A dynamic self-regulation actuator combined double network gel with gradient structure driven by chemical oscillating reaction

Self-regulation of the dynamic actuation of a chemical oscillating reaction-based gel was realized by altering the network structure of the gradient double network gel. We demonstrated that the propagation mode of the chemical wave was influenced by the network structure, and consequently determined the dynamic feature of the gel actuator.


Figure S1
Synthesis route of Ru(vmpy)(bpy) 2 (PF 6 ) 2 Synthesis of 1: 7.8 g RuCl 3 ·3H 2 O, 9.36 g 2,2'-bipyridine and 8.4 g LiCl were added to 50 mL DMF, then the mixture was refluxed for 9 h. 250 mL acetone was poured into the mixture and kept overnight. After filtration, the solid was gently washed by deionized water until the filtrate turned to green then washed by ether for three times. Vacuum drying gave a white solid (6.62 g, yield: 53 %).
Synthesis of 2: 25.6 mL N-butyllithium and 8.0 mL diisopropylamine were added to 30 mL THF in a three-neck flask, the solution was thoroughly stirred. 10 g 4,4'-dimethyl-2,2'-dipyridyl in 250 mL THF was slowly added to the three-neck flask from a dropping funnel, and the color turned to brown. 2 h later, 1.7 g paraformaldehyde was added in, the reaction continued for over 24 h, the mixture gradually turned to green and opaque. The mixture was quenched with ice water and extracted with ether, then evaporated. The crude product was purified via column chromatography

Preparation of the vinylated micro-gel crosslinker
The vinylated micro-gel was prepared via a two-step method, and the preparation process is as follow: Synthesis of VMG 2: 0.8 g GMA was added to 50 mL VMG 1 dispersion, the mixture was heated to 50 ℃ and kept for 8 h with mechanical stirring (350 r.p.m). After that, the VMG 2 dispersion was dialyzed against ethanol for 1 week to remove unreacted GMA. Stretching vibration of carbon-carbon double bond was found at 1690 cm -1 . The surface area mean particle size of the VMG 2 was 5.205 μm, and volume average particle size was 6.255 μm. Figure S4 ATR-FTIR spectrum and particle size analysis report of vinylated micro-gel Solvent exchange of the VMG 2 dispersion: The VMG 2 dispersion was then dialyzed against methanol for 4 days with changing methanol twice a day.

Storage:
The obtained VMG 2/water and VMG 2/methanol dispersion was stored at 4 ℃ for subsequent use.
Then 20 μL TEMED was added to the mixture as polymerization accelerator. The mixture was immediately injected into a self-made mold (two pieces of 10 cm ×10 cm hydrophilic glass separated by a piece of 1 mm thick silicon rubber with a square hole), and the polymerization was carried out at 0 ℃ for 6 h. The obtained gel was freeze-dried for subsequent use. Video S1 shows the continuous and cyclic bending-stretching actuation of MG 1 within 2500 s. Playback speed is 125×.
Video S2 shows the continuous and cyclic bending-stretching actuation of MG 2 within 2500 s. Playback speed is 125×.
Video S3 shows the continuous and cyclic bending-stretching actuation of MG 3 within 2500 s. Playback speed is 125×.