Surface orientation of per-fluorinated supramolecules on the self-assembled monolayers

Abstract

First of all, we describe the synthesis and characterization of supramolecules self-assembled into hexagonal columnar cylinder mesophases, 3, 4, 5-Tris[p-(n-5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 12-heptadecadodecan-l-yloxy)benzyloxy]benzoic Acid (12F8ABC, 6) and [4-(1-Pyrenyl)-butyl] 3, 4, 5-Iris-(12, 12, 12, 11, 11, 10, 10, 9, 9, 8, 8, 7, 7, 6, 6, 5, 5-heptadecafluoro-n-dodecan-l-yloxy)-benzoate (9, 12F8AOH) These molecules are per-fluorinated supramolecules substituting tail group with fluorine group. The fluorination of the dodecyl groups of these tapered building blocks engances dramatically their self assembly and thermal stability because of incompatibility between rigid perfluorocarbon and flexible perhydroxycarbon. Thermal and phase transition of them was confirmed by differential scanning calorimetry (DSC) data, polarized optical microscopy (POM) and X-ray diffraction (XRD) image. And then, we describe the orientation of per-fluorinated supramolecule on the various self-assembled monolayers. Here, we use 12F8ABG as per-fluorinated supramolecule because this molecule has higher ordered structure than 12F8AOH when their structures were observed by TEM. In other words, the way in which orientation of per-fluorinated hexagonal columnar meso-phases depends on surface properties is investigated. Surface is modified by various self assembled monolayers (SAMs), molecular orientation is controlled by these SAMs. SAM materials composed of thiol group (-SH) are coated on gold substrate. The supramolecule is coated on treated surface by solution spreading method. As a result, Homeotropic alignment of per-fluorinated columnar molecules occurs readily onto hydrophobic surface, treated by SAM containing alkyl group at one end. The planar alignment of them is favored on hydrophilic or fluorinated surface, modified by hydroxyl tailed or fluorine tailed SAM. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) are used as a tool of ob...