Showing papers on "Conductive polymer published in 2005"

Reversible conversion of conducting polymer films from superhydrophobic to superhydrophilic

Abstract: Controlling the wettability of a solid surface is important for myriad applications, ranging from self-cleaning surfaces to microfluidics to biomedicine. Recently, a variety of smart surfaces with reversibly switchable wettability have been developed. The reversible switching is realized through the adjustment of electrical potential, temperature, 8] and light illumination, adsorption of biopolymer, and treatment of selective solvents. Among these approaches, the switch of the electrical potential receives special attention because it is simple and conveniently controlled by electricity. Moreover, the switching is readily individually addressable when an array of small surfaces is involved. Lahann et al. constructed a reversibly switching surface by depositing a low-density carboxylate-terminated self-assembled monolayer on a gold surface. Electrical potential was used to trigger the conformational transition of the monolayer, resulting in switching of the surface wettability. However, the change in surface wettability is small (20 to 308 water contact angle), which is likely to limit its practical applications. It is reported that ZnO films and poly(N-isopropylacrylamide)-modified patterned surfaces can undergo reversible wettability switching between two extremes, superhydrophobicity (water contact angle> 1508) and superhydrophilicity (water contact angle< 58) through the use of ultraviolet light and a temperature change, respectively. The photoswitching requires several days to achieve the hydrophilic-to-hydrophobic conversion, and both the photoswitching and thermal switching are difficult to implement to individually address an array of small surfaces. Herein we report a simple electrochemical process to fabricate superhydrophobic conducting polypyrrole (PPy) films and demonstrate that their properties can be switched conveniently from superhydrophobic to superhydrophilic by changing the electrical potential. Conducting polymers (also called conjugated polymers or synthetic metals) such as polypyrrole (PPy) have been studied in great detail because their unique optical, electrical, and mechanical properties offer many new possibilities for device fabrication. Interest has recently developed in their surface properties such as wettability because of potential applications in corrosion protection, conductive textiles, and antistatic coatings, and in the immobilization of biopolymers and growth control of living cells. Usually the conducting polymers contain a positively charged conjugated backbone and negatively charged counterions (dopants). The wettability of conducting polymers depends greatly on the types of dopants used. For example, a PPy film containing a perfluorinated dopant exhibited hydrophobicity (water contact angle> 908), while ClO4 -doped PPy was hydrophilic. Furthermore, the doping level can be controlled by changing the electrical potential, resulting in reversibly switchable surface wettability. Scheme 1

Facile Synthesis of End-Functionalized Regioregular Poly(3-alkylthiophene)s via Modified Grignard Metathesis Reaction

Abstract: A simple method for the synthesis of end-functionalized regioregular poly(3-alkylthiophene)s is presented. Using a modified Grignard metathesis (GRIM) reaction, a series of polymers have been synthesized bearing functional groups on one or both ends of the polymer. This method has been demonstrated to work with a variety of different types of Grignard reagents (i.e., aryl, alkyl, allyl, vinyl, etc.). The reactivity of these depends on their nature, where allyl, ethynyl, and vinyl groups produced monofunctionalized polymers, and all others yielded difunctionalized polymers. The end group composition of the polymers was monitored by a combination of MALDI-TOF and 1H NMR and approaches 100% in most cases. By utilizing the proper protecting groups −OH, −CHO, and −NH2 groups have been incorporated onto the polymer ends. The main advantage of this method is that it allows for the in situ functionalization of regioregular polythiophene, generating a variety of end-capped polymers in one step. This approach is ad...

