Enhanced microwave synthesis: Fine-tuning of polyaniline polymerization

A series of energy- and time-efficient enhanced microwave syntheses (EMS) of polyaniline (PANI) have been performed and are discussed herein. The syntheses were performed at different microwave power levels while keeping the reaction system at a constant temperature of 24 ± 1 °C, with the samples extracted after 10 min of reaction. Molecular weights were determined with GPC (gel permeation chromatography) and showed that the molecular weight of the microwave-generated materials depends on applied power: the higher the power level, the greater the molecular weight. The chemical structure was investigated by FTIR and UV–vis spectroscopy, while the morphology was imaged using scanning electron microscopy (SEM). FTIR and UV–vis spectroscopy confirmed the formation of PANI, and SEM indicated the presence of a mixed morphology, with a prevalence of nanofibers with different aspect ratios. The conductivity of the samples (ca. 3–3.5 S cm–1) was found to be relatively independent of microwave power levels. Surface area measurements were carried out using Brunauer–Emmett–Teller (BET) method, with samples synthesized using EMS showing higher surface areas when compared with conventionally synthesized PANI. The fact that molecular weight depends on applied power implies that microwave-enhanced synthesis can be used to fine-tune PANI reaction conditions, directing it toward specific properties

Rapid microwave synthesis of polyaniline–C60 nanocomposites

Nanocomposites of C60 with the conducting polymer polyaniline (PANI) are obtained rapidly using enhanced microwave irradiation. Nanoparticles of C60 embedded in PANI nanofibres, as well as a coating of larger C60 clusters with PANI, are confirmed by SEM and TEM. An interaction between the C60 and PANI is indicated by both UV–vis and FTIR studies. The remarkable yield of 45% is obtained after only 10 min in the presence of 10% of C60

Self-assembled centimetre-sized rods obtained in the oxidation of o-phenylenediamine and aniline

© 2015 Society of Chemical Industry. Morphologically well-defined rods of approximately 1 cm in length are effectively and economically obtained by mixing ortho-phenylenediamine (30 mmol L-1) with ammonium persulfate (12.5 mmol L-1) in an acidic solution (0.37 mol L-1 HCl) at room temperature with and without the presence of 50 mmol L-1 aniline. These self-assembled, morphologically uniform products can be potentially scaled up and used as morphological templates to fabricate well-defined structures of other materials such as conducting polymers. The products were characterized using Raman, UV-visible, high-resolution NMR (1H and 13C) and mass spectroscopies, X-ray diffraction, scanning electron microscopy and elemental analysis. Apart from certain differences in visual appearance and in X-ray diffractograms, other analytical data suggest that there are no structural changes upon addition of aniline into the reaction mixture. NMR and mass spectra imply that all syntheses carried out either with or without aniline result in a mixture of two products, attributed to 2,3-phenazinediamine and 3-aminophenazin-2-ol. A formation mechanism based on hydrogen bonding and π-π stacking has been proposed

Self-assembly of nanostructures obtained in a microwave-assisted oxidative polymerization of aniline

For the first time, microwave assisted aniline oxidative polymerization is performed in the presence of acetic acid (CH3COOH) and ammonium hydroxide (NH4OH) at different microwave power levels. The reaction system is kept at constant temperature of 24±1°C. The products are investigated by Fourier Transform Infrared Spectroscopy (FTIR), Raman, solid-state Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies. EPR signals in polyaniline (PANI) originate from the polarons formed upon protonation and doping by acid. The microwave radiation causes an increase in the spin concentration which is slightly more evident for 8 W than for 93 W. The morphology is investigated by using scanning electron microscopy (SEM). SEM micrographs revealed the formation of nanorods (in the presence of CH3COOH) and nanospheres (in the presence of NH4OH). FTIR, Raman and solid-state NMR spectroscopies indicate the presence of PANI and aniline oligomers. X-ray Diffraction (XRD) measurements showed the presence of well-ordered structures

Synthesis of polyaniline by using CuCl2 as oxidizing agent

The reaction of aniline with copper(II) chloride in the presence of p-toluene sulfonic acid was investigated. The reactions were carried out in aqueous media for 24 h under a nitrogen atmosphere. The products obtained were characterized by FT-IR, UV–Vis XPS, SEM, N K-edge NEXAFS and CP MAS 13C NMR. Elemental analysis was also carried out to determine the elemental composition of the product. The results showed the presence of partially oxidized, partially protonated polyaniline with [CuCl3]− as the dopant counter ion. A decrease in the final pH and increase in the reaction yield was observed with an increase in the oxidant to monomer ratio. The increase in the yield is due to an increase in the oxidation potential of CuCl2 with an increase in its molar concentration. The low product yields achieved are attributed to the co-formation of a copper(II) chloride aniline coordination complex