2,6-ditiyofen-2-il-3,5-bis(4-(tiyofen-2-il)fenil)ditiyeno(3,2-b;2',3'-d)tiyofen sentezi ve elektrokromik özelliklerinin incelenmesi
Synthesis and electrochromic properties of 2,6-(thiophen-2-yl)-3,5-bis(4-(thiophen-2-yl)phenyl)dithieno(3,2-b;2',3'-d)thiophene
Yazar: SUZAN BAŞLILAR
Danışman: PROF. DR. TURAN ÖZTÜRK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı
Derece: Yüksek Lisans, 2013
Konu: Kimya = Chemistry

Özet:
Endüstriyel uygulamalar ve bilimsel çalışmalarda konjuge polimerler ilgi odağıdır. Ditiyenotiyofenler, tiyofen halkalarında bulunan kükürt atomları sayesinde iyi elektron vericidirler. Dithienothiophenes (DTT) ve DTT türevleri malzemeler, elektrokromik cihazlar, enerji depolama, organik alan etkili transistörler, fotovoltaik aygıtlar, yarı iletkenler ve organik alan etkili transistörler gibi alanlarda elektronik ve optoelektronik gibi alanlarda umut verici özellikleri sergiliyor.
Bu çalışmada, DTT Th4DTT türevi, sentezlendi ve bu malzeme elektrokimyasal uygulandı. Th4DTT, Fouriertransforminfrared (FTIR), nükleer manyetik rezonans (NMR) spektrometrisi, hızlı bombardımanı kütle spektroskopisi (FAB-MS), veya yüksek çözünürlüklü kütle spektroskopisi (HR-MS), ultraviyole ve görünür alan spektroskopisiyle (UV-VIS) karakterize edildi. Elektrokromik özellikleri incelemek için, döngülü voltametri (CV) kullanıldı. Elde edilen polimerin özelliklerini incelemek için, monomersiz ortamda, referans elektrot ve çalışma elektrotu olarak 2 Pt tel olarak ve karşı elektrot ve Ag / AgCl kullanıldı. Elektrokromik cihaz (Electrochromic Device, ECD), polyethylenedioxythiophene ile hazırlandı. Th4DTT ve ethylenedioxythiophene (EDOT) ayrı ayrı ITO üzerine elektropolimerizasyonla kaplandı. Polimer kaplanan ITO yüzeylerinin arasına jel elektrot sürülerek, ECD sandviç gibi hazırlandı. ECD'a 0 ila 1.8 V arasında gerilim uygulandığında cihazın rengi turuncudan koyu mavi renklere doğru değiştiği gözlendi. Cihazın çalışma aralığının 0,0-1,8 V olduğu belirlendi. Cihazın, 10 saniye arasında değişen % 28'lik iyi bir optik kontrastı ve karalılığının iyi olduğu gözlendi.

Abstract:
Conjugated polymers have been drawing great attention due to their important applications in industry. Dithienotiopenes (DTT) have three sulfur atoms which make them rich in sulfur and good electron donors. Dithienothiophenes (DTT) and their derivatives are exhibiting promising properties applicable to electronics and optoelectronics such as electrochromic devices, energy storage, organic field effect transistors, photovoltaic devices and semiconductors.
In this work, a DTT derivative Th4DTT was synthesized and its electropolymerization was performed. Th4DTTwas characterized by Fourier transform infrared (FTIR), ultraviolet?visible (UV?VIS) spectroscopy, nuclear magnetic resonance (NMR) spectrometry, fast bombardment mass spectrometry (FAB-MS) and high resolution mass spectroscopy (HR-MS). 
The solution of 1 (0.3g, 5.93mmol) was dissolved in DMF (250ml) at room temperature and covered. The solution was stirred until it became 00C in ice bath. NBS (0.316g, 1.77mmol) was added in dark environment. It was left stirring for 4 hours. After 4 hours it was allowed to warm to room temperature. The solution was poured into water. Stools were taken by filtration.  The product 2 was purified with crystallization in toluene. (Yellow powder, 0.346g, 88%)
To the mixture of Pd0(PPh3)4 (%5), K2CO3 (2ml, 2M) and 4,4,5,5-tetramethyl-2-(thiophen-2-yl)-1,3,2-dioxaborolane 3 (0.569g, 2.71mmol) dissolved in THF (150 ml) and stirred for 0.5 h at room temperature under nitrogen atmosphere.  4 (0.3g, 0.451mmol) was added to mixture and the mixture was stirred for 2 days at 60 0C. It was then cooled to room temperature, filtered through celite. The organic layer was extracted with dichloromethane and dried over Na2SO4. The solvent was evaporated under reduced pressure. (Orange powder, 0.226g, 75%)
The electroactivities of the monomer and the polymer were studied by CV. Into a three component CV cell was placed two Pt wires, as counter and working electrodes, and Ag/AgCl as a reference electrode along with TBABF4 (0.1 M) mixture as a supporting electrolyte in DCM.
