Neste trabalho, é descrito uma ponte de indutâncias mútuas que pode ser usada para medidas automáticas de susceptibilidade magnética AC, em freqüências até 1 kHz. Este susceptômetro utiliza um novo e alternativo arranjo para o \"probe\". O conjunto de bobinas, mantido em temperatura ambiente, é movimentado de tal forma a posicionar a amostra no centro de cada uma das bobinas secundárias. A amostra, cuja posição é fixa, tem sua temperatura controlada por um criostato de fluxo de Hélio. O acoplamento magnético do \"probe\" com materiais na vizinhança foi minimizado com o uso de uma blindagem magnética. Este \"probe\" tem uma sensibilidade de 10-7 emu com um campo magnético AC de 8 G rms e freqüência de 100 Hz. Neste trabalho, são apresentados também alguns resultados de susceptibilidade magnética AC, obtidos em supercondutores de alto Tc e compostos intermetálicos de terras raras. A relação entre transporte de cargas e propriedades magnéticas, de poliparafenileno (PPP) dopado com FeCl3 e poli(o-metoxianilina) (POMA) dopada com TFA e HCl, foi estudada utilizando as técnicas de Susceptibilidade Magnética AC (SMAC), Ressonância Paramagnética Eletrônica (RPE) e Ressonância Magnética Nuclear (RMN). Os resultados obtidos para o PPP foram interpretados em termos de três contribuições: presença do polaron paramagnético, cuja mobilidade aumenta com o aumento da temperatura; íons Fe3+ coordenados em sítios de baixa simetria da molécula FeCl3; e íons Fe3+ fortemente acoplados via interação de troca. A dependência com a temperatura do sinal de RPE da POMA pode ser entendido em termos da dinâmica dos polarons. O estreitamento da linha de RPE, devido a dopagem do material, pode ser explicada por dois processos diferentes. Em baixas temperaturas, predomina a interação de troca polaron-polaron, modulada pelas autuações de spin. Em altas temperaturas o \"motional narrowing\" é provocado pelo aumento de mobilidade do polaron. Em temperaturas intermediárias, é observado um efeito anômalo: a largura de linha cresce abruptamente, produzindo um pico em torno de 220 K. Este pico pode ser associado a contribuição não secular para a largura de linha. Acredita-se que o espalhamento do polaron por moléculas de oxigênio, promova um aumento no mecanismo de relaxação spin-rede. Os resultados de RMN para o 1H e 19F mostram que as componentes espectrais da largura de linha, são associadas com as fases amorfa e cristalina da POMA. Neste material, a taxa de relaxação spin-rede do 1H aumenta mais de uma ordem de grandeza com a dopagem. Isto pode ser explicado por um mecanismo de relaxação envolvendo acoplamento hiperfino núcleo-polaron. / A mutual inductance bridge which may be used for automatic measurement of ac magnetic susceptibilities from 4 K to room temperature, at frequencies up to 1 kHz, is described. The susceptometer employs an alternative and new arrangement for the probe. The coil set is kept at room temperature and moves in such a way to place the sample in the center of each of the secondary coils. The sample, motionless, has its temperature controlled by a helium flow refrigerator. Use of a magnetic shield minimizes coupling of the probe with nearby materials. This probe has a sensitivity of 10-7 emu in an ac magnetic field of 8G rms and frequency of 100 Hz. Typical results of ac magnetic susceptibility, obtained in high Tc, superconductors and rare earth intermetallic compounds are shown. AC Magnetic Susceptibility, Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) were used to study the relation between charge transport and magnetic properties of polyparaphenylene (PPP) doped with FeCl3 and poly(o-methoxyaniline) (POMA) doped with TFA and HCl. The results obtained in PPP can be interpreted in terms of three major contributions: the presence of the paramagnetic polaron, whose mobility increases with increasing temperature, Fe3+ ions coordinated in the low symmetry site of the FeCl3 molecule, and Fe3+ ions strongly coupled via exchange interaction. The temperature behavior of the EPR of POMA can be understood in terms of the dynamics of the polaron. Line narrowing, induced by doping the material, can be explained by two different processes. At low temperature, polarons are coupled via exchange interaction and the exchange narrowing of the line is caused by thermal spin fluctuations. At high temperature, motional narrowing is the most efficient mechanism. At intermediate temperatures, an anomalous effect is observed: linewidth increase abruptly, showing a peak at 220 K. This peak can be associated to the non-secular contribution to the line width. It is assumed that the spin-lattice relaxation mechanism is enhanced, at this temperature, due to the polaron scattering by paramagnetic oxygen molecules. 1H and 19F NMR data shows that the linewidth spectral components are associated with the amorphous and crystalline phases of the POMA. 1H spin-lattice relaxation rates, in this material, increases more than one order of magnitude after doping. This can be explained by a relaxation mechanism involving nucleus-polaron hyperfine coupling.

