Solvent-induced microstructure changes and consequences for electrochemical activity of redox-active conducting polymers

Electrochemical impedance spectroscopy (EIS) was used to demonstrate solvent-induced collapse of the microstructure of redox-active conducting polymers; the collapse was dependent on the nature of the polymer and had a significant effect on the redox activity of the materials. Conducting polymer films of terthiophene, poly(3-((2′:2″,5″:2?-terthiophene)-3′′-yl) acrylic acid) (PTAA) and poly(3,4-ethylenedioxythiophene) (PEDOT) were produced in an organic solvent (DCM, dichloromethane) and subsequently immersed in other organic solvents (DCM, acetonitrile) or in an aqueous solution (Tris buffer). Impedance diagrams over time implied shrinkage of the polymer upon solvent change, particularly in Tris buffer, that was more pronounced and more rapid for PTAA than for PEDOT. These changes were correlated with a loss of reversibility of electrochemical cycling and an increase of potential required for ion insertion into the polymer and could simply be understood in terms of the change in solvation of the polymer.     

The role of ion and solvent transport during the redox process of conducting polymers

The understanding of the redox behavior of conducting polymers is essential for a successful application of these so-called synthetic metals as functional coatings. The redox process involves the exchange of ions and solvent molecules. This so called doping/dedoping process involves changes of the mechanical and the electronic structure of the polymer. This paper discusses investigations at poly(3,4-ethylenedioxythiophene (PEDOT) and poly(pyrrole) (Ppy) by the electrochemical quartz crystal microbalance (EQCM) technique and electrochemical impedance spectroscopy (EIS). In the case of PEDOT a determination of the anion and the solvent fluxes was possible, and it was found that most anions replace solvent molecules upon their incorporation. The doping/dedoping mechanism of Ppy is more complicated. Here, the first redox cycles are characterized by a complex interplay of cation, anion and solvent fluxes with irreversible changes of the polymer structure. However, in combination with EIS new insights of the ion and solvent exchange and its influence on the electronic properties can be achieved.     

Electrically controlled cellular migration on a periodically micropatterned PEDOT:PSS conducting polymer platform

In the field of tissue engineering, the study of cellular adhesion and migration is of crucial interest. Conducting polymers such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) provide an outstanding interface with biology due to their soft nature, which is closer to the mechanical, chemical, and morphological properties of biological systems. In this work, periodically micropatterned PEDOT:PSS thin films are used as a platform to investigate cellular migration. Human cerebral microvascular endothelial cells (hCMEC) show alignment and linear motion along PEDOT:PSS microstripes of varying widths (10–30 μm). In addition, an electrochemical gradient is created on the PEDOT:PSS film along these microstripes to influence the cell behavior. hCMEC cells linearly change their velocities depending on the redox state of the conducting polymer film. This work demonstrates the potential of such conducting polymer platforms to combine, at the same time, several key physicochemical factors for controlling cellular migration. In the future, we envision that these conducting polymer platforms will deliver tools for tissue regeneration and lead to new opportunities in regenerative medicine. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47029.     

Trends in Conducting Polymer and Hybrids of Conducting Polymer/Carbon Nanotube: A Review

Several conducting polymers, including polyaniline, polypyrrole, polythiophene, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), poly(m-phenylenediamine), polynaphthylamine, poly(p-phenylene sulfide), and their carbon nanotube reinforced nanocomposites are discussed in this review. The physical, electrical, structural and thermal properties of polymers along with synthesis methods are discussed. A concise note on carbon nanotubes regarding their purification, functionalization, properties and production are reported. Moreover, the article focuses upon synthesis methods, properties and applications of conducting polymer/carbon nanotube nanocomposites are focused. Nanotube dispersion, loading concentration and alignment within conducting polymer/carbon nanotube nanocomposite affect their performance and morphology. The conducting polymer/carbon nanotube nanocomposites are substantially used in sensors, energy storage devices, supercapacitors, solar cells, EMI materials, diodes, and coatings.     

