STM and AFM images for supramolecular organization in monolayers of pyrene-functionalized asymmetric twist-bend nematic dimers

2D supramolecular organization of asymmetric liquid crystal dimers containing two chemically different mesogenic groups, namely: cyanobiphenyl and pyreneiminomethyl phenoxy groups, linked with an oligomethylene linker of different length (6 or 8 -CH2- units), was studied using scanning tunneling microscopy (STM). For this purpose, monolayers of these dimers were deposited on a HOPG substrate from their solutions in hexane by drop-casting and imaged at nanometer resolution after drying. A detailed discussion of two possible different supramolecular organizations is presented. Comparative analysis of the monolayer structure with already reported XRD data on 3D organization of the same molecules in a single crystal revealed significant differences resulting from: i) different ordering preferences in 2D and 3D systems and ii) effect of the interactions of the deposited molecules with the graphite substrate.