Macroassembly And Environment Responsiveness Based On Cucurbiturils Gel

Cucurbit[n]urils(CB[n], n=5-8) with its unique structure of center hydrophobic cavity and two identical cavity portals lined by the carbonyl groups of the glycoluril units, can selectively interact with guest molecules to form the molecule assembly. In this paper, Macro assembly gels with special pH and redox responsiveness was prepared due to the principle of cucurbit[n]urils molecular assembly. The reversibility of gels assembly could be controlled by change of the environment(pH, oxidizing and reducing).Cucurbit[7]uril/polyacrylamide hydrogel(CB[7]/PAAm gel) was prepared by CB[7] acted as crosslinking agent rather than conventional crosslinking agent(N, N-methylene double acrylamide) of polyacrylamide hydrogel. Structure of CB[7]/PAAm gel was characterized by FT-IR and 1H NMR. Self-assembly and pH responsiveness and mechanical properties of CB[7]/PAAm gel were researched. The results showed that: CB[7]/PAAm gel self-assembled in 5 days at room temperature, but the assmebly just needed 2 h at 70℃ environment. On one hand, CB[7]/PAAm gel transformed into sol in strong alkaline environment, on the other hand, CB[7]/PAAm sol transformed into gel in acidic environment. The CB[7]/PAAm gel, prepared in pH=0 environment, had a better tensile capacity than the one prepared in pH=7 environment.(Allyloxy)1CB[7] and 2-acryloyloxyethyl ferrocene carboxylate were synthesized.(allyloxy)1CB[7]/PAAm gel((C3H5O)1CB[7]/PAAm gel) and(2-acryloyloxyethyl ferrocene carboxylate)/PAAm gel(Fc/PAAm gel) were prepared. Structure of(allyloxy)1CB[7]/PAAm gel and Fc/PAAm gel was characterized by 1H NMR. Macroassembly and redox responsiveness of(C3H5O)1CB[7]/PAAm gel and Fc/PAAm gel were researched. The results showed that: two gels macroscopic assembled when the dosage of acrylamide was 1.30 g, N, N-methylene double acrylamide 0.06 g, azodiisobutyronitrile 0.02 g, and dimethyl sulfoxide 10 m L. But macroscopic assembly was not found when(C3H5O)1CB[7]/PAAm gel and PAAm gel were put together. Binding of the(C3H5O)1CB[7]/PAAm gel to Fc/PAAm gel in the reductive glutathione dimethyl sulfoxide solution and dissociation of the combined gels in oxidant NaClO solution were found to be reversible and reproducible.(C3H5O)1CB[7]/PAAm gel and Fc/PAAm gel are a new type macroscopic assembly materials with redox responsiveness.