V‑Shape Molecular Self-Adaption Triggered 2D Self-Assembled Polymorphism by Coadsorption of n-Tetradecane Solvent

The self-assembly of thienophenanthrene derivative with V-shape conjugated core and four tetradecanoxyl chains (TPTD-Nap) at different solution concentrations has been investigated at the liquid–solid interface by scanning tunneling microscopy. n-Tetradecane was chosen as the solvent because its alkyl chain is commensurate with the length of the molecular side chains. At saturated concentration, TPTD-Nap forms a linear pattern with long-range disorder and short-range order. As the concentration decreases, a highly ordered linear structure is observed. At low concentrations, TPTD-Nap molecules self-assemble into three types of nanostructures with reduced packing density because n-tetradecane molecules participate in the self-assembled process by the coadsorption at different levels. The most remarkable feature of the TPTD-Nap arrangements is the self-adaption of symmetric V-shape cores as well as the alkyl chain-length of the molecule and solvent. The former contributes to fabricate the backbone of the nanostructures, and the latter determines the self-assembled polymorphism by the coadsorption.