*2.2.2. Measurements of the equilibrium swelling ratio of poly(VP-co-Ru(bpy)3) gels*

The equilibrium swelling ratio of the gels was measured under the reduced and the oxidized state, by using the oxidizing and the reducing agents. Gels were put into two solutions of Ce(III) and Ce(IV) under the same acidity, [Ce2(SO4)3]=0.001M and [HNO3]=0.3M; [Ce3(SO4)2]=0.001M and [HNO3]=0.3M, respectively. The equilibrium swelling ratio of the gels was observed and recorded by using a microscope (Fortissimo Corp.WAT-

250D), a LED light (LEDR-74/40 W), and a video recorder (Victor corp. SR-DVM700). The analysis was conducted by using the image processing software (Image J 1.38x). Measurements of the equilibrium swelling ratio were performed in a water-jacketed cell made of acrylic plates.

**Figure 2.** Chemical structure of poly(VP-co-Ru(bpy)3) gel.

314 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

*Ru(bpy)3) solution* 

°C/min.

spectrophotometer.

day each in 75, 50, 25 and 0%.

*2.2.1. Synthesis of the poly(VP-co-Ru(bpy)3) gel* 

*2.1.2. Measurement of Lower Critical Solution Temperature (LCST) for the Poly(VP-co-*

*2.1.3. Measurement of optical oscillations for the poly(VP-co-Ru(bpy)3) solution* 

The poly(VP-*co*-Ru(bpy)3) solutions were prepared by dissolving the polymer (0.5 wt%) into an aqueous solution containing the three BZ substrates (malonic acid (MA) and sodium bromate (NaBrO3), nitric acid (HNO3)). The transmittance self-oscillations of the polymer solutions were measured under constant temperature and stirring. In order to detect the transmittance change which is based on the autonomous transmittance change, 570-nm wavelength was used. The time course of the transmittance at 570 nm was monitored by a

The gel was prepared as follows. 0.110g of Ru(bpy)3 as a metal catalyst for the BZ reaction was dissolved in 0.877g of vinylpyrrolidone (VP). 0.012g of N,N'-methylenebisacrylamide (MBAAm) as a cross-linker, and 0.020g of 2,2'-azobis(isobutyronitrile) (AIBN) as an initiator were dissolved in the methanol solution (3ml) (Figure 1). The two solutions were mixed together well, and then the mixed solution purged with dry nitrogen gas. The monomer solution was injected between Teflon plates separated by silicone rubber as a spacer (thickness: 0.5mm), and then polymerized at 60°C for 18 hours. After gelation, the gel strip was soaked in pure methanol for a week to remove unreacted monomers. The gel was carefully hydrated through dipping it in a graded series of methanol-water mixtures, for 1

*2.2.2. Measurements of the equilibrium swelling ratio of poly(VP-co-Ru(bpy)3) gels* 

The equilibrium swelling ratio of the gels was measured under the reduced and the oxidized state, by using the oxidizing and the reducing agents. Gels were put into two solutions of Ce(III) and Ce(IV) under the same acidity, [Ce2(SO4)3]=0.001M and [HNO3]=0.3M; [Ce3(SO4)2]=0.001M and [HNO3]=0.3M, respectively. The equilibrium swelling ratio of the gels was observed and recorded by using a microscope (Fortissimo Corp.WAT-

The lower critical solution temperature (LCST) of the polymer solution was measured under the reduced and oxidized states, by using Ce(SO4)2 as an oxidizing agent and Ce2(SO4)3 as a reducing agent, respectively. The polymer solutions (0.5 wt%) of poly(VP-*co*-Ru(bpy)3) were prepared by dissolving the polymer in a 0.3 M HNO3 aqueous solution and adding 5 mM Ce(SO4)2 or 5 mM Ce2(SO4)3, respectively. The LCST measurements were carried out with a spectrophotometer (JASCO, Model V-630) equipped with magnetic stirrers and a thermostatic controller. In this measurement, the 570 nm wavelength was used because it is the isosbestic point for the reduced and oxidized states of Ru(bpy)3. The transmittance (%) of the polymer solution at 570 nm was then recorded by raising the temperature at a rate of 0.5
