Fabrication of Polyaniline Nanostructures under Ultrasonic Irradiation: From Nanotubes to Nanofibers

Abstract

Summary: An ultrasonic irradiation assisted polymerization method has been used to prepare PANI nanotubes and nanofibers by using different doping concentrations of mineral or organic acids. It has been found that PANI nanotubes can be produced when the concentration of the dopant acid is low. However, PANI nanofibers can also be produced when the concentration of the dopant acid is high. For nanotubes synthesized at a low concentration of the dopant acid, the outer average diameter can be changed from about 150 nm using phosphoric acid to 200 nm using nitric acid as the dopant and the inter diameter is in the range of 10–50 nm. For nanofibers, the diameter ranges from about 50 nm using nitric acid to more than 110 nm using perchloric acid as the dopant. The mechanism of the formation of the nanotubes and nanofibers may be due to the formation of different kinds of micelles and the prevention of the second growth of the PANI by ultrasonic irradiation. The chemical structure of the PANI nanotubes and nanofibers are characterized by FTIR and UV‐vis absorption spectra and XRD patterns. The conductivity of the PANI nanofibers is comparable to that of conventional PANI samples.TEM images of PANI nanofibers synthesized under ultrasonic irradiation doped by perchloric acid.magnified imageTEM images of PANI nanofibers synthesized under ultrasonic irradiation doped by perchloric acid.

One-dimensional growth and electrochemical properties of polyaniline deposited by a pulse potentiostatic method

“…When the acidity increases, one-dimensional growth of PANI is promoted, resulting in better contact of the active materials with the electrolyte and in subsequently higher electroactivities. Heterogeneous growth of PANI on initially-formed nanofibrous polymer (secondary growth) was reported to be inhibited in chemical oxidative polymerization of aniline at high levels of acid doping [26]. The triggering of anisotropic growth of low-dimensional PANI at higher acidity in our study should be similarly related to the stronger electrostatic interactions between the polymer chains due to the larger number of positive charges, which originate from the higher degree of protonation [27].…”

Electrodeposited hybrid films of polyaniline and manganese oxide in nanofibrous structures for electrochemical supercapacitor

“…Great efforts have been devoted to avoid this secondary growth including aqueous/organic interfacial polymerization, rapidly-mixed reaction, ultrasonic irradiation, dilute polymerization, etc. to get PANI in fibrous structures [8][9][10][11]. Kaner and coworker demonstrated that the polymerization rate can be controlled through sequent feeding of oxidant solution into aniline solution and nanofibrous PANI was obtained with controlling the oxidant added into aniline solution in small amount [8].…”

“…Great efforts have been made to suppress this overgrowth by reducing the formation of nucleation sites on surfaces of PANI nanofibers produced in the early stage of polymerization through aqueous/organic interfacial polymerization, rapidly-mixed reaction, ultrasonic irradiation, dilute polymerization, etc. [8][9][10][11].…”

Chemical anchoring of silica nanoparticles onto polyaniline chains via electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of SiO2

“…Great efforts have been devoted to avoid this secondary growth including aqueous/organic interfacial polymerization, rapidly mixed reactions, etc. to get PANI in fibrous structures [26,28]. Kan's group discussed the effect of methanol on electrochemical formation of PANI nano-fibers.…”