Surface Of Polyacrylonitrile Research Articles

Fluorinated-PAN nanofibers: Preparation, optimization, characterization and fog harvesting property

For the first time, a new fluoroamine compound was synthesized by aminating the perfluoroacrylate compound. The synthesized fluroamine was used to modify the surface of polyacrylonitrile (PAN) nanofibers and the fog harvesting ability of the modified nanofibers was investigated. The results showed that the maximum fog harvesting capacity (335mg/cm2/h) was achieved at the time, the temperature and the amount of fluoroamine compound of 3h, 95°C and 8% (w/w) in the modification process, respectively. The fog harvesting capacity of fluorinated nanofibers was much higher than that of untreated PAN nanofibers (31mg/cm2h), which is due to the superhydrophobic nature of fluorinated nanofibers. The superhydrophobic property of the fluorinated nanofibers was evaluated by investigating the wettability properties including water contact angle and surface energy of prepared nanofibers. Furthermore, the average surface roughness of nanofibers was determined as 41.8 and 51.2nm for untreated and fluorinated nanofibers, respectively. The result indicated the superhydrophobic property of prepared nanofibers due to the increased surface roughness, high water contact angle (159°), and low surface energy value (17.1mN/m). Moreover, it was found that the fog harvesting capacity increases with increasing the distance of the nanofibers mat from humidifier because of increasing the water mobility. The results of nanofiber characterization showed that the fluoroamine molecules were covalently grafted onto the nanofiber surface through the formation of amidine group. Also, at the optimum condition, deposition of a layer with the thickness of 17nm on the nanofiber surface was detected. It was found that increasing the thickness of fluoroamine layer enhanced the hydrophobicity and fog harvesting capacity of nanofibers up to a certain level. The total surface area of nanofibers was decreased after the grafting process because of increasing the nanofiber diameter.

Electrospun polyacrylonitrile nanofibers functionalized with EDTA for adsorption of ionic dyes

The manipulation of nanofibers’ surface chemistry could enhance their potential application toward the removal of ionic dyes in wastewater. For this purpose, surface modification of electrospun polyacrylonitrile (PAN) nanofibers with ethylenediaminetetraacetic acid (EDTA) and ethylenediamine (EDA) crosslinker was experimented. The functionalized EDTA-EDA-PAN nanofibers were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) technique. The impregnation of EDA and EDTA chelating agents on the surface of PAN changed the distribution of nanofibers as proximity is increased (accompanied by reduced softness), but the nanofibrous structure of the pristine PAN nanofibers was not substantially altered. Adsorption equilibrium studies were performed with Freundlich, Langmuir and Temkin isotherm models with the former providing better correlation to the experimental data. The modified PAN nanofibers showed efficient sorption of methyl orange (MO) and reactive red (RR) from aqueous synthetic samples, evinced by the maximum adsorption capacities (at 25 °C) of 99.15 and 110.0 mg g−1, respectively. The fabricated nanofibers showed appreciable removal efficiency of the target dye sorptives from wastewater. However, the presence of high metal ions content affected the overall extraction of dyes from wastewater due to the depletion of the adsorbent's active adsorptive sites.

Natural Dye Cyanidin‐Based Polyacrylonitrile Conjugate as Environmental‐Friendly Thin Film Sensor

