Fig. 5. The proposed mechanism of the association/dissociation behaviours in the γCD–VC11(x,y) hydrogels leading to large volume changes. Green line: the pAAm main chain in the polymer network. Green ring: γCD unit. Yellow unit: the oxidized viologen moiety in VC11. Purple unit: the reduced viologen moiety in VC11. Grey line: the undecyl linker in VC11. The reduced monocation radical viologen unit (purple) can form a stacked dimer structure via cation–π electrostatic interactions. The viologen dimer is able to be included by another γCD unit to make a new cross-linking point. These two types of host–guest interactions result in the formation of supramolecular cross-linking, which contributes to the large deformation of the γCD–VC11(2,2) hydrogel. The xmonomer, xdimer, xCD-dimer values in Table S7† indicate the number of inclusion complexes in the supramolecular cross-linking, where 5.7 viologen dimers are formed in the single supramolecular cross-linking. 10.3 inclusion complexes of γCD with the undecyl units or with the viologen dimers are connected to form a supramolecular cascade structure.
