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Synthesis and Performance Research of Conducting Polymer with New Nano/Microstructures

Author: WangTaoQing
Tutor: ZhongWenBin
School: Hunan University
Course: Materials Science
Keywords: Conducting polymers Nanostructure Polyaniline Polypyrrole Adsorption Thermal stability Acid doping Soft template
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 253
Quote: 1
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Abstract

The nanostructured conducting polymers, such as polyaniline (PANI) and polypyrrole (PPy), have broad applications in conducting molecular wires, chemical sensors (such as actuators), and gas-separation membranes, etc, due to the advantages of both organic conductors and nanostructures. Thus, it is important to fabricate nanostructured conducting polymers with controllable morphology and sizes. Here, the PANI nanosheet with arrays of oriented nanofibers doped by nitric acid (HNO3), the PANI nanoring consisted of nanofiber doped by sulfuric acid (H2SO4), and the layered PPy network Plates doped by HNO3 was respectively synthesized by chemical oxidative polymerization. Additionally, the PPy nanowires in the presence of phosphonic acid, benzoic acid and ethanoic acid was also prepared. Moreover, a plausible mechanism, the effects of recipe and performance research of each nanostructures was systematically investigated. The main results are concluded as follows:(1) The PANI nanosheet with length up to several micrometers and the PANI nanoring with diameter of 700 nm, which are all consisted of nanofibers with diameter of 30 nm and length of 100 nm, were respectively prepared with the assistance of HNO3 and H2SO4 used as dopant by oxidative polymerization in the presence of cetyltrimethylammoniμm bromide (CTAB). It is found that the concentration of acid play an important role in forming these nanostructures. When the concentration of HNO3 and H2SO4 are in the range of 0.60-1.8 M and 0.18-1.2 M, respectively. The PANI nanosheet and the PANI nanoring can be facilely synthesized. The presence of CTAB is the necessary condition to synthesize the PANI nanosheet and the PANI nanoring, which could be synthesized in a wide concentration range of CTAB 0.010-0.035 M and 0.0055-0.033 M, respectively. The PANI nanosheet and the PANI nanoring are slightly effected, when the the concentration of aniline is respecticely in the range of 0.02-0.08 M and 0.015-0.067 M. However, with the increase of the concentration of aniline,the nanofiber is changed tighter. Furthermore, the feasible temperature of polymerization is 0℃. The XRD indicates that the PANI nanosheet and the PANI nanoring have a great crystalline; Moreover, the atomic emission spectrometry indicates that the PANI have a great adsorption to Pb2+, which can be up to 360 mg/g and 325 mg/g, respectively.(2) Polypyrrole (PPy) nanowire network plates with both average length and width in tens of micrometers were prepared in the presence of CTAB by using HNO3 as dopant and chemical oxidative polymerization methods. The plates have clear rims and are comprised of double layers of nanowire networks, where the diameter and length of nanowire is about 70 nm and 0.5-1μm. It is found that HNO3 play a key role in forming PPy nanowire network plates, which could be synthesized in a wide concentration range of HNO3 (from 0.5 to 2 M). Moreover, the PPy nanowires could be synthesized in a high or low concentration of HNO3. The system of preparing the PPy nanowire network plates appears to fit the concentration range of CTAB (from 0.01 to 0.021 M) and pyrrole (from 0.01 to 0.021 M), at about 15℃. The hydrochloric acid (HCl) and H2SO4 is not a feasible acid for preparing the PPy nanowire network plates. The form of PPy nanowire network plates is probably a cooperating result of three factors: HNO3 served as oxidant to polymerize pyrrole into oligomers, CTAB used as soft-template to prepare nanowires, and NO3- increasing the packing parameter of cationic surfactants to guide the form of“plate”. XRD indicates that the PPy nanowire network plates have a better crystalline than the PPy nanowires.(3) The uniform nanowires of polypyrrole (PPy) was respectively prepared by fixing the concentration of pyrrole in the presence of the phosphonic acid, benzoic acid,ethanoic acid and in the absence of acid. The range of concentration of recipes for prepared nanowires in the presence of different acid has been suggested by discussing the effect of recipes on morphologies. Moreover, the effects of recipe prepared PPy nanowires on the thermal stability of PPy nanowires was systematically investigated by thermogravimetric analysis (TGA). It indicates that the styles of acid play an important role in enhancing the thermal stability of PPy nanowires. The thermal stability of PPynanowires doped by organic acid and inorganic acid with the rigid group of molecular structure can be improved. The temperature of polymerization doped by benzoic acid can affect the thermal stability of PPy nanowires, which decrease with the decrease of temperature. Additionaly, The thermal stability of PPynanowires is litter effected by the the concentration of acid and CTAB.

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