Executive Summary : | Supramolecular polymers are polymers in which the monomeric units are linked by non-covalent interactions. It enables the development of rationally designed building blocks that are either assembled into molecular assemblies or bulk materials. Due to their properties such as reversibility and the high internal order, they show promising applications in materials science and biology. For these applications, it is important to understand their polymerization mechanism. Among the mechanisms currently reported, supramolecular polymers that form through cooperative interactions are considered important as they lead to long supramolecular polymers with narrow size distributions. This project focuses on the rational design of π-systems that exhibit cooperative supramolecular polymerization through dispersive interactions. The effects of side chain substituents, as well as the solvents on cooperativity, will be examined. The project will contribute to the establishment of general guidelines for cooperative supramolecular polymerization, which will have a significant positive impact on the field of supramolecular chemistry. The proposed research is built on a collaborative effort between experimentalists and computational scientists. The central idea of the project is that the cooperativity in supramolecular polymers is attributed to the presence of hydrogen bonds, dipolar interactions, and metal-metal interactions, but without taking into account the contribution of the dispersive forces. Preliminary studies have demonstrated that dispersion alone can contribute to cooperative supramolecular polymerization. In this project, first, the three π-systems will be synthesized that are expected to self-assemble through dispersive forces. We will use solution-state optical techniques to investigate the supramolecular polymerization mechanisms. Furthermore, the thermodynamic parameters and the extent of cooperativity will be determined using the theoretical models. Second, a software program will be developed utilizing evolutionary algorithms to automatically generate the stable configurations of self-assembled oligomers of π-systems. Third, semi-empirical and density functional theory methods as well as classical molecular dynamics simulations will be used to understand the driving forces for the cooperative phenomena. Additionally, the molecular mechanisms of self-assembly, as well as the effect of solvation on the dynamics of the stack, will be examined. The energy decomposition analysis method will be used to compare these systems with existing cooperative π-systems in an attempt to gain a deeper understanding of how different intermolecular interactions, including dispersion forces, hydrogen bonds, and dipolar interactions contribute to the cooperative supramolecular polymerization. Additionally, the cooperativity will be adjusted by varying the dispersive forces, and their effects on the dynamics of the stack will be investigated. |