Modulation of Monomers to Obtain Higher-Order Architectures of Supramolecular Assemblies of Chiral π-Systems

Abstract

Secondary nucleation is a promising approach for synthesizing higher order supramolecular assemblies beyond traditional one-dimensional (1D) and 2D structures. Typically, during the cooperative self-assembly process, a small seed is formed by primary nucleation of the monomers, followed by elongation or it can also trigger secondary nucleation-elongation process. Hence, it is important to understand how to control the primary nucleation-elongation and secondary nucleation-elongation events to yield desired supramolecular structures with controlled topologies. Using chiral cyclic ether functionalized PDI derivatives (THF-PDI-R and THF-PDI-S), here we show that by modifying the state of monomers in self-assembly, it is possible to control primary and secondary nucleation events. When a 30 vol% water is added to PDI monomers in dioxane (thermodynamically formed), the self-assembly process is governed by both primary and secondary nucleation events, yielding 1D fibres and branched structures. Interestingly, these PDIs also form kinetically trapped monomers via rapid cooling. Allowing dormant monomers (kinetically trapped) to self-assemble results in the formation of bow-tie-like spherulites. By homo-seeding of dormant monomers, 1D fibres are formed because the self-assembly is governed by primary nucleation-elongation. Thus, our results indicate that controlling the monomer state required for self-assembly enables control over nucleation events and the architectures of supramolecular assemblies.