenylene (TP6EO2M) on −CO 2 H and −CH 3 self-assembled monolayers (SAMs) has been investigated in order to determine whether the surface free energy could be used to control anchoring in such a system. Irrespective of the SAMs used we found that the alignment tends to be with the director in the plane of the surface. To understand why the different SAM types produce the same bulk behavior we considered the adsorption of TP6EO2M from dilute solutions. In the case of −CH 3 surfaces we found the first adsorbed DLC layer lies with its triphenylene core close to the hydrophobic SAM, leaving the hydrophilic chains extending from the surface. For the −CO 2 H surfaces the first DLC layer is believed to be edge-on again, leading to hydrophilic chains extending away from the surface. These adsorbed DLC layers give rise to planar alignment of the bulk nematic and columnar phases.

The alignment of the columnar hexagonal (Colh) phase of the discotic liquid crystal 2,3,6,7,10,11-hexakis(undecyloxy)triphenylene on well-characterized surfaces comprised of thiol-on-gold self-assembled monolayers (SAMs) has been studied using polarizing optical microscopy in combination with evanescent wave ellipsometry. Homeotropic alignment is preferred for both COOH- and CH3-functionalized SAMs (both high and low energy surfaces). Even when the SAM layer is comprised of edge-on oriented triphenylene units, evanescent wave ellipsometry shows that the liquid crystal aligns predominantly in a homeotropic (face-on) manner. These results confirm the view that the surface acts primarily as a mechanical barrier and although the chemical nature of the surface can enhance the ease or quality of the alignment of the Colh phase, it is of secondary importance.