Organic Photovoltaics : Mechanisms, Materials, and Devices

Abstract: Foreword 1 Alan J. Heeger, Nobel Laureate, University of California at Santa Barbara Foreword 2 Aloysius F. Hepp and Sheila G. Bailey, Photovoltaic and Space Environments Branch, NASA Glenn Research Center Preface Acknowledgements Editors Contributors General Overviews The Story of Solar Cells J. Perlin Inorganic Photovoltaic Materials and Devices: Past, Present, and Future A.F. Hepp, S.G. Bailey, and R.P. Raffaelle Natural Organic Photosynthetic Solar Energy Transduction R.E. Blankenship Solid-State Organic Photovoltaics: A Review of Molecular and Polymeric Devices P.A. Lane and Z.H. Kafafi Mechanisms and Modeling Simulations of Optical Processes in Organic Photovoltaic Devices N-K. Persson and O. Inganas Coulomb Forces in Excitonic Solar Cells B.A. Gregg Electronic Structure of Organic Photovoltaic Materials: Modeling of Exciton-Dissociation and Charge-Recombination Processes J. Cornil, V. Lemaur, M.C. Steel, H. Dupin, A. Burquel, D. Beljonne, and J-L. Bredas Optimization of Organic Solar Cells in Both Space and Energy-Time Domains S-S. Sun and C.E. Bonner Materials and Devices Bulk Heterojunction Solar Cells H. Hoppe and N.S. Sariciftci Organic Solar Cells Incorporating a p-i-n Junction and a p-n Homojunction M. Hiramoto Liquid-Crystal Approaches to Organic Photovoltaics B. Kippelen, S. Yoo, J.A. Haddock, B. Domercq, S. Barlow, B. Minch, W. Xia, S.R. Marder, and N.R. Armstrong Photovoltaic Cells Based on Nanoporous Titania Films Filled with Conjugated Polymers K.M. Coakley and M.D. McGehee Solar Cells Based on Cyanine and Polymethine Dyes H. Tian and F. Meng Semiconductor Quantum Dot Based Nanocomposite Solar Cells M.H. Wu, A. Ueda, and R. Mu Solar Cells Based on Composites of Donor Conjugated Polymers and Carbon Nanotubes E. Kymakis and G.A.J. Amaratunga Photovoltaic Devices Based on Polythiophene/C60 L.S. Roman Alternating Fluorene Copolymer-Fullerene Blend Solar Cells O. Inganas, F. Zhang, X. Wang, A. Gadisa, N-K. Persson, M. Svensson, E. Perzon, W. Mammo, and M.R. Andersson Solar Cells Based on Diblock Copolymers: A PPV Donor Block and a Fullerene Derivatized Acceptor Block R.A. Segalman, C. Brochon, and G. Hadziioannou Interface Electronic Structure and Organic Photovoltaic Devices Y. Gao The Influence of the Electrode Choice on the Performance of Organic Solar Cells A.B. Djurisic' and C.Y. Kwong Conducting and Transparent Polymer Electrodes F. Zhang and O. Inganas Progress in Optically Transparent Conducting Polymers V. Seshadri and G.A. Sotzing Optoelectronic Properties of Conjugated Polymer/Fullerene Binary Pairs with Variety of LUMO Level Differences S. Sensfuss and M. Al-Ibrahim Polymer-Fullerene Concentration Gradient Photovoltaic Devices by Thermally Controlled Interdiffusion M. Drees, R.M. Davis, and R. Heflin Vertically Aligned Carbon Nanotubes for Organic Photovoltaic Devices M.H-C. Jin and L. Dai Index

