Electrochemically prepared poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrenesulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, was characterized by cyclic voltammetry CV, UV-vis spectroscopy, in situ conductivity, and XPS spectroscopy and was compared with electrochemically prepared PEDT/tosylate and chemically prepared PEDT/PSS. CV analysis shows that the polymer synthesis is strongly affected by the nucleophilic character of the counteranion. Although CV and UV-vis spectroscopy show that the structure and degree of polymerization (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS is able to explain the different conductivity values for these materials (ranging from 1 S cm -1 for PEDT/PSSNa to 400-450 S cm -1 for PEDT/tosylate) based on doping level and composition. In particular, critical results are observed to be the ratios between sulfonate and thiophene units in the polymers: the higher the PEDT concentration, the higher the conductivity. XPS also explains by solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles the often reported conductivity enhancement of chemically prepared PEDT/PSS upon treatment with polar solvents.

Novel poly(2,7-carbazole)s (i.e., poly(N-octyl-2,7-carbazolediyl) and poly(N-(4-hexylbenzoyl)-2,7-carbazolediyl)) and their alternating thiophene, bithiophene, and 3,4-ethylenedioxy-2,5-thienylene copolymers have been investigated by cyclic voltammetry, UV−vis spectroelectrochemistry, electrochemical quartz crystal microbalance, in-situ electron spin resonance, and in-situ conductivity techniques. All polymer films undergo reversible oxidation and partially reversible reduction processes. In poly(N-octyl-2,7-carbazolediyl), two isoelectronic oxidation processes produce radical cations and dications with charge localization at the carbazole subunits. The presence of a strong electron-withdrawing substituent onto the nitrogen atom in the homopolymer leads to an increase by 3 orders of magnitude of the conductivity (i.e., 1 × 10-2 S/cm). Similarly, in alternating copolymers, the oxidative charge is more delocalized over the polyconjugated backbone with in-situ conductivities in the range of 4 × 10-2−4 × 10-3 S/cm.

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New low-gap thiophene-based regular copolymers are produced by anodic coupling of 3,4ethylenedioxythiophene-2,5-substituted thieno [3,4-b]pyrazine (TP), cyclopenta[2,1-b;3,4-b′]dithiophen-4-one (CO), and 4-dicyanomethylene-4H-cyclopenta [2,1-b;3,4-b′]dithiophene (CN). The copolymers are characterized by cyclic voltammetry, FTIR reflection-absorption and UV-vis spectroscopy, electrochemical quartz crystal microbalance analysis, and in situ pand n-conductivity measurement. The copolymers show low optical gaps (measured at the maximum absorption) and electrochemical gaps (measured from redox potentials) in the range 0.8-1.3 eV. The CN-based polymer displays the lowest reported electrochemical gap (0.8 V). Random copolymers of CO and 3,4-ethylenedioxythiophene (EDT) have also been produced and compared with the relevant regular copolymer. Copolymerization of CO with increasing amounts of EDT decreases the gap. From an analysis of redox potential as a function of EDT fraction, it is found that the gap is limited by the redox potentials of the individual homopolymers. Localization of n-doping carriers in the polythiophene chains is progressively increased by donor-acceptor alternation and then by copolymerization till the expected intrinsic conductivity is made completely p-type.

In a quest for thermoelectric polymeric materials novel polycarbazole and polyindolocarbazole derivatives were synthesized. Alkyl side chains on the carbazole cycle and different side chains (alkyl or benzoyl) on the nitrogen atom of the backbone unit were introduced. Optical, electrochemical, electrical, and thermoelectric properties were investigated on these polymers and on two poly(diindolocarbazole)s. Band structure calculations were used to predict which polymers might be promising as thermoelectric materials. The best combination of Seebeck coefficient and conductivity (power factor) was around 10 -7 Wm -1 K -2 with copolymers comprising thiophene units alternating with carbazole or indolocarbazole. This family of polymers possesses good Seebeck coefficients, but there is still a need to improve the electrical conductivity, to produce useful thermoelectric materials.

Summary: New polyindolocarbazoles (PIC) and polydiindolocarbazoles (PDIC) have been synthesized using Yamamoto polymerization reaction. These polymers have been investigated by cyclic voltammetry, UV‐Vis‐NIR spectroelectrochemistry, electrochemical quartz crystal microbalance, in situ electron spin resonance, and in situ conductivity techniques. Two redox oxidation processes, each involving one electron per repeat unit, produce radical cations (free or π‐dimerized) and dications. Each one‐electron redox process is generally split into two due to the stabilization of mixed‐valence states. The oxidative charge is delocalized over the polyconjugated backbone with neutral‐polaron conductivities in the range 0.002–0.04 S · cm−1 and polaron‐bipolaron conductivities in the range 0.04–0.5 S · cm−1. Conductivities are higher when nitrogen atoms are involved in the conjugation pathway.Structure of P3IC, P3DIC, P2IC, and P2DIC.magnified imageStructure of P3IC, P3DIC, P2IC, and P2DIC.

The adsorption of some substituted ferrocene molecules (Fc-R) on indium−tin-oxide electrodes has been investigated by cyclic voltammetry in acetonitrile. Adsorption occurs with carboxyl-substituted (R = −COOH and −(CH2)6COOH) and to a lesser extent with amino-substituted (R = −CH2N(CH3)2) ferrocenes. Adsorption from the neutral (ferrocene) carboxyl-substituted molecule produces layers with a coverage of 1 × 10-10 mol cm-2 which increases to 4 × 10-10 mol cm-2 from the oxidized (ferrocenium) molecule in air-saturated solution. In the latter case, adsorption occurs on a thin layer of amorphous iron oxide produced by oxidative decomposition of the ferrocenium. Electrodes modified by amorphous iron oxide layers are able to give stable monolayers from the carboxyl-terminated molecules, particularly with R = −(CH2)6COOH due to self-assembly. The layer structures are discussed on the basis of the adsorbate structure and the electrochemical parameters.