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|Ultra-Fast and Green Synthesis for Water Soluble Polyaniline and its Applications
|, Sami ur Rahman
|University of Peshawar, Peshawar.
|Ultra-Fast and Green Synthesis for Water Soluble Polyaniline and its Applications To search for new materials which are more effective and superior for greater performance, material scientists worked to developed new routes which are easier, low cost and environment friendly. Moreover, the time factor is also very important, that how fast the materials could be prepared. Chemical oxidative polymerization of aniline is a promising way to tailor the properties and solubility of Polyaniline (PANI). The large consumption of chemicals and time are still the major drawbacks of this technique. This research project is designed to synthesize soluble PANI through an ultra-fast and a green route by using a novel anionic and environment friendly dopant. By this method the ma terial was synthesized in a very short period of time (5-10 min.) with excellent yield (98.62%) and high conductivity (10 S/cm). The synthesized PANI was not only soluble in water but also in N-Methyl Pyrrolidone (NMP), Dimethyl Formamide (DMF), Dime thyl Sulfoxide (DMSO), Tetrahydrofuran (THF) and Ethanol. After optimization of the reaction parameters, the obtained polymer was system atically characterized for physico-chemical and electrochemical properties. Physiochemi cal properties such as structural determination, optical properties, morphology, elemental composition, crystalinity and thermal stability were studied by Fourier Transform Infra red Spectroscopy (FTIR), UltraViolet-Visible Spectroscopy (UV-vis), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Diffraction (EDX), X-ray Powder Diffrac tion (XRD) and Thermogravimetric Analysis (TGA) respectively. These techniques con firmed that the dopant phytic acid sodium salt has successfully incorporated into the pol-ii ymer chain. Among all the synthesized PANI samples i.e. P-0.5, P-1PA, P-3PA, P-5PA, P-7PA and P-10PA, the optimized case P-5PA has a desirable nanoscale fibrous porous interconnected morphology. DC conductivity was measured by Four-Probe Conductome ter. Electrochemical performance was studied by Cyclic Voltammetry (CV), Gal vanostatic Charge Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS), CV and impedance results confirmed that the optimized case i-e P-5PA electrode exhibits high electrocatalytic performance and capacitive behavior with very low charge transfer resistance (Rct) of 7.439 Ohm at 0.6 V. To further check the capacitve nature of the elec trode material, GCD analysis was performed in both three electrode system and two elec trode system. In three electrode system the specific capacitance of the material was calcu lated from GCD at various current densities ranging from 1 Ag-1 to 40 Ag-1 . At 1 Ag-1 , the specific capacitance was 832.5 ± 1.400 Fg-1 and 528 ± 1.357 Fg-1 at a very high current density 40 Ag-1 . Stability was further checked for 1000 cycles at a high current density of 40 Ag-1 having retention 95.26%. For practical application, the synthesized material was fabricated into symmetric supercapacitor device (two electrode system) and was checked by GCD for various cur rent densities ranging from 1 to 40 Ag-1 . At 1 Ag-1 , the capacitance was 531.5 ± 2.177 Fg-1 and 355.35 ± 2.195 Fg-1 at 40 Ag-1 . Stability of the device was also checked for 1000 cycles at a current density of 40 Ag-1 having excellent retention i.e. 90%. Further more the PANI symmetric supercapacitor showed significant enhancement in both the energy density and the power density. It delivered an energy density of 73.82 Wh kg-1 at iii the power density of 500 W kg-1 . More importantly, the energy density was very stable with the increase in the power density. The energy density reached up to 49.35 Wh kg-1 even at a power density as high as 20000 W kg-1 , which was much higher than most of current commercial supercapacitors. Furthermore aniline was also polymerized on chitosan film prefabricated on glass slides to obtain conductive patches. After optimization morphology, elemental composi tion and functional groups detection of the Patches were done by SEM, Atomic Force Microscopy (AFM), EDX and FTIR. Among all the polymeric patches (Patch-0.5, Patch 1, Patch-3, Patch-5, Patch-7, Patch-10), Patch-5 has a more uniform nanoscale granular homogeneous surface topography indicating that polymerization of PANI proceeded ef fectively and uniformly on the chitosan surface. Sheet resistance was measured by four probe conductometer. Electronic properies of the optimized conductive polymeric Patch 5 were studied by CV and UV-vis in phosphate buffer solution (pH 7.4) as a physiologi cal medium. The results indicate that our methodology of polymerizing the aniline in the presence of phytic acid sodium salt as a dopant on the surface of chitosan film leads to a conductive polymeric patch of chitosan grapted PANI that shows conductivity for ex tended period of time (21 days) in physiological conditions. This fabrication technique for conductive polymeric patches can find applications in the field of tissue engineering, especially, in cardiac muscles.
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