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Special Issue "Conjugated Polymers"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 January 2011)

Special Issue Editor

Guest Editor
Prof. Dr. Geoffrey M. Spinks (Website)

1 School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW, 2522, Australia
2 Intelligent Polymer Research Institute (IPRI), University of Wollongong, Wollongong, NSW, 2522, Australia
Interests: conjugated polymers; carbon nanotubes; hydrogels; polymer nano-composites; mechanical behaviour; mechanical actuation

Special Issue Information

Dear Colleagues,

The science and technology of conjugated polymers continues to be a vibrant and exciting research area nearly 30 years after the initial explosion of interest in these materials. In the late 1970s and early 1980s the (re-)discovery of conjugated polymers like polyacetylene, polyaniline and polypyrrole ignited an intense investigation of the properties of these inherently conducting materials. An initial surge of applications were also proposed that included plastic electronics, batteries, sensors and mechanical actuators. Now, nearly 30 years later we are seeing the commercialisation of some of these areas. Issues relating to stability and processing have been tackled to enable mass production of various products.

The science of conjugated polymers continues to be a rich area of interest for fundamental studies in physics and chemistry. We are now able to design and assemble conjugated polymers from the molecular level and through a better understanding of structure – property relationships we can build increasingly sophisticated structures. Many applications for conjugated polymers rely on their facile and reversible electrochemistry, where the polymer can be oxidised and reduced with simultaneous change in properties. The switchable properties is the basis of the application as transistors, sensors, re-chargeable batteries, solar cells, capacitors and even mechanical actuators. The molecular level processes occurring during switching are, however, quite complex and the understanding of charge transport within and between molecules as well as associated ion and solvent exchange with surrounding media are continually being developed. Through this better understanding, we are able to tune the molecular structures and assemble devices from the nano to the macro level for improved performance. Furthermore, we are able to develop devices to operate at smaller and smaller dimensions. Single molecule devices can be achieved with conjugated polymers and applications in nanotechnology and micro-electomechanical systems (MEMS) are well-suited to conjugated polymers.

Finally, the use of conjugated polymers as a link between the electronic world and the biological world is a very exciting new direction. Conjugated polymers have the potential to revolutionise bionics: to enable sensing of biological systems in situ but also to modify biological functions including directing new cell growth for the repair of organs. Conjugated polymers can match the mechanical properties of biological tissue and can be chemically tuned to be biocompatible and potentially biodegradable. While much work still needs to be done in this area, the opportunity for controllable interactions with living tissue through a bio-conjugated polymer is close at hand:

Even after 3 decades of work on conjugated polymers, new areas are emerging and the special joint issue of the journals International Journal of Molecular Sciences, and Materials is a great chance to showcase the recent developments in the science and technology of these fascinating materials.

Prof. Dr. Geoffrey M. Spinks
Guest Editor

Keywords

  • conjugated polymer
  • conductivity
  • electro-activity
  • characterisation
  • plastic electronics
  • solar cells
  • electrochromics
  • actuators
  • batteries
  • capacitor

Related Special Issue

Published Papers (5 papers)

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Research

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Open AccessArticle Quinacridone-Diketopyrrolopyrrole-Based Polymers for Organic Field-Effect Transistors
Materials 2013, 6(3), 1061-1071; doi:10.3390/ma6031061
Received: 29 January 2013 / Revised: 7 March 2013 / Accepted: 8 March 2013 / Published: 18 March 2013
Cited by 4 | PDF Full-text (300 KB) | HTML Full-text | XML Full-text
Abstract
Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. [...] Read more.
Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. In this paper, semiconducting polymers based on well-known pigments, namely, quinacridone and diketopyrrolopyrrole, are synthesized and characterized. The π-stacking distances are found to be 3.5–3.8 Å, which is fairly narrow for semiconducting polymers, indicating that they possess strong intermolecular interactions. Interestingly, polymer orientation is influenced by the composition of alkyl side chains. While the edge-on orientation is observed when the linear alkyl groups are introduced for all the side chains, the face-on orientation is observed when the branched alkyl groups are introduced either in the quinacridone or diketopyrrolopyrrole unit. It is found that the electronic structure of the present polymers is mostly affected by that of the diketopyrrolopyrrole unit, as evidenced by the absorption spectra and computation. Although the field-effect mobility of the polymers is modest, i.e., in the order of 10−4–10−3 cm2/Vs, these findings could be important information for the development of semiconducting polymers. Full article
(This article belongs to the Special Issue Conjugated Polymers)
Open AccessArticle Preparation of Polyaminopyridines Using a CuI/l-Proline-Catalyzed C-N Polycoupling Reaction
Materials 2012, 5(11), 2176-2189; doi:10.3390/ma5112176
Received: 2 August 2012 / Revised: 10 October 2012 / Accepted: 1 November 2012 / Published: 5 November 2012
Cited by 4 | PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
Polyaminopyridines (PAPy) were chemically prepared from amino-bromopyridines by a CuI/l-proline-catalyzed C-N polycondensation reaction. The formation of the polymer was confirmed by GPC, XRD, XRF, FTIR, UV-vis (λmax = 400 nm), 1H and 13C NMR. The number-average molecular weights ( [...] Read more.
Polyaminopyridines (PAPy) were chemically prepared from amino-bromopyridines by a CuI/l-proline-catalyzed C-N polycondensation reaction. The formation of the polymer was confirmed by GPC, XRD, XRF, FTIR, UV-vis (λmax = 400 nm), 1H and 13C NMR. The number-average molecular weights (Mn) were estimated by end-group analysis using X-ray fluorescence (up to 6000 Da). TGA analysis of PAPy with higher Mn showed greater thermal stability up to 170 oC. Viscosity measurements of polymer in formic acid at 30 oC indicated a polyelectrolyte nature of PAPy solutions. Furthermore, the amorphicity of the material was observed by X-ray diffraction analysis. Full article
(This article belongs to the Special Issue Conjugated Polymers)
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Open AccessArticle Synthesis, Characterization and Photophysical Properties of Pyridine-Carbazole Acrylonitrile Derivatives
Materials 2011, 4(3), 562-574; doi:10.3390/ma4030562
Received: 10 February 2011 / Revised: 24 February 2011 / Accepted: 9 March 2011 / Published: 11 March 2011
Cited by 5 | PDF Full-text (245 KB) | HTML Full-text | XML Full-text
Abstract
We synthesized three novel highly fluorescent compounds, 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, and 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile by Knoevenagel condensation. The first two were synthesized without solvent in the presence of piperidine as a catalyst; the third was synthesized without a catalyst and with N,N-dimethylformamide as a solvent. [...] Read more.
We synthesized three novel highly fluorescent compounds, 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, and 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile by Knoevenagel condensation. The first two were synthesized without solvent in the presence of piperidine as a catalyst; the third was synthesized without a catalyst and with N,N-dimethylformamide as a solvent. In solution, the molar absorption coefficients showed absorptions at 380, 378, and 396 nm, respectively; in solid state, absorptions were at 398, 390, and 442 nm, respectively. The fluorescence emission was at 540, 540 and 604 nm, respectively, the 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile showed a red shift in the emission of 64 nm compared to the other two compounds. The fluorescence quantum yield for the compounds in powder form showed values of 0.05, 0.14, and 0.006, respectively; compared with the value measured for the Alq3 reference, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile had a lightly higher value. The third harmonic generation measurement for 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile yielded a χ(3) value of 5.5 × 10−12 esu, similar to that reported for commercial polymers. Full article
(This article belongs to the Special Issue Conjugated Polymers)
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Review