AbstractNatural dye cyanidin extracted from red cabbage and adsorbed on the surface of polyacrylonitrile (PAN) in the presence of epichlorohydrin coupling agent to form transparent environmental‐friendly thin‐film sensor was achieved. The potential thin film showed successful sensor behavior and demonstrated gradual and reversible sensing change in the pH range of 2.0–11.0. Visual and Lucid color change of the thin film was observed at inclined pH value; fuchsia color at pH 1–3, purple color at pH 6–8, and blue color at pH 10–11. Structural identification of the thin‐film sensor provided evidence of physical adsorption of cyanidin on the surface of PAN via epichlorohydrin coupling agent as prevailed by FTIR spectroscopy. Moreover, the thin‐film sensor demonstrated thermal stability up to 105°C, as onset degradation temperature, as verified by thermogravimetric analysis (TGA) and its first derivative (DTG) techniques. Moreover, the pH‐sensing change of the 1‐mm‐thick thin film was checked by UV‐Vis technique. The oligomer formation of cyanidin, mediated by epichlorohydrin, lead to the formation of stable and successful adsorption on the surface of PAN with uniform and soft appearance. The concept of the reversible stability and response time of the thin film sensor were also proved. The cyanidin‐based PAN conjugate sensor act as a novel environmental‐friendly sensor with the following specifications: low cost, easy fabrication, high sensing capacity, appropriate reversible stability, and response time specifications. Such exquisite specifications of the thin‐film sensor adapt it to put into service in optoelectronics and microelectronic devices.

Fluorescent nanofibrous membrane (FNFM) for the detection of mercuric ion (II) with high sensitivity and selectivity

A highly sensitive and selective fluorescent nanofibrous membrane (FNFM) for the detection of mercuric ions (II) was prepared via electrospinning and subsequent immobilization. In this process, fluorescent chemosensor dithioacetal-modified perylenediimide (DTPDI) was introduced on the surface of polyacrylonitrile (PAN) nanofibers with high stability under mechanical force by electrostatic interaction. Because DTPDI can be detached from PAN nanofibers due to the hydrolysis of dithioacetals in the presence of Hg2+ and form an oil-soluble fluorescence dye AL. According to the linear correlation between AL and Hg2+, the obtained FNFM could be employed for the detection of Hg2+. Results reveal that the FNFM exhibits high sensitivity for the detection of Hg2+ and no interference from other metal ions. The limit of detection for Hg2+ can reach as low as 1ppb. In addition, the strong fluorescence of FNFM still can be observed even after the repeated use for 7 times. Therefore, FNFM can be developed as a rapid, portable and stable sensor for the detection of Hg2+. Moreover, FNFM can execute other functions by changing the probe immobilized on the surface of nanofiber.

Mesoporous MgAl2O4 and MgTiO3 nanoparticles modified polyacrylonitrile nanofibres for 2-chloroethyl ethyl sulfide degradation

Degradation of 2-chloroethyl ethyl sulfide (2-CEES), a stimulant of sulfur mustard, was investigated on the surface of polyacrylonitrile (PAN) nanofibres embedded with magnesium aluminate and magnesium titanate nanoparticles. The magnesium aluminate and magnesium titanate nanoparticles were prepared by the hydrothermal method and characterized by X-ray diffractometry, scanning electron microscopy and nitrogen adsorption BET. These metal oxide nanoparticles were mixed with PAN solution individually and then electrospun to produce nanofibres. Later, they were studied against the degradation of 2-CEES at room temperature (30±2 °C) using gas-chromatography coupled with flame ionization detector. The degradation and reaction kinetics data reveal that the 2-CEES degraded faster with higher amount of embedded metal oxide nanoparticles in PAN nanofibres. Moreover, the degradation yield of 2-CEES was higher in the case of PAN nanofibres embedded with magnesium aluminate nanoparticles relative to PAN nanofibres embedded with magnesium titanate nanoparticles. Fourier-transform infrared (FTIR) studies showed that the PAN nanofibres embedded with magnesium aluminate and magnesium titanate nanoparticles degrade 2-CEES by the formation of covalent/alkoxide bonds between the surface reactive oxide/hydroxyl group of metal oxide nanoparticles and 2-CEES. The result explores the role of modified PAN nanofibres with magnesium aluminate on the effective degradation of 2-CEES and possesses a suitable candidate for protective application.