Semiconducting polymers: chemistry, physics and engineering

Abstract: Foreword. Preface. List of Contributors. VOLUME 1. Synthetic Methods. 1 Synthetic Methods for Semiconducting Polymers (Alberto Bolognesi and Maria Cecilia Pasini). 1.1 Introduction and Overview. 1.2 Synthetic Pathways for PA. 1.3 Conjugated Polymers by Step-Growth Polymerizations. 1.4 Block Copolymers. 1.5 Towards Autoorganized Devices. References. 2 Processable Semiconducting Polymers Containing Oligoconjugated Blocks (Joannis K. Kallitsis, Panagiotis K. Tsolakis, and Aikaterini K. Andreopoulou). 2.1 Introduction. 2.2 Rod-Coil Block Copolymers. 2.3 Alternating Conjugated-Nonconjugated Polymers. References. Structure/Morphology. 3 Interfacial Aspects of Semiconducting Polymer Devices (Richard A. L. Jones). 3.1 Introduction. 3.2 Some Basics of Polymer Blend Thermodynamics and Dynamics. 3.3 Surface Segregation, Surface-driven Phase Separation, Wetting and Self-Stratification. 3.4 Morphology in Thin Films of Semiconducting Polymer Blends. 3.5 Surface Segregation in Polymer-doped Conducting Polymers. 3.6 Interface Structure. 3.7 Conclusions. References. Electronic Structure of Interfaces. 4 Electronic Structure of Surfaces and Interfaces in Conjugated Polymers (Michael Logdlund, Mats Fahlman, Stina K.M. Jonsson, and William R. Salaneck). 4.1 Introduction. 4.2 Photoelectron Spectroscopy. 4.3 Theoretical Approaches. 4.4 Materials. 4.5 Charge Storage States in Conjugated Polymers. 4.6 Interface Formations in Conjugated Systems. 4.7 Summary. References. Photophysics. 5 Photophysics of Conjugated Polymers (Lewis Rothberg). 5.1 Introduction and Overview. 5.2 Definitions and Terminology. 5.3 Spectroscopy. 5.4 Photophysics. 5.5 Summary. 5.6 Conclusion. References. 6 Photophysics in Semiconducting Polymers: The Case of Polyfluorenes (Christoph Gadermaier, Larry Luer, Alessio Gambetta, Tersilla Virgili, Margherita Zavelani-Rossi, and Guglielmo Lanzani). 6.1 Introduction. 6.2 Experimental. 6.3 Low-Dimensional Physics in Conjugated Chains. 6.4 Ground-State Absorption and cw Photoluminescence. 6.5 Long-Lived Photoexcitation in Polyfluorenes (PFs). 6.6 Singlet Exciton Dynamics. 6.7 On-Chain Emissive Defects. 6.8 Charged Excitations and Their Photogeneration Mechanism. 6.9 Intrachain Dynamics. 6.10 Three-Pulse Time-Resolved Experiments. 6.11 Light-Emitting-Diode-Related Dynamics in the Ultrafast Timescale. References. 7 Spectroscopy of Photoexcitations in Conjugated Polymers (Z. Valy Vardeny and Markus Wohlgenannt). 7.1 Introduction. 7.2 Experimental Methods. 7.3 Experimental Results: cw PA Spectroscopy. 7.4 Transient Pump-and-Probe Spectroscopy. 7.5 Multiple-Pulse Transient Spectroscopy. 7.6 ODMR Spectroscopy: Measurement of Spin-Dependent Polaron Recombination Rates. 7.7 Summary. References. Transport/Injection. 8 Charge Transport in Neat and Doped Random Organic Semiconductors (Vladimir I. Arkhipov, Igor I. Fishchuk, Andriy Kadashchuk, and Heinz Bassler). 8.1 Introduction. 8.2 Charge Generation. 