| Summary: | 博士 === 國立中興大學 === 材料科學與工程學系所 === 98 === The water-soluble sulfonated polyaniline (SPANI)/carboxylic groups containing multi-walled carbon nanotube (c-MWCNT) composites with core-shell tubular structure have been prepared by solution mixing of c-MWCNT and SPANI aqueous colloids. Fourier-transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), field- emission scanning (SEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize their structure and morphology of composites. The results of Raman, UV-Vis and XPS spectra revealed the presence of electrostatic interaction between the C-N+ species of the SPANI and the COO- species of the c-MWCNTs. The addition of c-MWCNTs can improve the thermal stability of SPANI specimens. The conductivity of 3 wt% SPANI/c-MWCNT composites at room temperature is sixteen times higher than that of SPANI. The above results demonstrate that the addition of a small number of c-MWCNTs into SPANI matrix can efficiently form a conducting network in the well dispersed composites, thus increasing the electrical properties of the composites. In addition, similar methodology has been applied to fabricate the water-soluble sulfonated polypyrrole (SPPy)/c-MWCNT composites by aqueous mixing of c-MWCNT dispersions and SPPy colloids.
The electrochemical performances of these SPANI/c-MWCNT composites have been investigated using cyclic voltammetry and electrochemical impedance spectro- scopy. The incorporation of the c-MWCNTs to SAPNI increases the electrochemical activity of SPANI/c-MWCNT composite films and promotes the electron transfer of the redox processes. Furthermore, the presence of c-MWCNTs also leads to more active sites for electrochemical reactions and a faster electron transfer than pure SAPNI. In addition, the morphology of SPANI/c-MWCNT composites measured by SEM and atomic force microscopy indicates the presence of well-distributed tubular structures that are individually coated with ED-SPANI on the surface of composite films. The relatively rough topography of composite films would provide a large surface area for electrolyte access. Therefore, it is expected that the difference in the structure of the composite films can result in high electrochemical properties of the electrodes constructed from these composite films.
The electrospinning process has been successfully used to fabricate ultrafine fibers consisting of the mixture of SPANI and poly(ethylene oxide) (PEO). The key factor of fiber formation with uniform size of fibers were dependent on the solution viscosity. The SEM images showed that the average diameter of SPANI/PEO electrospun fibers were evidently decreased with increasing loading of SPANI content. This trendency may be attributed to the increase in the net charge density of the solution with the presence of SPANI, which favors the formation of thin fibers. The conductivity of SPANI/PEO electrospun fibers fabricated with the weight ratio of SPANI/PEO at 0.33 is about five times of magnitude higher than that of electrospun fibers with SPANI/PEO at 0.2. In addition, conducting composite fibers were also obtained through electro- spinning of SPANI/PEO solution containing different contents of c-MWCNTs. HRTEM images confirmed that the c-MWCNTs were encapsulated within the fibers as individual elements, mostly aligned along the fiber axis. The measured results showed that the electrical conductivity of the electrospun fiber mats improved with increasing the content of c-MWCNTs.
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