Graphene oxide-embedded nanocomposite membrane for solvent resistant nanofiltration with enhanced rejection ability

Herein, novel solvent resistant nanofiltration membranes with enhanced rejection ability are synthesized by embedding graphene oxide (GO) sheets into polyethyleneimine (PEI) matrix, using polyacrylonitrile (PAN) ultrafiltration membrane as support layer. Dopamine is employed to modify the surface of PAN for enhancing the adhesive strength between the active and support layer and meanwhile promoting the dispersion of GO within PEI. Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, and contact angle measurement are conducted to probe the microstructures of the membranes. The nanofiltration performances in terms of solvent uptake, area swelling, solvent flux, and solute rejection of the membranes are systematically investigated using four commonly-used solvents, including ethanol, acetone, ethyl acetate, and n-heptane. It is found that GO sheets are horizontally-aligned within PEI matrix and generate unique transfer pathways through the GO edges, allowing small-sized molecules to transport while rejecting big-sized solute molecules. Consequently, the membranes display enhanced solute rejection and adequate solvent flux. 3.0wt% GO sheets increase the rejection of polyethylene glycol (Mw 200) from 66.2% to 96.8% with the acetone flux of 15.7Lm−2 h−1, particularly. In addition, the incorporation of GO donates promising long-term operation stability and excellent solvent resistance for practical application.

Tectomer grafted nanofiber: Synthesis, characterization and dye removal ability from multicomponent system

The surface of polyacrylonitrile (PAN) nanofiber was modified by Tectomer and its dye removal ability from binary systems was studied. The characteristics of nanofibers were investigated by FTIR, AFM, SEM, BET and BJH methods. FTIR showed successful grafting of Tectomer to the surface through the formation of imine group. Decrease in the average roughness and total surface area of nanofiber were detected by AFM and BET analysis, respectively. The adsorption capacity of Tectomer grafted nanofiber for Direct Red 80 and Direct Red 23 was 1250 and 1111mg/g, respectively. Adsorption of dyes follows the Langmuir isotherm and pseudo-second order kinetics.

Simultaneous Chemical and Optical Patterning of Polyacrylonitrile Film by Vapor-Based Reaction.

The surface of polyacrylonitrile (PAN) film is treated with ethyleneamines (EDA) in a simple chemical vapor phase reaction. Successful introduction of amine functional groups on the cyano group of PAN backbone is verified by FT-IR and NMR measurements. Further UV-vis and photoluminescence analyses show a red shift of the emission peak after repeated EDA treatment, which might be attributed to the formation of imine conjugation from newly formed carbon-nitrogen bonds on the PAN backbone. Further confocal laser scanning microscopy reveals that selective patterning of EDA on PAN films is possible via local polydimethylsiloxane masking. The results indicate that both chemical and optical patterning on PAN film can be realized via a single reaction and show the potential of this novel methodology in selective patterning.

Preparation and research of PAN/ZnO anti-static composite nano-fiber

In order to improve the anti-static performance of polyacrylonitrile( PAN) fiber,with PAN fiber as raw material,N,Ndimethyl acetamide( DMAC) as solvent,prepared PAN spinning solution. Then added different ratios of nano-Zn O,with good conductivity,to the PAN spinning solution by the method of ultrasound and mechanical stirring,prepared PAN / Zn O composite spinning solution. After that,PAN / Zn O nano-fibers with anti-static property were prepared by electrostatic spinning technique. The spin-ability of PAN spinning solution and PAN / Zn O spinning solution as well as the influence of different ratios of nano-Zn O to the crystallinity and the volume resistivity of PAN / Zn O nano-fiber are studied. The results indicate that the spinning solution has good spin-ability; when the concentration was 12%,spinning voltage was 18 k V,receiving distance was 15 cm,advancing speed was 0. 0005 mm / s,under the condition of electrostatic spinning,can get nanofibers with uniform fiber diameter,good parallel straight degree and smooth surface;with the increase of nano-Zn O content,the surface of PAN / Zn O nano-fibers become rough but no obvious change in crystallinity,and the volume resistivity decreases.

Surface modification of polyacrylonitrile fibre by nitrile hydratase from Corynebacterium nitrilophilus.

