Stimuli-responsive hydrogels have been actively researched, and some of them have been put into practical use. When we create and use stimuli-responsive hydrogel materials, controlling stimuli responsiveness of hydrogels is a very important issue. In this research, we prepared hydrogels having single-network (SN) or double-network (DN) gel structures with the host-guest interaction groups cyclodextrin and methyl viologen and evaluated their stimuli responsiveness. The results of the tensile and compression tests showed that the hydrogels with SN and DN structures exhibited opposite stimuli responsiveness in response to the redox reaction of methyl viologen through the association and dissociation of the host molecule, β-cyclodextrin, and the guest molecule, methyl viologen. Spectroscopic measurements and rheological studies all indicated that this difference in stimuli responsiveness originated from the polymer-network structures. In addition, a chemically cross-linked DN gel was prepared and its redox responsiveness was evaluated.

All other chemicals were purchased from KANTO Chemical Co., Inc. and used as received. All solvents utilized in this research were reagent grade (99.9 %). Aqueous dispersion of Micromica (MEB-3, diameter is 2.0-3.0 µm) was provided from Katakura & Co-op Agri Corporation. Laponite (Laponite-RD) was provided from ALTANA Corporation.1 H NMR spectra were recorded on a Varian model 400-MR spectrometer. 13 C NMR spectra were recorded on a Varian model NMR System 700 spectrometer. ESI-Ms spectra were collected on a mass spectrometer (Water/Micromass, ZQ-4000). 90 degree peeling test and shear adhesive strength were carried out using Imada MX2-500N-FA equipped with Imada, ZTA-50N. The rate of extending samples was 10 mm/sec. Attenuated total reflection infrared (ATR-IR) spectroscopy was conducted by using Shimadzu FTIR-8400S. Rheology data was measured by using Anton-Paar, MCR-301 with a 25 mm diameter parallel plate attached to a transducer.The gap was set at 1.0 mm. Thermogravimetric analysis (TGA) was conducted by using Shimadzu Manufacturing Co., Ltd. TGA-50. X-ray diffraction (XRD) patterns were obtained using Bruker, D2 Phaser. High concentration hydrogels shown in Figure 5 in the manuscript and in Figure S5 were prepared by evaporating water of the hydrogel prepared in session 3-1 in the air.