pH-Induced cucurbituril hydrogels: Understanding microenvironment of the aggregates through excited state reactivity of dibenzyl ketones
•Unprecedented understanding about molecular mobility and reactivity within CB7 hydrogels based on photochemical and NMR diffusion experiments.•Qualitative measure of structural rigidity of CB7 aggregates.•Effect of acidity, temperature, and concentration on hydrogel stability studied.•Studies suggest high tunability of physical and mechanical properties.•Indication of possible aggregation of CB7 to form super cages.
The supramolecular chemistry of cucurbituril aggregates arising from peripheral interactions to form hydrogels is a relatively new and less explored aspect of the cavitand family. The hydrogels formed by cucurbituril (CB7) in aqueous media is understood to consist of CB7 networks linked through CH⋯O interactions with readily manipulable material and mechanical properties, and is envisioned to contain high application potential. Therefore, understanding the microenvironmental properties of this newly emerging CB-based hydrogels is important. In this reported study we present our understanding about the microenvironmental characteristics of the CB7 hydrogels inferred from (a) the modified photoreactivity of non-C2-symmetric dibenzyl ketones (DBK) encapsulated within the hydrogels, and (b) NMR diffusion experiments. Reaction selectivity in DBK photochemistry offered insight regarding the structural integrity and effects of pH, temperature, and concentration on the aggregates, while the diffusion studies were useful in developing a qualitative idea about the equilibrium dynamics of the CB7 aggregates that constitute the hydrogels.
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Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 324, 30 June 2016, Pages 53–61