Jump to: Research

Open AccessReview Polythiophenes Comprising Conjugated Pendants for Polymer Solar Cells: A Review
Materials 2014, 7(4), 2411-2439; doi:10.3390/ma7042411
Received: 8 January 2014 / Revised: 7 March 2014 / Accepted: 14 March 2014 / Published: 27 March 2014
Cited by 20 | PDF Full-text (1510 KB) | HTML Full-text | XML Full-text
Abstract
Polythiophene (PT) is one of the widely used donor materials for solution-processable polymer solar cells (PSCs). Much progress in PT-based PSCs can be attributed to the design of novel PTs exhibiting intense and broad visible absorption with high charge carrier mobility to [...] Read more.
Polythiophene (PT) is one of the widely used donor materials for solution-processable polymer solar cells (PSCs). Much progress in PT-based PSCs can be attributed to the design of novel PTs exhibiting intense and broad visible absorption with high charge carrier mobility to increase short-circuit current density (Jsc), along with low-lying highest occupied molecular orbital (HOMO) levels to achieve large open circuit voltage (Voc) values. A promising strategy to tailor the photophysical properties and energy levels via covalently attaching electron donor and acceptor pendants on PTs backbone has attracted much attention recently. The geometry, electron-donating capacity, and composition of conjugated pendants are supposed to be the crucial factors in adjusting the conformation, energy levels, and photovoltaic performance of PTs. This review will go over the most recent approaches that enable researchers to obtain in-depth information in the development of PTs comprising conjugated pendants for PSCs. Full article
(This article belongs to the Special Issue Conjugated Polymers)
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Open AccessReview Influence of Molecular Conformations and Microstructure on the Optoelectronic Properties of Conjugated Polymers
Materials 2014, 7(3), 2273-2300; doi:10.3390/ma7032273
Received: 13 January 2014 / Revised: 3 March 2014 / Accepted: 7 March 2014 / Published: 19 March 2014
Cited by 24 | PDF Full-text (998 KB) | HTML Full-text | XML Full-text
Abstract
It is increasingly obvious that the molecular conformations and the long-range arrangement that conjugated polymers can adopt under various experimental conditions in bulk, solutions or thin films, significantly impact their resulting optoelectronic properties. As a consequence, the functionalities and efficiencies of resulting [...] Read more.
It is increasingly obvious that the molecular conformations and the long-range arrangement that conjugated polymers can adopt under various experimental conditions in bulk, solutions or thin films, significantly impact their resulting optoelectronic properties. As a consequence, the functionalities and efficiencies of resulting organic devices, such as field-effect transistors, light-emitting diodes, or photovoltaic cells, also dramatically change due to the close structure/property relationship. A range of structure/optoelectronic properties relationships have been investigated over the last few years using various experimental and theoretical methods, and, further, interesting correlations are continuously revealed by the scientific community. In this review, we discuss the latest findings related to the structure/optoelectronic properties interrelationships that exist in organic devices fabricated with conjugated polymers in terms of charge mobility, absorption, photoluminescence, as well as photovoltaic properties. Full article
(This article belongs to the Special Issue Conjugated Polymers)

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