Polyacrylonitrile Microspheres Research Articles

Exfoliated MXene nanosheet by double layer forces for preparing magnetic adsorbents of toxic metal ions and recycling with hyperthermic effect

The conventional etching method for exfoliating MXene using hydrofluoric acid solution is time-consuming and inefficient in productivity. A double layer force is generated through polarization among the heterogeneous layers of MXene due to their different dielectric properties. The exfoliated MXene by the polarization method in an acidic solution was employed to synthesize magnetic MXene (MXFe) with Fe3O4 nanoparticles. MXFe was coated on polyacrylonitrile microspheres (PANs) as precursors (PAN@MXFe) by Pickering emulsion polymerization. The core@shell polyvinyltetrazole@MXFe (PVT@MXFe) was obtained as the adsorbent after subsequent cyano-tetrazole conversion of PAN@MFs for the removal of toxic metal ions. The maximum adsorption capacities of Hg(II) on the MXFe and PVT@MXFe coating 2 wt% of MXFe were 579 and 324 mg/g, respectively, indicating the high use efficiency of MXFe. At 8.5 kHz of high frequency, hyperthermia occurs on the PVT@MXFe, facilitating the desorption of the toxic metal ions from the adsorbents. Compared with reuse using an acidic solution, the PVT@MXFe can be reused repeatedly 10 times without obvious damage under the AMF. Our proposed polarization exfoliation method not only provides a novel methodology to exfoliate MXene but also develops an ideal adsorbent for universal adsorption, simple separation, stable regeneration, and low secondary pollution.

Preparation of reusable cross-linked amidoxime polyacrylonitrile microspheres and their efficient adsorption of Cu (II) and Pb (II)

Preparation of reusable cross-linked amidoxime polyacrylonitrile microspheres and their efficient adsorption of Cu (II) and Pb (II)

Microfluidic preparation of monodisperse hollow polyacrylonitrile microspheres for ICF

Hollow polyacrylonitrile (PAN) microspheres can be used as fuel carriers in inertial confinement fusion (ICF) experiments due to their high tensile strength, low permeability to hydrogen isotopes, and resistance to tritium radiation corrosion. Monodisperse oil in water in oil (O1/W/O2) compound droplets were fabricated by the microfluidic technique and then monodisperse hollow polyacrylonitrile microspheres were prepared by the solvent evaporation method. The stability of O1/W/O2 compound droplets was improved by the addition of the surfactant (Dow Corning 749), which reduced the interfacial tension between the O2 phase and the W phase as well as the Laplace pressure on the surface of the compound droplets. The sphericity and the surface quality of the microspheres were also improved by the introduction of DMF droplets into the O2 phase to avoid emulsification, decreasing the DMF mass transfer rate. Therefore, fine monodisperse PAN microspheres with the diameter range of 700–800 µm were successfully prepared. Moreover, the size relationship between the compound droplets and the resulting microspheres was also evaluated, which can be used to predict the sizes of the PAN microspheres. The results provide a method for controllable preparation of monodisperse hollow PAN microspheres for ICF experiments.

Fabrication of solvent-free hollow PAN microspheres with an easily-assembled double-T emulsion generator

In this study, the solvent-free polyacrylonitrile (PAN) microspheres were successfully fabricated using an easily -assembled double-T emulsion generator. The effects of removing solvent methods and CO2 replacing period during the supercritical drying on the PAN microspheres were ascertained. As suggested from the experimental results, the supercritical drying method could more effectively remove solvent than the vacuum drying and solvent washing. After the supercritical drying, the sphericity of PAN microspheres remained, and the percentage contraction was less than 5%. By Stereomicroscope, Field Emission Scanning Electron Microscope (FESEM), energy dispersive X-ray analysis (EDS), confocal microscope as well as white light interferometer, the solvent-free PAN microspheres structures were characterized. There was a trace amount of Si after treatment, whereas it was found to be almost removed, which satisfies the experiment requirements. By contrasting the results of the treatments with different CO2 replacing periods in the supercritical drying, the replacing period of 2 h was found as the optimal condition. In the future, the solvent-free PAN microspheres will have a potential application in the inertial confinement fusion experiment.

