Electrochemical stability of polywtetraethyldisilanylene.oligo2,5-thienylene.x DSmT; m refers to the number of thienylene units. films is investigated by means of in situ UV-vis-NIR spectroscopy, in situ and ex situ fluorescence spectroscopy, gel-permeation chromatography, and FT-IR spectroscopy. It is found that a Si-Si bond in DSmT film with ms3 to 5 is cleaved at potentials as low as 0.5 V versus AgrAgq in acetonitrile, resulting in dissolution of oligothiophene-like species. The decomposed products are oxidized to form another polymer film on the surface of an original DSmT film and a doping reaction observed earlier takes place on the composite polymer film. q1998 Elsevier Science S.A. All rights reserved.

A strain of Thiobacillus Denitrificans (TD) isolated from the soil was selected to reduce the corrosion caused by Sulfate Reducing Bacteria (SRB). The optimal pH was determined as 7.0 for the growth of TD. The growth environment of TD was found to be similar to that of SRB. Thus they can be cultured together. When they were grown together, it was observed that TD reduced the corrosion caused by SRB, being attributed to that TD might consume corrosive sulfides produced by SRB and restrict the SRB biofilms from accumulation. Scanning probe microscopy observations ex-situ demonstrated that the topography of mixture biofilm formed in the mixed culture of TD and SRB was more compact than that for SRB along. Therefore, the process of charge transfer is baffled, leading to a decrease of the corrosion caused by SRB.

Electrochemical formation and overoxidation of polyaniline (PAn) were investigated in solutions containing different anions. The anions promoted PAn growth in the order, H2SO4>HCI>HCIO4. The growth rate of PAn in the presence of two different types of anion was governed by the anion with lesser promoting effect. The addition of a small amount of HCIO4 into the H2SO4 solution greatly inhibited the initial monomer oxidation and the growth of the polymer. Similar promoting/depressing effects of anions were observed on electrochemical degradation of PAn films. The effects of anions were possibly related to the stability of complexes between the anion and protonated monomer, and the anion and protonated PAn chains.

Electrochemistry of poly[(tetraethyldisilanylene)quinque(2,5-thienylene)] (DSST) has been investigated in acetonitrile with cyclic voltammetry, potentiostatic oxidation and spectroelectrochemical measurements. In multicycle voltammograms of a DS5T film there are a pair of redox peaks attributable to anion-doping and dedoping. During potential cycling or electrolyzing at certain positive potentials, the polymer is subject to decomposition to some extent. An irreversible oxidation subpeak for the decomposition of the polymer is observed in the first-cycle voltammogram with low scan rates. Spectroelectrochemical measurements demonstrate that the slow decomposition process tends to be inhibited by further oxidation of its decomposed product, followed by redepositing of a solid film onto the DS5T film. The further oxidation of the decomposed product also leads to some unexpected observations in the spectroelectrochemistry of DS5T. Moreover, if the forward potential scanning is returned at more positive potentials, two pairs of oxidation/reduction peaks occur in the cyclic voltammogram of DS5T and the polymer film becomes much more unstable at the potential of the second oxidation peak.

Electrochemical polymerization of ring-substituted dimethylaniline was performed in aqueous acid solutions to obtain soluble conducting polyaniline. The conductivity values of polydimethylanilines obtained were in the range of 10-1- 10-7Scm-1 depending on the preparation conditions. The molar masses of the oxidation products were in the order of 10.3 gregardless of the monomer structure. These conductive oligomers were easily soluble in polar organic solvents. Soluble conducting oligomers were also obtained by chemical polymerization with iron (Ⅲ) species.