Chiral and Morphological Anisotropy of Supramolecular Polymers Shaped by a Singularity in Solvent Composition

Understanding the role of solvent in translating molecular anisotropy to supramolecular polymers is in the early stages. A solvent's influence on the strength of different noncovalent interactions can explain anisotropic growth in some cases, but its effect on cooperative processes, particularly in mixed solvents, remains obscure. We report the self-assembly of a series of chiral perylene bisimides in water-cosolvent mixtures, and the results highlight the fascinating influence of solvent-solute interactions on supramolecular anisotropy, both chiral and morphological. The initial assembly is agnostic to solvent composition, resulting in weakly chiral, spherical nanostructures. In an extremely narrow solvent composition range, the nanospheres transform into long, prominently chiral supramolecular polymers. Further, chirality can be fully reversed by changing the good (achiral) cosolvent. We elucidate how solvent modulates specific noncovalent interactions and governs the kinetics and thermodynamics of key processes, such as spontaneous phase segregation, secondary nucleation, and cooperative growth. In the context of supramolecular polymerization, our results encourage one to steer the focus away from the physical attributes of a solvent (polarity, phase diagram, etc.) and toward the complexities of solvent-solute interactions.