Molecular self–assembly, a promising strategy for modifying surfaces on the nanometre scale, is of great importance for developing functional materials in electronics, photonics, catalysis, and 2D crystal engineering. However, the association of the free components into an ordered structure at the interface between a liquid and a crystalline solid, i.e. the liquid-solid interface, is a complex process involving an interplay of interactions between assembling molecules, solvent and substrate. Therefore, understanding the complexity of molecular mechanisms controlling the self-assembly process at the liquid-solid interface presents the foundation for rational design and fine-tuning of properties of the materials.<br/>In this work, we are shifting attention to the physical chemistry of the processes at a molecular level through a systematic study of the influence of several key variables (e. g. concentration, temperature, molecular structure) on the overall process of self-assembled molecular network formation. The overarching idea is to correlate experimental results with analytical thermodynamic models to improve the understanding of supramolecular chemistry in two dimensions by obtaining quantitative data. For this purpose, a series of isophthalic acids have been chosen as a model system. The effect of the concentration on the adsorption behaviour, focusing on the surface coverage, has been evaluated at the nanoscale level using scanning tunneling microscopy (STM). Our preliminary results confirm the existence of a critical concentration above which self-assembly occurs, and interestingly, the change in the molecular structure (the length of the alkyl chain) has a remarkable impact on its value. Additionally, we have observed a highly cooperative behaviour of studied systems. While the notion of cooperativity is often present in the context of molecular adsorption, limited studies in the literature show quantitative evidence for such behaviour and its origin is still poorly understood.

Exploring fundamentals of the formation of self-assembled molecular networks at the liquid-solid interface: a case study on isophthalic acids

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