Polymeric electrolytes

If the surface of a metal or carbon electrode is covered with a layer of some functional material, the electrode often shows characteristics that are completely different from those of the bare electrode. Electrodes of this sort are generally called modified electrodes [9] and various types have been developed. Some have a mono-molecular layer that is prepared by chemical bonding (chemical modification). Some have a polymer coat that is prepared either by dipping the bare electrode in a solution of the polymer, by evaporating the solvent (ethanol, acetone, etc.) of the polymer solution placed on the electrode surface, or by electrolytic polymerization of the monomer in solution. The polymers of the polymer-modified electrodes are either conducting polymers, redox polymers, or ion-exchange polymers, and can perform various functions. The applications of modified electrodes are really limit-... 

Electrolytic polymerization or electrolytically initiated polymerization, or shortly electro-initiated polymerization or electropolymerization, generally means initiation by the electron transfer processes which occur at the electrodes of an electrolytic cell containing monomer and electrolyte, in that by controlling the electrolysis current it is possible to control the generation of initiating species. Under appropriate conditions it may proceed by a free radical, anionic or cationic mechanism. In addition to the electrolytic addition polymerization, production of polymers through condensation reaction by electrolytic means should also be covered. Examples of each of these propagation mechanisms have now been reported in the literature. 

At the end of an introductory chapter, let us again make a brief account of the characteristics and potentialities of the electrolytic polymerization process from the point of view of polymer chemistry. 

As described in the previous chapter, in the work on electrolytic polymerization which has appeared in the literature, the active species were formed by an electrode reaction from the compounds added to the reaction system and thus initiated polymerization. However, the possibility has been considered of direct electron transfer from the cathode to monomer or from monomer to the anode forming radical-anion or -cation, followed by initiating polymerization. Polymerization of styrene initiated by an electron has been observed when the monomer was exposed to the electric discharge of a Tesla coil (74), y-radiation (75, 16) and to cathode rays from a generator of the resonant transformer type (77). 

The previous chapters refer to electrolytic formation of one constituent of an essentially chemical initiating system. In this chapter the author would like to call attention to another type of electrolytic polymerization where catalytically active complexes are formed at the cathode and initiate polymerization. 

In some instances of electrolytic polymerization studies, it is conceivable that the polymerization may proceed simultaneously by a free-radical, an anionic, or a cationic mechanism in the same reaction mixture. To discriminate among the various propagation mechanisms, the analysis of copolymer compositions is often used. 

Photochemical initiators are utilized for the production of lithographic plates and for radiation curing coatings and inks but not in the manufacture of plastics. Electrolytic polymerizations find apphcations in the coating of metal sheets by plastics. 

Note added in proof A recent study of dipole moment, electrophoretic behavior, conductance, n.m.r. and absorption spectra, and derivative formation by G. B. Kauffman, J. H. Tsai, R. M. Kallo, R. C. Fay, and C. K. J0rgensen has demonstrated conclusively that while the yellow isomer is indeed cis, the red compound is an electrolytic polymerization isomer, irans-[Ir ((C2H6)2S) 4CI2] fra s-[Ir (C2Ht)2S) 2CI4I. 

A systematic materialization of functional molecules by their incorporation in the conducting polymer matrix was demonstrated by electrolytic polymerization of pyrrole, thiophene, aniline etc., in the presence of negatively charged functional molecules. This method is one of the most smart procedure to incorporate the functional molecule. The incoiporation of the functional molecules is driven electrostatically by the positive charges of the partially oxidized conductive polymer matrices through a doping process. When anionic... 

Hiraishi, K., Masuhara, A., Nakanishi, H., Oikawa, H., Shinohara, Y, 2009. Evaluation of thermoelectric properties of polythiophene films synthesized by electrolytic polymerization. Jpn. J. Appl. Phys. 48, 071501. 

These polymerizations, sometimes also called electrolytic polymerizations, are carried out in an electrical field. The field is applied to initiate chain growth. Passage of an electrical current... 

Fig. 2. Electrolytic polymerization of conducting polymers using a functional molecular anion.

Utilizing an electrocopolymerization technique, various conducting copolymer layered structures were constructed. The copol)mier composition, and the thickness of the polymerized copolymer, are controlled easily in the electrolytic polymerization process (Fig. 7). Fig. 8 is an example of such depth profile-controlled multilayers, consisting of polypyrrole and copoly(pyrrole/3-methylthiophene). The present method will allow nm-level thickness control. 

Yamazaki, T, Y. Murata, K. Komatsu, K. Furukawa, M. Morita, N. Maruyama, T. Yamao, and S. Fujita. 2004. Synthesis and electrolytic polymerization of the ethylenedioxy-substituted terthio-phene-fullerene dyad. Org Lett 6 4865 868. 

Electrolytic polymerizations were described in the section dealing with cationic polymerizations. Anionic polymerizations can also be initiated in an electric field. When LiAlHj or NaAl(C2H5)4 are used as electrol3Tes in tetrahydrofuran solvent living polymers can be formed from a-methylstyrene [190]. The deep red color of carbanions develops first at the cathode compartments of divided cells. 

It also was shown that the SEI formed by GBL solvent on the cathode retarded the exothermic reactions between electrolyte and cathode, which is a ground of high safety performance of the cells. By applying these phenomena, it is possible to reduce the reactivity of the cathode surface with the liquid electrolytes by deactivating their active sites. The addition of a very small amount (0.1-0.2%) of aromatic compounds such as biphenyl (BP), o-terphenyl (oTP), and m-terphenyl (mTP) improved cycleability of the cathode, which originated from the electrolytic polymerization to form a thin and highly LP conductive film covering the cathode surface. 

The author and his research group have established several methods for synthesis of functional molecules incorporating conducting polymers by hybridizations, which are shown in Table 9.1 [4]. In principle, there are three methods of obtaining conducting polymers. They are electrolytic polymerization (electrochemical polymerization), chemical polymerization and photopolymerization (photopolymerization and photosensitized polymerization). Table 9.1 shows examples of how to obtain functional molecules incorporating conducting polymers. 

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