Department of Chemical Engineering
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Browsing Department of Chemical Engineering by Author "AL-OGAİDİ, Saad"
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thesis.listelement.badge SYNTHESIS AND POLYMERIZATION OF BENZIMIDAZOLE BASED MONOMERS VIA A DONOR – ACCEPTOR APPROACH(2015-06-25) AL-OGAİDİ, Saad; CİHANER, AtillaA new series of fluorescent donor-acceptor-donor (D-A-D) type monomers based on benzimidazole acceptor unit bearing cycloalkane appendages, called 4,7-di-2,3- dihydrothieno[3,4-b][1,4]dioxin-5-ylspiro[benzimidazole-2,1'-cyclopentane] (E5E), 4,7-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-ylspiro[benzimidazole-2,1'- cyclohexane] (E6E) and 4,7-di-2-thienylspiro[benzimidazole-2,1'-cyclohexane] (T6T), were synthesized and polymerized via potentiostatic and potentiodynamic methods. The effect of ring size on benzimidazole unit and the kind of donor moiety in D-A-D system has been studied systematically on the electrochemical and optical properties. The optical studies showed that ring size of the benzimidazole unit has no effect on the absorbance and fluorescence properties, whereas the oxidation potential of E5E, E6E and T6T monomers varied with respect to both the ring size and donor unit: 0.89 V, 0.83 V and 1.22 V vs Ag/AgCl, respectively. All polymers have ambipolar (p- and n-type doping) and electrochromic properties. While the polymer films PE5E and PE6E are green at neutral state and transparent at oxidized state, the polymer PT6T has no appreciable color change between its neutral and oxidized state. The polymers bearing 3,4-ethylenedioxythiophene unit as donor units (PE5E and PE6E) exhibited lower band gap values (1.21 eV and 1.18 eV, respectively) than PT6T (1.53 eV). When compared to PT6T, PE5E and PE6E polymers are more stable under ambient condition. While PE5E retained 76% of its electroactivity after 4000 cycles, PE6E has 65% of its electroactivity after 2000 cycles.