Content uploaded by Bernhard Wessling
Author content
All content in this area was uploaded by Bernhard Wessling on Nov 08, 2017
Content may be subject to copyright.
Conductive Polymers as Organic Nanometals
Abstract
This chapter discusses the metallic character and the nanoparticle structure and dynamics, the precondition for these properties and for eventual nanotechnology, the principal insolubility of organic metals (or: conductive polymers), and some actual technical applications ultimately based on their nanocharacter and on dispersion and the macrotechnology, with dramatic effects in the nanoscale. Several potential applications are actually not seriously approached, even though their feasibility has been shown. It seems that industrial development groups refrain from working with PAni as long as they are conceptually and mentally biased toward either a direct polymerization approach or a "solution" technique. The development of electrochromic windows, sensors, and gas separation membranes would need a reproducible nanotechnology for applying PAni to the substrate. With two basically different and long-term industrial uses of polyaniline, in corrosion protection and in the manufacture of printed circuit boards, both based on and only feasible with dispersion technologies, the dispersion concept has shown its value and has allowed the first significant commercial application of conductive polymers. There will be many more industrial applications in the future, as soon as the new useful property combinations of organic metals, especially polyaniline, are broader known, and more confidence has been built up in the market based on the first pioneering applications.
... The discovery that organic molecules, normally considered as insulating, were able to conduct electricity was a real breakthrough in the field of organic chemistry [1][2][3], and organic molecules' conductivity became a hot topic [2][3][4][5]. The application of conductive polymers grew rapidly, along with the comprehension of the conductivity phenomenon and charge recombination [2,6]. ...
... Lai et al. obtained the new DMZ HTM by coupling the dimethoxytriphenylamine onto the bifluorenylidene scaffold (tetrabenzo [5,5]fulvalene), which was obtained from the dimerization of dibromofluorenone [107]. This is a particular case in which the ethylene is the central scaffold or at least at center of a more complex scaffold. ...
Since the introduction of Perovskite Solar Cells, their photovoltaic efficiencies have grown impressively, reaching over 25%. Besides the exceptional efficiencies, those solar cells need to be improved to overcome some concerns, such as their intrinsic instability when exposed to humidity. In this respect, the development of new and stable Hole Transporting Materials (HTMs) rose as a new hot topic. Since the doping agents for common HTM are hygroscopic, they bring water in contact with the perovskite layer, thus deteriorating it. In the last years, the research focused on “dopant-free” HTMs, which are inherently conductive without any addition of dopants. Dopant-free HTMs, being small molecules or polymers, have still been a relatively small set of compounds until now. This review collects almost all the relevant organic dopant-free small-molecule HTMs known so far. A general classification of HTMs is proposed, and structure analysis is used to identify structure–property relationships, to help researchers to build better-performing materials.
... Since then, the conductive polymers field developed enormously, and they were used in several organic electronic applications such as OLED, OPV, OFET, but not only those [1,16,17]. In the past, organic molecules were known to behave as insulants being their native conductivity of organic materials (molecules and polymers) often minimal, so that they can be induced to enhance their conductivity by the doping process [9,[18][19][20]. This roughly means that the organic structures need to be oxidized to become cationic and thus be able to receive electrons on one side leaving the holes to flow in opposite directions. ...
Perovskite solar cells are a hot topic of photovoltaic research, reaching, in few years, an impressive efficiency (25.5%), but their long-term stability still needs to be addressed for industrial production. One of the most sizeable reasons for instability is the doping of the Hole Transporting Material (HTM), being the salt commonly employed as a vector bringing moisture in contact with perovskite film and destroying it. With this respect, the research focused on new and stable “dopant-free” HTMs, which are inherently conductive, being able to effectively work without any addition of dopants. Notwithstanding, they show impressive efficiency and stability results. The dopant-free polymers, often made of alternated donor and acceptor cores, have properties, namely the filming ability, the molecular weight tunability, the stacking and packing peculiarities, and high hole mobility in absence of any dopant, that make them very attractive and a real innovation in the field. In this review, we tried our best to collect all the dopant-free polymeric HTMs known so far in the perovskite solar cells field, providing a brief historical introduction, followed by the classification and analysis of the polymeric structures, based on their building blocks, trying to find structure–activity relationships whenever possible. The research is still increasing and a very simple polymer (PFDT–2F–COOH) approaches PCE = 22% while some more complex ones overcome 22%, up to 22.41% (PPY2).
... Furthermore, PANI has very low solubility and its solution has insufficient viscosity and elasticity for processing. Even after doping, the PANI emeraldine salts do not have high enough solubility and they are still in dispersion state in solvents [9,[11][12][13]. Preparing pure pristine PANI conductive textiles via conventional fiber spinning methods always encounters challenges. ...