The interest in conjugated polymers has been two-fold. A rich variety of intriguing physical phenomena, combined with its immense technological implications in the area of molecular electronics, sensors etc. has inspired the researchers all over the globe. The work presented in this thesis is focussed on one of the most widely studied conjugated polymers, namely polyaniline (PANI), which is well known for its high conductivity and remarkable stability in the proton-doped form. The thesis is divided into two chapters and each chapter is further divided into several parts. In the first chapter, we take a look at some novel systems based on PANI that exhibit interesting electrical and optical properties. To begin with, we report the synthesis and characterization (Part I, Chapter 3) a new class of highly conducting polyaniline doped with electron deficient Lewis acids, namely the boron trihalides (BX3, X = F, Cl, and Br). We discuss the various attributes of this interesting class of materials that set it apart from the conventional proton-doped PANI systems. It is known that the conductivity in doped PANI is greatly influenced by the presence of structural disorder. Previous studies have associated the conductivity in doped PANI with the partial crystallinity that is achieved upon proton doping. At the same time, the amorphous regions that have a high degree of disorder were believed to suppress the metallic nature in these doped systems. In view of this "higher-crystallinity-higher-conductivity" picture, it is interesting to note that the BX3 doped PANI remain absolutely amorphous despite being more conducting than previously known samples. Through our investigation, we have been able to address some of the most important and long-standing questions pertaining to the nature of the charge carriers and the role of disorder in doped PANI. A detailed study of the transport properties in Part II, Chapter 3 helps us to understand the mechanism of charge transfer in these novel systems. With the help of our results, we establish that the present systems do not belong to the family of quasi one-dimensional conductors, in stark contrast to the conventional proton-doped samples. Instead, our systems are best described as granular metals, where the conduction mechanism is controlled by the size of the conducting grains and the nature of the grain boundaries. Through a comprehensive study of the magnetic properties based on d. c. magnetic susceptibility and EPR spectroscopy, we further establish that the intrinsic conductivity of these samples are much higher than the previously known systems. By studying the interaction of the mobile charge carriers and the localized spins in the systems, we have established that our samples are far less disordered, and therefore qualify as superior systems when compared to the more conventional proton-doped PANI. One of the serious disadvantages of the conventional protonated PANI lies in its thermal instability. On heating above 75 ±C in air, the polymer backbone undergoes an irreversible aerial oxidation that disrupts the extended conjugated structure. This is marked by a rapid drop in conductivity by a few orders of magnitude. BF3-doped PANI, which has the highest conductivity sample among the present series of samples, exhibits a remarkable thermal stability in air (Part III, Chapter 3). Upon heating, the conductivity initially increases and then reaches a saturation value. The polymer can be heated at temperatures as high as 225 ±C, without any signs of degradation. With the help of temperature dependent conductivity, XPS and FTIR spectroscopy we have tried to understand this unexpected phenomenon. In Part IV, Chapter 3, we report the synthesis and characterization of a novel class of functionalized PANI that exhibit an intense deep-blue photoluminescence. A de- tailed characterization based on absorption, photoluminescence, XPS, NMR and FTIR spectroscopy has been carried out to study the chemical state of this new class of light- emitting polymers. Further, we note that the synthetic procedure followed in this work can provide a very general route to the synthesis of diversely useful derivatives of PANI. In Chapter 4, we have investigated the microscopic origin of conductivity in doped PANI. Among the several factors that can influence the conductivity of doped polymers, one is the microstructural order. To understand this better, we carried out a detailed investigation, based on scanning tunneling microscopy (STM) and spectroscopy (STS) of undoped and doped PANI films (Part I, Chapter 4). We have shown for the ¯rst time that solution processed thin films of undoped PANI has an abundance of PANI anorods self organized over very large areas. Further, we observe that this ordered orphology is Preface vii very sensitive to the choice of dopants and the doping procedure. We have shown that the morphological order can greatly influence the electronic structure and therefore the properties of these systems. To understand the role of dopant-polymer interaction in controlling the conductivity of doped PANI, we carried out x-ray photoelectron spectroscopy (XPS) studies on a large number of partially and fully doped samples (Part II, Chapter 4). We find an interesting trend in the higher binding energy feature and the asymmetry of the N and C 1s spectra, which correlates directly with the respective conductivities of different samples. The analysis of these spectra brings out interesting facts about the chemical state and the electronic structure of these samples. In summary, we have reported new PANI based systems with improved electrical and interesting optical properties, and have studied various factors that influence the properties of these as well as some of conventional doped PANI systems.