Development of antimicrobial polyacrylonitrile microspheres for water disinfection

ABSTRACTPolyacrylonitrile (PAN)‐based antimicrobial polymeric microspheres were synthesized and characterized in the present study. In first approach, hydrolysis of PAN microsphere was performed in alkaline medium to generate carboxylic groups, followed by iodination to obtain iodine incorporated hydrolyzed polymeric microspheres. In second approach, pendant nitrile groups of the PAN microspheres were reduced by lithium aluminum hydride to generate amino functionality. Incorporation of antimicrobial agent was achieved by reacting glycidyltrimethylammonium chloride onto the amine‐terminated microspheres. Polymeric samples obtained by both approaches were characterized by analytical, morphological, and spectral techniques. Hydrolyzed microspheres showed higher aqueous swelling capacity, absorbing almost 2000% water in 10–12 days. Both iodinated hydrolyzed polyacrylonitrile (I2HPAN) and quaternized polyacrylonitrile (QPAN) microspheres showed prominent zone of inhibition against both gram‐positive (Staphylococcus aureus) and gram‐negative (Escherichia coli) bacteria. Concentration and time‐dependent bacterial mitigation was observed when different amounts of both I2HPAN and QPAN microspheres were mixed with bacterial solution. I2HPAN established higher killing efficacy than QPAN. PAN‐based antimicrobial microspheres have strong potential to be used as broad spectrum antimicrobial matrices insoluble for water disinfection. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47968.

Switchable electrorheological activity of polyacrylonitrile microspheres by thermal treatment: from negative to positive.

The study focuses on the effect of thermal deformation degree of polyacrylonitrile (PAN) particles on the electrorheological (ER) properties of their suspensions. The heat-treated PAN particles are manufactured as ER materials using a thermocatalytic processes. The molecular structures of ER materials are analyzed to confirm a stabilization or a carbonization degree. We categorized the prepared ER particles into three basic types according to their deformation degree: Thermal dried PAN, stabilized PAN, and pre-carbonized PAN. The raw, stabilized, and pre-carbonized PAN particle-dispersed suspensions showed positive ER properties. The ER properties are enhanced as the heat-treatment temperature increases due to improved dielectric property. However, the thermal dried PAN particle ER suspensions showed negative ER behavior though the particles have higher conductivity and dielectric constants than those of the host fluid, which is contrary to the conduction model. XRD results indicate that the ER materials could show contradictory ER behavior even if they have the same molecular structures due to their crystallinity. This discovery is expected to boost the development of both positive ER and negative ER suspensions based on carbonaceous ER materials.

Preparation of polyacrylonitrile- based porous hollow carbon microspheres

Hollow carbon microspheres were successfully fabricated in a convenient fashion by employing polyacrylonitrile (PAN) emulsions as precursors. The obtained hollow carbon microspheres were shown high monodispersity, tunable pore structures—gradient pore diameters and uniform orientation of pores. Through varying the flowing rates of three phases and solidification time, the PAN microspheres with different sizes and densities could be simply synthesized. Besides the relationship between the solidification time and the density of microspheres as well as their gas barrier properties were studied in this paper. These structured microspheres have great potential applications in various areas, including foam targets, carbon molecular sieve, cargo storage, medical instruments and so on.

Preparation and dispersity of carbon nanospheres by carbonizing polyacrylonitrile microspheres

Polyacrylonitrile microspheres of about 240 nm were synthesized and used as a precursor for preparing carbon nanospheres (CNs) by oxidation and sequential carbonization.

Fabrication of thick-walled polyacrylonitrile (PAN) with high uniformity by an easily assembled double-T droplet generator

Thick-walled PAN microspheres with good wall thickness uniformity and sphericity were obtained by adjusting the solidifying temperature and the viscosity of O2phase.

The structure and electrochemical properties of carbonized polyacrylonitrile microspheres

A hard carbon microsphere (HCS) material with a uniform walnut kernel structure was prepared using polyacrylonitrile (PAN) asa a carbon precursor by a stabilization–carbonization method. The PAN–HCS preserves the original ellipsoidal shapes of natural polyacrylonitrile granules. Structural analysis shows that PAN–HCS is a kind of disordered carbon containing micropores and graphite-like micro-crystallites. The effects of heat-treatment temperature varying from 800 to 1500 °C on electrochemical performance were systemically studied. PAN–HCS–1250 obtained at 1250 °C as a negative material for lithium-ion batteries exhibits a reversible capacity of about 350 mAh g− 1 at 20 mA g− 1 with an excellent rate capability and cycling stability.

