We report a joint computational and experimental study on the concentration-dependent self-assembly of a flat C3-symmetric molecule at surfaces. As a model system we have chosen a rigid molecular module, 1,3,5-tris(pyridine-4-ylethynyl)benzene, which can undergo self-association via hydrogen bonding (H-bonding) to form ordered 2D nanostructures. In particular, the lattice Monte Carlo method, combined with density functional calculations, was employed to explore the spontaneous supramolecular organization of this tripod-shaped molecule under surface confinement. We analyzed the stability of different weak H-bonded patterns and the influence of the concentration of the starting molecule on the 2D supramolecular packing. We found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration-dependent scanning tunneling microscopy investigation of the molecular self-assembly at a graphite-solution interface revealed supramolecular motifs, which are in perfect agreement with those obtained by simulations. Therefore, our computational approach represents a step forward toward the deterministic prediction of molecular self-assembly at surfaces and interfaces.

With the use of a single building block, two nanoporous patterns with nearly equal packing density can be formed upon self-assembly at a liquid-solid interface. Moreover, the formation of both of these porous networks can be selectively and homogenously induced by changing external parameters like solvent, concentration, and temperature. Finally, their porous properties are exploited to host up to three different guest molecules in a spatially resolved way.

A density functional and Monte Carlo simulation study of end-grafted polymers immersed by simple fluids is presented. The polymer molecules are modeled as freely jointed tangent hard spheres with the end segments linked to the surface. The authors analyze an influence of the chain length, the grafting density, and a nature of solvent on the brush structure. Adsorption of hard-sphere mixtures on the modified surface is also discussed. The theory precisely approximates simulation data.

A density functional approach to describe adsorption of Lennard-Jones fluids on a surface modified with grafted chains is proposed. The theory is extended to the solute retention in chromatography with chemically bonded phases. The chain molecules are modeled as freely jointed tangent spheres with end segments linked to the surface. The segments interact via Lennard-Jones potential. The effects of grafting density and molecular interactions are discussed. The results are compared with the Monte Carlo simulation data. The theory predicts the most important features of the retention process.

Directing the self-assembly of organic molecules towards low-dimensional superstructures has been an attractive method of fabrication of functional materials with programmable architecture. In this contribution, using theoretical modeling, we demonstrate how fine tuning of directional intermolecular interactions which are encoded in a simple organic building block allows for the creation of surface-confined assemblies with largely diversified morphology. To that end the self-assembly of a model tripod-shaped molecule adsorbed on a triangular lattice was simulated using the canonical ensemble Monte Carlo method. The simulations were performed for flat, rigid building blocks built of four discrete segments (core plus three arm segments) and equipped with adjustable peripheral interaction centers providing directional intermolecular bonds. The simulated results revealed that changes in the directionality of interactions imposed on the centers are responsible for the emergence of different molecular structures including ordered porous networks, chain and ladder structures and chiral patterns. The obtained assemblies were analyzed and classified with respect to their structural and energetic properties. Our theoretical investigations showed that small changes in the position of the outer interaction centers in a tripod functional molecule can have dramatic effect on the morphology of the resulting 2D structures. On the other hand, these findings can be helpful in predicting the self-assembly of organic tripod molecules with the different interaction patterns discussed in this study. This information, can be relevant, for example, to synthetic chemists seeking for an optimal building block able to self-assembly into a 2D superstructure with predefined properties.