<p>Major efforts have been spent during recent years in worldwide attempts to achieve an electronic paper technology; the common name for novel flexible displays utilizing substrates such as paper, plastics or thin metal sheets. Various kinds of technology are available that potentially will be used for an electronic paper, which differs from each other mainly with respect to the choice of active materials, substrates and manufacturing techniques. There are many applications for electronic paper technology, ranging from high-resolution displays used in electronic books to updateable large-area billboards. The latter suggests a novel electronic display function that could extend the utilization of cellulose-based paper, which is one of the most common materials ever produced by mankind, by using the paper as a thin and flexible carrier. The requirement for fast update speed in such large area applications would probably be a bit more relaxed compared to traditional display technologies, while low-power consumption and bi-stability are among the factors that should be further emphasized, together with the utilization of well-established printing techniques to enable low-cost manufacturing of the displays. The choice of active materials is therefore crucial in order to reach these objectives in reality and this paves the way for printable conjugated polymers with electrochromic properties. Chemical synthesis of these materials during the last decades has resulted in a vast variety of electrochromic polymers with custom-tailored functionality covering a broad range of optical absorption and electrical conductivities.</p><p>This thesis review the studies done on the electrochemical switching of poly(3,4-ethylenedioxythiophene) (PEDOT). For this material both the electrical conductivity and the optical absorption is controlled by the oxidation state. Active matrix addressed displays that are printed on flexible substrates have been obtained by arranging electrochemical smart pixels, based on the combination of electrochemical transistors and electrochromic display cells, into cross-point matrices. The resulting polymer-based active-matrix displays are operated at low voltages and the same active material can be used in electrochemical transistors and conducting lines and in electrochromic display cells employing the electronic and the opto-electonic properties of the material, respectively. In addition to this, a switchable optical polarizer is briefly discussed. This is a device utilizing electrochromism of stretch-aligned polyaniline (PANI). The combination of two identical devices in a vertical architecture, orthogonally oriented with respect to each other, results in a filter in which the orientation of the polarized optical absorption is governed by the voltage polarity applied to the device.</p> / Report code: LiU-TEK-LIC- 2006:18

Conjugated polymers have been found useful in a wide range of applications such as solar cells, sensor elements and printed electronics, due to their optical and electronic properties. Functionalization with charged side chains has enabled water solubility, resulting in an enhanced interaction with biomolecules. This thesis focus on the emerging research fields, where these conjugated polyelectrolytes (CPEs) are combined with biomolecules for biological sensing and DNA nanowire assembling. CPEs have shown large potential in biomolecular detection where the optical read out is due to the geometrical alternation in the backbone and aggregation state. This thesis focused on transferring the biomolecular detection to a surface of CPEs. The characterization of the CPE layer show that a hydrogel can be formed, and how the layer can undergo geometrical changes upon external stimulus such as pH change. A selective sensor surface can be created by imprinting ssDNA or an antibody in the CPE layer. The discrimination for complementary DNA hybridization and specific antibody interaction can be monitored by surface plasmon resonance or quartz crystal microbalance. We have also taken the step out from the controlled test tube experiments to the complex environment of the cell showing the potential for staining of compartments and structures in live and fixed cell. Depending on the conditions and CPE used, cell nuclei, acidic vesicles and cytoskeleton structure can be visualized. Furthermore, the live staining shows no sign of toxic effect on cultured fibroblasts. CPEs can also be a valuable element when assembling electronics in the true nano regime. I have used DNA as building template due to its attractive size features, with a width of around 2 nm and a length scale in the µm regime, and the inbuilt base-paring recognition elements. This thesis shows how DNA can be decorated with CPEs and stretched on surfaces into a model for aligned semiconducting nanowire geometries. Not only making the template structures is of importance, but also how to place them on the correct surface position, i.e. on electrodes. Strategies for positioning DNA nanowires using transfer printing and surface energy patterning methods have therefore been developed in the thesis. The stretched DNA decorated with CPE also offers a way to further study the molecular binding interaction between the two molecules. Single molecular spectroscopy in combination with polarization has given information of the variation of the CPE binding along a DNA chain.

A novel polymer semiconductor with side chains thermally cleavable at a low temperature of 200 °C was synthesized. The complete cleavage and removal of the insulating 2-octyldodecanoyl side chains were verified with TGA, FT-IR, and NMR data. The N-H groups on the native polymer backbone are expected to form intermolecular hydrogen bonds with the C=O groups on the neighboring polymer chains to establish 3-D charge transport networks. The resulting side chain-free conjugated polymer is proven to be an active p-type semiconductor material for organic thin film transistors (OTFTs), exhibiting hole mobility of up to 0.078 cm2V-1s-1. This thermo-cleavable polymer was blended with PDQT to form films that showed a higher performance than the pure individual polymers in OTFTs. MoO3 or NPB was used as a hole injection buffer layer between the metal electrodes and the polymer semiconductor film layer in OTFT devices. This buffer layer improved hole injection, while its use in the OTFT, improved the field-effect mobility significantly due to better matched energy levels between the electrodes and the polymer semiconductor.

