Browsing by Author "Pekel, Lutfiye Canan"

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Citation - WoS: 2
Citation - Scopus: 2
New electrochromic copolymers based on spiro bipropylenedioxythiophene and 3,4-ethylenedioxythiophene
(Elsevier Science Sa, 2014) Pekel, Lutfiye Canan; Karabay, Bads; Cihaner, Atilla; Chemical Engineering
Two alkylenedioxythiophene derivatives, Spiro bipropylenedioxythiophene (Spiro-BiProDOT) and 3,4-ethylenedioxythiophene (EDOT), were integrated electrochemically in order to attain low band gap electrochromic copolymers. EDOT has a functionality of two, which causes a linear polymer, whereas Spiro-BiProDOT has a functionality of four and its polymerization results in a network polymer. Therefore, by playing the monomer feed ratio, the crosslink degree can be adjusted for the copolymers obtained electrochemically from EDOT and Spiro-BiProDOT monomers in an electrolyte solution of 0.1 M tetrabutyl ammonium hexafluorophosphate dissolved in dichloromethane. It was found that copolymers showed different electrochemical and optical properties at their various redox states when compared to their homopolymers. For example, they could be switched from dark blue in the neutral state to reddish blue at intermediate state and finally to transparent blue in the oxidized state with 45-51% of the transmittance change at 575-595 nm. pi-pi* transition bands of the copolymers can be shifted to higher wavelengths when compared to poly(Spiro-BiProDOT) by increasing the amount of the EDOT units in the polymer backbone. They have low band gaps in the range of 1.65 and 1.73 eV. (C) 2014 Elsevier B.V. All rights reserved.
Citation - WoS: 46
Citation - Scopus: 47
A Pure Blue To Highly Transmissive Electrochromic Polymer Based on Poly(3,4-Propylenedioxyselenophene) With a High Optical Contrast Ratio
(Amer Chemical Soc, 2015) Karabay, Baris; Pekel, Lutfiye Canan; Cihaner, Atilla; Chemical Engineering
A new derivative of 3,4-propylenedioxyselenophene bearing naphthalenylmethyl appeandages on the bridge, called 3,4-dihydro-3,3-bis((naphthalen-2-yl)methyl)-2H-selenopheno[3,4-b][1,4]dioxepine (ProDOS-Np-2), was synthesized and polymerized via potentiostatic and potentiodynamic methods. The electrochemically obtained polymer film (PProDOS-Np-2) is pure blue at the neutral state and highly transparent at the oxidized state. An increase in the size of the substituents on the bridge resulted in an increase in the optical contrast ratio. Upon moving from naked bridge to benzyl and to naphthalenylmethyl substituents on the bridge center, the optical contrast changed from 51% to 65% and finally to 84%, which is the second highest reported optical contrast ratio in polyselenophene family. When compared to polythiophene analogue, the PProDOS-Np-2 has lower oxidation potential and band gap, higher optical contrast ratio, coloration efficiency, robustness, and stability. The polymer film preserved its properties even after thousands of cycles under ambient conditions.