Supramolecular Depolymerization in the Mixture of Two Poor Solvents: Mechanistic Insights and Modulation of Supramolecular Polymerization of Ionic π‐Systems

Solvents are fundamentally essential for the synthesis and processing of soft materials. Supramolecular polymers (SPs), an emerging class of soft materials, are usually stable in single and mixtures of poor solvents. In contrast to these preconceived notions, here we report the depolymerization of SPs in the mixture of two poor solvents. This surprising behavior was observed for well‐known cationic perylene diimides (cPDIs) in the mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPA but readily depolymerize into monomers in 50–70 vol% IPA containing water. This is due to the selective solvation of the π‐surface of cPDIs by alkyl chains of IPA and ionic side chains by water, as evidenced by molecular dynamic simulations. Moreover, by systematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity. Mixtures of poor solvents are always not poor. Water and amphiphilic organic solvents (poor solvents), that individually promote the supramolecular polymerization of cationic π‐systems, readily depolymerize them into monomers in their mixtures (good solvent). Segregation of water and organic solvents around the molecular surface of the π‐system is the key for this surprising phenomenon.