Conductive Electroactive Polymers solvent

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. 

In the quest for such membranes conducting electroactive polymers provide several unique capabilities. Conducting polymer membranes such as polypyrroles (1, 2) or polyanilines (3) can be prepared by electropolymerisation and deposition of the monomer or by solvent casting of the polymer. 

Shi et al. have developed another method for the electrochemical polymerization of high oxidation potential monomers in boron fluoride ethyl ether (BFEE) which could yield highly conducting PT films (Scheme 9.4) [32]. As observed in the case of the electropolymerization of 3-methylthiophene, bithiophene 2T and terthiophene 3T, such improvement stems from the lower oxidation potentials at which the electropolymerization occurs in BFEE compared with those required in common electrolytes. Recent development of this strategy by the Reynolds group has shown that thiophene, 3-methylthiophene, 3-bromothiophene and 3,4-dibromothiophene can be polymerized in BFEE to yield homogeneous, electroactive polymer films, where their electrochemical polymerization in common electrochemical solvents has proved much more difficult [33],... 

On the other hand, the electrodes attaching electroactive polymer films and polymer CMEs having ionic, electronically conductive, or redox property have been widely studied. Electronically conducting polymers, which are usually more conductive than redox polymers, can be doped to increase their intrinsic conductivity. Such films are now popular because they are technically easier to modify by applying polymer onto an electrode compared to covalent monolayer formation. Polymer films generally adhere satisfactorily to electrodes simply by forces of chemisorption or by being insoluble in the contacting solvent. 

Yoshino et al. [320] reported the successful electropolymerization of selenophene in 1983. Selenophene has been electropolymerized in a small number of solvent/electrolyte systems, with the best results being achieved using benzonitrile/LiBF4 [321]. For selenophene the conditions for deposition are even worse than for thiophene since oxidation is more difficult and overoxidation dominates. Electroactive polymer chains are short (pd = approximately 10) and conductivity is low (approximately 10 S cm ) [322]. 

Nemat-Nasser S, Wu Y (2003) Comparative experimental study of ionic polymer-metal composites with different backbone ionomeis and in various cation forms. J Appl Phys 93 5255-5267 Nemat-Nasser S, Zamani S (2006) Modeling of electrochemomechanical response of ionic polymer-metal composites with various solvents. J Appl Phys 100 064310 Oguro K, Kawami Y, Takenaka H (1992) Bending of an ion-conducting polymer film-electrode composite by an electric stimulus at low voltage. J Micromach Soc 5 27-30 Palmre V, Lust E, Janes A et al (2011) Electroactive polymer actuators with carbon aerogel electrodes. J Mater Chem 21 2577-2583... 

Technically important electrochemical reactions of pyrrole and thiophene involve oxidation in non-nucleophilic solvents when the radical-cation intermediates react with the neutral molecule causing polymer growth [169, 191], Under controlled conditions polymer films can be grown on the anode surface from acetonitrile. Tliese films exhibit redox properties and in the oxidised, or cation doped state, are electrically conducting. They can form the positive pole of a rechargeable battery system. Pyrroles with N-substituents are also polymerizable to form coherent films [192], Films have been constructed to support electroactive transition metal centres adjacent to the electrode surface fomiing a modified electrode,... 

In most polymer films, the electroactivity of the redox centers depends on the ionic conductivity of the film. This is usually achieved either by the penetration of supporting electrolyte ions through pores in the film or by the presence in the film of numerous fixed charge sites plus mobile counterions. In many cases, solvent permeation into the polymer facilitates ionic penetration and mobility. If the polymer film possesses electronic, rather than ionic, conductivity, the electron-transfer reactions will most likely occur at the polymer/solution interface and the advantage of a three-dimensional reaction zone will be reduced. 

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