Design and synthesis of novel donor-acceptor type monomers and investigation of optoelectronic properties of their polymers

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü, Türkiye

Tezin Onay Tarihi: 2010

Öğrenci: ELİF KÖSE ÜNVER

Danışman: LEVENT KAMİL TOPPARE

Özet:

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.