Preparation and Characterization of Polyacrylonitrile and Polyacrylonitrile/β-cyclodextrins Microspheres

Polyacrylonitrile (PAN) and PAN/β-cyclodextrin (β-CD) microspheres were prepared via an electrospinning method. The PAN microspheres could be successfully obtained in a suitable range of concentrations of electrospun PAN solutions. When β-CD was added to the PAN solutions, electrospun PAN/β-CD composite spheres were prepared. The morphology of the spheres was characterized by scanning electron microscopy (SEM); it showed that the spheres had uniform diameter and a smooth surface. The composition of the composite microspheres was studied by Fourier transform infrared spectroscopy (FTIR). The results showed that the β-CD was incorporated in the polymer microspheres.

Preparation of Porous Carbon Material by Carbonizing Polyacrylonitrile Microspheres

PAN microspheres were crosslinked with divinyl benzene (DVB) and styrene (St), and then pre-oxidized under atmospheric pressure, porous carbon microspheres were produced by carbonizing the pretreated microspheres under nitrogen protection. Morphology and structure characterizations of the materials were performed by employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption test, etc. The results show that the primitive PAN microspheres display flower-like structures, while the carbonized pretreated PAN microspheres exhibit a high porosity as well as specific surface area and have a good adsorption of methylene blue (MeB) dye.

Catalyst-free synthesis of multi-walled carbon nanotubes from carbon spheres and its implications for the formation mechanism

A route to producing multi-walled carbon nanotubes (MWCNTs) was reported, in which polyacrylonitrile microspheres (PANMSs) were assembled into one-dimensional strings of carbon spheres and transformed to carbon nanotubes at 1000°C. It was found that the diameters of the MWCNTs are uniform and correlated with the size of the PANMSs used. Structures of intermediate products obtained by stopping the reaction have been examined by high-resolution transmission electron microscopy. The observations indicate that the formation of MWCNTs follows a different mechanism from the well-studied vapor–liquid–solid mode. It involves a direct self-assembly and solid-state structural transformation of PANMSs under the promotion of nitrogen atoms as shown by the X-ray photoelectron spectra of the resulting samples. On the basis of these observations, a sphere-string-tube mechanism was proposed for the MWCNT formation.

Synthesis of monodispersed polyacrylonitrile microspheres by dispersion polymerization

AbstractMonodispersed polyacrylonitrile (PAN) microspheres shape have been successfully synthesized by dispersion polymerization in the presence of polyvinylpyrolidone (PVP) as stabilizer. Transmission Electron Microscopy (TEM) and Particle Size and Distribution Analyzer were used to characterize the morphology and dispersibility of PAN microspheres, respectively. Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) were applied to characterize the structure of PAN. Finally, the crystallinity of PAN microspheres was investigated by X‐ray Diffraction (XRD). The results show that PAN microspheres have a regular sphere shape and narrow dispersity with a monodispersity index of 1.17. The crystallization of PAN and the existence of PVP layer affect the morphology of PAN microspheres. The effects of various polymerization factors on the particle size distribution of PAN microspheres have also been studied. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and Characterization of Polyacrylonitrile Microspheres by Soapless Emulsion Polymerization

Polyacrylonitrile(PAN) microspheres were synthesized by soapless emulsion polymerization of acrylonitrile(AN) in water. The effects of monomer and initiator concentration on the conversion of AN and the diameter of microspheres were investigated. The results showed that when the concentration of monomer increases, the conversion of AN decreases while the diameter of PAN microspheres increases. When the concentration of initiator increases, the conversion of AN and the diameter of PAN microspheres both increase. For this method of PAN microspheres synthesis, the highest conversion of AN is about 60% and the diameter can be controlled in need ranging from approximately 140 to 500nm.

Synthesis of Monodispersed Co(Fe)/Carbon Nanocomposite Microspheres with Very High Saturation Magnetization

Through the complexation of cyano groups in polyacrylonitrile (PAN) microspheres with cobalt (iron) ions under mild conditions, cobalt (iron)-containing PAN microspheres could be prepared effectively, then after pyrolyzation of the composite microspheres at 800 °C under N2 atmosphere, Co(Fe)/carbon nanocomposite microspheres could be prepared, and the metal content is up to ∼71 wt % in the Co(Fe)/carbon nanocomposite microspheres. Thermogravimetric analysis, transmission electron microscopy, and vibrating sample magnetometry investigation proved that almost all the cobalt nanoparticles were embedded in the interior of the carbon microspheres, which protected the metal nanocrystals (Co or Fe) from oxidation. The microspheres possess high magnetization (Ms is up to ∼161 emu/g) and show near-zero remanence and coercivity (Hc is down to ∼0.012 KOe) at room temperature, suggesting that they are outstanding soft ferromagnets with high magnetic susceptibilities and practically nil hysteresis loss.