Electrochemical and electrogravimetric behaviors of conducting polymer. Theoretical aspects and application to co-polymer films based on juglone

Redox mechanisms of conducting polymers are not yet fully understood. Attractive analytical tools and pertinent models are necessary to achieve this goal. In this paper, numerical simulations based on a theory dealing with ions transfer through electroactive film/electrolyte interface was developed to predict the behavior of a conducting polymer called poly(JUG-co-JUGA). The main advantage of this approach is that it can be applied for any polymer assuming a mixed conducting material and a thin enough film neglecting the transport effect. It is the first time where the same model allows both classical cyclic electrogravimetry (current and mass over a potential scan) and ac-electrogravimetry (electrochemical impedance and mass/potential transfer functions) to be estimated theoretically. Moreover and to our knowledge the electrochemical behavior of poly(JUG-co-JUGA) was examined through these techniques for the first time. It is shown herein that the cation transfer is preponderant but the free solvent motion must be taken into account. This effect is not detected by classical electrochemical measurements but only by combining electrochemical characterization to gravimetric measurements.     

Optimization of the electropolymerization of 1-amino-9,10-anthraquinone conducting films from aqueous media

The optimum conditions for the electrochemical preparation of poly(1-amino-9,10-anthraquinone), PAAQ, films in environmentally safe aqueous solutions were investigated. The conducting polymer films were prepared by electrochemical oxidation of 1-amino-9,10-anthraquinone, AAQ, in sulfuric acid solutions in the potential range from 0.0 to +1.3 V. The influence of scan repetition, scan rate, and monomer concentration on the formation process and the properties of the polymer film were studied. The electrochemical response of the formed polymer film was investigated in both aqueous and non-aqueous media. The polymer films were found to be stable in aqueous acidic media. In non-aqueous solutions, like acetonitrile, dimethyl sulfoxide and dioxin, the polymer films showed remarkable degradation. The best electrochemical response of the PAAQ films was found to be in the potential range between +0.3 and +0.9 V. The presence of quinone units in the polymer film chain suggests promising applications of these conducting polymers in lightweight (rechargeable) batteries, electrochromic display devices, and biosensor and corrosion protection.     

Synthesis and corrosion protection performance of polydiphenylamine

In recent years, the conducting polymers are used in organic coatings as a replacement of chromate based pigments. The effectiveness of polydiphenylamine (PDPA) in the vinyl coating towards the corrosion protection of steel in acidic environment has been found out. The polymer PDPA was synthesized by chemical oxidation of diphenylamine by ammoniumpersulfate in hydrochloric acid medium. The polymer was characterized by FTIR and XRD. The corrosion protection performance of the PDPA containing 0–5% in vinyl coating on steel in 0.1N HCl has been assessed by electrochemical impedance spectroscopy. Coatings containing more than 3% PDPA are found to offer excellent corrosion protection of steel in acid media due to redox property of PDPA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

One-dimensional conducting polymer nanocomposites: Synthesis, properties and applications

Intrinsically conducting polymers have been studied extensively due to their intriguing electronic and redox properties and numerous potential applications in many fields since their discovery in 1970s. To improve and extend their functions, the fabrication of multi-functionalized conducting polymer nanocomposites has attracted a great deal of attention because of the emergence of nanotechnology. This article presents an overview of the synthesis of one-dimensional (1D) conducting polymer nanocomposites and their properties and applications. Nanocomposites consist of conducting polymers and one or more components, which can be carbon nanotubes, metals, oxide nanomaterials, chalcogenides, insulating or conducting polymers, biological materials, metal phthalocyanines and porphyrins, etc. The properties of 1D conducting polymer nanocomposites will be widely discussed. Special attention is paid to the difference in the properties between 1D conducting polymer nanocomposites and bulk conducting polymers. Applications of 1D conducting polymer nanocomposites described include electronic nanodevices, chemical and biological sensors, catalysis and electrocatalysis, energy, microwave absorption and electromagnetic interference (EMI) shielding, electrorheological (ER) fluids, and biomedicine. The advantages of 1D conducting polymer nanocomposites over the parent conducting polymers are highlighted. Combined with the intrinsic properties and synergistic effect of each component, it is anticipated that 1D conducting polymer nanocomposites will play an important role in various fields of nanotechnology.     

