Tuning Preferential Molecular Adsorption and Self-Assembled Molecular Network Formation at the Liquid-Solid Interface: The Impact of Annealing and Confinement

We report on the selective adsorption and the formation of self-assembled molecular networks (SAMNs) at the interface between a liquid and highly oriented pyrolytic graphite (HOPG) from equimolar mixtures of alkoxylated dehydrobenzo[12]annulene (DBA) derivatives (DBA-OCn [n = 6, 11, or 16]) that differ in the length of their six alkoxy chains. As revealed by scanning tunneling microscopy at the liquid-solid interface on pristine HOPG at room temperature, every component in the mixtures forms separate domains, where the larger molecules tend to occupy the larger surface area. In contrast, following a hot deposition protocol, preferential monolayer formation of the larger DBA-OCns is observed. Under nanoconfinement conditions restricting the surface area, only the largest molecule in a mixture is found to form SAMNs. Therefore, preferential adsorption in multicomponent mixtures is successfully achieved upon hot deposition or self-assembly under nanoconfinement conditions. Thermodynamic factors contribute to preferential adsorption. Molecular mechanics simulations support the experimental results and contribute to explaining the underlying mechanism.