In this study, using a barbed Y-connector as the spinneret, camphoric acid (CSA) doped polyaniline (PANI) and polyethylene oxide (PEO) were electrospun into side-by-side bicomponent fibers. Fiber mats obtained from this side-by-side spinneret were compared with those mats electrospun from blended PEO and PANI in terms of fiber morphology, electrical conductivity, thermal stability, mechanical properties, and relative resistivity under tensile strain. The influence of different content ratio of insulating PEO (3/4/5 w/v% to solvent) and conductive PANI-CSA (1.5/2.5/3.5 w/v% to solvent) on the abovementioned properties was studied as well. Results showed that this side-by-side spinning was capable of overcoming the poor spinnability of PANI to produce fibers with PEO carrying PANI on the surface of the bicomponent fibers, which demonstrated higher electrical conductivity than blends. Although the addition of PANI deteriorated mechanical properties for both side-by-side and blended fibers when compared to the pure PEO fibers, the side-by-side fibers showed much better fiber strength and elongation than blends. In addition, the superior ductility and decent relative electrical resistivity of the side-by-side fibers imparted them great potential for flexible sensor applications.
... 1−29 The reasons for this are the many possible applications of conductive polyaniline, 30−34 even for biomedical applications (for example, in tissue engineering). 35,36 Due to the polymeric nature of PANI-ES products and their insolubility in common solvents, 37 independent of whether they are obtained through electrochemical, 33 chemical, 33,38 enzymatic, or enzyme-mimicking 39,40 routes, the analysis of the chemical structure of PANI-ES-type products is often difficult or impossible. By using p-aminodiphenylamine (PADPA) instead of aniline, the situation in terms of product analysis is much better. ...
Many previous studies have shown that (i) the oxidation of aniline or the aniline dimer p-aminodiphenylamine (PADPA) in a slightly acidic aqueous solution can be catalyzed with heme peroxidases or multicopper laccases and that (ii) subsequent reactions lead to oligomeric or polymeric products, which resemble chemically synthesized polyaniline in its conductive emeraldine salt form (PANI-ES), provided that (iii) an anionic "template" is present in the reaction medium. Good templates are anionic polyelectrolytes, micelles, or vesicles. Under optimal conditions, their presence directs the reactions in a positive way toward the desired formation of PANI-ES-type products. The effect of four different types of anionic templates on the formation of PANI-ES-like products from PADPA was investigated and compared by using Trametes versicolor laccase (TvL) as a catalyst in an aqueous pH 3.5 solution at room temperature. All four templates contain sulfonate groups: the sodium salt of the polyelectrolyte sulfonated polystyrene (SPS), micelles from sodium dodecylbenzenesulfonate (SDBS), vesicles from a 1:1 molar mixture of SDBS and decanoic acid, and vesicles from sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Although with all four templates, stable, inkjet-printable solutions or suspensions consisting of PANI-ES-type products were obtained under optimized conditions, considerably higher amounts of TvL were required with SDBS micelles to achieve comparable monomer conversion to PANI-ES-like products during the same time period when compared to those with SPS or the two types of vesicles. This makes SDBS micelles less attractive as templates for the investigated reaction. In situ UV/vis/near-infrared, electron paramagnetic resonance (EPR), and Raman spectroscopy measurements in combination with an high-performance liquid chromatography analysis of extracted reaction products, which were deprotonated and chemically reduced, showed seemingly small but significant differences in the composition of the mixtures obtained when reaching reaction equilibrium after 24 h. With the two vesicle systems, the content of unwanted substituted phenazine units was lower than in the case of SPS polyelectrolyte and SDBS micelles. The EPR spectra indicate a more localized, narrower distribution of electronic states of the paramagnetic centers of the PANI-ES-type products synthesized in the presence of the two vesicle systems when compared to that of the similar products obtained with the SPS polyelectrolyte and SDBS micelles as templates. Overall, the data obtained from the different complementary methods indicate that with the two vesicle systems structurally more uniform (regular) PANI-ES-type products formed. Among the two investigated vesicle systems, for the investigated reaction (oxidation of PADPA with TvL and O 2 ), AOT appears a somewhat better choice as it leads to a higher content of the PANI-ES polaron form.
... It has been noted that conductive polymers and binders have been widely used due to their promising results such as surface area increment (Xinping et al., 2013), biocompatibility (Qiao et al., 2007), enhanced electron transfer (Morávková et al., 2012) and economical synthesis procedure (Qiao et al., 2007). Conductive polymers like polyaniline, polypyrrole, polyacetylene, polythiophene have been widely investigated in fuel cells and batteries (Wessling, 2000). Among them, polyaniline (PANI) has been extensively used for various purposes because of its thermal-stability (Kulkarni et al., 1989), electrical conductivity, corrosion-resistant, acid-base properties and affordable process for polymerization (Dominis, 2001). ...