Redox Active p-Nitrophenyl Units bond to Electrodeposited Conducting Polythiophene Films

Summary Two new thiophene derivatives bearing redox active p-nitrophenyl units were synthesized and electropolymerized to conducting polymers. It is found that not only the structure of monomer, but also the employed polymerization conditions have considerable effect on the electroactivity of the bonded redox groups of resulting polymer films. Depending on used conditions such as polymerization time, the polymerization of the same monomer could result in a polymer with well-defined redox transition of the nitrophenyl group or a polymer, in which the redox group is completely electrochemical inaccessible. Using designed experiments, we explained this phenomenon. These investigations provide further knowledge about the behaviors of redox group attached to electrode surface.     

Synthesis and electrochemical characterization of soluble poly(p-phenylene vinylene) derivatives containing olefinic bonds at the side chain

A new kind of soluble poly(p-phenylenevinylene) (PPV) derivative containing free olefinic bonds at the side chain is prepared and studied by electrochemical measurement. The electrochemical investigations reveal that the free olefinic bonds in these polymers are electroactive; a new redox reaction occurs prior to the oxidation of PPV backbone in the cyclic voltammetry. The lower oxidation potential of the olefinic bonds hints that it is possible for these olefinic bonds to react with oxygen, which is desirable to remove the harmful oxygen in the light-emitting polymer devices. The merits and possibility of such polymers containing olefinic bonds in the fabrication of the light-emitting devices are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2535–2539, 1999     

Syntheses and electrochromic and fluorescence properties of three double dithienylpyrroles derivatives

Three double dithienylpyrroles derivatives have been successfully prepared by performing a Knorr–Paal condensation between 1,4-di(thiophen-2-yl) butane-1,4-dione and various aromatic diamines. Additionally, their corresponding polymer films were synthesized via electropolymerization. Their electrochemical, spectroelectrochemical and electrochromic behaviors were further investigated by thermogravimetric analysis, scanning electron microscopy, cyclic voltammetry, UV–vis absorption and fluorescence emission spectra. Scanning electron microscopy and thermogravimetric analysis demonstrated that the polymer films possessed homogeneous, compact and smooth layer structures and thermal stabilities (up to nearly 180 °C). Cyclic voltammograms and UV–vis absorption spectra studies showed that the polymer films have stable, well-defined, reversible redox processes, low optical band gaps (E_g < 2.2 eV) and multicolor electrochromic behaviors. Additionally, the fluorescence spectra study showed that all of the monomers and polymers exhibited different intensity emission bands at different wavelengths.     

A new processable donor–acceptor polymer displaying neutral state yellow electrochromism

We report here the synthesis of a new solution processable neutral state yellow polymeric electrochromic material containing 2,5-bis-dithienyl-1H-pyrrole (SNS)-donor and 1,8 naphthalimide-acceptor (SNS–NI) as a subunit. The electrochemical and optical properties were investigated via cyclic voltammetry (CV), UV–Vis absorption and fluorescence emission measurements, respectively. Besides, electrochromic performance of poly(SNS–NI) has been compared to the both the film preparation method and poly(1-phenyl-2,5-dithiophen-2-ylpyrrole) [poly(SNS–P)] as a standard polymer. In the poly(SNS–NI), yellow color of the polymer film at neutral state converted to green and then dark blue upon the polymer film fully oxidized in the positive regime. SNS–NI polymer film prepared via spin casting process exhibits a high contrast ratio in the near-IR region (ΔT% = 56% at 890 nm), a response time of about 1 s, high coloration efficiency (299 cm² C⁻¹) and retained its performance by 98.6% even after 5000 cycles. Finally, the results clearly indicate that both electronic nature of the molecule and film preparation method have a major impact on electrochromic performance of these polymers.     

Electroactive polymer blends

The rapid development of two new classes of electrically active polymer materials, electronically conducting and electroactive polymers and ion-conducting polymers respectively, offers new possibilities for application of both classes of material, especially in combination with each other. While some of these combinations have been attempted before, they all met serious problems due to poor interpenetration of the two polymers. The recent availability of solubilized and soluble electroactive and conductive polymers has greatly advanced the possibilities of reducing the interpenetration problem. Some experimental studies using the combination of solubilized electroactive polypyrrole with poly(ethylene oxide) in an electroactive polymer blend electrode for solid-state polymer batteries are discussed. The opportunities for using polymer blends for solid-state electrochemical polymeric devices, and avenues for the development of materials for such devices, are also reviewed.     

