Polymeric electrochromic materials that has as one of the three complementary colors (red, green, and blue) in the neutral form and become transparent via oxidation (or reduction), has a crucial importance towards use of these materials in electrochromic devices and displays. To reflect red or blue color in neutral state, the materials have to absorb at only one dominant wavelength. On the contrary, to have a green color, there should exist at least two simultaneous absorption bands in the red and blue regions of the visible spectrum where these bands should be controlled with the same applied potential. The transmissivity in the oxidized state is significantly important in addition to the neutral state color of the polymer. The optical contrast between the states is the decisive point for use of these materials for many electrochromic applications, especially as smart windows and displays. Hence, the material should possess two absorption bands with definite maximum points, and upon oxidation these bands should simultaneously vanish to have a transmissive state. A donor&ndash / acceptor approach can be utilized to solve this puzzle. It has been shown that insertion of alternating donor&ndash / acceptor units on the polymer backbone leads to a significant decrease in band gap due to the increased double bond character in the structure. In this study novel donor-acceptor type polymers were synthesized, and electrochromic properties were investigated in detail. PBDT is the first green electrochromic material which has a highly transmissive sky blue oxidized state. PDETQ was shown to be one of the few examples of neutral state green polymeric materials in literature. PDEQ has a bluish green color in the neutral state and a highly transmissive light blue oxidized state.

Synthesis of new electroactive monomers are highly desired since these compounds can be utilized as active layers in many device applications such as ECDs, LEDs and solar cells. Pyrrole and selenophene bearing polymers were also proven to be excellent candidates as electrochromic materials. Benzothiodiazole can be coupled to to pyrrole and selenophene yield materials that can be polymerized to give donor acceptor type polymers. These donor-acceptor type materials / Poly(4,7-di(1H-pyrrol-2-yl)benzo[c][1,2,5]thiadiazole P(PYBTPY) and poly(4,7-di(selenophen-2-yl)benzo[c][1,2,5]thiadiazole P(SEBTSE) were synthesized via bromination, stannylation and Stille coupling reactions. Electrochemical and electrochromic properties of the polymers were examined in detail.

Organic semi-conductors are of great interest since these compounds can be utilized as active layers in many device applications such as ECDs, LEDs and solar cells. Incorporating the benzotriazole units into the polymer backbone enhances the optical properties of donor units. Hexyl thiophene and pyrrole are commonly used as electron donor materials. Benzotriazole can be coupled to hexyl thiophene or pyrrole to yield materials which can be polymerized to give donor acceptor type polymers. These materials are promising components in fast switching polymeric electrochromic devices and highly efficient photovoltaic devices. During thesis studies,poly(2-dodecyl-4,7-bis(4-hexylthiophen-2-yl)-2H-benzo[d][1,2,3]triazole) (PHTBT) and poly(2-dodecyl-4,7-di(1H-pyrrol-2-yl)- 2H- benzo [d] [1,2,3] triazole) (PPyBT) will be synthesized via N-alkylation, bromination, stannylation and Stille coupling reactions. Electrochromic and photovoltaic properties of the polymers will be investigated in detail.

A proven strategy, donor-acceptor approach, to reduce the band gap of conjugated materials and possibly improve the photocurrent is to incorporate electron-rich and electron-deficient units in an alternating fashion in a polymer chain. For this purpose, a wise selection of donor and acceptor moieties in a monomer structure results in desired finishing properties of polymeric materials. In this study, fourteen novel monomers were synthesized to explore the acceptor and donor effects on the electronic and optoelectronic properties. Dibenzophenazine, dibenzopyrido]quinoxaline, tetrahydro- dibenzophenazine, thiadiazoloquinoxaline, pyrazinoquinoxaline, thienopyrazine, benzoselenadiazole, thienoselenadiazole were used as acceptor moieties, while thiophene, 3-hexylthiophene and 2,3-dihydrothienodioxine (EDOT) were used as the donor components in these donor-acceptor molecules. To synthesize desired monomers, well-known synthetic methods were performed, including bromination, nitration, reduction and condensation. Bromination was achieved by two different ways depends on the aim, NBS and Br2/HBr medium. For the nitration, HNO2 and H2SO4 were used together. Fe metal in refluxing acetic acid was used as the reducing agent in case of nitro group reductions. On the other hand, Zn metal/AcOH system was chosen for the reduction of both nitro groups and thiadiazole structure to amine, simultaneously. Finally, the Stille Coupling was used to obtain resulting acceptor-donor-acceptor monomers. These synthesized monomers were polymerized by electrochemically and investigated their properties by methods such as spectroelectrochemistry, kinetic and colorimetry studies. Spectroelectrochemistry experiments were performed in order to investigate key properties of conducting polymers such as band gap, maximum absorption wavelength, the intergap states that upon doping and evolution of polaron and bipolaron bands. Switching time and optical contrast of the polymers were evaluated via kinetic studies.

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.

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.

2-Dodecyl benzotriazole (BTz) and benzothiadiazole (BTd) containing copolymers poly(4-(2-dodecyl-2H-benzo[d][1,2,3]triazol-4-yl)benzo[c][1,2,5]thiadiazole (P1), poly(4-(5-(2-dodecyl-7-(thiophen-2yl)-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)benzo[c][1,2,5] thiadiazole (P2) and poly(4-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d] [1,2,3]triazol-4-yl) -3-hexylthiophen-2-yl) benzo[c][1,2,5] thiadiazole (P3) were synthesized via Suzuki polymerization. Electrochemical and optical properties of the polymers were analyzed. The fabrication of solar cells were carried out and current density-voltage (J-V) and incident photon to charge carrier efficiency (IPCE) measurements were done to characterize the solar cells.

The interest towards organic semi-conductors increased due to their tunable band gaps, redox properties, processability and low cost in the field of conducting polymers. Electrochromic materials have the ability to change color by altering their redox state. In the context of low cost flexible display device technology, requirements can be fulfilled with accessible multi-colored electrochromic polymers. In this study, we report the chemical synthesis and electrochromic properties of two spray processable, ambipolar, fluorescent and multi-color to transmissive electrochromic polymers. The electrochromic properties of these polymers were examined by cyclic voltammetry, spectroelectrochemistry, kinetic studies. Polymers, PTBTPh and PTBTTh, have multi-colored oxidation states and easily accessible ndoped states, which allowed us to achieve transmissive films in a low working potential. Electrochemical and spectral results showed that both polymers are potential materials for electrochromic display devices.

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.