The templated growth of polyaniline through porous sol-gel films on ITO substrates has been performed. The polyaniline-silica composites have been synthesized by electrochemical reactive insertion in potentiodynamic and potentiostatic conditions. When the polymer is synthesized by potential step experiments, the shape of the chronoamperograms indicates two regimes for the electrochemical polymerization of PANI. Electropolymerization happens faster within the silica pores than on bare ITO electrodes due to confinement effects of oligomeric species formed upon oxidation. The electrochemical capacitance of the silica-PANI hybrids is several time higher than the capacitance of ITO/PANI synthesized under the same conditions. The silica matrix avoids the electric collapse between vicinal conducting fibres in ITO/silica-PANI but allows the diffusion of ionic species that are in contact with the conjugated polymer, increasing therefore the conducting surface exposed to the electrolytic solution.

The electrochemical oxidation of the aniline dimers 2-aminodiphenylamine ͑2-adpa͒ and 4-aminodiphenylamine ͑4-adpa͒ has been performed in strongly acidic medium on platinum, graphite, and indium tin oxide electrodes. The resulting films have been characterized by a number of electrochemical, microscopic, and spectroscopic techniques in order to gain some insight on their respective chemical structures. Both poly͑2-adpa͒ and poly͑4-adpa͒ are electroactive species which differ significantly one from another. It was found that aged poly͑4-adpa͒ displayed electrochemical, morphologic and spectroscopic characteristics similar to those shown by polyaniline. On the contrary, poly͑2-adpa͒ is really a mixture of three oligomerization products. The two main oligomers contain both open-ring and cycled phenazine centers, although their chemical structures seem to differ in the cap-end of the chain growth. The third oligomer is a minor product which seems a highly symmetric macrocycle involving several 2-adpa molecules.

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SummaryModified electrodes with poly(2,2'-dithiodianiline),PDTDA, were prepared from the corresponding monomer by cyclic voltammetry between 0.0 V and 1.5-1.6 V on gold or stainless steel respectively. The potentiodynamic method proved to bring about good quality and adherent thin films. The wide potential window shown by this modified electrode allowed attempting the insertion of copper in the polymeric matrix using several strategies. The response of this modified electrode copper was checked in the presence of γ-aminobutyric acid (GABA). Copper loaded on PDTDA/Au electrodes showed the highest sensitivity along with a stable and reproducible response for the detection of GABA. The surface morphology and composition analysis by SEM and XPS shows that copper is deposited in the polymeric matrix as uniformly scattered microparticles. The surface of these particles is mainly composed of Cu(I) species.

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The redox process undergone by the electrochemically synthesized poly͑2,2Ј-dithiodianiline͒, poly͑DTDA͒, has been examined in acetonitrile-water mixtures by electrochemical and spectroscopic techniques. The spectroscopic properties of this material are equivalent to those exhibited by the chemically synthesized one. The polymeric structure displays a ladder structure, with S-S bonds serving as interconnections between two adjacent polyaniline chains. The kinetic reversibility of the RS-SR 2RS − reaction is very poor for the DTDA monomer species, and this irreversibility is retained in the polymeric material. According to the results presented, the hypothesis that poly͑DTDA͒ could display a high energy density due to the simultaneity of the leucoemeraldine emeraldine and dithiolate disulfide electrochemical transformations does not seem justified. During the past two decades, the family of organic disulfide compounds has been investigated as promising positive electrodes for high-energy density lithium batteries.1-6 However, commercial systems are making use of diverse lithium intercalation materials as actual positive electrodes. 7 The generic nature of organic disulfide compounds jointly with their low cost, low toxicity, high theoretical energy density, and low operating temperature make these materials particularly promising for energy storage devices. In addition, other chemical properties such as their stability, redox behavior, and kinetic reversibility can be modified by the appropriate choice of the organic groups linked to the disulfide moiety RS-SRЈ. Contrary to these expectations, Liu et al. reported the occurrence of a large separation between the anodic and cathodic peak potentials for different organic disulfides.5 From these results it follows that, as a general rule, slow electrode reaction rates should be inherent to these kinds of materials. Later, Naoi et al. 8,9 proposed that the involved redox processes should become more reversible in order to make the application of disulfide compounds to electrodes in energy storage devices feasible. It was then realized that the use of proper electrocatalysts would be essential to improve the performance of the charging-discharging process. For instance, it was claimed that electropolymerized polyaniline was able to enhance the redox process of 2,5-dimercapto-1,3,4-thiadiazole ͑DMcT͒.9 On carbon electrodes the peak separation was found to be as large as 1.5 V. However, it was reduced to just 0.5 V when the electron transfer was done on a polyaniline filmed electrode. The improvement was attributed to the formation of adducts between S atoms in DMcT and N sites in polyaniline.The model of disulfides was further extended by introducing polysulfides as a new group of organic-polymeric energy storage materials. Because polysulfides contain many S atoms in their structure, it was expected that these materials could exhibit higher energy density than single disulfides. 10 Particularly, it was reported that the tetrasulfide compound prepared by reaction of SCl ...