Rapid Mixing Polymerization Research Articles

Enhanced adsorptive degradation of Congo red in aqueous solutions using polyaniline/Fe0 composite nanofibers

Abstract In this study, a simple approach was described for the fabrication of composite nanofibers (CNFs) of polyaniline/Fe 0 (PANI/Fe 0 ) using a template-free method for the reductive degradation and removal of Congo red (CR) from aqueous solutions. The PANI/Fe 0 CNFs were prepared via rapid mixing polymerization of aniline monomers with Fe(III) chloride as an oxidant, followed by reduction of polymerization by products (Fe(II)/Fe(III)) as the Fe precursor. The PANI/Fe 0 CNFs were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), High Resolution-Transmission Electron Microscopy (HR-TEM), Brunauer–Emmett–Teller (BET) method, X-ray Diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometry (VSM). These CNFs exhibited enhanced performance relevant to the adsorptive degradation/decolourization of CR, compared to PANI NFs and Fe 0 nanoparticle counterparts. Batch experiments with a minimum dosage (1 g/L) of PANI/Fe 0 CNFs showed complete degradation of 50 mg/L CR after 5 min of reaction. The CR degradation efficiency increased with decrease in initial concentration and solution pH, whereas it decreased with decrease in dosage of the CNFs. The CR degradation rate followed a pseudo-first-order kinetic model. Identification of the CR degradation products using liquid chromatography–mass spectrometry (LC–MS) revealed that the degradation mechanism proceeds through reductive cleavage of the azo linkage, resulting in the formation of 4-aminonaphthalenesulfonate ions and surface-adsorbed aromatic species, all being adsorbed on the CNFs surface at higher dosage. Six consecutive CR removal experiments using the same CNFs demonstrated that the CNFs retained the original CR removal efficiency up to 5th cycle, confirming their high recycling ability. Finally, the CNFs could be separated from the degradation fluid by exploiting external magnetic field.

Evaluating protection performance of zinc rich epoxy paints modified with polyaniline and polyaniline-clay nanocomposite

Abstract Cloisite 30B nano clay was delaminated in the presence of aniline monomers using supercritical CO 2 (ScCO 2 ) process. Rapid mixing polymerization of aniline monomers was done in supercritical CO 2 to produce exfoliated polyaniline clay (PAniC) nanocomposites with high barrier properties. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and XRD analysis have been used to characterize morphology and structure of the synthesized products. The synthesized products were added to a commercial zinc rich epoxy primer to improve its initial barrier properties. Barrier properties of unmodified and modified primers were then studied by determining water vapour transmission (WVT) rate of their free films, free corrosion potential ( E corr ) and electrochemical impedance spectroscopy (EIS) measurements of carbon steel coated panels. Results showed that samples modified with PAniC nanocomposites had better barrier properties compared to PAni modified and original primers. The coating resistance of PAniC modified primer was at least one order of magnitude higher than other primers at the begining of immersion. After one year of immersion, the coating resistance of original, PAni modified and PAniC modified primers were found to be 267, 1610 and 5540 ohm, respectively.

Polyaniline nanofibers and nanocomposites: Preparation, characterization, and application for Cr(VI) and phosphate ions removal from aqueous solution

Interfacial and rapid-mixing polymerization were used for preparation of polyaniline nanofiber (PANI). PANI nanocomposites were prepared by in situ oxidative polymerization of aniline in acidic medium using ammonium persulphate as initiator in the presence of natural silica (PANIS), acid treated natural silica (PANISA), fiber glass (PANIFG), and poly(ethylene terephthalate) powder from waste bottles (PANIPET). The pure PANI nanofibers and their nanocomposites were characterized by FTIR, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The characteristic absorption bands of polyaniline nanofiber in pure polyaniline and nanocomposites were observed by FTIR. XRD also confirms the formation of PANI nanofiber, the SEM images have clearly shown the formation of pure PANI nanofiber alone and in the nanocomposites. The nanocomposites were used for removal of Cr(VI) and phosphate ion pollutants from aqueous solutions. The adsorption experiments reveal that PANISA nanocomposite was potential for removal of Cr(VI) and phosphate. PANISA nanocomposite takes less time to reach adsorption equilibrium and less amount of PANISA was needed to achieve maximum adsorption in comparison with other nanocomposites. This behavior was attributed to the large surface area, due to, increase in number of pores and channels in the structure of PANISA after treatment with acid. It was also found that the Pseudo-second-order kinetic model well represents the experimental data for all nanocomposites.

Synthesis and electrochemical properties of conducting polyaniline/graphene hybrids by click chemistry

Conducting polyaniline nanofiber-grafted graphene oxide (PANINF-GO) hybrids were prepared by click chemistry reaction and in situ rapid mixing polymerization. The resulting composites exhibited excellent electrochemical properties.

Effects of Preparation Approaches and Oxidizing agents on the Yield, Morphology and Thermal stability of Polyaniline

Abstract Evidence of the control of yield and different morphological features of polyaniline (PANI), along with their higher thermal stability is reported. The syntheses were performed by varying the reaction time from 2 to 6 hours for three different methods using three different oxidizing agents. The freshly prepared PANI was investigated by means of fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The polymer yield was increased with the increasing of reaction time from 2 to 6 h for all oxidants in the synthesis approaches; while the reverse trend was observed for KPS in rapid mixing polymerization and mechanical stirring methods. The highest yield was obtained for 6 h reaction time using APS through mechanical stirring method. FESEM analysis showed the growth of regular and uniform PANI nanoparticles, along with the prevention of secondary growth and agglomeration of primary nanofibers using all three oxidizing agents for sonochemistry and rapid mixing polymerization method, except H2O2 in the case of later technique. However, irregular and agglomerated PANI was found for all oxidants in mechanical stirring method. TGA data showed that PANI synthesized by mechanical stirring method is thermally more stable than those prepared by sonochemistry and rapid mixing polymerization.

