Opto-electronics of non-fully conjugated molecules was demonstrated successfully in this research as light emitting diodes (LEDs). A series of benzoxazole poly[2,2-(m-2-hydroxyl phenylene)-4-4¡¦-hexafluoroisopro- pane-bibenzoxazoles] (6F-PBO-OH, Am) and benzimidazole poly[2,2¡¦- (2-hydroxy-o-phenylene)-5,5¡¦-bibenzimiazole] (OH-Pbi, B(1-m)) were copolymerized for coil-like non-fully conjugated poly-(Am-co-B(1-m)) for luminescence investigation. UV-Vis absorption of the non-fully conjugated copolymers showed superposition of individual absorption response from the two chemical components of the copolymer. However, the photoluminescence (PL) and the electroluminescence (EL) emissions had a red shift with increasing OH-Pbi content. It seemed to suggest that OH-Pbi was more charge delocalized than 6F-PBO-OH. In mono-layer LEDs, the diode threshold voltages were about at 2 ~ 3 V and the EL showed a green emission. Tunable emission was not observed in varying the m value of the copolymers. Composites of copolymer, poly(Am-co-B(1-m)) and multi-wall carbon nanotube (MWNT) were in-situ synthesized for mono-layer LED fabrication. Few MWNT aggregation was observed via the field-emission scanning electron microscopy. It was a success in dispersing MWNT in the copolymers. There was a red shift with MWNT addition in the PL and the EL emissions. The diode threshold voltages were about at 2 ~ 5 V and the EL emission still showed a green emission. According to this study, MWNT was inconsequential on the PL and the EL emissions of the copolymers up to 2 wt. %.

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Polymer photovoltaic cell (PV cell) utilizes a polymer to absorb photons for generating excitons. When excitons are separated into electrons and holes, the device has the photovoltaic effect. Polymer light emitting diode (PLED) injects electrons and holes respectively from cathode and anode into a polymer emission layer. Some of the electrons and the holes would recombine to induce light emission. This research used a heterocyclic aromatic rigid-rod polymer poly-p-phenylene- benzobisoxazole (PBO) as the opto-electronic layer, and a conducting material of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) as the hole transport layer. PV cells were fabricated using indium-tin-oxide (ITO) as anode and aluminium as cathode. Same layer arrangement was applied for PLEDs. These two kinds of devices were measured for electrical and optical response. It was evidenced that the addition of PEDOT:PSS layer facilitated the separation of excitons into electrons and holes at the PBO/PEDOT:PSS interface. Insertion of a LiF layer between PBO layer and Al cathode reduced their energy band gap and facilitated charge transport leading to an enhanced efficiency for PV cells and PLEDs. Thickness variations were found on spun PBO layer. According to emission intensity, we knew that the PBO layer quality was significant for electroluminescence. Introduction of a PEDOT:PSS layer improved the interface between ITO and PBO. The thickness of PEDOT:PSS layer depended on the ITO surface roughness. With a PEDOT:PSS layer, the opto-electronic efficiency of PV cell and PLED was improved.

Luminescent emission of non-fully conjugated homopolymers was successfully demonstrated as light emitting diodes (LEDs) in this research. Coil-like heterocyclic aromatic poly[2,2-(2,5-dialkyloxyphenylene)-4-4¡¦-hexafluoroisopropanebibenzoxazo- les] (6F-PBO-CnOTpA, with n = 10, 15, and 20) was synthesized, and polymer composites of 6F-PBO-CnOTpA was in-situ synthesized with acidified multi-wall carbon nanotube (MWNT- COOH). The non-fully conjugated coil-like heterocyclic aromatic homopolymer was synthesized by reacting 2,2,bis-(3-amino-4-hydroxy[henyl]-hexafluoropropane with 2,5-dialkyloxyterephthalic acid (CnOTpA) for 6F-PBO-CnOTpA, with n = 10, 15, and 20. In addition, MWNT was acidified for connecting the carboxylic group (-COOH) to reduce its aspect ratio and entropy induced aggregation. MWNT-COOH was analyzed using elemental analysis (EA) and viscometry to validate the effects of acidification period. The EA result seemed to suggest that the oxygen content increased, and the carbon and the hydrogen contents decreased with acidification period. The inherent viscosity (£binh) decreased according to acidification period suggesting that the aspect ratio was indeed decreased. A hole transport layer of PEDOT¡GPSS was applied for multi-layer LEDs,. The LEDs all showed a threshold voltage about 4 V also for the composites of 6F-PBO-CnOTpA in-situ polymerized with MWNT-COOH. The 6F-PBO-CnOTpA LEDs with and without MWNT-COOH showed an electroluminescence emission range of 400 to 750 nm.

