Interchain interactions between π-systems have a strong effect on the properties of conjugated organic materials that find application in devices such as light emitting diodes (OLEDs), organic photovoltaics (OPVs), and field effect transistors (FETs). We have prepared covalently-stacked oligo(1,4-phenylene ethynylene)s and oligo(1,4-phenylene vinylene)s to study the influence of chain-chain interactions on the electronic structure of closely packed conjugated units. These serve as models for segments of conjugated materials in thin film devices. Extension of this concept has allowed us to prepare multi-tiered systems that display the influence of pi-stacking. The stacked architectures were prepared by multi-step synthesis of the scaffolds, followed by metal-catalyzed cross coupling reactions (Sonogashira, Heck, Suzuki couplings) to incorporate the conjugated oligomers. The optical and electrochemical properties of these stacked compounds and polymers were compared to their unstacked linear counterparts. These studies provide a platform for the exploration of the nature of charge carriers and excitons in a broad class of materials that have significant potential in addressing challenges in power generation, lighting and electronics.

The goal of the thesis is to incorporate materials with either fluorescent or conductive properties in silk fibers, by feeding silkworms with a diet containing these materials. To achieve this, one would have to breed (rear) silkworm from eggs into larvaes, then to feed the silkworms with this special diet containing fluorescent or conductive materials. Samples of silk were then collected either from spun cocoons or via removing the silk producing organs (silk glands) from the silkworms via dissection. The samples were then analyzed with absorbance spectrometer, spectrofluorometer or via photoluminesecent measurement to determine if any materials had been incorporated into the silk fibers.   Silkworms were successfully reared from eggs up to moths, once the silkworm larvae had grown enough in size their diet were switches from their regular food (silkworm chow) to food containing conjugated molecules or polymers with fluorescent or conductive properties. A total of 14 materials were tested. One material gave a clear positive result and that was from the fluorescent compound Rhodamine B. Other fluorescent materials, Nile red and POWT yielded some results indicating their presence in the silk but the results were not conclusive. The rest of the materials all failed with being incorporated within the silk fibers; this was due to their lethality, size, lack of zwitterionic properties and such.  The properties of the materials are of great importance for the uptake process, where a small zwitterionic molecule has a great change of being taken up and incorporated in the silk fibers. Whereas a big materials such as a polymer without any zwitterionic will in most cases just follow through the food in the digestive track without any uptake.

Despite tremendous achievements, the field of conjugated polymers is still in its infancy, mimicking the more mature inorganic, i.e. silicon-based, technologies. We may though look forward to the realisation of electronic and electrochemical devices with exotic designs and device applications, as our knowledge about the fundamentals of these promising materials grow ever stronger. My own contribution to this development, originating from an idea first put forward by my tutor, Professor Magnus Berggren, is a design for a switchable polymer-based diode. Its architecture is based on a modified version of a recently developed highly-rectifying diode,12 where an intermediate molecular layer has been incorporated in the bottom contact. Due to its unique ability to switch its internal resistance during operation, this thin layer can be used to shift the amount of (forward) current induced into the rectifying structure of the device, and by doing so shift its electrical characteristics between an insulating and a rectifying behaviour (as illustrated below). Such a component should be of great commercial interest in display technologies since it would, at least hypothetically, be able to replace the transistors presently used to address the individual matrix elements. However, although fairly simple in theory, it proved to be quite the challenge to fabricate the device structure. Machinery errors and contact problems aside, several process routes needed to be evaluated and only a small fraction of the batches were successful. In fact, it was not until the very last day that I detected the first indications that the concept might actually work. Hence, several modifications might still be necessary to undertake in order to get the device to work properly.

Polymer electrochromism on PEDOT coated fibres was successfully achieved. The electrochromic property of the PEDOT polymer is an excellent property. This feature gives way to many more research works at present and in the future also. The electrochromic property of the PEDOT polymer is utilized in this thesis work to design an electrochromic display pixel. The polymer coating over the fibres were obtained by using In-situ polymerization technique. The coated-fibres were used to design a display-pixel. Electrochemistry is performed successfully on the designed pixel to study electrochromism over the pixels. An electrochemical fibre transistor is designed successfully using the polymer coated fibres. / Polymer Electrochromism on PEDOT coated fibres

This thesis presents the first reported grafted PPE - polycaprolactone-g-PPE; the first PPE based sensing model: biotinylated grafted PPE/streptavidin coated sphere; the first photocrosslinkable PPE ¨C allyloxy PPE; and the new mechanism which demonstrates morphology control on a single molecular level

ABSTRACT SYNTHESIS OF BENZIMIDAZOLE CONTAINING DONOR ACCEPTOR ELECTROCHROMIC POLYMERS Akpinar, Hava Zekiye M. Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare February 2011, 60 pages Donor-acceptor-donor (DAD) type benzimidazole (BIm) and 3,4-ethylenedioxythiophene (EDOT) bearing monomers (4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3 dihydrothieno[3,4b][1,4] dioxin-7-yl)-2-benzyl-1H-benzo[d]imidazole (M1), 2,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-1H-benzo[d]imidazole (M2) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-2-ferrocenyl-1H-benzo[d]imidazole (M3)) were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance were reported in detail. Keywords: Benzimidazole, EDOT, Donor-Acceptor Type Polymers, Electrochromism, Conjugated Polymers.

ABSTRACT SYNTHESIS OF BENZIMIDAZOLE CONTAINING DONOR ACCEPTOR ELECTROCHROMIC POLYMERS Akpinar, Hava Zekiye M. Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare February 2011, 60 pages Donor-acceptor-donor (DAD) type benzimidazole (BIm) and 3,4-ethylenedioxythiophene (EDOT) bearing monomers (4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3 dihydrothieno[3,4b][1,4] dioxin-7-yl)-2-benzyl-1H-benzo[d]imidazole (M1), 2,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-1H-benzo[d]imidazole (M2) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-2-ferrocenyl-1H-benzo[d]imidazole (M3)) were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance were reported in detail.

In this study, optical and electrochemical properties of regioregular and soluble alkyl substituted propylenedioxyselenophene based electrochromic polymers, namely poly(3,3-dibutyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C4), poly(3,3-dihexyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C6), and poly(3,3-didecyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C10), which were synthesized via electrochemical polymerization, were investigated. It is noted that these unique polymers have low band gaps (1.54 &ndash / 1.64 eV) and they are exceptionally stable under ambient atmospheric conditions. For example, polymer films retained 84-96 % of their electroactivity after five thousands cycles. The percent transmittance of PProDOS-Cn (n= 4, 6, 10) films found to be between 55-59 %. Furthermore, these novel soluble PProDOS-Cn polymers showed electrochromic behavior: a color change form pure blue (L = 57.31, a = -13.18, b = - 42.68) to highly transparent state (L = 91.74, a = 2.52, b = -1.30) state in a low switching time (1.0 s) during oxidation with high coloration efficiencies (328 &ndash / 864 cm2/C) when compared to their close analogues.

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.

<p>Polymer electrochromism on PEDOT coated fibres was successfully achieved. The electrochromic property of the PEDOT polymer is an excellent property. This feature gives way to many more research works at present and in the future also. The electrochromic property of the PEDOT polymer is utilized in this thesis work to design an electrochromic display pixel.</p><p> </p><p>The polymer coating over the fibres were obtained by using In-situ polymerization technique. The coated-fibres were used to design a display-pixel. Electrochemistry is performed successfully on the designed pixel to study electrochromism over the pixels. An electrochemical fibre transistor is designed successfully using the polymer coated fibres.</p> / Polymer Electrochromism on PEDOT coated fibres