Anisotropic Growth Control of Polyaniline Nanostructures and Their Morphology-Dependent Electrochemical Characteristics

Abstract

Polyaniline (PANI) is one of the most widely investigated conducting polymers and is considered to be of practical use for many future applications. Here, we first demonstrate that the anisotropic growth of PANI at the nanometer scale can be kinetically controlled by employing a polymeric stabilizer, poly(N-vinylpyrrolidone). The polymerization rate became slower in the presence of the stabilizer (the rate constants calculated at the initial stage decreased with increasing concentration of the stabilizer), yielding PANI nanostructures with lower aspect ratios. Therefore, it is believed that the stabilizer sterically restricts the directional fiber growth mechanism governing PANI chain growth in aqueous solution. Three PANI nanostructures, specifically nanospheres, nanorods, and nanofibers, were fabricated and their oxidation/protonation levels were investigated systematically. It was found that the nanofibers had the most outstanding oxidation/protonation level accompanied by structural ordering (note that the only difference between the polymerization conditions in each case was the concentration of the stabilizer). We also examine the electrochemical properties of PANI nanostructure electrodes in three-electrode and two-electrode (actual capacitor cell) configurations. The intrinsic charge-transport ability of individual nanostructures strongly affected the electrochemical properties of the electrodes. Briefly, the nanofiber electrode had faster electrode kinetics and better capacitance than the nanorods and nanospheres. Lastly, an extrinsic factor, the interparticle contact resistance, also turned out to noticeably influence the capacitances of the electrodes.

Recent Advances in Nanostructured Conducting Polymers: from Synthesis to Practical Applications

“…For the chemical route, these include oxidant/monomer ratio and washing post-treatment [9], the chemical effects of the solvent (solvent-free versus solvent-limited syntheses) [10], effects of the dopant (D-tartaric acid [11], aromatic and amphiphilic sulfonate [17]), and the polymerization kinetics [94,95]. For the electrochemical approach, investigations of the deposition potential and temperature [96] and chloroform as the environment [97] have been undertaken.…”

Interaction of Polyaniline with Surface of Carbon Steel

“…Nanostructure and chain ordering in this polymer are strongly dependent on many synthesis parameters such as temperature, reagent concentrations, acidity of the reaction medium, and method of reagent mixing. PANI may be prepared in the form of nanoparticles with different shapes: nanospheres or granules [41][42][43][44][45], nanosheets [46,47], nanofibers [48,49], and nanotubes [50][51][52]. The mechanisms of PANI macromolecules ordering and nanostructure formation under different conditions are discussed in literature [53,54].…”

Au/Ag NPS Decorated PANI For Electrochemical and Biomedical Applications

“…Several methods for the synthesis of metal NPs have been reported by various research groups like template method, photochemical preparation, electrochemical methods or electro-deposition of metal nanoparticles, reduction of metal salts etc. [5,[17][18][19][20][21][22][23][24][25].…”