Doping of Poly (3,4-ethylenedioxythiophene) (PEDOT) by FeCl3 | Chapter 9 | Chemical and Materials Sciences: Research Findings Vol. 4

 

Academic and industrial researchers have focused on developing conducting polymers that are stable in their conductive state during application, easy to process, and economical to produce. Conducting polymers, often referred to as synthetic metals, have garnered significant attention since Shirakawa and colleagues discovered that polyacetylene can achieve exceptionally high electrical conductivity. The study aims to investigate the structural, electrical, and thermal properties of the resulting material. Poly(3,4-ethylenedioxythiophene) (PEDOT) has been chemically synthesised using 3,4-ethylenedioxythiophene (EDOT) (Aldrich) as a monomer in an aqueous solution with FeCl3 as the oxidant. Doping of PEDOT using Camphor Sulfonic Acid (CSA) and FeCl3 was carried out separately for a 5-hour duration, and the resulting material was then subjected to various analyses. To detect structural changes after doping, infrared spectroscopic analysis, wide-angle x-ray diffraction analysis have been carried out. Elemental analysis (C, H, N, S, and O) of undoped and all doped samples was carried out using Thermofinniagn, Italy, model FLASH EA 1112 series, and ICP - Atomic Emission Spectroscopy made by Jobin Yvon, France, model JY Ultima–2 was used to detect Fe contents in all samples. PEDOT has been chemically synthesised by oxidation, coupling with FeCl3 as an oxidation reagent, and then treated with hydrazine to de-dope the prepared polymer. For complete confirmation, FTIR spectroscopy studies were carried out. The results of thermal analysis show that after doping PEDOT with FeCl3, the glass transition temperature (Tg) value decreases. It is observed that in the case of FeCl3-doped PEDOT, sulfur contents decrease while Fe contents increase compared to undoped PEDOT, indicating that it is quite likely that the S of PEDOT is getting replaced by Fe after doping with FeCl3. The utilization of FTIR analysis verified the successful synthesis of PEDOT, as well as the desired doping with FeCl3 and CSA. The crystal structure of the samples was analyzed using XRD, revealing modifications following doping. Additionally, the XRD results allowed for the calculation of sample crystallinity, which increased after doping with FeCl3 but decreased after doping with CSA. Using the four-probe method, electrical conductivity (σ) measurements were obtained, showing a significant increase in conductivity after doping with both FeCl3 and CSA, with the undoped sample having a conductivity of 3.41X10-3S/cm. A plot of Log σ versus 1/T was created, revealing that the undoped PEDOT had metallic characteristics above 308 K, while both doped samples displayed semiconducting behavior in the temperature range from ambient to 383̊ K. An indigenously designed apparatus similar to Lee's method was used for measuring the thermal conductivity, which revealed that all samples exhibited comparatively small thermal conductivity values. However, these values were found to increase upon doping and with a temperature rise. The thermal conductivity of all the samples was also measured using the FOX 50 instrument, a commercially available apparatus for the measurement of thermal conductivity. The values of thermal conductivity of all the samples were found to match the laboratory-designed instrument.

 

Author(s) Details

Ashish B. Chourasia
Department of Electronic Science, H.P.T. Arts and R.Y.K. Science College, Nashik-422 005, India.

Deepali S. Kelkar
Department of Physics, Govt. Institute of Science, Nagpur, India.

 

 

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