Fate of Host-Stabilized Charge Transfer Complexation Based on Cucurbit[8]uril: Inducing Cyclization of PNIPAM and Dissociation in Self-Assembly of the Cyclic Polymer.

Host-stabilized charge transfer (HSCT) complex based on cucurbit[8]uril has been widely used in building novel supramolecular structures, which could further self-assemble into nano-objects. High stability of the HSCT interaction during the assembly process is always assumed or defaulted. However, the stability during self-assembly has never been well characterized in previous studies. In this work, we realized cyclization of linear PNIPAM by CB[8]-based HSCT interaction first. And then we found unexpectedly that during the heating-induced self-assembly of the cyclic PNIPAM, dissociation of the HSCT interaction took place. In this process, charged CB[8] complex was released from the aggregates of the cyclic polymer to solution, and it could be recaptured by newly added guest molecules. This HSCT dissociation was driven by the incompatibility of the hydrophobicity of the PNIPAM aggregates and the cationic nature of the HSCT complex. To the best of our knowledge, this assembly induced dissociation phenomenon has not been reported in literature.