Polyacrylonitrile Fiber Mats Research Articles

Electroless Deposition for Robust and Uniform Copper Nanoparticles on Electrospun Polyacrylonitrile (PAN) Microfiltration Membranes.

Filtration membranes coated in metals such as copper have dramatically improved biofouling resistance and pathogen destruction. However, existing coating methods on polymer membranes impair membrane performance, lack uniformity, and may detach from their substrate, thus contaminating the permeate. To solve these challenges, we developed the first electroless deposition protocol to immobilize copper nanoparticles on electrospun polyacrylonitrile (PAN) fibers for the design of antimicrobial membranes. The deposition was facilitated by prior silver seeding. Distinct mats with average fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm were evaluated for filtration performance. Well-dispersed copper nanoparticles were conformal to the fibers, preserving the open-cell architecture of the membranes. The copper particle sizes ranged from 20 to 140 nm. Infrared spectroscopy revealed the PAN fiber mats' relative chemical stability/resistance to the copper metallization process. In addition, the classical cyclization of the cyano functional group in PAN was observed. For model polystyrene beads with average sizes of 3 μm, Cu NP-PAN fiber mats had high water flux and separation efficiency with negligible loss of Cu NP from the fibers during flow testing. Fiber size increased flux and somewhat decreased separation efficiency, though the efficiency values were still high.

Development of Quaternized Chitosan Integrated with Nanofibrous Polyacrylonitrile Mat as an Anion-Exchange Membrane.

A two-phase anion-exchange membrane was prepared from quaternized chitosan (QCS) integrated with an electrospun polyacrylonitrile (PAN) scaffold by spin coating. To synthesize QCS, glycidyltrimethylammonium chloride in various amounts was introduced into the structure of CS. The characterization of the cast cross-linked QCS (CQCS) membranes by impedance spectroscopy revealed the ionic conductivity (IC) in the range of 2.8 × 10-4 to 8.2 × 10-4 S cm-1 and the degree of quaternization (DQ) of 26.4-51.0%, where the CQCS film with the DQ of 51.0% showed excellent performance. When CQCS was reinforced with a PAN fiber mat, the newly developed composite membrane demonstrated the highest IC of 34 × 10-4 S cm-1 at 80 °C, low swelling, and an almost eightfold increase in tensile strength at a fully hydrated state compared to pristine materials. Moreover, the CQCS/PAN membrane was chemically stable and revealed increasing hydroxide transport during 1 month immersion in alkaline media.

Flow-induced bending deformation of electrospun polymeric filtration membranes using the “leaky” bulge test

In service, hydraulic flow is usually perpendicular to the plane of electrospun fiber mats for water filtration, inducing an out-of-plane deformation. In this paper, we have investigated the out-of-plane deformation response of wet electrospun polyacrylonitrile fiber mats with distinct average constituent fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm, but with nominally similar thicknesses and areal densities using the classical bulge testing technique. The resultant pressure-deflection relationships are incompatible with constitutive models for out-of-plane deformation of continuum materials. Rather, the fiber mats exhibited a one-half dependence (p∼h12) governed by fiber deflection, and pressure asymptote indicative of steady-state fluid percolation, but influenced by the mats areal densities. In addition, the apparent bending rigidity increased with increasing fiber diameter. In the range tested for fiber mats with average fiber size of 232 nm, increase in mat thickness did not noticeably alter measured rigidities, although evidence of slight increase in pressure asymptote is observed. Cyclic flow rate tests provided evidence of good recoverability as well as minimal topological modifications.

Preparation and characterization of electrospun polyacrylonitrile fiber mats containing Garcinia mangostana

Garcinia mangostana-loaded electrospun polyacrylonitrile (PAN) fiber mats with antibacterial and anti-tuberculosis properties were fabricated from PAN solution containing G. mangostana extract in dimethylformamide. 10% PAN solution was mixed with G. mangostana in amounts of 10, 15, 20, and 30 wt% based on the weight of PAN powder used in the experiment. The PAN solutions were processed using the electrospinning process. Both untreated (neat) and G. mangostana-loaded PAN fibers were smooth in appearance, and the average diameter of samples was ~215 and ~245 nm, respectively. Morphologies, release characteristics, antimicrobial efficiencies against Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Streptococcus agalactiae, Streptococcus pyogenes, and anti-tuberculosis properties of the neat electrospun and 10–30% G. mangostana-loaded e-spun fiber mats were investigated. In vitro release studies of G. mangostana from e-spun PAN fiber mats were determined using the total immersion method in acetate buffer and phosphate buffer solutions containing Tween 80 and methanol. The cumulative released amount of G. mangostana from the samples proportionally increased with the increase of G. mangostana incorporated in the spinning solutions. This study demonstrated a convenient procedure with the potential to develop the antimicrobial and anti-tuberculosis properties of electrospun fibrous membranes containing G. mangostana, which are beneficial in filtration applications for respirators, face masks, and air-conditioning filters.