Marine paint fomulations: Conducting polymers as anticorrosive additives

Within coating technology, there is increasing interest in the development of efficient anticorrosive additives able to replace the conventional inorganic anticorrosive pigments usually added to paints, which may have detrimental effects on both environment and health. A number of recent studies have evidenced that the modification of a paint formulation by the addition of a low concentration of conducting polymer (0.2–0.3%, w/w) increases significantly the protective properties of the coating. Here we focus on the principles of anticorrosive additives based on conducting polymers for marine paints. The article reviews the most important findings achieved in recent studies. The relevant factors that are determinant for the anticorrosive protection imparted by conducting polymers, as the doping level, the miscibility with paint, the electrochemical stability, etc., are discussed in detail.     

Characterization of polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) film and its application for the immobilization of vitamin B12

Vitamin B12 (B12) - possessing a redox active cobalt centre - is a candidate to be used as a mediator in bioelectrochemical processes. In order to exploit the possible redox activity of B12, Pt has been modified by a bio-conform conducting layer polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) PPy/PIPES. The electrochemical and spectral behaviour of this film proved to be similar to PPy/dodecyl-sulfate (DS), widely considered and accepted as one of the best combinations of conducting polymer films. The capability of the PPy/PIPES film for acting as adsorbant in the accumulation of B12 has been evidenced by the electrochemical quartz crystal microbalance (EQCM) technique. B12 could also be incorporated into the polymer layer during its electrochemical deposition. The results proving the preserved redox activity of B12 within the film open new perspectives towards redox mediated bioelectrochemical applications based on the immobilization of this biomolecule.     

Solid state electrochemistry and spectroelectrochemistry of poly(arylene bisimide–alt-oligoether)s

Two electroactive polymeric arylene bisimides, namely poly[(4,7,10-trioxatrideca-1,13-diyl)-(1,4,5,8-naphthalenetetracarboxylic bisimide-N,N′-diyl)] and its perylene analogue – poly[(4,7,10-trioxatrideca-1,13-diyl)-(3,4,9,10-perylenetetracarboxylic bisimide-N,N′-diyl)] have been synthesized and studied by cyclic voltammetry, UV–vis-NIR as well as Raman spectroeletrochemistry. Contrary to low molecular weight arylene bisimides, which show a clear two electron, double-step electrochemical reduction (neutral form to radical anion and from radical anion to dianion), in the synthesized polymers multielectron transfers are observed, accompanied with a strong electrochromic effect. However, as probed by cyclic voltammetry, their first reduction step is retarded and covers a wider potential range. We attribute this effect to macromolecular nature of the compounds being reduced and their structural inhomogeneity caused by π-stacking induced nanoaggregation of bisimide segments of the polymer chains. The second redox step seems unaffected by the polymeric nature of the electroactive compounds and yields a reduction peak similar to that registered for low molecular weight bisimides. Raman spectroelectrochemical data, combined with the established vibrational model of the perylene derivative – (poly[(4,7,10-trioxatrideca-1,13-diyl)-(3,4,9,10-perylenetetracarboxylic bisimide-N,N′-diyl)]) – enabled us to determine the mechanism of the first step of the electrochemical reduction process. The electrochemically induced shifts of the Raman bands unequivocally show that the reduction process results in the transformation of the carbonyl group into a radical anion. The surplus negative charge is delocalized on the six-member imide ring with the aromatic core very little affected.     

An in situ Raman spectroelectrochemical study of the controlled doping of single walled carbon nanotubes in a conducting polymer matrix

The interaction of single wall carbon nanotubes (SWCNT) and the conducting polymer poly(3,4-ethylendioxythiophene/polystyrenesulfonate) (PEDOT/PSS) was studied by in situ Raman spectroelectrochemistry. The mixing of SWCNT with PEDOT/PSS caused a partial doping of SWCNT which was indicated by the change of relative intensity of the SWCNT Raman features. We have demonstrated for the first time that in situ Raman spectroelectrochemistry is a method of choice for precise and effective control of doping level of composites of conducting polymers and SWCNT. For electrochemical doping of SWCNT embedded in PEDOT/PSS the bleaching of RBM and TG modes of the SWCNT is delayed as compared to that in pure SWCNT. The delay is of about 0.2 V. This potential difference vanishes at higher potentials. The delayed response to doping is observed for both the SWCNT and the polymer matrix features. In the latter case the response is specific for individual polymer bands. Furthermore, during p-doping most of the polymer bands exhibit a subsequent monotonous bleaching. This contrasts with the behavior of the pristine polymer where the intensity changes are non-monotonous.     