Neste trabalho, é descrito uma ponte de indutâncias mútuas que pode ser usada para medidas automáticas de susceptibilidade magnética AC, em freqüências até 1 kHz. Este susceptômetro utiliza um novo e alternativo arranjo para o \"probe\". O conjunto de bobinas, mantido em temperatura ambiente, é movimentado de tal forma a posicionar a amostra no centro de cada uma das bobinas secundárias. A amostra, cuja posição é fixa, tem sua temperatura controlada por um criostato de fluxo de Hélio. O acoplamento magnético do \"probe\" com materiais na vizinhança foi minimizado com o uso de uma blindagem magnética. Este \"probe\" tem uma sensibilidade de 10-7 emu com um campo magnético AC de 8 G rms e freqüência de 100 Hz. Neste trabalho, são apresentados também alguns resultados de susceptibilidade magnética AC, obtidos em supercondutores de alto Tc e compostos intermetálicos de terras raras. A relação entre transporte de cargas e propriedades magnéticas, de poliparafenileno (PPP) dopado com FeCl3 e poli(o-metoxianilina) (POMA) dopada com TFA e HCl, foi estudada utilizando as técnicas de Susceptibilidade Magnética AC (SMAC), Ressonância Paramagnética Eletrônica (RPE) e Ressonância Magnética Nuclear (RMN). Os resultados obtidos para o PPP foram interpretados em termos de três contribuições: presença do polaron paramagnético, cuja mobilidade aumenta com o aumento da temperatura; íons Fe3+ coordenados em sítios de baixa simetria da molécula FeCl3; e íons Fe3+ fortemente acoplados via interação de troca. A dependência com a temperatura do sinal de RPE da POMA pode ser entendido em termos da dinâmica dos polarons. O estreitamento da linha de RPE, devido a dopagem do material, pode ser explicada por dois processos diferentes. Em baixas temperaturas, predomina a interação de troca polaron-polaron, modulada pelas autuações de spin. Em altas temperaturas o \"motional narrowing\" é provocado pelo aumento de mobilidade do polaron. Em temperaturas intermediárias, é observado um efeito anômalo: a largura de linha cresce abruptamente, produzindo um pico em torno de 220 K. Este pico pode ser associado a contribuição não secular para a largura de linha. Acredita-se que o espalhamento do polaron por moléculas de oxigênio, promova um aumento no mecanismo de relaxação spin-rede. Os resultados de RMN para o 1H e 19F mostram que as componentes espectrais da largura de linha, são associadas com as fases amorfa e cristalina da POMA. Neste material, a taxa de relaxação spin-rede do 1H aumenta mais de uma ordem de grandeza com a dopagem. Isto pode ser explicado por um mecanismo de relaxação envolvendo acoplamento hiperfino núcleo-polaron. / A mutual inductance bridge which may be used for automatic measurement of ac magnetic susceptibilities from 4 K to room temperature, at frequencies up to 1 kHz, is described. The susceptometer employs an alternative and new arrangement for the probe. The coil set is kept at room temperature and moves in such a way to place the sample in the center of each of the secondary coils. The sample, motionless, has its temperature controlled by a helium flow refrigerator. Use of a magnetic shield minimizes coupling of the probe with nearby materials. This probe has a sensitivity of 10-7 emu in an ac magnetic field of 8G rms and frequency of 100 Hz. Typical results of ac magnetic susceptibility, obtained in high Tc, superconductors and rare earth intermetallic compounds are shown. AC Magnetic Susceptibility, Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) were used to study the relation between charge transport and magnetic properties of polyparaphenylene (PPP) doped with FeCl3 and poly(o-methoxyaniline) (POMA) doped with TFA and HCl. The results obtained in PPP can be interpreted in terms of three major contributions: the presence of the paramagnetic polaron, whose mobility increases with increasing temperature, Fe3+ ions coordinated in the low symmetry site of the FeCl3 molecule, and Fe3+ ions strongly coupled via exchange interaction. The temperature behavior of the EPR of POMA can be understood in terms of the dynamics of the polaron. Line narrowing, induced by doping the material, can be explained by two different processes. At low temperature, polarons are coupled via exchange interaction and the exchange narrowing of the line is caused by thermal spin fluctuations. At high temperature, motional narrowing is the most efficient mechanism. At intermediate temperatures, an anomalous effect is observed: linewidth increase abruptly, showing a peak at 220 K. This peak can be associated to the non-secular contribution to the line width. It is assumed that the spin-lattice relaxation mechanism is enhanced, at this temperature, due to the polaron scattering by paramagnetic oxygen molecules. 1H and 19F NMR data shows that the linewidth spectral components are associated with the amorphous and crystalline phases of the POMA. 1H spin-lattice relaxation rates, in this material, increases more than one order of magnitude after doping. This can be explained by a relaxation mechanism involving nucleus-polaron hyperfine coupling.