Preparation of polyaniline-coated polyacrylonitrile fiber mats and their application to Cr(VI) removal

A composite nanofibers mat containing polyacrylonitrile (PAN) as core and polyaniline (PANI) as sheath had been successfully prepared via solution spinning followed by in situ polymerization, and its hexavalent chromium (Cr(VI)) removal potential was investigated. By altering the processing parameters, bead-free and uniform PAN nanofibers with average diameter of 469nm could be obtained. The morphological evolution of the PANI/PAN composite fiber mats could be controlled through regulating the molar ratio of oxidant to monomer. The PANI/PAN composite fiber mats presented a superior Cr(VI) adsorption performance. Moreover, the factors affecting the performance of Cr(VI) removal from the aqueous solutions were investigated systematically. The experimental data were fitted to various kinetic models and isothermal adsorption, and the thermodynamic parameters of adsorption process were calculated as well. The PANI/PAN adsorbents were also proven to have good recycling capability, and the mechanism of adsorption and regeneration was investigated in detail.

Supported palladium nanoparticles on preoxidated polyacrylonitrile fiber mat for coupling reactions

Nanoporous preoxidated polyacrylonitrile fiber mat was prepared by electrospinning and thermal treatment for the immobilization of palladium catalyst. The fiber morphologies were characterized by scanning electron microscopy (SEM). Infrared spectra and X-ray powder diffraction characterizations (XRD) showed that thermal treatment of fiber mat could change the linear polyacrylonitrile structure into ladder structure. XRD was used to study the chemical nature of the palladium in the fiber mat. The catalytic activity and stability of the fiber supported palladium catalyst have been evaluated by the Mizoroki-Heck and Sonogashira cross-couplings. The larger structure of the fiber mat can greatly facilitate its separation and recycling. The excellent catalytic performance and easy recycling made this novel fiber mat supported palladium catalyst hold great potential for the green chemical processes.

CuBTC metal-organic frameworks enmeshed in polyacrylonitrile fibrous membrane remove methyl parathion from solutions

A method is presented to immobilize Cu-BTC metal-organic framework (MOF-199) particles by enmeshing them in nonwoven polyacrylonitrile (PAN) nanofibers creating a fibrous membrane with the potential ability to remove chemical warfare agents or pesticides from solution. These membranes were shown to effectively adsorb methyl parathion, an organophosphate pesticide. Based on solubility theory and experimental results, partitioning was determined to be the main mechanism of removal. After 2 hours, the PAN/MOF-199 membranes removed 88 % more methyl parathion than the unmodified PAN membranes and 62 % as much as the MOF-199 crystal powder. Since the MOF particles were enmeshed in the PAN fiber mats, the MOF particles were in a workable and flexible substrate. Potential applications of these functionalized fibrous membranes include protective clothing for agricultural workers or military personnel as well as filtration media.

Preoxidated polyacrylonitrile fiber mats supported copper catalyst for Mizoroki–Heck cross-coupling reactions

Porous preoxidated polyacrylonitrile (PAN) fiber mats, which was prepared by electrospinning and then followed by thermal treatment, has been used for the immobilization of copper catalyst. FT-IR/ATR spectra and XRD pattern show that the linear polymer structure of the PAN fiber mat can be converted into the ladder molecular structure at the high temperature. The morphology of the copper catalyst supported on the preoxidated PAN fiber mats was examined by scanning electron microscopy (SEM). The catalytic activity and stability of the fiber mat supported copper catalyst have been evaluated using the Mizoroki–Heck cross-coupling reaction of aryl iodides with different acrylates. It was found that the catalytic activities of fiber mat supported copper catalyst could be significantly promoted by addition of small amount of additives, such as ethylene glycol.

