Off–On Pathway Complexity in Self-Assembly of Cadmium Cholate Hydrogel with Topological Evolution Triggered by Secondary Nucleation

Tuning supramolecular hierarchical structures based on a meticulous mechanistic understanding has been a less-explored area of supramolecular chemistry. We have serendipitously discovered that the hydrogelation of cadmium cholate involves an unusual process involving the transformation of an initially formed turbid suspension to an opaque gel via a transparent gel. Microscopic investigation revealed an evolution of diverse nanostructures as a function of time, suggesting a pathway complexity involved during the self-assembly process. The initial transformation from a suspension to a transparent gel occurs via an off-pathway mechanism. The subsequent change from a transparent to an opaque gel, interestingly, follows an on-pathway aggregation process. This shift from off- to on-pathway mechanisms directly influenced the crystallinity and mechanical stiffness of the hydrogel. A thorough analysis of the underlying pathway complexity has led us to an unprecedented facet of synthetic supramolecular self-assembly.