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.

2-Dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating copolymers poly((9,9-dioctylfluorene)-2,7-diyl-(2-dodecyl-benzo[1,2,3]triazole)) (P1), poly((9,9-dioc-tylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl benzo[1,2,3]triazole)) (P2), poly((9,9 dioctylfluorene)-2,7-diyl-(4,7-bis(3-hexylthien-5-yl) 2-dodecyl-benzo[1,2,3]triazole)) (P3) were synthesized via Suzuki polycondensation. Synthesized monomers and copolymers were characterized by Nuclear Magnetic Resonance (1H-NMR, 13C-NMR). Optical and electronic properties of resulting alternating copolymers were investigated by means of Cyclic Voltammetry (CV), Ultraviolet&ndash / Visible Spectroscopy and spectroelectrochemistry. All three polymers showed both p and n doping behaviors and multicolored electrochromic states. In order to learn switchingtimes and percent transmittance changes kinetic studies were also performed. Thermal properties of the polymers were investigated via Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Due to the convenient HOMO and LUMO levels, band gaps, strong absorptions in the visible region and thermal stability, polymers were tested in Organic Solar Cell (OSC) device applications. The preliminary investigation indicated that polymers had promising power conversion efficiencies.

In this study, a novel series of conjugated monomers containing furan and fluorene units / 2,7-di(furan-2-yl)-9H-fluoren-9-one (FOF), 2-(2-(furan-2-yl)-9H-fluoren-7-yl)furan (FFF), and 2-(2-(furan-2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan (FHF) were synthesized and their electrochemical polymerization were achieved via potential cycling. Optical and electrochemical properties of the polymers, poly(2,7-di(furan-2-yl)-9H-fluoren-9-one) (PFOF), poly(2-(2-(furan-2-yl)-9H-fluoren-7-yl)furan (PFFF) and poly(2-(2-(furan-2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan) (PFHF) were investigated and it was found that polymer films exhibit reversible redox behavior (Epox = 1.083 V for PFOF, Epox= 0.915 V for PFFF and Epox= 0.985 V for PFHF) accompanied with a reversible electrochromic behavior, orange to green for PFOF, yellow to dark blue for PFFF and orange to green for PFHF during oxidation. Their band gap values (Eg) were found to be 2.32, 2.49 and 2.61 eV for PFOF, PFFF and PFHF, respectively.

A heterocyclic aromatic rigid-rod polymer poly-p-phenylene-benzobisoxazole (PBO) was applied as the opto-electronic layer¡Fand a conducting material of poly(3,4-ethylenedioxythio-phene):poly(4-styrenesulfonic acid) (PEDOT: PSS) was used as the hole transport layer. Aluminum (Al) and indium tin oxide (ITO) were served as device cathode and anode¡Arespectively, fabricated into a bi-layer structure of ITO/PEDOT:PSS/PBO/Al for electrical and luminescence responses. This research demonstrated an increase of current density and a decrease of threshold voltage with a decrease of PBO layer thickness from 90 nm to 27 nm to facilitate electron tunneling and electron-hole recombination. With a lower spin coating speed, polymer chain would aggregate and inter-penetrate resulted in red-shift of electroluminescence (EL) emission spectrum. Furthermore, micro-cavity effect might influence EL spectrum by varying layer thickness. Modulation of PBO layer thickness led to tunable EL emission color. It was also demonstrated that an increase of current density and a slightly decrease of threshold voltage with a PEDOT:PSS film thickness changing from 96 nm to 17 nm at a constant PBO layer thickness of 90 nm. Micro-cavity effect thus influenced EL emission for a tunable emission color. Photolithography was applied to obtain ITO substrate of grating depth of periodic variation and then coated with a PEDOT:PSS leading to a grated PEDOT:PSS layer of periodic thickness. This led to ITO/PEDOT:PSS/PBO/Al device showing broadened EL emission spectra.