Preparation of porphyrinated polyacrylonitrile fiber mat supported TiO_2 photocatalyst and its photocatalytic activities

Fe(III)meso-tetraphenylporphyrinated polyacrylonitrile fiber mat supported TiO_2 photocatalyst (PANC/ TiO_2 mat) was prepared via copolymerization and electrospinning. SEM images showed that well-defined fibers with diameters around 1.47 \pm 0.26 \mu m were fabricated from Fe(III)meso-tetraphenylporphyrin (FeTPP)-acrylonitrile copolymer (PANC) and TiO_2 mixture. The XRD characterizations demonstrated that the electrospinning process had no effect on the anatase structure of TiO_2. The photocatalytic activity of the PANC/TiO_2 mat was examined for the photodegradation of methyl red in aqueous solution under the irradiation of visible light. The results showed that this PANC/TiO_2 fiber mat was very efficient for the photodegradation of methyl red, with a degradation percentage over 94%. It is worth noting that the PANC/TiO_2 mat could be easily recovered and reused 3 times without any destruction of fiber morphologies.

Preparation of Hydrolyzed Electrospun Polyacrylonitrile Fiber Mats as Chelating Substrates: A Case Study on Copper(II) Ions

Ultrafine polyacrylonitrile (PAN) fiber mats were prepared by electrospinning and subsequently hydrolytically treated with a sodium hydroxide ethanolic/aqueous solution to impart the ability to chelate metal ions. This was achieved through the conversion of the nitrile functional groups on the surface of the PAN fibers into imine conjugated sequences, which was confirmed by Fourier-transform infrared spectroscopy. The chelating property of the hydrolyzed electrospun PAN fiber mats (i.e., H-ePAN fiber mats) was evaluated against Cu(II) ions. The amounts of the Cu(II) ions adsorbed onto the H-ePAN fiber mats were influenced by the initial pH and the initial concentration of the metal ion solutions. At the optimal pH of 5.0, the amounts of the Cu(II) ions adsorbed onto the H-ePAN fiber mats increased with an initial increase in the time the materials were in contact with the metal ion solution to finally reach the maximal, plateau values after about 5 h of immersion. The maximal adsorption capacity of the H-...

Polyacrylonitrile fiber mat‐supported palladium catalyst for Mizoroki–Heck reaction in aqueous solution

AbstractA novel palladium catalyst immobilized on polyacrylonitrile fiber mats (Pd/PAN) was prepared by electrospinning. The catalytic activity and recyclability of the microwave‐assisted Pd/PAN fiber mats were examined for the Mizoroki–Heck cross‐coupling of aryl iodides with three different acrylates in aqueous solution. The morphology of the prepared Pd/PAN fiber mats was characterized by scanning electron microscopy. The large size of the PAN fiber mat‐supported palladium catalyst enables much easier separation from the reaction mixture by simple filtration. Density functional theory calculation indicates that the chelation energy of palladium chloride (PdCl2) with propionitrile (model of PAN) is considerable smaller than that of PdCl2 with water, suggesting that the stability and reactivity of the Pd/PAN fiber mats catalyst could be improved through the surface derivatization with polar functional groups. Copyright © 2011 John Wiley & Sons, Ltd.

Electrospun nanocomposite fiber mats as gas sensors

Electrospinning was used to spin nanocomposite fiber mats from polymer solutions containing nanoparticles. The base polymer was polyacrylonitrile (PAN), and the nanoparticles included iron oxide, antimony tin oxide and zinc oxide with diameters ranging from 10 to 70 nm. The electrospun nanocomposite fiber mats were characterized by scanning electron microscopy (SEM), scanning probe microscopy (SPM) and Fourier transform infrared (FTIR) spectroscopy. The average fiber diameter was found to decrease from 200 nm for neat PAN fibers to 50–150 nm for nanocomposite fibers. The porosity increased from 70% for PAN fiber mat to an average of 86% for nanocomposite fiber mats. The fiber mats were used as a sensor in conjunction with FTIR spectroscopy to detect CO 2 gas. The absorbance spectra showed a higher sensitivity with a fiber mat, regardless of its type, than without, indicating gas adsorption on the fiber mat. The highest sensitivity was obtained with PAN/Fe 2O 3 fiber mat. As the underlying mechanism is physisorption rather than chemisorption, the response time was short and the sensor could be used repeatedly.