Topological Impact on Kinetic Stability of Supramolecular Polymers
Résumé
Kinetically formed metastable molecular assemblies have attracted increasing interest especially in the field of supramolecular polymers. In most cases, metastable assemblies are ensembles of aggregates based on the same supramolecular motif but with different lengths or sizes, and therefore their kinetic stabilities are experimentally indistinguishable. Herein, we demonstrate a topological effect on kinetic stabilities in a complex mixture of metastable su-pramolecular polymers. Our azobenzene-incorporated monomer at ambient temperature kinetically forms complex mixtures of supramolecular polymers with cyclized and open-ended randomly coiled topologies, while upon heating we obtained thermodynamically stable crystalline fibers. Through the direct visualization of the complex supramolecular polymer mixtures by atomic force microscopy, we demonstrate that the cyclized supramolecular polymer has superior kinetic stability compared to the open-ended species toward the thermal transformation into crystalline fibers. Since the superior kinetic stability of the cyclized species can be attributed to the absence of aggregate termini, we could convert them fully into the thermodynamic species through photo-induced opening of the cyclized structures.
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