고려대학교

초록/요약

ABSTRACT The present study desribes methods for systhesis and characterization of conducting nanocomposites consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and carbon nanotubes (CNTs). The nanocomposites were synthesized using two different strategies: In the first strategy, a new and practical method for fabricating water dispersed multiwalled carbon nanotubes (MWNTs) and conducting polymer PEDOT nanocomposites with enhanced conductivity and thermal stability. The conducting nanocomposites were prepared by physicochemical modification of MWNTs with poly(styrene sulfonate) (PSS), followed by an in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT) in the presence of PSS-wrapped MWNTs. Morphological analysis of the resulting MWNT-PSS:PEDOT composites revealed the presence of PSS on the outer surface of the tubes with a core-shell structure and the association of PEDOT with the PSS bound to MWNTs. In comparison to the control PEDOT:PSS films, the composite film showed improved electrical properties along with thermal stability at high temperature (120oC), thus demonstrating its potential for application to robust optoelectronic devices. In the second strategy, a general procedure is reported for synthesizing the organic dispersed singlewalled carbon nanotubes (SWNTs) and PEDOT nanocomposites. The preparation of the composites involved the non-covalent modification of SWNTs with poly ionic liquids (PIL) to provide water-soluble PIL-functionalized SWNT. After the anion exchange reaction with lithium salts having hydrophobic anions, the organo soluble PIL-functionalized SWNT was formed. The organo soluble SWNT-PIL was used as a dopant for the polymerization of PEDOT. Compared to the control PEDOT:PIL films, the composite films showed improved electrical and thermal stabilities, indicating that PIL could play a dual role by increasing the solubility of SWNTs in organic solvents and providing effective anchoring sites for bonding with PEDOT chains. The effectiveness of nanotube inclusion for improvement of conductivity and thermal stability was studied in each strategy. The sheet resistance of the MWNT-PSS:PEDOT composites film decrease from 4.4x103 ohms/square to 2.1x102 ohms/square as the MWNT content was increased from 0 to 0.2 wt%, respectively. Moreover, the resistance of the control PEDOT:PSS film increases dramatically over time, while MWNT-PSS:PEDOT composites film shows only a minimal change when these films were stored at 120oC in an oven for 300 h. In the case of organic dispersed SWNT-PIL:PEDOT composite, comparison with PEDOT:PIL, the composite with about 0.2 wt% SWNT content, showed decrease by more than two orders of magnitude from 105 to 103 ohms/square of surface resistance, and 56oC higher in the onset temperature. This was attributed to the fact that the carbon nanotubes were well-dispersed improving the contact between neighboring CNTs, so this might be the reason for decrease of sheet resistance and prevent thermal degradation since without local heat in the composites.