A Coformer Approach for Supramolecular Polymerization at High Concentrations

Insolubility of functional molecules caused by polymorphism sometimes poses limitations for their solution‐based processing. Such a situation can also occur in the preparation processes of supramolecular polymers formed in a solution. An effective strategy to address this issue is to prepare amorphous solid states by introducing a “coformer” molecule capable of inhibiting the formation of an insoluble polymorph through co‐aggregation. Herein, inspired by the coformer approach, we demonstrated a solubility enhancement of a barbiturate π‐conjugated compound that can supramolecularly polymerize through six‐membered hydrogen‐bonded rosettes. Our newly synthesized supramolecular coformer molecule features a sterically demanding methyl group in the π‐conjugated unit of the parent molecule. Although the parent molecule exhibits low solubility in nonpolar solvents due to the formation of a crystalline polymorph comprising a tape‐like hydrogen‐bonded array prior to the supramolecular polymerization, mixing with the coformer compound enhanced the solubility by inhibiting mesoscopic organization of the tapes. The two monomers were then co‐polymerized into desired helicoidal supramolecular polymers through the formation of heteromeric rosettes. A barbiturate π‐conjugated compound is poorly soluble in nonpolar solvent because of its organization through its hydrogen‐bonding motifs into a crystalline polymorph prior to supramolecular polymerization. Mixing a “supramolecular coformer” compound with the parent compound provide highly soluble co‐aggregates, enabling supramolecular polymerization at high concentrations.