8.3 Charge-Carrier Hopping in Noncrystalline Organic Materials. 8.4 Experimental Techniques. 8.5 Experimental Results. 8.6 Conclusions. References. 9 Charge Transport and Injection in Conjugated Polymers (Paul W.M. Blom, Cristina Tanase, and Teunis van Woudenbergh). 9.1 Introduction. 9.2 Charge Transport. 9.3 Charge Injection. References. VOLUME 2. Applications. 10 Physics of Organic Light-Emitting Diodes (Ian H. Campbell, Brian K. Crone, and Darryl L. Smith). 10.1 Introduction. 10.2 Thin Films of Organic Semiconductors. 10.3 Device Electronic Structure. 10.4 Single-Layer Devices. 10.5 Multilayer Devices. 10.6 Conclusions. References. 11 Conjugated Polymer-Based Organic Solar Cells (Gilles Dennler, Niyazi Serdar Sariciftci, and Christoph J. Brabec). 11.1 Introduction. 11.2 Conjugated Polymers as Photoexcited Donors. 11.3 Bulk-Heterojunction Solar Cells. 11.4 Determining Parameters of Bulk-Heterojunction Solar Cells. 11.5 From Basics to Applications. 11.6 Conclusions. References. 12 Organic Thin-Film Transistors (Gilles Horowitz). 12.1 Introduction. 12.2 The MISFET - A Reminder. 12.3 The Organic Transistor - What's Different? 12.4 Charge-Transport Mechanisms. 12.5 Concluding Remarks. References. 13 n-Channel Organic Transistor Semiconductors for Plastic Electronics Technologies (Howard E. Katz). 13.1 Plastic Electronics Technology and Organic Semiconductors. 13.2 n-Channel OFET Semiconductors. 13.3 Conclusion. References. 14 Photochromic Diodes (Xavier Crispin, Peter Andersson, Nathaniel D. Robinson, Yoann Olivier, Jerome Cornil, and Magnus Berggren). 14.1 Introduction. 14.2 Photochromic Molecules. 14.3 Organic Diodes. 14.4 Electronic Switches - Device Concepts. 14.5 Conclusions. References. 15 Organic/Polymeric Thin-Film Memory Devices (Yang Yang, Jianyong Ouyang, Liping Ma, Jia-Hung Tseng, and Chih-Wei Chu). 15.1 Introduction. 15.2 Review of Polymer and Organic Memory. 15.3 OMO Nanoparticle Layered Memory Devices. 15.4 Polymer-Blend Composite System. 15.5 Advanced Memory Device Architecture. 15.6 Conclusion. References. 16 Biosensors Based on Conjugated Polymers (Hoang-Anh Ho and Mario Leclerc). 16.1 Introduction. 16.2 Different Types of CPs. 16.3 Colorimetric Methods. 16.4 Fluorometric Methods. 16.5 Electrochemical Methods. 16.6 Conclusions and Perspectives. References. Processing. 17 Manufacturing of Organic Transistor Circuits by Solution-Based Printing (Henning Sirringhaus, Christoph W. Sele, Timothy von Werne, and Catherine Ramsdale). 17.1 Introduction to Printed Organic Thin-Film Transistors. 17.2 Overview of Printing-Based Manufacturing Approaches for OTFTs. 17.3 High-Resolution, Self-Aligned Inkjet Printing. 17.4 Performance and Reliability of Solution-Processed OTFTs for Applications in Flexible Displays. 17.5 Conclusions. References. 18 High-Resolution Composite Materials for Organic Electronics (Graciela Blanchet). 18.1 Introduction. 18.2 Building Blocks. 18.3 Large-Area Printing Process and Devices. 18.4 Printable Materials. 18.5 Conclusion. References. Subject Index.