The electropolymerization of Th4DTT on ITO was performed in TBABF4 (0.1 M) in DCM solution under the constant potential of +1.5 V, for which the charge was optimized as 20 mC.
A mixture of TBABF4:PMMA:PC:ACN was prepared with a weight ratio of 3:7:20:70. TBABF4 and PMMA are dissolved in ACN. The mixture was stirring and heating until it became homogeneous. PC was added to plasticize the solution. Stirring and heating were continued until a gel was obtained.
Th4DTT and EDOT were separately prepared via electropolymerization on ITO. The gel electrolyte was spread between the two layers for the preparation of the ECD. The electropolymerization of Th4DTT on ITO was performed in TBABF4 (0.1 M) in DCM solution under the constant potential of +1.5 V (2.5x10-2C). The PEDOT layer was constructed by electropolymerization of EDOT (0.01 M in ACN) in 0.1 M TBABF4 in ACN under the constant potential of 1.4 V (1.9x10-2C).
Th4DTT was electropolymerized in a cyclic voltammetry cell, using Pt wires as counter and working electrodes and Ag/AgCl as a reference electrode. The oxidation and reduction potentials of the polymer were determined to be 1.37 and 0.89. A linear change in the cyclic voltammetry of the monomer-free polymer was observed at various scan rates i.e. 50, 100, 150, 200 and 250 mV/s.
P(Th4DTT) electrochemically coated on ITO cleaned with a monomer free solution to remove the unreacted monomers. The ITO was placed in a cuvette for a UV? VIS measurement. The changes in the absorbance were from 0 to +1.7 V. The neutral form of the polymer had two absorption peaks at 335 and 426 nm. When applied voltage increases, reduction were observed in the neutral state?s peaks and a new bipolaron peak appeared at 721 and 1051 nm. The color of the polymer changed from orange to green then blue as the bathochromic shift took place.
Electrochromic materials ability to change color sharply and rapid switching between oxidized and neutral states are important. The switching time is the time taken from the highest transmittance value to the lowest. The switching experiments were performed at four different and fixed wavelengths 721 nm from 0 to 1.5 V. The switching time was found to be 5 s for each wavelength and the optical contrast was 31% at 731 nm.
The configuration of the ECD can be represented as ITO/P(Th4DTT)||gel electrolyte||PEDOT/ITO. While constructing the ECD, anodically coloring P(Th4DTT) was kept in its neutral form and cathodically coloring PEDOT was in its oxidized state. The color of P(Th4DTT) at 0.0 V was observed to be orange and the color of PEDOT layer was a transparent blue. When 0 V was applied, the color of the ECD was observed to be brown. As the potential was increased up to 1.2 V, the color of the ECD turned to green. When 1.8 V applied, the color of ECD turned to dark blue.
Chronoabsorptometry technique was used to perform the switching time measurements. The wavelength of the measurement was found to be 611 nm. The switching potentials were applied from 0 V to 1.8 V and the optical contrast (% ?T) was found to be 28%. The switching time was determined to be 10s.
An ECD?s stability gives information about the lifetime of the device. Tests indicated that the ECD had a good stability with a continuous redox switching under applied potential range between 0.0 and 1.8 V even after 500 cycles.
In conclusion, electrochromic properties were then investigated by cyclic voltammetry (CV). Monomer-free experiment was conducted using Pt wire as a working and counter electrode and Ag/AgCl as a reference electrode. Electrochromic device (ECD) was constructed with polyethylenedioxythiophene. Th4DTT and EDOT were electropolymerized separately on ITO, and ECD was prepared sandwiching two ITO layers using a gel electrode. ECD had potential range of 0.0?1.8 V for operating the device between orange and dark blue colors. It had a good optical contrast of 28% with a switching time of 10 second. The ECD displayed a good stability.