Alkylated Graphene Nanosheet Composites with Polyaniline Nanofibers

We demonstrate a simple method to prepare alkylated graphene/polyaniline composites (a-GR/PANI) using solution mixing of exfoliated alkyl Iodododecane treated graphene oxide sheets with polyaniline nanofiber; polyaniline nanofibers (PANI) prepared by using rapid mixing polymerization significantly improve the processibility of polyaniline and its performance in many conventional applications. Also, polyaniline nanofibers exhibit excellent water dispersibility due to their uniform nanofiber morphology. Morphological study using SEM and TEM analysis showed that the fibrous PANI in the composites a-GR/PANI mainly adsorbed onto the surface or intercalated between the graphene sheets, due especially to the good interfacial interaction between the alkylated gaphene and the polyaniline nanofibers. The existence of polyaniline nanofibers on the surface of the garphene and the alkylated graphene sheets was confirmed by using FT-IR, FT-Raman and X-ray diffraction analysis. Due to the good interfacial interaction between the alkylated graphene and the polyanilines nanofibers, the composite (a-GR/PANI) exhibited excellent dispersion stability in DMF compared to the same composite (GR/PANI) without alkylation. The electrical conductivity of the (GR/PANI) composite was 9% higher than that of pure PANI and the same weight percent for the composite after alkylation was 13% higher than that of pure PANI nanofibers.

Fabrication of Polyaniline/Silver Nanocomposite Under Gamma-ray Irradiation

Polyaniline (PANI)/silver composite was one-step synthesized under γ-ray irradiation. The structure of the composite was characterized by Fourier transform infrared spectroscopy, UV-Visible, and X-ray diffraction, which indicated that PANI and face-centered-cubic silver were synthesized under γ-ray irradiation. The reaction mechanism were discussed, which revealed that the PANI was formed by the reaction of aniline cation radicals formed by the reaction of aniline cation and ·OH, and Ag was formed by the reaction of Ag+ and e−aq. The morphology of the composite consisted of PANI nanofibers and Ag nanoparticles, and the mechanism of the morphology formation was discussed, which revealed that the rapid mixing like polymerization process might play an important role. It was revealed that the transport behavior of the composite well fitted with the variable-range-hopping model in 80–300 K and deviated from the model below 80 K.

Polyaniline nanofibers synthesized by rapid mixing polymerization

Polyaniline (PANI) nanofibers were chemically synthesized by a rapid mixing polymerization with aniline concentration of 0.5 M. The time needed for the formation of PANI in the reaction medium decreased with increase of the molar ratio of ammonium peroxydisulphate (APS)/aniline and temperature. Morphological study showed at the end of polymerization, only the ones prepared with low molar ratio of APS/aniline (e.g. 0.25 and 0.50) and temperature (e.g. 0 and 20 °C) are nanofibers with diameters of ∼50 nm, though the initially formed products are all nanofibers, while with increasing of molar ratio of APS/aniline to 1 and temperature to 20 °C or higher, agglomerates of PANI nanofibers with diameters of ∼100 nm and larger sized irregular particles were formed. The yield of PANI nanofibers was in the range of 13.4–42.3%, which is favorable for mass production of PANI nanofibers. Conductivity measurement, UV–vis and FTIR spectra were performed to characterize the products. The conductivity of the PANI nanofibers increased with molar ratio of APS/aniline at low temperature, while decreased at higher temperature, which might be resulted from the degradation of PANI molecules in the presence of more APS molecules at higher temperature.

Formation of Polyaniline Nanofibers: A Morphological Study

Polyaniline (PANI) powders were prepared by solution precipitation, rapid mixing polymerization, and interfacial polymerization to find the key factors that influence the formation and growth of PANI nanofibers. In chemical oxidative polymerization of aniline, the morphology of the product is mainly determined by aniline concentration. In the case of lower aniline concentration, PANI nanofibers were formed and can be preserved and collected as final product, while in the case of higher aniline concentration, larger sized PANI particles or agglomerates were obtained owing to the growth of the nanofibers. Without participation of the oxidizing step, solid PANI samples with compact structures and dissimilar morphologies were achieved by random accumulation of PANI molecules.

Sonochemical synthesis of polyaniline nanofibers

Conventionally, micro-sized irregular polyaniline (PANI) particles were synthesized by dropwise addition of the ammonium persulfate (APS) solution into the aniline (ANI) solution with mechanical stirring. By replacing the mechanical stirring with an ultrasonic irradiation, PANI nanofibers in diameters of ∼50 nm and lengths of 200 nm to several micrometers were prepared. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that at the early stage of polymerization, the polymers formed in both the mechanical stirred and ultrasonicated systems are in the form of nanofiber. However, with continuing of the reaction, these primary nanofibers grow and agglomerate into irregular shaped PANI particles in the mechanical stirred system, while in the case of the ultrasonic irradiation, the growth and agglomeration are effectively prevented, preserving thus the PANI nanofibers in the final product. By increasing the APS/ANI molar ratio from 0.5 to 2.5, the aspect ratios of the PANI nanofibers decreased. The PANI nanofibers exhibit higher solubility than the irregular shaped PANI particles. Although the yield, as well as the conductivity of the ultrasonic synthesized PANI nanofibers, was slightly lower than the irregular shaped PANI particles, the ultrasonic synthesis approach is one of the facile and scalable approaches in synthesizing PANI nanofibers in comparison with other ones without use of templates (e.g., the interfacial polymerization and rapid mixing polymerization). UV–Vis and Fourier transformed infrared (FTIR) spectra indicated ultrasound had no significant effect on the chemical structure of the PANI.