Previously, nitrile hydratase (NHase) from Corynebacterium nitrilophilus was obtained and showed potential in polyacrylonitrile (PAN) fibre modification. In the present study, the modification conditions of C. nitrilophilus NHase on PAN were investigated. In the optimal conditions, the wettability and dyeability (anionic and reactive dyes) of PAN treated by C. nitrilophilus NHase reached a similar level of those treated by alkali. In addition, the chemical composition and microscopically observable were changed in the PAN surface after NHase treatment. Meanwhile, it revealed that cutinase combined with NHase facilitates the PAN hydrolysis slightly because of the ester existed in PAN as co-monomer was hydrolyzed. All these results demonstrated that C. nitrilophilus NHase can modify PAN efficiently without textile structure damage, and this study provides a foundation for the further application of C. nitrilophilus NHase in PAN modification industry.

Enzymatic surface modification of polyacrylonitrile and its copolymers: Effects of polymer surface area and protein adsorption

Polyacrylonitrile (PAN) is a widely used polymer in the textile industry. PAN contains cyano groups on the surface due to which it possess low hydrophilicity and limits its application. Thus, there is a need to modify the functional groups on the surface of PAN for its industrial demand to improve moisture uptake, dyeability with ionic dyes, without affecting mechanical properties. A number of strategies such as chemical treatment, plasma treatment, enzymatic treatment etc. have been applied for the surface modification of polymer but enzymatic treatment are advantageous over plasma treatment and chemical treatment. In enzymatic treatment, reaction is limited to polymer surface only, and provides milder condition with less damage to polymer. In present study, it was found that enzyme system of Amycolatopsis sp.IITR215 was effective enzyme system for modification of surface nitrile groups of polyacrylonitrile. PAN powder was treated with the cell free extract of Amycolatopsis sp.IITR215 and it was found that the nitrile metabolizing enzymes of this strain were efficiently able to transform -CN to -COOH groups present on the surfaces of PAN powder. The formation of carboxyl group was quantified by ammonia released and dye binding assay. Further, confirmation of carboxyl group on polymer was done by FTIR and XPS. This study indicates that, specific adsorption of enzyme probably plays an important role in the enzymatic surface modification of polymer.

One-step self-assembly fabrication of amphiphilic hyperbranched polymer composite membrane from aqueous emulsion for dye desalination

Organic solvent usually was used in a polymer-based membrane fabricating process. In this study, otherwise pure water was utilized to prepare the polymer composite membrane. A pure aqueous emulsion was firstly prepared through directly dissolving a commercially available amphiphilic hyperbranched polymer (HBP), Boltorn W3000 into water. As the cross-linking agent, glutaraldehyde, glycol, triethylamine, or tetraethyl orthosilicate was then added into the emulsion, respectively. Finally, the HBP was self-assembled onto the surface of polyacrylonitrile (PAN) ultrafiltration membrane by immersing the PAN substrate into the emulsion to form the composite membrane. The homogeneous dispersion of the HBP in the emulsion was confirmed by transmission electron microscopy, and the formation of the composite membrane was characterized by IR spectra, field emission scanning election microscopy and atomic force microscopy. Importantly, the composite membrane performed an excellent separation performance in dye retention and desalination. For example, with the operation pressure of 0.5MPa, the retention of methyl blue could reach 97.0% with a flux of 55.0Lm−2h−1, while the salt retention was lower than 12.0%. This work thus not only illustrated a new approach for the preparation of nanofiltration membrane in aqueous solution, but also produced a potentially useful polymer-based composite membrane for highly efficient dye desalination.

