Solvent demixing-controlled supramolecular polymerization

Supramolecular polymers are fundamental mimics of biological assemblies with diverse functions. However, a major challenge in this field is predicting monomer solubility and controlling the colloidal stability of the resulting assemblies in solution. Consequently, the preparation of supramolecular polymers typically requires solvent mixtures, which can introduce miscibility gaps during sample processing —an effect that remains poorly understood. Here, we demonstrate that solvent demixing drives supramolecular polymerization. Detailed investigations of a proof-of-concept amphiphilic Pd(II) complex 1 reveal a thermally induced transition from kinetically controlled nanoparticles to thermodynamically stable supramolecular polymers in water/1,4-dioxane mixtures. Combined experimental and theoretical analyses demonstrate that annealing triggers solvent demixing into a dioxane-rich phase, increasing local monomer concentration and promoting nucleation and growth into one-dimensional nanostructures. Our findings draw parallels to biological compartmentalization and uncover a key physicochemical mechanism that challenges conventional solubility-based paradigms, offering a new perspective for the design and control of supramolecular polymerization