Date

2006

Author

Çamurlu, Pınar

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In this study three different 3-ester substituted thiophene monomers were synthesized via esterification reaction of 3-thiophene ethanol with adipoyl chloride or sebacoyl chloride or octanoyl chloride in the presence of triethylamine at 00C. Characterizations of the monomers were performed by 1H-NMR, 13C-NMR, FTIR, DSC, TGA techniques. Electrochemical behavior of the monomers both in presence or absence of BFEE were studied by cyclic voltammetry. Results showed the astonishing effect of BFEE on the polymerization, where free standing films of the homopolymers could be synthesized. Copolymers of the monomers with thiophene or 3-methyl thiophene were synthesized at constant potential electrolysis and the resultant polymers were characterized by FTIR, DSC, TGA, SEM and conductivity measurements. Second part of the study was devoted to investigate the one of most interesting property of conducting polymers, the ability to switch reversibly between the two states of different optical properties, ‘electrochromism’. In recent years there has been a growing interest in application of conducting polymers in electrochromic devices. Thus, electrochromic properties of the synthesized conducting polymers were investigated by several methods like spectroelectrochemistry, kinetic and colorimetry studies. Spectroelectrochemistry experiments were performed in order to investigate key properties of conjugated polymers such as band gap, maximum absorption wavelength, the intergap states that appear upon doping and evolution of polaron and bipolaron bands. Switching time and optical contrast of the homopolymers and copolymers were evaluated via kinetic studies. Results implied the possible use of these materials in electrochromic devices due to their satisfactory electrochromic properties like short switching time and stability. Generally the homopolymers displayed color changes between yellow, green and blue colors upon variation of applied potentials. Fine tuning of the colors of the polymers were accomplished by techniques like copolymerization and lamination. These studies were supported with experiments like spectroelectrochemistry and FTIR. Results showed the possible control of the color of the electrochromic material in a predictable, controlled and reproducible manner. Yet, it was possible to achieve different tones of yellow, green, orange color in neutral state of these materials. As the last part of the study, dual type electrochromic devices based on polymers of 3-ester substituted thiophenes with poly(3,4-ethylenedioxythiophene) were constructed, where the former and the later functioned as anodically and cathodically coloring layers respectively. Spectroelectrochemistry, switching ability, stability, open circuit memory and color of the devices were investigated and the results revealed that these devices have satisfactory electrochromic parameters.

Subject Keywords

Conducting polymers., Electrochromic devices.

URI

http://etd.lib.metu.edu.tr/upload/12607773/index.pdf
https://hdl.handle.net/11511/16522

Collections

Graduate School of Natural and Applied Sciences, Thesis