Surface modification by self-assembled coating with amphiphilic comb-shaped block copolymers: A solution to the trade-off among solubility, adsorption and coating stability

Surface coating with amphiphilic block copolymers containing a long hydrophobic anchor block in polar solvent often suffered from the damaging impact of micelles, often leading to a significant decrease in adsorption amount and packing density. In this study, a series of amphiphilic comb-shape block copolymers, poly[poly(ethylene glycol) methyl ether acrylate]-b-poly(styrene-co-N,N-dimethylacrylamide) (P(PEGMEA)-b-P(St-DMA)) were synthesized successfully by reversible addition-fragmentation chain transfer (RAFT) polymerization with fluorescencelabelled RAFT agent. The chain structure and chemical composition of copolymers were characterized by 1H NMR, FTIR and GPC. The surface self-assembled coating through physical adsorption of P(PEGMEA)-b-P(St-DMA) in ethanol on the surface of polyacrylonitrile (PAN) membrane was investigated by XPS, ATR-FTIR, SEM and water contact angle measurements. The antifouling properties of the modified membranes were evaluated using BSA as a model protein. It was found that the introduction of appropriate DMA (DMA/St in the range of about 0.1 to 0.2) into the hydrophobic segment can significantly increase the solubility of copolymers and alter their aggregation behaviors, alleviate the impact of micelles, increase adsorbed amount of copolymers, and thus can enhance the hydrophilicity and anti-fouling properties of membranes. Moreover, the stability analysis indicated that P(PEGMEA)-b-P(St-DMA) with appropriate DMA in the hydrophobic anchor block can form a relatively stable coating on the surface of PAN membrane. Consequently, the adjustment of the structure and composition of anchor segment may be a potential solution to the trade-off among solubility, adsorption amount and coating stability when amphiphilic block copolymers were used to surface modification by self-assembled coatings. Open image in new window

Enhanced vibration damping of carbon fibers-ZnO nanorods hybrid composites

In this study, ZnO nanorods are grown on the surface of polyacrylonitrile based carbon fibers using a low temperature hydrothermal synthesis technique. Bi-layered carbon fiber-ZnO nanorod hybrid composite with epoxy matrix is prepared and tested for vibrational attenuations using dynamic mechanical analysis. Results revealed that the growth of ZnO nanorods on top of carbon fiber increases the damping performance by 50% while causing a slight decrease (∼7%) on the storage modulus. The enhanced damping of the hybrid composites can be related to the frictional mechanisms between the ZnO nanorod/epoxy and nanorod/nanorod interfaces combined with piezoelectric effect of ZnO.

Chemical interaction between carbon fibers and surface sizing

AbstractFunctional groups on the surface of Polyacrylonitrile (PAN)‐based carbon fibers and in fiber surface sizing are likely to react during the curing process of composites, and these reactions could affect the infiltration and adhesion between the carbon fibers and resin. T300B‐3000‐40B fibers and fiber surface sizing were heat‐treated at different temperatures, and the structural changes of both the fiber surface sizing and extracted sizing after heat treatment were investigated by Fourier transform infrared spectroscopy. The results show that the concentration of epoxy groups in both the fiber surface sizing and extracted sizing decreased with increasing heat‐treatment temperature and decreased to zero after treatment at 200°C. The concentration of epoxy groups in the extracted sizing was lower than that of the fiber surface sizing after treatment under the same conditions; this indicated that the rate of reaction between the carbon fibers and fiber surface sizing was higher than the reaction rate of the fiber surface sizing system. X‐ray photoelectron spectroscopy analysis reveals that the content of CO bonds and activated carbon atoms on the surface of the desized treated carbon fibers was the highest when the heat‐treatment temperature was 150°C; this proved the reaction between the carbon fibers and the fiber surface sizing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation and characterization of a new kind of UV-grafted ion-recognition membrane

A new kind of alkali metal ion-recognized membrane material compound named poly (styreneco-allyl oxygen)-4-tert butyl-calix [4] arene was synthesized by 4-tert-butyl calyx [4] arene and poly(styrene-co-allyl alcohol) as raw materials. Then a new ion recognition functional membrane was prepared by UV irradiation method via grafting the compound onto the surface of polyacrylonitrile (PAN) micro porous membrane. ATR-FTIR, SEM, AFM and SPM were used to test the surface structure of the functional membrane. The results showed that the functional membrane could form spindle structure on the surface of PAN membrane by the self-assembly way. Control transport experiment for non-functional material (PAA) grafted membrane and functional material grafted membrane were tested in our work, and the data showed that the functional material grafted membrane was able to identify Li+, Na+ and K+ while the PAA grafted membrane have not the ion-recognition ability. The recognition sequence of the functional membrane was K+>>Na+>Li+.

