Synthesis polymer-electrolyte complexes

M. Kawahara, J. Morita, M. Rikukawa, K. Sanui, and N. Ogata. Synthesis and proton conductivity of thermally stable polymer electrolyte Poly(benzimidazole) complexes with strong acid molecules. Electrochimica Acta 45, 1395-1398 2000. 

Poly(oxyethylene) combinations with various other comonomers [46], are of interest as solid polymer electrolytes after complex formation with Li(I) (complexation with Na(I), K(I), Mg(II), Ba(II), etc. has also been studied) [1,5,46-48]. The synthesis is carried out by direct interaction of the ligand and metal ions in solution or, if cross-linked poly(oxyethylene) is employed, by immersing the polymer ligand into a solution of the metal salt. Poly(oxypropylene), modified polysiloxanes, cross-linked phosphate esters and ethers [46,49,50], and structurally different ligands such as 2,5-dimercapto-1,3,4-thiadiazol-polyaniline [51] have also been used as polymer ligands, The developments in this field are reviewed in [46], In this review the segmental motion of Li(I) in a poly(oxyethylene) is described as shown in Fig. 5-4. 

Measurement of Ionic Conductivity. The synthesis of solvent-free metal salt complexes of polyethylene oxides prompted detailed electrical measurements with the thought that these materials might prove to be useful electrolytes, in a hydrous environment, for high energy density batteries (13-15). Many fundamental properties of these polymer electrolytes have been examined and a large literature on the subject is available (16-17). We prepared a disk of one of our polyether complexes and measured its conductivity by impedance methods. 

DI NOTO v, ZAGO v, BISCAZZO s, VITTADELLO M (2003a), Hybrid inorganic-organic polymer electrolytes synthesis, FT-Raman studies and conductivity of Zr[(CH2CH20)8,7]p/(LiC104)j network complexes , Electrochim Acta, 48, 541-554. 

Thienyl)ethanol as a starting material will give monomers with an ether linkage in the substituent at the 3-position. Such monomers, once polymerized, have exhibited the ability to complex cations such as Li in a loose crown ether type structure [70]. This in turn leads to enhanced conductivity of the polymer when such cations are part of the supporting electrolyte. An added benefit of electropolymerization of polythiophene originates from the fact that sulfur has a tendency to physisorb to metals such as gold and platinum, which are electrode materials. Hence they may enhance the adsorption of polymer to the electrode and thus improve the physical stability of the system, as well as the extent of polymer/electrode interaction. The synthesis of these type of monomers (e.g., 60) is shown in Scheme 10-28. 

Conductivity within conducting electroactive polymers (CEPs) is a complex issue. A polymer that can exhibit conductivity across a range of some 15 orders of magnitude most likely utilizes different mechanisms under different conditions. In addition to the electronic conductivity exhibited by CEPs, they possess ionic conductivity because of the solvent or electrolyte incorporated during synthesis. The experimental parameters encountered during synthesis (as listed and discussed in Chapter 2) have an effect on the polymer conductivity. In particular, the electrochemical conditions, the solvent, the counterion, and monomers used during synthesis influence the electronic properties of the resulting polymer. 

The synthesis of MEEP involves the reaction of poly(dichlorophosphazene) with the sodium salt of methoxy ethoxy ethanol. The byproduct in this reaction is sodium chloride which has to be separated from the polymer completely, since even traces of the ionic impurities would lead to spurious results. However, unfortunately MEEP is also soluble in water and therefore separation from sodium chloride is rendered extremely difficult. A cumbersome and lengthy dialysis procedure is required to effect the separation and purification of the polymer. Further MEEP is also hydrophilic and residual water in the polymer is an undesirable feature for a solid electrolyte particularly when involved with alkali metal salt complexes. Additionally the dimensional stability of MEEP is poor and has been commented upon above. 

Polypyrrole and many of its derivatives can be synthesized via simple chemical or electrochemical methods [120]. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but less developed. Different synthesis routes produce polypyrrole with different forms chemical oxidations generally produce powders, while electrochemical synthesis leads to films deposited on the working electrode and enzymatic polymerization gives aqueous dispersions [Liu. Y. C, 2002, Tadros. T. H, 2005 and Wallace. G. G, 2003]. As mentioned above the electrochemical polymerization method is utilized extensively for production of electro active/conductive films. The film properties can be easily controlled by simply varying the electrolysis conditions such as electrode potential, current density, solvent, and electrolyte. It also enables control of thickness of the polymers. Electrochemical synthesis of polymers is a complex process and various factors such as the nature and concentration of monomer/electrolyte, cell conditions, the solvent, electrode, applied potential and temperature, pH affects the yield and the quality of the film... 

Apart from metallic salts, simultaneous chemical synthesis and doping of polypyrrole has been achieved by an halogenic electron acceptor, as bromine or iodine, in several solvents [27-31]. Both PPy-l2 and PPy-Br2 complexes have conductivities in the order of 1 to 30 S cm [30]. PPy-Cl2 prepared polymers have conductivities from 10 to 0.5 S cm [27]. The loss of conductivity with respect to PPy-Br2 or PPy-h has been associated with a partial chloration of the pyrrole ring, with some loss of conjugation. Both PPy-l2 and PPy-Br2 complexes show a good stability upon repeated redox cycling in both aqueous and organic electrolytes [31]. 

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