Self-assembly of molecular tripods in two dimensions: structure and thermodynamics from computer simulations

Controlled self-organization of molecular building blocks into low-dimensional ordered superstructures is a promising method of fabrication of functional materials with tunable physico-chemical properties. In this contribution we use the Parallel Tempering Monte Carlo simulation method to study the self-assembly of tripod molecules adsorbed on a triangular lattice being an analog of a graphite surface. In the adopted approach the molecules were assumed to be flat rigid C-3-symmetric structures composed of a central segment connected with three n-membered arms. Our primary objective was to examine the effect of molecular size, n on the topology of the corresponding phase diagrams and to identify stable ordered phases with different morphologies. It was demonstrated that for the tripod molecules with sufficiently long arms (n > 1), the self-assembly leads to the formation of scalable chiral porous networks with hexagonal void spaces. For these systems the phase coexistence was found to be described by phase diagrams with the same overall topology. On the other hand, the simulations performed for the small tripods with n = 1 revealed the formation of compact patterns, resulting in a substantial change in the shape of the phase diagram. The insights from our theoretical investigations can be helpful in designing 2D self-assembled molecular architectures comprising C-3-symmetric functional units.