Polyaniline: Thin films and colloidal dispersions (IUPAC Technical Report)

Abstract: Several workers from various institutions in six countries have prepared thin films and colloidal polyaniline dispersions. The films were produced in situ on glass supports during the oxidation of anilinium chloride with ammonium peroxydisulfate in water. The average thickness of the films, assessed by optical absorption, was 125 ′ 9 nm, and the conductivity of films was 2.6 ′ 0.7 S cm - 1 . Films prepared in 1 mol 1 - 1 HCI had a similar thickness, 109 ′ 10 nm, but a higher conductivity, 18.8 ′ 7.1 S cm - 1 . Colloidal polyaniline particles stabilized with a water-soluble polymer, poly(N-vinylpyrrolidone) [poly(1-vinylpyrrolidin-2-one)], have been prepared by dispersion polymerization. The average particle size, 241 ′ 50 nm, and polydispersity, 0.26 ′ 0.12, have been determined by dynamic light scattering. The preparation of these two supramolecular polyaniline forms was found to be well reproducible.

Carbon nanotube--conducting-polymer composite nanowires.

Abstract: Polypyrrole/carbon nanotube (PPy/CNT) composite nanowires were prepared by a template-directed electrochemical synthetic route, involving plating of PPy into the pores of a host membrane in the presence of shortened and carboxylated CNT dopants (without added electrolyte). Cyclic voltammetric growth profiles indicate that the CNT is incorporated within the growing nanowire and serves as the sole charge-balancing “counterion”. Transmission electron microscopy images indicate high-quality straight PPy/CNT nanowires with a smooth and featureless surface and a uniform diameter. The presence of the CNT dopant imparts high conductivity (Ohmic I−V behavior) onto these PPy/CNT nanowires. By combining the attractive properties of CNTs, conducting polymers, and nanowires, the new nanocomposite opens up new opportunities, ranging from chemical sensors to molecular electronic devices.

Flash welding of conducting polymer nanofibers

Abstract: The welding of certain polymeric nanofibers can be accomplished by exposure to an intense short burst of light, such as is provided by a camera flash, resulting in an instantaneous melting of the exposed fibers and a welding of the fibers where they are in contact. The preferred nanofibers are composed of conjugated, conducting polymers, and derivatives and polymer blends including such materials. Alternatively, the nanofibers can be composed of colored thermoplastic polymeric fibers or opaque polymers by proper selection of the frequency or frequency range and intensity (power) of the light source. The flash welding process can also be used to weld nanofibers which comprise a blend of polymeric materials where at least one of the materials in the blend used to form the nanofiber is a conductive, conjugated polymer or a suitable colored thermoplastic. Alternatively the material blend used to form the nanofibers may comprise a polymeric material containing a colored additive, which is not necessarily a polymer, for example carbon black, or a colored nano-particulate organic or inorganic material, dye or pigment.

A Processable Green Polymeric Electrochromic

Abstract: We report electrochemical and optical properties of the first electrochemically and chemically prepared green, soluble conducting polymer in its neutral form. Oxidative electrochemical and chemical polymerization of dioctyl-substituted 2,3-di(thien-3-yl)-5,7-di(thien-2-yl)thieno[3,4-b]pyrazine (3b) results in a soluble polymer (4b) with novel optical properties. The neutral polymer 4b absorbs both blue (above 600 nm) and red light (below 500 nm), reflecting a saturated green color. In the oxidized form, these absorptions are depleted, resulting in a transmissive pale brown polymer with very strong absorption in the near-infrared. Electrochemical and spectroelectrochemical semiconductor band gaps of 4b were found to be ca. 1.3 eV. Molecular weight analysis showed that soluble polymers have different conjugation length from oligomers to polymers. Since the monomer 3b has low oxidation potential (0.48 V vs Ag/Ag+), mild oxidizing agents (i.e., CuCl2) initiate chemical polymerization. The oxidant/monomer rati...

Ionic liquids in the synthesis and modification of polymers

Abstract: Ionic liquids are organic salts that are liquid at ambient temperatures, preferably at room temperature. They are nonvolatile, thermally and chemically stable, highly polar liquids that dissolve many organic, inorganic, and metallo-organic compounds. Many combinations of organic cations with different counterions are already known, and the properties of ionic liquids may be adjusted by the proper selection of the cation and counterion. In the last decade, there has been increasing interest in using ionic liquids as solvents for chemical reactions. The interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction. In recent years, ionic liquids have also attracted the attention of polymer chemists. Although the research on using ionic liquids in polymer systems is still in its infancy, several interesting possibilities have already emerged. Ionic liquids are used as solvents for polymerization processes, and in several systems they indeed show some advantages. In radical polymerization, the kp/kt ratio (where kp is the rate constant of propagation and kt is the rate constant of termination) is higher than in organic media, and thus better control of the process can be achieved. Ionic liquids, as electrolytes, have also attracted the attention of researchers in the fields of electrochemical polymerization and the synthesis of conducting polymers. Finally, the blending of ionic liquids with polymers may lead to the development of new materials (ionic liquids may act as plasticizers, electrolytes dispersed in polymer matrices, or even porogens). In this article, the new developments in these fields are briefly discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4675–4683, 2005

