Polarons, bipolarons and charge interactions in polypyrrole: Physical and electrochemical approaches

Nechtschein, M.; Devreux, F.; Genoud, F.; Vieil, E.; Pernaut, Jean Michel; Geniès, E.M.

doi:10.1016/0379-6779(86)90143-8

Cited by 159 publications

(38 citation statements)

References 17 publications

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“…A single oxidised pyrrole chain was modelled by constraining three pyrrole rings (numbers 4, 5 and 6 of Figure 1) to the same plane and introducing a net charge of þ1 (corresponding to the extraction of one electron from the uncharged polypyrrole chain), a structure which is called a polaron. [8,9,30,31] The net charge þ1 was distributed between these three rings constrained into the same plane (for further information concerning how oxidised polypyrrole was modelled, please check ref. [19] ).…”

Section: Models and Simulation Techniquementioning

confidence: 99%

Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the Polymer

Cascales

Otero

2005

Macro Theory & Simulations

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Summary: Polypyrrole is one of the most widely‐studied conducting polymers due to its steady electrochemical response and good chemical stability in different solvents, including organic and inorganic ones. In this work, we provide for the first time valuable information in atomic detail concerning the steady and dynamic properties of pyrrole rings as a function of the oxidation state of the polymer. The study was carried out by Classical molecular dynamics simulation, where the system was modelled by 256 polypyrrole chains of 10 pyrrole rings each. Water was explicitly introduced in our simulations. Besides the uncharged or reduced state, two steady oxidation states of the polymer have been simulated by introducing a net charge (+1) on 85 and 256 of the polypyrrole chains. To balance the charges emerging in these oxidised states, 85 and 256 chloride ions (Cl−1) respectively, were introduced into the system. From an analysis of the simulated trajectories, the orientation and relaxation times of water and pyrrole rings were evaluated for the different oxidation states of the polymer across the polypyrrole/water interface. The calculated densities for different oxidation states describe the swelling or shrinking process during electrochemical oxidation or reduction respectively. The rotational relaxation times calculated for the polypyrrole rings decrease with increasing oxidation of the polymer, which is in a good agreement with experimental electrochemical data. Almost no variation in pyrrole ring orientation was measured for the different oxidation states of the polymer, even compared with polypyrrole bulk. As regards the water structure in the vicinity of the polypyrrole/water interface, both the orientation and orientation relaxation time were strongly affected by the presence of charges in the polymer. Thus, the water dipole was strongly orientated in the vicinity of the water/polypyrrole interface and its orientational relaxation time increased by one order of magnitude compared with bulk water, even when only one‐third of the total polymer chains were oxidised. The results attained in this work were validated with experimental results, when they were available.Polypyrrole ring orientation and water orientation at the polypyrrole/water interface. (a) 256 rPPy and (b)171 rPPy + 85 oPPy.imagePolypyrrole ring orientation and water orientation at the polypyrrole/water interface. (a) 256 rPPy and (b)171 rPPy + 85 oPPy.

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Section: Models and Simulation Techniquementioning

confidence: 99%

Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the Polymer

Cascales

Otero

2005

Macro Theory & Simulations

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“…In addition, redox reactions (including spectroelectrochemical behavior) of the electroconducting polymer (polypyrrole) can be analyzed (12,13) using the Nernst equation in terms of a polaron/bipolaron model (3). This model treats the polymers in several monomer units having +1 or +2 charges, and describes the redox reactions of the polymers by these units.…”

Section: (E Vs Log [O]/[r]mentioning

confidence: 99%

“…Figure 6 shows the curve fitting of the calculated hAbs vs. E to the experimental plots at 410, 910, and 530 nm. The fitting was performed using the following equations [12] 83 = e3,py/e3,pyl [13] 84 = e3,py2/%,Pyl [14] where el,pyl is the molar absorption coefficient of Py+~, at 410 nm, e2,pyl that of Py+~' at 910 nm, and e3,py, e3,pyl, and e3,py2, respectively, are those of Py, Py+~, and py § at 530 nm. In addition, e3,pyl/C at 530 nm was used as a parameter.…”

Section: Monomer Unit Model--thismentioning

confidence: 99%

“…One of the most interesting aspects of these polymers is their spectroelectrochemical behavior (5-7). For these electroconducting polymers, spectroelectrochemical studies have been intensively carried out (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). The absorption spectra are quantitatively analyzed using the Nernst equation, and the formal electrode potentials and "n-values" (the number of electrons transferred during the redox reactions) are then obtained (8-11).…”

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Analyses of Spectroelectrochemical Behavior of Polypyrrole Films Using the Nernst Equation: “Monomer Unit Model” and Polaron/Bipolaron Model