Following the discovery of electronic conductivity in doped polyacetylene, various studies on conducting polymers have been investigated. These polymers are essentially characterized by the presence of conjugated bonding on polymer backbone, which facilitates formation of polarons and bipolarons as charge carriers. Poly(3,4-ethylenedioxythiophene) (PEDOT) is an interesting polymer because of high electronic conductivity, ease of synthesis and high chemical stability. Electrochemically prepared PEDOT is more interesting than the polymer prepared by chemical routes because it adheres to the electrodes surface and the PEDOT coated electrodes can directly be used for various applications such as batteries, supercapacitor, sensors, etc. A majority of the studies described in the thesis are based on PEDOT. Studies on polyanthanilic acid and reduction of hydrogen peroxide on stainless steel substrate are also included. Chapter 1 provides an introduction to conducting polymers with a focus on synthesis, electrochemical characterization and applications of PEDOT. In Chapter 2, microscopic and impedance spectroscopic characterization of PEDOT coated on stainless steel (SS) and indium tin oxide (ITO) coated glass substrates are described. Electrosynthesis of PEDOT is carried out on SS electrodes by three different techniques, namely, potentiostatic, galvanostatic and potentiodynamic techniques. The SEM images of PEDOT prepared by the galvanostatatic and potentiostatic routes indicate globular morphology. However, it is seen that porosity increases by increasing the current or the potential. In the cases of both galvanostatic and potentiostatic routes, the oxidation of EDOT to form PEDOT takes place continuously during preparation. However, in the case of potentiodynamic experiment between 0 and 0.9 V vs. SCE (saturated calomel electrode), the formation of PEDOT occurs only when the potential is greater than 0.70 V. During multicycle preparation to grow thicker films of PEDOT, formation of PEDOT takes place layer by layer, a layer of PEDOT being formed in each potential cycle. PEDOT prepared in the potential ranges 0-0.90 V and 0-1.0 V show globular morphology similar to the morphology of the galvanostatically and potentiostatically prepared polymer. If prepared in the potential ranges 0-1.1 V and 0-1.2 V, the PEDOT films have rod-like and fibrous morphology. This is attributed to larger amount of PEDOT formed in each cycle in comparison with lower potential ranges and also to partial oxidation of PEDOT at potentials ≥ 1.10 V. PEDOT is also electrochemically prepared on ITO coated glass substrate. Preparation is carried out under potentiostatic conditions in the potential range between 0.9 and 1.2 V. Atomic force microscopy (AFM) studies indicate a globular topography for PEDOT films prepared on ITO coated glass plates. The height and width of globules increase with an increase in deposition potential. The PEDOT coated SS electrodes are subjected to electrochemical impedance spectroscopy studies in 0.1 M H2SO4. The Nyquist plot of impedance consists of a depressed semicircle, which arises due to a parallel combination of the polymer resistance and double-layer capacitance (Cdl). Impedance data are analyzed. Studies on electrooxidation of methanol, formic acid, formaldehyde and ethanol on nanocluster of Pt and Pt-Ru deposited on PEDOT/C electrode are reported in Chapter 3. Studies on electrooxidation of small molecules are important in view of their promising applications in fuel cells. Films of PEDOT are electrochemically deposited on carbon paper. Nanoclusters of Pt and bimetallic Pt-Ru catalysts are potentiostatically deposited on PEDOT/C electrodes. Catalysts are also prepared on bare carbon paper for studying the effect of PEDOT. The presence of PEDOT film on carbon paper allows the formation of uniform, well dispersed nanoclusters of Pt as well as Pt-Ru catalysts. TEM studies suggest that the nanoclusters of about 50 nm consist of nanoparticles of about 5 nm in diameter. Electrooxidation of methanol, formic acid, formaldehyde and ethanol are studied on Pt-PEDOT/C and PtRu-PEDOT/C electrodes by cyclic voltammetry and chronoamperometry. The data for oxidation of these small