A short procedure for the synthesis of 2,2-di(3-thienyl)-1,3-dioxolan is described. The route developed is convenient (only two synthetic and one chromatographic steps are required) and efficient (66% overall yield from 3-bromothiophene). This compound was transformed into the ketone, cyclopenta [2,1-b:3',4'-b']dithiophen-4-one by a known process. Optimized syntheses of symmetric aryl ketones, 1-alkyl-3-methylimidazolium and 1-alkyl-2-methyl-3-methylimidazolium liquid salts are also reported.Electrochemical capacitors are energy conversion devices which consist of two active electrode materials that are in contact with an appropriate electrolyte. 1 First, electronically conducting polymers such as polythiophene derivatives, have recently received some attention as electrode materials due to their potentially high power densities which originate from fast redox switching (e.g. fast ionic transport). 2 Second, conventional liquid solvent-salt and polymer-salt were used as electrolyte (to insure ionic conduction between the two polymer electrodes) in these capacitors. 2 Thiophene derivatives are among the most widely investigated model compounds for electrically conducting material since they give rise to polymers which may be both p-and n-type doped. 2-7 Within this family of polymers, poly(cyclopenta[2,1-b:3',4'-b']dithiophen-4-one, (CDT) 5, introduced by Lambert and Ferraris, 8 stands out for its electrochemical properties, high stability in the conducting state and propensity to multiple redox cycling, making it a stable p-and n-dopable conductor suitable for application as supercapacitors composites as we have recently shown. 9 Roncali et al. have also reported that the polymer obtained from the 1,3-dioxolane derivative of the title compound 5 displayed similar electrochemical properties. 10 Since, many of the precursors of small band gap conducting polymers are substituted-4-methylidene derivatives of 5, 4,9-16 ketone 5 is an important intermediate in the synthesis of a variety of low band gap conducting polymers. 17On the other hand, room-temperature ionic liquids have also attracted interest as solvents for synthesis and catalysis applications, which have recently been reviewed. 18 These liquid salts can replace classic organic solvents which may be volatile and/or hazardous. Much of the progress realized to date render these room-temperature molten salts more stable, chemically and thermally. These liquids are entirely composed of ions and in this state, they resemble the ionic melts which are generally produced by heating normal metallic salts such as sodium chloride to high temperature (e.g. NaCl to over 800°C). Some other useful features of these ionic liquid systems include the greater solubilities of organic species, the prevalence of high coulombic forces resulting in the absence of any significant vapor pressure and the availability of air and moisture stable, water immiscible ionic liquids (e.g. imidazolium salts of PF 6 -or BF 4 -). Such systems are able media for the development of completely nove...

The electrochemical oxidation of 3-(4-fluorophenyl) thiophene (FPT) at a platinum electrode in pure 1-ethyl-2,3-dimethylimidazolium bis ((trifluoromethyl)sulfonyl) amide, EDMITFSI, and 1,3-diethyl-5-methylimidazolium bis ((trifluoromethyl)sulfonyl) amide, DEMITFSI, yielded an electroactive polymer. This polymer (PFPT) was similar to that prepared from common nonaqueous media such as tetraethylammonium tetrafluoroborate/acetonitrile, but it was characterized by slower ion insertion kinetics. A rapid loss of electroactivity of the polymer was observed upon cycling in pure ionic liquid, and that was attributed to gradual deswelling of the polymer. X-ray photoelectron spectroscopy measurements demonstrated that the doping processes of PFPT when cycled in pure ionic liquid were similar to those occurring in acetonitrile-based electrolyte and involved the incorporation of the anions (TFSI-) of the ionic liquid when the polymer was oxidized to the p-doped state. The expulsion of these anions and the incorporation of the ionic liquid cationic species were observed upon reduction of the polymer to the fully n-doped state.

A new class of low band gap thiophene polymers prepared from (E)-R-cyanoethylene thiophene derivatives were electrochemically and physically evaluated as active electrode material for electrochemical supercapacitors. The corresponding polymers were prepared by electrochemical polymerization of these monomers from a nonaqueous solution (acetonitrile) containing tetraethylammonium tetrafluoroborate. The electrochemical properties and the stability under cyclic voltammetry of the polymers were found to be strongly dependent on their electronic configuration, especially in the case where the monomer has two different aromatic heterocycles. The range of stable electroactivity of the polymers in organic media spans about 2 V. Since poor stability was observed by cyclic voltammetry for poly- and poly-(E)-R-[(2-furanyl)methylene]-2-thiopheneacetonitrile were evaluated as electrode materials for an electrochemical supercapacitor. Stability tests upon potential cycling between the n-and p-doped states and a potential range of about 2 V have shown a 60% decrease of the voltammetric charge for poly-(E)-R-[(2-thienyl)methylene]-2-thiopheneacetonitrile following 2000 cycles. Preliminary galvanostatic charge-discharge cycling experiments for the best system indicated an energy density of 8.6 W h/kg while it delivered a power density of 1.6 kW/kg for a discharge time of 20 s.

Polymers derived from diheteroaryl-(cyanovinylene), synthesized by chemical polymerization of the monomers in the presence of 6 equivalents of FeCl3 in chloroform, were characterized by elemental analysis, energy-dispersive analysis by X-ray, and X-ray photoelectron spectroscopy. The electrochemical performances of composite electrodes prepared from chlorinated poly-(E)-α-[(2-thienyl)methylene]-2-thiopheneacetonitrile (poly-1), poly-(E)-α-[(3-methyl-2-thienyl)methylene]-2-thiopheneacetonitrile (poly-2), and poly-(E)-α-[(2-furanyl)methylene]-2-thiopheneacetonitrile (poly-3), with acetylene black (A.B., 45 wt %) and polytetrafluoroethylene (5 wt %) have been investigated in 1 M Et4NBF4 /acetonitrile using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge cycling. The effect of the structure of the polymers on their electrochemical properties is in good agreement with anticipated effects for methyl and furan groups. The results indicated p- and n-doping levels up to 0.3 electrons per heterocycle for the three polymers. These values make those polymers interesting candidates for use in electrochemical supercapacitors in which specific capacity and energy of about 30 Ah/kg and 55 Wh/kg of polymer may be achieved. The best cyclability was demonstrated with poly-1 and poly-2, in particular during cycling in their n-doping state with a doping level of 0.16 and 0.17 electrons per thiophene unit, respectively, maintained after 1000 cycles. Preliminary charge/discharge galvanostatic cycling with a poly-1-based supercapacitor yielded specific energy and power of 42 Wh/kg and 11 kW/kg of polymer, respectively, during the first 60 cycles and 30 Wh/kg and 9 kW/kg after 1800 cycles, for a discharge time of about 10 s. Moreover, cycling experiments performed separately on negative and positive electrodes have shown that the capacity loss is associated essentially with the n-doping process at the negative electrode. © 2001 The Electrochemical Society. All rights reserved.