## 3 Mechanisms and Process of Electrolytically Polymerized MCF Rubber  
In this section, we first describe the electrolytic polymerization model of MCF rubber, because all the following investigations are based on this model. Figure 8 shows the physical model of the solidification of MCF rubber by electrolytic polymerization proposed in our previous study [22]. Using this model can help to clarify the mechanisms behind the MCF rubber enhancement, long-term stability and high sensitivity. With the application of the magnetic field, the magnetic clusters align along the lines of the magnetic field, which runs in a transverse direction to the two electrodes, as indicated by E in the figure. The C=C are arrayed in the same direction as the magnetic clusters. As a result, solidification of the MCF rubber is guessed to expand in the direction of the applied magnetic field. When a magnetic field is not applied, the C=C bonds simply undergo solidification, and the direction of the polymerization is random. As a result, the thickness of the solidified MCF rubber and the solidification effect are very small. At the cathode, the surface of the MCF rubber becomes rugged, as shown in [22], due to the tip of the growing magnetic clusters. Cationic polymerization occurs at the anode, and anionic polymerization at the cathode (A and F in Figure 8). With the application of electricity, each polyisoprene of a particle in the NR-latex is guessed to be mutually polymerized to bind between the ends of C=C bonds in a coordinated way, and many C=C bonds be formed in a long chain, as indicated by B in Figure 8. At the same time, the C=C bonds are vulcanized by radical polymerization, as shown by G in Figure 8. If the NR-latex includes sulfur S, the C=C bonds are vulcanized by radical polymerization, as shown by C in Figure 8. In addition, from the results of the last Section 2, where we showed that enhancement of the solidified needle-shaped MCF rubber depends on the MF in the MCF rubber liquid, it can be guessed that radical polymerization occurred as a result of the carboxyl group COOH of the oleic acid coating Fe\({}_{3}\)O\({}_{4}\), bonding C=C, and Fe\({}_{3}\)O\({}_{4}\), as shown by D in Figure 8.  
As shown in our previous study [22], the magnetic clusters that align along the magnetic field form needle-like structures. Figure 9a is an SEM image of part of a magnified magnetic cluster involved in the electrolytically polymerized solid MCF rubber of the image shown in our previous study [22]. The MCF rubber liquid consisted of 12-g Ni, 3-g MF (M-300) and 12-g NR-latex. MCF rubber was  
Figure 8: Physical model of electrolytic polymerization of the MCF rubber by the NM [22]. Note that G in the figure was added in the present study. electrolytically polymerized by a 30-min application of 6 V and 2.7 A, a 1-mm space between electrodes, and Magnet 2. The molecules of the NR-late coiled around the magnetic clusters. Figure 9b shows the mapping by X-ray diffraction (XRD) of Figure 9a. The electrolytic polymerized MCF rubber presents a complicated configuration of intertwined NR-latex, Fe\({}_{3}\)O\({}_{4}\) and Ni, indicating that these ingredients of NR-latex do not exist independently. Figure 10a,b present SEM and XRD images of the anode side surface, corresponding to A in Figure 8, and Figure 10c,d are those of the cathode side, corresponding to F in Figure 8. The MCF rubber sample is that shown in Figure 9. Figure 10b shows that on the anode-side surface, the quantity of Ni and Fe\({}_{3}\)O\({}_{4}\) particles involved in the NR-latex is larger than that of C. In contrast, Figure 10d shows that on the cathode-side surface, the quantity of C is larger than that of Ni and Fe\({}_{3}\)O\({}_{4}\) particles. The electrolytic polymerization of NR-latex is thus thought to be different at the anode and cathode sides of the MCF rubber. This is the typical distinction.