organic molecules reveal that PEDOT imparts a greater catalytic activity for the Pt and Pt-Ru catalysts. Results of these studies are described in Chapter 3. In Chapter 4, PEDOT is coated on SS substrate to investigate phenol oxidation. Studies on electrochemical oxidation of phenol are interesting because it is important to remove phenol from contaminated water or industrial effluents. Deactivation of the anode due to the formation and adsorption of polyoxyphenylene on its surface is a common problem for a variety of electrode materials, during phenol oxidation. Investigations on suitable anode materials, which can undergo no or moderate poisoning by polyoxyphenylene, are interesting. In the present study, it is shown that the electrooxidation rate of phenol is greater on PEDOT/SS electrodes than on Pt. Deactivation of PEDOT/SS electrode is slower in relation to Pt. The oxidation of phenol on PEDOT/SS electrode occurs to form both polyoxyphenylene and benzoquinone in parallel. Cyclic voltammetry of phenol oxidation is studied by varying the concentration of phenol, sweep rate and thickness of PEDOT. Ac impedance studies indicate a gradual increase in polymer resistance due to adsorption of polyoxyphenylene during multi sweep cyclic voltammetry. This investigation reveals that PEDOT coated on a common metal or alloy such as SS is useful for studying electrooxidation of phenol, which is generally studied on a noble metal based electrodes. Electrochemically prepared PEDOT is used for supercapacitor studies and the results are presented in Chapter 5. Generally, electronically conducting polymers possess high capacitive properties due to pseudo-faradaic reactions. PEDOT/SS electrodes prepared in 0.1 M H2SO4 are found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes are studied. Specific capacitance values as high as 250 F g-1 in 1 M oxalic acid are obtained during the initial stages of cycling. However, there is a decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. Self-doped PANI is expected to possess superior electrochemical characteristics in relation to PANI. The self-doping is due to the presence of an acidic group on the polymer chain. However, self-doped PANI is soluble in acidic solutions against insolubility of PANI. In the present study, poly(anthranilic acid), PANA, is encapsulated in porous Nafion membrane by chemical and a novel electrochemical methods. PANA present in solid form in Nafion membrane does not undergo dissolution in acidic solutions. The methods of preparation and various electrochemical, optical and spectroscopic characterizations studies of PANA-Nafion are described in Chapter 6. Electroreduction of H2O2 is studied on sand-blasted stainless steel (SSS) electrode in an aqueous solution of NaClO4 and the details are reported in Chapter 7. The cyclic voltammetric reduction of H2O2 at low concentrations is characterized by a cathodic peak at -0.40 V versus standard calomel electrode (SCE). Cyclic voltammetry is studied by varying the concentration of H2O2 in the range from 0.2 mM to 20 mM and the sweep rate in the range from 2 to 100 mV s-1. Cyclic voltammograms at concentrations of H2O2 higher than 2 mM or at high sweep rates consist of an additional current peak, which may be due to the reduction of adsorbed species formed during the reduction of H2O2. Amperometric determination of H2O2 at -0.50 V vs. SCE provides the detection limit of 5 μM H2O2. A plot of current density versus concentration has two linear segments suggesting a change in the mechanism of H2O2 reduction at concentrations of H2O2 ≥ 2 mM. From the rotating disc electrode study, diffusion co-efficient of H2O2 and rate constant for reduction of H2O2 are evaluated. Thus, stainless steel, which is inexpensive and a common alloy, is useful for studying electrochemical reduction of H2O2 and also for analytical application. This work is initiated to study the reduction of H2O2 on PEDOT/SS electrodes. As a result of preliminary experiments, it is found that PEDOT does not exhibit any influence on the kinetics of H2O2 reduction. Therefore studies conducted using bare stainless steel are included in this chapter. Results of the above studies are described in the thesis.