Synthetic Strategies for Controlling the Morphology of Proton Conducting Polymer Membranes

Abstract: The nanostructure and morphology of proton conducting polymers is of considerable interest in the search for next generation materials and optimization of existing ones. Synthetic methodologies for tailoring molecular structures that promote nanoscopic phase separation of ionic and non-ionic domains, and the effect of phase separation on parameters such as proton conductivity, are considered. Rather than distinguish proton conducting polymers according to chemical class, they are categorized under sub-headings of random, block, and graft copolymers. The synthetic methodology available to access archetypal polymer structures is dependent on the nature of the monomers and restrictive compared to conventional non-ionic polymer systems. Irrespective of the methodology, ionic aggregation and phase separation are consistently found to play an important role in the proton conductivity of low ion exchange capacity (IEC) membranes, but less of a role in high IEC membranes. Significant research is required to further develop relationships between polymer architecture, morphology, and electrolytic properties.

Narrow Pore-Diameter Polypyrrole Nanotubes

Abstract: Bulk quantities of electrically conducting nanotubes of polypyrrole having narrow pore diameter (6 nm) can be synthesized rapidly by chemical oxidative polymerization of pyrrole in the presence of stoichiometric amounts of V2O5 nanofibers. The V2O5 nanofibers act as templates for polymerization and yield, as the initial product, polypyrrole nanotubes with pores filled with V2O5. The V2O5 dissolves readily in aq. 1.0 M HCl, yielding hollow polypyrrole nanotubes having conductivity of ∼2 S/cm. As-synthesized polypyrrole nanotubes spontaneously reduce noble metal ions to the corresponding metal nanoparticles at room temperature without any capping or dispersing agents. For example, 3−5 nm size nanoparticles of Ag, Au, and Pd, etc., deposit readily on the surface of the tubes which then migrate spontaneously to the pore, and, in the case of Ag, coalesce in the core, yielding 4−8 nm diameter coaxial cables of Ag surrounded by a 20−30 nm thick polypyrrole fiber sheath.

Plastic Electronic Devices Through Line Patterning of Conducting Polymers

Abstract: A novel method for the preparation of transparent conducting-polymer patterns on flexible substrates is presented. This method, line patterning, employs mostly standard office equipment, such as drawing software, a laser printer, and commercial overhead transparencies, together with a solution or dispersion of a conducting polymer. The preparation of a seven-segment polymer-dispersed liquid-crystal display using electrodes of the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrene sulfonate) (PEDOT/PSS) is described in detail. Furthermore, a method to fabricate an eleven-key push-button array for keypad applications is presented. Properties of the electrode films and patterns are discussed using microscopy images, atomic force microscopy, conductivity measurements, and tests of film stability.

Electrochemical thin film deposition of polypyrrole on different substrates

Abstract: Polypyrrole is one of the important conductive polymers that are widely used in energy storage systems, biosensors and electronics. The electrochemical synthesis of polypyrrole has advantages of simple process, mass production and low cost. In this study, polypyrrole thin films were deposited on different electrode substrates by cyclovoltammetric (CV), galvanostatic and potentiostatic deposition methods. Results demonstrated that the galvanostatic deposition method could provide higher electrochemical activity for the films. Different electrode materials including gold, glassy carbon and ink-made carbon composite electrodes were investigated for polypyrrole deposition. The conductive films on all substrates exhibited p-type conjugate polymer characteristics. However, the substrate properties had great impact on the stability of the deposited thin film and some composite carbon substrate materials demonstrate the best performance. The mechanism of the instability of polypyrrole was suggested. The study also demonstrates the feasibility of using carbon ink to make composite electrodes for possible applications in energy storage systems and electrochemical sensors. D 2004 Elsevier B.V. All rights reserved.