Synthesis,spectroscopy, and electrochemical investigation of new conjugated polymers containing thiophene and 1,3,4-thiadiazole in the main chain

Novel photoluminescent donor–acceptor poly(p-phenylenevinylene)-type conjugated polymers containing thiophene and 1,3,4-thiadiazole units in the main chain were synthesized from 2,5-bis(5-bromomethyl-2-thienyl)-1,3,4-thiadiazole and 1,3/1,4-benzenedialdehyde by Wittig–Horner reaction. The synthesized polymers were characterized by the use of thermal analysis and spectroscopic (infrared, UV-visible absorption, and photoluminescence) measurement. The resultant material exhibited bluish green, green, and orange fluorescence in their solution and thin film and solid forms, respectively. The redox property of the polymers has also been studied by cyclic voltammetry. The optical and electrochemical studies reveal that these novel polymers are new promising materials for the development of efficient polymer light-emitting diodes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication of network films of conducting polymer-linked polyoxometallate-stabilized carbon nanostructures

The ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo₁₂O₄₀³⁻), to form stable anionic monolayers on carbon nanoparticles and multi-wall nanotubes is explored here to produce stable colloidal solutions of polyoxometallate covered carbon nanostructures and to disperse them within conducting polymer, poly(3,4-ethylenedioxythiophene), i.e. PEDOT, or polyaniline multilayer films. By repeated alternate treatments in the colloidal suspension of PMo₁₂O₄₀³⁻-protected carbon nanoparticles or nanotubes, and in the acid solution of a monomer (3,4-ethylenedioxythiophene or aniline), the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional organized arrangements (networks) of interconnected organic and inorganic layers on electrode (e.g. glassy carbon) surfaces. In hybrid films, the negatively charged polyoxometallate-covered carbon nanostructures interact electrostatically with positively charged conducting polymer ultra-thin layers. Consequently, the attractive electrochemical charging properties of conducting polymers, reversible redox behavior of polyoxometallate, as well as the mechanical and electrical properties of carbon nanoparticles or nanotubes can be combined. The films are characterized by fast dynamics of charge transport, and they are of potential importance to electrocatalysis and charge storage in redox capacitors.     

Free radical copolymerization of functional water-soluble poly(N-maleoylglycine-co-crotonic acid): polymer metal ion retention capacity, electrochemical, and thermal behavior

In this study, the water-soluble polymers of N-maleoyl glycine (MG) with crotonic acid (CA) were copolymerized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the functional groups in the copolymers on the metal ion retention capacity, electrochemical and thermal behavior, since that important requirements for their use in technological applications are: high solubility in water, chemical stability, a high affinity for one or more metal ions, and selectivity for the metal ion of interest. The metal complexation properties of poly(MG-co-CA) for the metal ions were investigated at pH 3, 5, and 7 in aqueous solution. The metal ion investigated were: Cu(II), Co(II), Cr(III), Ni(II), Cd(II), Zn(II), and Fe(III). The polymeric systems showed high metal ion retention for Zn (II) and Fe(III) at different pH. At different pHs, the MRC of the poly(MG-co-CA) for Fe(III) ions varied from 122.1 to 146.2 mg/g and from 120.5 to 133.5 mg/g, (samples 1 and 2 at pH 3 and 7, respectively). The MRC had the highest retention values for both copolymer systems at pH 7. The copolymers presented higher thermal decomposition temperature (TDT) in comparison with copolymer–metal complexes at pH 3 and 5. The cyclic voltammetry (CV) for poly(MG-co-CA) (20 mM) was compared with the CV of the [poly(MG-co-CA)–Fe(III)] copolymer complex. Moreover, [poly(MG-co-CA)–Fe(III)] showed a redox wave difference between +0.25 and +0.50 V possibly due to the presence of metal complexed with the polymer. The electrochemical characterization of the copolymer poly(MG-co-AC) shown the reduction of carboxylic acid groups of the N-maleoylglycine and crotonic acid moiety to hydroxyl group. The results support the assumption that the copolymer presents convenient electroactivity.