Polyaniline (PANI), when doped with small-molecule acids, is an attractive candidate for organic and polymer electronics because of its high electrical conductivity. Its utility as functional components in electrical devices, however, has been severely restricted because such PANI has limited processibility stemming from its limited solubility in common solvents. To overcome this barrier, we have developed water dispersible PANI that is template polymerized in the presence of a polymer acid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), or PAAMPSA. The polymer acid serves two roles: it acts as a dopant to render PANI conductive and excess water soluble pendant groups provide dispersibility of PANI in aqueous media. While the introduction of polymer acids renders the conducting polymer processible, such gain in processibility is often accompanied by a significant reduction in conductivity. As such, PANI that is doped with polymer acids has only seen limited utility in organic electronics. Given the promise of conducting polymers in organic electronics in general, this thesis focuses on the elucidation of processing-structure-property relationships of PANI-PAAMPSA with the aim of ultimately improving the electrical conductivity of polymer acid-doped PANI. By controlling the molecular weight and molecular weight distribution of the polymer acid template, we have improved the conductivity of PANI-PAAMPSA from 0.4 to 2.5 S/cm. The conductivity increases with decreasing molecular weight of PAAMPSA, and it further increases with narrowing the molecular weight distribution of PAAMPSA. Strong correlations between the structure and the conductivity of PANI-PAAMPSA are observed. In particular, the crystallinity of PANI increases with increasing the conductivity of PANI-PAAMPSA. Given that the crystallinity qualifies the molecular order in PANI-PAAMPSA, we observe a linear correlation between molecular order and macroscopic charge transport in PANI-PAAMPSA. PANI-PAAMPSA forms electrostatically stabilized sub-micron particles during polymerization due to strong ionic interactions between the sulfonic acid groups of PAAMPSA and aniline. When cast as films, the connectivity of these particles must play an important role in macroscopic conduction. The size and size distribution of PANI-PAAMPSA particles is strongly influenced by the molecular characteristics of polymer acid template. Templating the synthesis of PANI-PAAMPSA with a higher molecular weight PAAMPSA results in larger particles, and templating with a PAAMPSA having a larger molecular weight distribution results in a large size distribution in the particles. Because conduction in PANI-PAAMPSA films is governed by how these particles pack, the macroscopic conductivity of PANI-PAAMPSA films increases with increasing particle density, that is reducible from the molecular characteristics of PAAMPSA. Moreover, PANI-PAAMPSA particles are structurally and chemically inhomogeneous. The conductive portions of the polymer preferentially segregate to the particle surface. Conduction in these materials is therefore mediated by the particle surface and conductivity thus scales superlinearly with particle surface area per unit film volume. We further have improved the electrical conductivity of PANI-PAAMPSA by more than two orders of magnitude via post-processing solvent annealing with dichloroacetic acid (DCA). Since DCA is a good plasticizer for PAAMPSA and its pKa is lower than that of PAAMPSA (pKas of DCA and PAAMPSA are 1.21 and 2.41, respectively, at room temperature), DCA can effectively moderate the ionic interactions between PANI and PAAMPSA, thereby relaxing the sub-micron particulate structure arrested during polymerization. PANI-PAAMPSA can thus rearrange from a “compact coil” to an “extended chain” conformation upon exposure to DCA. Efficient charge transport is thus enabled through such “extended chain” PANI-PAAMPSA structure. DCA-treated PANI-PAAMPSA exhibits an average conductivity of 48 S/cm. The DCA treatment is not only specific to PANI-PAAMPSA. This treatment can also enhance the conductivity of commercially-available poly(ethylene dioxythiophene) that is doped with poly(styrene sulfonic acid), or PEDOT-PSS. Specifically, DCA-treated PEDOT-PSS exhibits a conductivity of 600 S/cm; this conductivity is the highest among polymer acid-doped conducting polymers reported so far. PANI-PAAMPSA can effectively function as anodes in organic solar cells (OSCs) whose active layer is a blend of poly(3-hexylthiophene), P3HT, and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Specifically, the OSCs with PANI-PAAMPSA anodes exhibit an average short circuit current density of 1.95 mA/cm², open circuit voltage of 0.52 V, fill factor of 0.38, and efficiency of 0.39 %. The use of DCA-treated PANI-PAAMPSA as anodes increases device performance (i.e., short circuit current density and thereby efficiency) of OSCs by approximately two and a half fold. The OSCs with DCA-treated PANI-PAAMPSA anodes exhibit short circuit current density and efficiency as high as 4.95 mA/cm² and 0.97 %, respectively. We demonstrated several factors that govern the electrical conductivity of polymer acid-doped conducting polymers. Design rules, such as those illustrated in this study, can enable the development of conducting polymers that is not only easily processible from aqueous dispersions, but also sufficiently conductive for electronic applications, and should bring us closer to the realization of low-cost organic and polymeric electronics. / text

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