Amemiya

Hashimoto

Fujishima

et al. 1991

J. Electrochem. Soc.

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q ABSTRACT A series of the absorption spectrum changes in polypyrrole films were analyzed using the Nernst equation by two models. One is the " m o n o m e r unit model" and the other is the "polaron/bipolaron model." In the first model, formal electrode potentials and the n-values were obtained and usec~ to fit calculated hAbs vs. E curves to the experimental plots at three wavelengths. In the second model, the "apparent" excess chemical potentials were introduced to correct for the large deviations between the Nernst equation and the Nernst plots obtained from the absorption spectra. The calculated hAbs vs. E curves were then fitted to the experimental plots. The "apparent" excess chemical potentials were assigned as corrections for species concentrations. Advantages of the monomer unit model over the polaron/bipolaron model are pointed out in the precise analyses of the spectroelectrochemical behavior of the films.Electroconducting polymers, such as polypyrroles, polythiophenes, and polyanilines, have been recently receiving m u c h attention because they can be easily prepared by electrochemical polymerization, are stable in air, and also have unique electronic, electrochemical, and optical properties (1-4). One of the most interesting aspects of these polymers is their spectroelectrochemical behavior (5-7). For these electroconducting polymers, spectroelectrochemical studies have been intensively carried out (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). The absorption spectra are quantitatively analyzed using the Nernst equation, and the formal electrode potentials and "n-values" (the number of electrons transferred during the redox reactions) are then obtained (8-11). Furthermore, Marque and Roneali (11) carried out comparative spectroelectrochemical studies of three-substituted polythiophenes and analyzed the deviations of the Nernst plots) from linearity in terms of (i) the coulombic interactions between charged sites, and (ii) the mechanical work required to expand the polymer lattice by the insertion of counterions and solvent molecules. The c o m m o n and important points and/or assumptions in these studies (8)(9)(10)(11) are that the redox reactions of these polymers can be described by one " m o n o m e r unit," not by several m o n o m e r units of the polymers. From now on, we call the treatment of the redox reactions of electroconducting polymers in terms of m o n o m e r units as "monomer unit model."In addition, redox reactions (including spectroelectrochemical behavior) of the electroconducting polymer (polypyrrole) can be analyzed (12, 13) using the Nernst equation in terms of a polaron/bipolaron model (3). This model treats the polymers in several monomer units having +1 or +2 charges, and describes the redox reactions of the polymers by these units. Therefore, the number of electrons transferred during the redox reactions are + 1 or +2 by this model. According to such analyses (13), excess chemical potentials must be introduced to explain nonNernstian behavior of the polymer. They we...

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“…In order to characterize the encapsulated chains properly, it is important to answer the following questions: The ESR spectra show two lines that are both expected: one at g = 2.003 represents the polymer [3], the other at g = 4.28 represents the paramagnetic Fe 3+ ions in a non-cubic environment [5]. Both signals originate from non-interacting spins because the signal intensities follow accurate Curie laws between 3Κ and room temperature.…”

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The low-field conductivity of zeolite-encapsulated molecular wires

et al. 1993

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The first measurements of an upper bound for the low-field conductivity of a molecular wire are presented here. We were able to encapsulate polypyrrole with chain lengths more than 10 monomers within the channels of different zeolites. Although the chains are fully oxidized by intrazeolite Fe 3+ ions, and should conduct (when included in a bulk polymer), they do not exhibit, in the zeolite, significant ac conductivity up to 1 GHz. This suggests that other strategies than low field conductivity are needed to inject charges and transmit information through isolated molecular wires.In common biological processes information is transmitted and processed at the molecular scale, while the best artificial integrated circuits (memories) achieve only a scale of about 1 μπι. There has been substantial interest in the design of "molecular electronic" devices based on molecular units. This concept poses enormous challenges, including the problem of access to molecule-sized structures, defects and heat dissipation. Moreover the physical aspects of electron-transfer at the molecular scale deserve further investigation. In a project aimed at the understanding and design of conducting nanostructures, we have recently succeeded in the preparation of zeolite-encapsulated chains of polypyrrole [1], polythiophene, and other conjugated polymers. The first measurements of an upper bound for the low-field conductivity of a molecular wire are presented here.During the past twenty years, research in the field of organic conductors has resulted in many "molecular wires", in the form of stacks or bundles of polymer chains. However, these species are always associated in crystals, fibers or films, which causes electronic interchain coupling. These interactions are often weak but nevertheless determine most of the bulk electronic properties.Signals in biological systems are usually transmitted through membranes or other organized structures, in order to limit interference and to spatially separate events from each other. We have developed systems that mimic the stabilizing function of membranes by encapsulating conjugated polymers in an inorganic host with nanometer size ordered pores: a molecular sieve [1].

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Polarons, bipolarons and charge interactions in polypyrrole: Physical and electrochemical approaches

Cited by 159 publications

References 17 publications

Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the Polymer

Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the Polymer

Analyses of Spectroelectrochemical Behavior of Polypyrrole Films Using the Nernst Equation: “Monomer Unit Model” and Polaron/Bipolaron Model

The low-field conductivity of zeolite-encapsulated molecular wires

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