Browsing by Author "Onal, Ahmet M."

Now showing 1 - 3 of 3

Cross-exchange of donor units in donor-acceptor-donor type conjugated molecules: Effect of symmetrical and unsymmetrical linkage on the electrochemical and optical properties
(2020) Eroglu, Deniz; Ergun, Emine Gul Cansu; Onal, Ahmet M.; 0000-0002-3941-4345; I-7385-2017
A series of donor-acceptor-donor type molecules were synthesized using carbazole (C) and thiophene (T) as donor units. The donors were connected symmetrically and unsymmetrically to the acceptor unit of benzothiadiazole (B). With having four combinations, CBC, CBT, TBT and CTBTC, changes in the electrochemical and optical behaviors of the monomers were investigated using cyclic voltammetry, differential pulse voltammetry, UV-Vis and Fluorescence spectrometry techniques. Replacing one of the symmetrical C units in CBC with T unit caused a slight red shift in lower energy absorption band. On the other hand, having both C and T units symmetrically in the monomer structure exhibited about 70 nm red shift in the optical absorption. Electrochemical polymerization of the monomers was studied via potential cycling. In the case of formation of polymer films, the effect of exchange and combination of the donors on the electrochemical and optical properties was investigated. (C) 2020 Elsevier Ltd. All rights reserved.
Effect of Thiophene Units on the Properties of Donor Acceptor Type Monomers and Polymers Bearing Thiophene-Benzothiadiazole- Scaffolds
(2016) Cansu-Ergun, Emine G.; Akbayrak, Merve; Akdag, Akin; Onal, Ahmet M.; 0000-0002-0058-905X; 0000-0003-3283-2146; 0000-0002-3941-4345; 0000-0003-0644-7180; 0000-0003-3283-2146; A-7063-2010; N-5377-2016; I-7385-2017; AAS-5007-2020; HCG-9312-2022
In this article, a series of benzothiadiazole and thiophene based donor-acceptor-donor (D-A-D) type monomers and their corresponding polymers, via potential cycling, were reported. Effect of increasing number of thiophene units in the electron rich donor segment on the electrochemical and photophysical properties of the monomers and their corresponding polymers were reported. Electrochemical and optical properties were determined by cyclic voltammetry, UV-Vis and emission spectrometry. Monomers with one, two and three thiophene units on both sides of benzothiadiazole (TBz, T2Bz, T3Bz) exhibited better conjugation and intramolecular charge transfer with increasing thiophene length. On the other hand, the inverse trend was observed in their corresponding polymers (PTBz, PT2Bz, PT3Bz). Blue shift of the absorption edge in polymer thin films resulted in wider optical bandgap (from 1.70 eV to 1.99 eV) with increasing donor/ acceptor ratio on the polymer chain. Based on our experimental and theoretical studies, molecular weight or branching on these polymers together with degree of stiffness and conformational degree of freedom might be an explanation for these controversial observations. (C) 2016 The Electrochemical Society. All rights reserved.
Neutral-State Black Electrochromic Polymer With Enhanced Supercapacitor Electrode Performance
(JOURNAL OF ENERGY STORAGE, 2024-11-15) Ergun, Emine Gul Cansu; Onal, Ahmet M.
Neutral-state black electrochromic materials are attracting attention, especially in the applications of displays, car-rear views, sensors, and electronic papers. This study aimed to obtain a black electrochromic polymer via electrochemical techniques. For this aim, the monomer of a green-electrochromic polymer, 4-(3,3-dihexyl-3,4dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-7-(3,3-dihexyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-8-yl)-2cyclohexyl-2H-benzo-[d]imidazole (PBP), was copolymerized with 3,4-ethylenedioxythiophene (EDOT) with 2:1 and 2:2 (PBP: EDOT) monomer feed ratios. The resulting copolymer films were investigated in terms of their electrochromic properties. Equal feeded copolymerization resulted in a neutral-state black electrochromic polymer (L:11.5, a:1.5, b:-2.55) with satisfying responses in the electrochromic device application (100 % electroactivity maintenance after 300 switches with 1.4 s response time). Furthermore, increasing the quantity of EDOT in the copolymer chain improved the capacitive characteristics, showing that the equal-fed copolymer is a good candidate for a supercapacitor electrode (4.07 mF/cm(2)). The supercapacitor device application showed that the equal feeded copolymer has superior specific capacitance retention of 97 % after 500 charge/discharge cycle, with 100 % coulombic efficiency in each cycle. Moreover, the supercapacitor is capable of lighting a 1.5 V LED for >30 s.