Structural evolution and its effect on optical absorption/emission behavior of derivatives of PFs upon heat treatment at different temperatures were studies by means of a combination of x-ray diffraction, transmission electron microscopy and molecular simulation. The main physical characteristics from results of this study over a series of PFs with alkyl side-chains may be summarized as the following: (1) The crystal structure of poly (9,9-di-n-octyl- 2,7-fluorene, PF8) and poly(9,9-bis(2- ethylhexyl)- 2,7-fluorene, PF26) are determined via a combination of selected area electron diffraction and molecular simulation. In PF8 case, there are 8 chains in an orthorhombic unit cell with dimensions a = 2.56 nm, b = 2.34 nm, c (chain axis) = 3.32 nm, space group P212121, and calculated density of 1.041 gcm-3. On the other hand, in PF26 case, there are 3 chains in a trigonal unit cell with dimensions a = 1.67 nm, b = 1.67 nm, c (chain axis) = 4.04 nm, space group P3, and calculated density of 0.991 gcm-3. (2) All the simulation results indicate that branched side-chains in the case of PF26 tend to fill the space among backbones. In contrast, the linear side-chains in the case of PF8 appear to embrace the neighboring backbone, favoring formation of layered structure. (3) As a consequence, co-planrity of PF backbones is decreased by the attached alkyl side-chains. This in turn results in lowered conjugation length, and in favor of blue light emission.

Fully conjugated heterocyclic aromatic rod-like polymer poly-p-phenylene- benzobisoxazole (PBO) and coil-like poly-(3-hexylthiophene) (P3HT) were applied as opto-electronically active layer. The two polymers mixed with nano-carbon particles, having excellent optical absorption and electric conductivity, of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) or esterified multi-wall carbon nano-tube (MWNT-COOC10H21) as well as a hole transporting layer of PEDOT:PSS. Photovoltaic (PV) cells of indium-tin-oxide (ITO)/PEDOT:PSS/nano-carbon particle:fully conjugated polymer/Al were fabricated for optical and electrical characterizations. Tri-layered structure of ITO/PEDOT:PSS/PBO/PCBM/Al produced a straight current-voltage relation showing no PV effects. Upon changing the active layer into PCBM doped P3HT layer (PCBM:P3HT), it produced good PV effects suggesting that the doped layer had a penetrating network to facilitate the PV effects. When PCBM or MWNT-COOC10H21 was doped into P3HT, the device PV effects were increased significantly with nano-carbon particle concentration. The direct-current electric conductivity parallel to the film surface (£m¡ü)was increased with the nano-carbon particle concentration. By changing the thickness of hole transporting PEDOT:PSS and of opto-electronically active layers, it was found that when the PEDOT:PSS layer was decreased from 90 nm to 32 nm, there was a slight increase of PV cell efficiency. The active layer of PCBM:P3HT with a thickness of 99 nm had the best optical absorption and charge transport leading to an increase of PV cell efficiency.

A novel polymer semiconductor with side chains thermally cleavable at a low temperature of 200 °C was synthesized. The complete cleavage and removal of the insulating 2-octyldodecanoyl side chains were verified with TGA, FT-IR, and NMR data. The N-H groups on the native polymer backbone are expected to form intermolecular hydrogen bonds with the C=O groups on the neighboring polymer chains to establish 3-D charge transport networks. The resulting side chain-free conjugated polymer is proven to be an active p-type semiconductor material for organic thin film transistors (OTFTs), exhibiting hole mobility of up to 0.078 cm2V-1s-1. This thermo-cleavable polymer was blended with PDQT to form films that showed a higher performance than the pure individual polymers in OTFTs. MoO3 or NPB was used as a hole injection buffer layer between the metal electrodes and the polymer semiconductor film layer in OTFT devices. This buffer layer improved hole injection, while its use in the OTFT, improved the field-effect mobility significantly due to better matched energy levels between the electrodes and the polymer semiconductor.