Compatibility of metal oxides when used as a coating material on anode surface in benthic microbial fuel cells.
... It has been noted that conductive polymers and binders have been widely used due to their promising results such as surface area increment (Xinping et al., 2013), biocompatibility (Qiao et al., 2007), enhanced electron transfer (Morávková et al., 2012) and economical synthesis procedure (Qiao et al., 2007). Conductive polymers like polyaniline, polypyrrole, polyacetylene, polythiophene have been widely investigated in fuel cells and batteries (Wessling, 2000). Among them, polyaniline (PANI) has been extensively used for various purposes because of its thermal-stability (Kulkarni et al., 1989), electrical conductivity, corrosion-resistant, acid-base properties and affordable process for polymerization (Dominis, 2001). ...
Modification of electrode material from the environmental point of view and scale-up is as important as increasing the power density in benthic microbial fuel cells (BMFC). Here, we examined two different materials for an anode and their modification via surface treatment and surface coating. Polyaniline incorporated carbon cloth (PANI/CC), acid-treated carbon cloth (CC), grooved and acid treated graphite plate (GGP), and polyaniline coated graphite plate (PANI/GP) are used in this study. Modified anodes were compared through electrochemical techniques. It was observed that kinetic activity of PANI/CC was 376 times higher than CC anode, while PANI/GP possesses 1.8 times more kinetic activity than GGP. Power density was recorded and observed decreasing order as follows PANI/CC > CC > PANI/GP > GGP. A mechanism of electron transport model is proposed based on the structural properties of polyaniline coated carbon nanocomposites that enhances the electron flow efficiently for the generation of power with high degree. Polyaniline coated anode materials show greater wettability than their respective surface treated counterparts. Further enhancement in power generation was successfully achieved by recharging with acetate. The study tried to compare the different material and their modifications in the same environment and helps to optimize the system further based on the results obtained.
ZnO Nanoparticle was doped on PVC solution at different concentrations and made films with different thicknesses. The conductivity is measured for different applied fields and temperatures for ZnO nanoparticle doped and undoped films. The plot of ln σ versus 1/T × 10⁻³ K shows the nonlinear nature. From the plot, it is found that the conductivity increases more sharply for the doped sample than the undoped sample within the intermediate range of temperature. The activation energy is calculated for different regions from the plot and found to increase with the increase of doping.
Electromagnetic wave absorption has attracted wide attention due to electromagnetic wave pollution and radiation. The dielectric loss coating magnetic nanoparticles structure has a significant influence on electromagnetic wave absorption properties. In this manuscript, magnetic nanoparticles (CoS2) coated polyaniline (PANI) are synthesized via a facile and simple two-step strategy (a microwave assisted hydrothermal reaction followed an in-situ free radical chemical oxidative polymerization). The CoS2 nanoparticles are coated by PANI which is used as the matrix of electron conduction during converting electromagnetic energy into thermal energy. The electromagnetic wave absorption properties of [email protected]2 nanocomposites can be adjusted by changing the mass ratios of CoS2 and PANI. Compared with that of CoS2 nanoparticles or PANI, the electromagnetic wave absorption properties of [email protected]2 nanocomposites were significantly enhanced due to impedance matching and dielectric loss. When the mass ratio of PANI and CoS2 is 1:3, this nanocomposite exhibits excellent electromagnetic wave absorption. The maximum reflection loss can reach to −54.6 dB at electromagnetic wave frequency of 12.1 GHz and effective absorbing bandwidth is 4.76 GHz ranging from 9.63 to 14.39 GHz under corresponding nanocomposites thickness of 2.1 mm. Hence, [email protected]2 nanocomposites have potential application in electromagnetic wave absorption.
In tissue engineering, the use of scaffolds helps establish a synergistic relationship between the scaffolds and the tissues by improving cell–scaffold interaction. This interaction is enhanced when physiologically relevant biophysical cues are replicated in the artificial scaffolds. Here, we present a novel scaffold that mimics the natural anisotropy of the native extracellular matrix of tissues, fabricated by electrospinning a combination of three polymers: polycaprolactone (PCL), polyvinylidene fluoride (PVDF) and polyaniline (PANI). The scaffolds were characterized for their morphology, surface and mechanical properties. Rat cardiomyoblast (H9c2) cells, cultured on the PCL–PANI–PVDF scaffold, demonstrated cell alignment, penetration and proliferation across the entire surface area of the scaffold without any external chemical or physical stimuli. The PCL–PANI–PVDF scaffold, unlike other scaffolds, does not require post-processing or specific temperature conditions of storage, prior to use. These acellular scaffolds fabricated through polymer blending, open new avenues for research on functional acellular scaffolds for tissue engineering, based on synthetic materials.
