Nonylbithiazol centered comonomer synthesis and electrochemical characterization

Abstract

Since the first appearance of the conducting polymers in the late 70s, many researchers have been focused on the conducting polymers to commercialize them with applications such as thin film transistors, polymer light-emitting diodes (LEDs), and electrochromic devices. The poly(alkylbithiazoles) has received considerable attention because of its n-doping capability and usage in light emitting diode construction, this new class of conjugated polymer exhibit interesting thermochromic and electrochemical behavior especially nonyl derivative shows unusual optical properties. The most general use of carbon fibers is to reinforce composite materials due to its unique properties such as high strength, high modulus and low density. In order to achieve this, the surface properties them were studied recently and modification surfaces by electropolymerizing 3-methyl thiophene, terthiophene, pyrrole, E DOT and their copolymers and by electrocopolymerizing acrylamide, carbazole, thiophene, carbazole, pyrrole, carbazole, indole onto the fibers have investigated in detail. Conducting polymers, such as polypyrrole, polyaniline, poly thiophene, arid their derivatives, were reported as electrode materials for supercapacitors. Super-capacitors can be classified into two types the double-layer which store the energy within the electrochemical double-layer at the electrode-electrolyte interface and the redox supercapacitors. For redox supercapacitors, among several types of electrode materials employing of conducting polymers has received much attention due to -their use in both aqueous and organic electrolytes and their wide potential working range. The electrochemical impedance spectroscopy (EIS) is one of the most effective and the reliable method to extract information about electrochemical characteristics of the electrochemical system for instance double-layer capacitance, diffusion impedance, determination of the rate of the charge transfer and charge transport processes, solution resistance etc. EIS was used to explain behavior of the polymer coated electrodes by established theories employing two models which are known as uniform and porous medium.In this study, the synthesis and characterization of a novel donor acceptor donor type ENBTE comonomer and its electrochemically prepared polymer on carbon fiber, Pt button and ITO plate is reported. Cyclic voltammetry of the polymer in 0.1 $MEt_4 NBF_4/CH_2Cl_2$ exhibits a very well defined and reversible redox processes and this comonomer can be either p-doped or n-doped. The half-wave oxidation potentials of the polymer $(E_{1/2})$ were observed at 0.303 Vand 0.814 V versus Ag/AgCl. The polymer is electrochromic; the onset for the $pi$ to $pi^{ast}$ transition (Eg) of 1.75 eV with a $lambda_{max}$ at 2.15 eV and the homogeneous and high quality film of the polymer is stable of its optical properties offering fast switching time which is less than 0.25s. The morphological studies reveal that the polymer was deposited as a continuous and very well adhering film to surface of the carbon fiber microelectrode. All these properties make this polymer favorable for use in electronic devices. Capacitive behavior of the carbon fiber microelectrode/PENBTE film was firstly noticed from CV experiments which exhibit a rectangular shape, for a galvanostatically prepared polymer film with a charge of 5 C $cm^{-2}$ which specific capacitance value was obtained about ~340 mF $cm^{-2}$. EIS studies revealed that high capacitance values observed in lower frequency region. The electrochemical impedance data were fitted two equivalent circuit models to find out numerical values of the proposed components. Simulation results showed that proposed electrical equivalent circuit was successfully applied to the experimental data to explain the interface between the carbon fiber microelectrode, the polymer film and the electrolyte. The slope the galvanostatic charge/discharge curve is 0.9985 and -0.9998 respectively indicates that IR drop is negligible and triangular shape of the charge discharge curve is typical for ideal capacitor behavior suggest that very good capacitive performance. The galvanostatic charge/discharge characteristic of a film was investigated and the morphology of the films electrodeposited at different deposition charges were monitored using FE-SEM. From the obtained results, we can conclude the employed comonomer in polymer electrode shows very good capacitive behavior on carbon fiber microelectrode. The measured capacitance values are quite promising for super capacitor constructions with a good engineering.

Özet

Bu çalışmada yeni elektron alıcı-verici-alıcı türündeki bis(3,4-etilen-dioksitiyofen)-(4,4'-dinonil-2,2'-bitiyazol) komonomer inin sentezi, karakterizasyonu ile karbon fiber, Pt elektrot ve İTO kaplı cam üzerine elektrokimyasal polimerizasyonu çalışılmıştır. Polimerin 0.1 M'hk Et4NBF4 /DCM elektrolit çözelti ortamındaki döngülü voltamogramı çok iyi ve tersinir redoks davranışı göstermektedir. Ayrıca bu komonomer hem p-katkılandırma hem de n-katkılandırma özelliklerine sahiptir. Polimerin yarı dalga (Em) potansiyeli Ag/AgCl referans elektroda karşı 0.303 V ve 0.814 V değerlerinde olduğu gözlemlenmiştir. Polimer elektrokromiktir: $pi$- $pi^{ast}$ geçişlerinin başlangıcından band aralığı (Eg) değeri 1.75Volarak hesaplanmıştır ve $lambda_{max}$ değeri de 2.15 eV dur. Polimerin homojen ve kaliteli filmi 0.25 s den daha az zamanda anahtar lama özelliği ile kararlı optik özellikler sunmaktadır. Morfolojik çalışmalar ise polimerin karbon fiber mikro elektrot yüzeyine homojen ve sürekli şekilde biriktirildiğini göstermektedir. Bütün bu özellikler polimerin elektronik cihazlarda kullanıma elverişli olduğunun bir göstergesidir. Karbon fiber mikroelektrot/poli (3,4-etilen-dioksitiyofen)-(4,4'-dinonil-2,2'-bitiyazol)in kapasitif davranışı ilk önce sabit akımda (5C $cm^{-2}$) yük ile hazırlanmış olan polimer filmin dikdörtgen şekil gösteren döngülü voltamogramında fark edilmiştir. Polimer filmin spesifik kapasitansı yaklaşık olarak -340 mF $cm^{-2}$ elde edilmiştir. İki adet eşdeğer devre, elektrokimyasal empedans verileri ile önerilen bileşenlerin nümerik değerlerini bulabilmek için eşleştirilmiştir. Filmin sabit akımda yükleme/boşaltma özelliği, çözücünün ve biriktirme yükünün filmin kapasitif davranışı üzerindeki etkisi de incelenmiştir. Elektrokimyasal olarak farklı biriktirme yükleri ile hazırlanmış filmlerin morfolojisi FE-SEM ile görüntülenmiştir.