Catalytic graphitization of PAN-based carbon fibers with electrodeposited Ni-Fe alloy

Ni-Fe alloy was electrodeposited on the surface of polyacrylonitrile (PAN)-based carbon fibers, and catalytic graphitization effect of the heat-treated carbon fibers was investigated by X-ray diffractometry and Raman spectra. It is found that Ni-Fe alloy exhibits significant catalytic effect on the graphitization of the carbon fibers at low temperatures. The degree of graphitization of the carbon fibers coated with Ni-Fe alloy (57.91% Fe, mass fraction) reaches 69.0% through heat treatment at 1 250 °C. However, the degree of graphitization of the carbon fibers without Ni-Fe alloy is only 30.1% after being heat-treated at 2 800 °C. The catalytic effect of Ni-Fe alloy on graphitization of carbon fibers is better than that of Ni or Fe at the same temperature, indicating that Ni and Fe elements have synergic catalytic function. Furthermore, Fe content in the Ni-Fe alloy also influences catalytic effect. The catalytic graphitization of Ni-Fe alloy follows the dissolution-precipitation mechanism.

Controllable fabrication of cadmium phthalocyanine nanostructures immobilized on electrospun polyacrylonitrile nanofibers with high photocatalytic properties under visible light

A novel photocatalyst of nanostructured cadmium phthalocyanine (CdPc) immobilized on the surface of polyacrylonitrile (PAN) nanofibers had been successfully fabricated by a simple combination of electrospinning technique and the solvent-thermal process. FE-SEM micrographs indicated that the nanostructured CdPc uniformly immobilized on the surface of PAN nanofibers without agglomeration. And the obtained CdPc/PAN composite nanofibers exhibited high visible light photocatalytic activity for the degradation of rhodamine B. Moreover, this photocatalyst could be easily separated for reuse due to the one-dimensional nanostructural property of the CdPc/PAN composite nanofibers.

Self-assembly functionalized membranes with chitosan microsphere/polyacrylic acid layers and its application for metal ion removal

Multilayer composite membranes with high removal capability for metal ion were prepared using electrostatic self-assembly (ESA) technique. Especially, self-assembled multilayer of chitosan microspheres and PAA were formed onto charged surface of polyacrylonitrile (PAN) membranes. It was confirmed that the alternate multilayer of chitosan and PAA were deposited on the base membrane surface. The formation of the ESA layer-by-layer of chitosan/PAA or chitosan microspheres/PAA onto the base membrane surface functionally equipped the membrane with removal capability for Cu2+. Especially, membranes with chitosan microspheres/PAA ESA layers on the surface showed relatively higher adsorption capability as compared with membranes with chitosan/PAA ESA layers. Besides, the influence of the pH of metal ion solution on the metal ion adsorption property of ESA modified membrane was investigated. It was proposed that the layer-by-layer self-assembled deposition of chitosan microspheres would be a new approach to functionalize membrane with high adsorption capability for metal ions.

Protein Adsorption on a Glycosylated Polyacrylonitrile Surface: Monitoring with QCM and SPR

A simple and efficient method to fabricate a glycosylated surface on a polyacrylonitrile-based film is described. Construction and protein adsorption processes were monitored in situ using a QCM. A PANCHEMA film was deposited on the gold surface of the quartz crystal, and the glycosylated surface was then constructed through surface modification. Con A and BSA were used as probes to study the specificity of this surface to proteins. It can recognize Con A, while showing no specific interaction with BSA. The binding affinity indicates the presence of strong multivalent interactions between Con A and the glucose residues (cluster glycoside effect). Reproducibility and repeatability of the glycosylated polymer surface are sufficient to allow specific adsorption of Con A.