In recent years, the application of fluorescent conjugated polymers for sensing chemical and biological analytes has received much attention from many researchers. A promising development in this direction was the fabrication of conducting polymer-based sensors for the detection of metal ions, small organic molecules and biomolecules. Herein, we have designed, synthesized and studied a series of copolymers containing alternate phenylene and 2,5- or 2,6-substituted pyridine rings. The basic N-atom of the pyridine ring and the adjacent –OH group from the phenyl ring provide binding sites for metal ions. Another series of water-soluble conjugated polymers with propoxy sulfonate side chains are investigated for biosensor applications. Significant quenching of the polymer fluorescence upon addition of viologen derivatives was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers can be useful in the application of metal and biological sensors. / Singapore-MIT Alliance (SMA)

Understanding the fundamental chemistry of conjugated polymers and fullerenes has been the subject of intense research for the last three decades, with the last ten years seeing increased research toward the application of these materials into functional organic electronic devices such as organic photovoltaic devices (OPVs). This field has seen significant advances is cell efficiency in just the last few years (to >10%), in large part due to the development of new donor and acceptor materials, the fine tuning of fabrication parameters to control material nanostructure, as well as the introduction of new interfacial materials such as ionically functionalized conjugated polymers, also known as conjugated polyelectrolytes (CPEs). This dissertation aims to further understand the fundamental chemistry associated with charge injection processes in CPEs and ionically functionalized fullerenes. The role of ionic functionality on electrochemical, chemical, and interfacial charge injection processes is explored. The results presented demonstrate the use of ionic functionality to control the spatial doping profile of a bilayer structure of anionically and cationically functionalized CPEs to fabricate a p-n junction (Chapter II). The role of ionic functionality on chemical charge injection processes is explored via the reaction of polyacetylene and polythiophene based CPEs with molecular oxygen (Chapters III and IV). The results show the dramatic effect of ionic functionality, as well as the specific role of the counterion, on the photooxidative stability of CPEs. The control of reaction pathway via counterion charge density is also explored (Chapter IV) and shows a continuum of reaction pathways based on the charge density of the counter cation. Finally, the role of ionic functionality on interfacial charge injection processes in a functional OPV is explored using a cationically functionalized fullerene derivative (Chapters V and VI). Cell performance increases due to an increase in open-circuit voltage and substantial reduction in series resistance resulting from the high conductivity of the interfacial fullerene layer. The chemical origin of this high conductivity is explored in Chapter VI and shown to likely be the result of chemical reactions occurring between the counter anion and the fullerene core. This dissertation contains coauthored, previously published and unpublished work.

Orientador: Deuber Lincon da Silva Agostini / Resumo: Neste trabalho foram produzidas nanofibras eletrofiadas constituídas de poli(álcool vinílico) (PVA) com poli(3,4-etilenodioxitiofeno):poli(estireno sulfonado) (PEDOT:PSS) (PVA/PEDOT:PSS) e nanofibras de poli(álcool vinílico) (PVA) com polipirrol (PPy) (PVA/PPy) com propriedades elétricas para utilização como sensores de gás. O PVA é um polímero isolante, solúvel em água com elevado peso molecular que lhe confere as características ideais para a produção de nanofibras, sendo este usado como polímero de suporte para os polímeros condutores PEDOT:PSS e PPy. Foram investigados o efeito das diferentes concentrações de PVA na produção das nanofibras eletrofiadas, onde a concentração de 6% apresentou os melhores resultados na formação de nanofibras. Também foram investigados a influência das concentrações de PEDOT:PSS e PPy na estrutura e propriedades das nanofibras eletrofiadas, através da análise morfológica e resistividade elétrica, no qual obteve-se a formação de nanofibras para todas as concentrações. Em seguida as nanofibras foram depositadas em eletrodos interdigitados para a realização das caracterizações elétricas e teste como sensor de gás, no qual comprovou-se a sensibilidade das nanofibras constituídas de condutor/isolante na presença de gás amônia (NH3). / Abstract: In this work were produced electrospunnanofibers of polyvinyl alcohol (PVA) with poly(3,4-ethylenedioxythiophene):poly(sulfonated styrene) (PEDOT:PSS) (PVA/PEDOT:PSS) and poly(vinyl alcohol) nanofibers (PVA) with polypyrrole (PPy) (PVA/PPy) with electrical properties for use as gas sensors. PVA is a high molecular weight water soluble insulating polymer which gives it the ideal characteristics for the production of nanofiber, which is used as a support polymer for the PEDOT:PSS and PPy conductive polymers. It wasinvestigated the effect of different PVA concentrations on the production of electrospunnanofibers, where the 6% concentration showed the best results in the formation of nanofibers. The influence of PEDOT:PSS and PPy concentrations on the structure and properties of nanofibers was also investigated, through morphological analysis and electrical resistivity, which obtained the formation of nanofibers for all concentrations. Then the nanofibers were deposited on interdigitated electrodes to perform the electrical characterization and test as a gas sensor, which proved the sensitivity of conductor / insulating nanofibers in the presence of ammonia gas (NH3). / Mestre

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18292号 / 工博第3884号 / 新制||工||1596(附属図書館) / 31150 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 中條 善樹, 教授 澤本 光男, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM