## 2 Electrolytic Polymerization  
### Rubber  
Rubber is divided into diene and non-diene rubbers or natural and synthetic rubbers and categorized as shown in Figure 11 (Appendix A). For diene rubber, the latex in a liquid state as in NR, CR, isoprene rubber (IR), and butadiene rubber (BR) can be solidified by electrolytic polymerization. This can be achieved because diene rubber contains C=C bonds and water, which has been elucidated in the previous research [9; 10; 11; 12]. These latexs are electrolytes that contain enough water to be provided by electrolysis. Nitrile rubber (NBR) and SBR, however, cannot be provided with electrolytic polymerization and cannot be solidified because they have potentially high viscosity. In contrast, non-diene rubber contains C-C bonds such that electrolytic polymerization cannot be utilized. However, by utilizing PVA and mixing water-soluble diene-rubber such as NR-latex or CR-latex, the silicone oil in a liquid state (Q) can be solidified by electrolytic polymerization. Basically, Q is structured as the basis of dimethylpolysiloxane (PDMS) and PVA is an emulsifier, allowing PDMS and PVA to be combined by emulsion polymerization. The anionized hydroxy group of PVA and NR-latex or CR-latex are bonded by hydrogen bonding. This mechanism has been elucidated in previous research [15]. However, when the water-soluble diene-rubber rubber is not mixed with water-insoluble non-diene rubber, electrolytic polymerization might become possible, provided the non-diene rubber contains a fair portion of C=C bonds in its molecular structure and liquid state. As another way of validating electrolytic polymerization using PVA and mixing NR-latex or CR-latex except for Q, the electrolytic polymerization of urethane rubber (U) is demonstrated in this study. The U used in this study was polyurethane (C7 with hardness measured by C-type durometer, hardness meter (Kobunshi Keiki, Co., Ltd., Kyoto, Japan), Exseal Co. Ltd., Gifu, Japan). It was emulsified by PVA, with either NR-latex, CR-latex, or their composite latexs bonded with the anionized hydroxy group of the PVA by hydrogen bonding. The MCF rubber liquid consisted of 3 g Ni powder with particles in the order of microns and bumps on the surface (No. 123 by Yamaishi Co. Ltd., Noda, Japan), 3 g PVA, 0.75 g water-based MF with 40 wt% Fe\({}_{3}\)O\({}_{4}\) (W-40, Ichinen-Chemicals Co., Ltd., Shibaura, Japan), 3 g CR-latex (671A, Showa Denko Co. Ltd., Tokyo, Japan), 0.5 g TiO\({}_{2}\) (Anatase type,Fujifilm Wako Pure Chemical Co., Ltd., Osaka, Japan), 3 g NR-latex (without sulfur, Ulacol, Rejitex Co. Ltd., Atsugi, Japan), or S-500 (NR-latex with sulfur, Rejitex Co. Ltd., Atsugi, Japan). U and PVA must be mixed in an advance combination as in Q [15] because if U is combined with a single NR-latex or CR-latex, or their mixture, they are solidified during stirring. They must also be stirred under cooling conditions with ice water. Subsequently, the MCF rubber liquid was electrolytically polymerized, where a static magnetic field of 312 mT was applied to a pair of stainless electrodes with a 1 mm gap using permanent magnets as paired opposites via the application of a constant electric field at 20 V and 2.7 A, for 5 min. Incidentally, as provided throughout the experiment of this study, the magnetic field strength and electric current can be determined by optimum magnitude, as has been presented in the previous studies [15]. It can be measured with the Gauss meter probe, which is a traditional instrument for magnetic field measurement. Based on many experiments, 312 mT was confirmed to be the optimal magnetic field strength in the production method proposed in this study. With a gap of 1 mm between electrodes, permanent magnets were paired opposites via a constant electric field at 2.7 A with a voltage range of 6-30 V, for 5-30 min. Therefore, 312 mT and 2.7 A were used during this study. Figure 1 shows images of liquid MCF rubber before electrolytic polymerization and electrolytically polymerized MCF rubber.