The unparalleled large-scale commercial application of poly(3,4-ethylenedioxythiophene), otherwise known as PEDOT, continues to fuel a need for literature about it that is concise, easily available, but sufficiently comprehensive. Designed to meet the requirements of readers from different areas of expertise and experience with the substance, PEDOT: Principles and Applications of an Intrinsically Conductive Polymer provides a comprehensive overview of chemical, physical, and technical information about this preeminent and most forwardly developed electrically conductive polymer. An indispensable resource for researchers, developers, and users of PEDOT-written by the researchers who succeeded in commercializing it A necessary response to the massive interest-as well as patents and papers-spawned by PEDOT, this handbook provides basic knowledge and explores technical applications, based on information generated by universities and academic research, as well as by industrial scientists. Available in various formulations and conductivities, this versatile PEDOT can be adapted for the needs and specific industrial applications of its different users. Although valuable information exists in handbooks on polythiophene chemistry and physics, under which PEDOT falls, until now, few if any books have focused exclusively on this important conducting polymer-certainly not one that so completely elucidates both its experimental and practical aspects. This book: Begins with a brief history of conducting polymers and polythiophenes Describes the invention of PEDOT and its commercial outgrowth, PEDOT:PSS Emphasizes key technical and commercial aspects and usage of PEDOT and how they have stimulated scientific research in a wide range of fields Explains the chemical and physical background for PEDOT in terms of its primary use and incorporation in products including cellular phones and flat panel displays Valuable for readers at any level of familiarity with PEDOT, this one-stop compilation of information offers specialists several unpublished results from the authors’ celebrated work, as well as often overlooked information from patents. Balancing sufficient detail and references for further study, this book is a powerful tool for anyone working in the field. © 2010 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business.
SEM investigation of polyaniline (PAni) layers showed that it is composed of around 10 nm small globular primary particles. This is in accordance with other earlier results.
We have measured the temperature dependence of the conductivity and thermoelectric power of conducting polyaniline (PAni) dispersed in PETG copolyester and in poly(methylmethacrylate) (PMMA). Near room temperature, the blends (like unblended PAni) show a change to metallic sign for the conductivity temperature dependence, whereas this sign change does not occur for the blends. As temperature decreases, the blends show a much smaller decrease of conductivity than the blends and even unblended PAni. A simple model involving metallic conduction in addition to tunnelling between metallic particles can give a good account of all the conductivity data. The thermopower of all the blends is small and increases as temperature increases.
We report on the conductivity of submicrometre metal particles, which experience a size-induced metal-insulator transition (SIMIT). Also, their frequency behaviour and their dependence on temperature are quite different from bulk metal properties. Investigations of the conductivity of thin polyaniline layers have revealed that the two systems have some prominent properties in common; for instance both systems exhibit a pronounced relaxation process. A comparison and discussion of the similarities are presented.
Corrosion protection of metals can be obtained by coating them with polyaniline dispersions, resulting in a signifiecant and reproducible shift of the corrosion potential. Scanning electron micrograph indicate that the passivation is a multistep process, beginning with an etching stage in wh8ch grain boundaries become visible (see Figure). In the second step the metal surface is coated—non-electrochemically—with an oxide layer. The exact mechanism of formation of this layer remains to be explored.
This contribution is not really a review, but rather a reflection on possible prospective applications of intrinsically conducting polymers in various domains.
Blending polyaniline (PAn) with a host polymer has the advantage of reducing the amount of polyaniline necessary for conductivity, increasing the stability of this conduction, and enhancing the overall mechanical integrity, versatility, and processability of PAn. PAn blends have generally been observed to be immiscible, reducing many of the above mentioned advantages. In this work, PAn was solution blended with poly(vinyl pyrrolidone) (PVP) in either NMP or DMAc, both polar solvents with an amide linkage. We have found PAn to be miscible with PVP under certain processing conditions. The extent of this compatibility and resulting mechanical properties were assessed by DMA, DSC, TGA, SAXS, and light microscopy. DSC thermograms exhibit a single Tg for all blends ranging from 3 to 30% by weight PAn. Light microscopy and SAXS also suggest no phase separation. TGA results show that NMP binds very tightly to both PAn and PVP, with solvent cast blends retaining up to 20 wt% NMP, even after relatively vigorous drying. Electrical conductivity measurements of cast films show conductivity to range from 10-3 to 2 S/cm over the same composition range.
Electrically conductive polymer composites were obtained. Intrinsically conductive ingredient was poly(aniline).