Amounts Of Polyacrylonitrile Research Articles

Integrating the in vitro antioxidant activity of Polyacrylonitrile/Polyindole composites

AbstractIn this study, five compounds belonging to the Polymer composites (PCs) family, have been prepared with different amounts of polyacrylonitrile and polyindole in the composite. The PCs have inherently bactericidal activity, owing to the nitrile and indole groups. Antioxidant activity was assessed by using reducing power activity, superoxide radical scavenging activity and hydroxyl radical scavenging activity. In our study, butylated hydroxy toluene (BHT), ascorbic acid and α‐tocopherol, which are considered synthetic standard antioxidants, were used to compare antioxidant activity. In addition, since it is known that the MDA levels resulting from the oxidation of fats in Saccharomyces cerevisiae yeast cells are inversely proportional to the antioxidant properties, it gave an idea about the in vitro antioxidant properties of the new synthesized PCs. Reducing force capacity, superoxide radical scavenging activity and hydroxyl radical scavenging activity were found to be higher at 100 μg mL−1 concentration compared to 50 μg mL−1 concentration.

Alignment of linear polymeric grains for highly stable N-type thin-film transistors

Summary Temperature-insensitive properties are attractive for most electronics, including polymeric semiconducting devices. Especially, polymeric field-effect transistors (FETs) with high mobility have been important research targets due to their broad applications. However, polymeric FETs with stable charge transport operating at extremely cold or hot zones are faced with enormous challenges. In this study, the polyacrylonitrile was found to significantly tune the sizes of pre-aggregates of polymers in solutions and the crystallinity of the polymeric films. The orientation of 5–25 μm linear grains in the films were prepared through the bar-coating process with polyacrylonitrile as an additive, which stabilized the electron mobility over a wide range of temperatures. The linear-grain morphology of the film contributed to reducing the holes and grain boundaries in the transport paths of carriers. Typically, the top-gate FETs based on P(NDI2OD-T2) displayed a stable electron transporting behavior from 200 to 460 K, with mobility greater than 3.5 cm2V−1s−1.

Improving the air-stability of n-type organic thin-film transistors by polyacrylonitrile additive

Semiconducting and insulating polymer blend transistors have been studied to improve their air stability and create stretchable devices for skin electronics. Electron-transporting (or n-type) semiconducting polymers have significant problems regarding their device stability and performances. In this study, we tried to solve the stability issue of the n-type organic thin-film transistors (OTFTs). In order to extend the device lifetime, polyacrylonitrile (PAN) was introduced as an additive to the typical n-type naphthalenediimide (NDI)-based polymer, namely, P(NDI2T-OD) or N2200. PAN was well mixed with P(NDI2T-OD) to produce homogeneous solutions in chloroform/chlorobenzene mixtures when the PAN proportion was less than 5 wt%. The stability of the OTFTs stored in air was evaluated based on the electron mobility μe, threshold voltage Vth, and Ion/Ioff ratio. Adding a small amount of PAN can significantly improve the stability and μe values of the OTFTs probably due to the gas barrier and water trapping characteristics of the PAN.

Dynamic adsorption–desorption of methyl ethyl ketone on MCM-41 and SBA-15 decorated with thermally activated polymers

Three series of mesoporous adsorbents designed for removal of methyl ethyl ketone vapor (MEK) were synthesized: MCM-41 was decorated with various amounts of novolac resin (Nov) and polyacrylonitrile (PAN), while SBA-15 was modified with PAN. The composites were thermally activated towards an enhancement of MEK adsorption capacity and tested in a fixed bed adsorber. Structural features of parent silicas were investigated by XRD, while textural parameters of the composites were studied by low-temperature nitrogen adsorption. A surface composition was examined by DRIFT and XPS. It was found that decoration of the silica surface with small amounts of PAN improved the monolayer adsorption capacity. The MEK breakthrough curves and desorption profiles were employed for calculation of the monolayer capacity and total pore volume (VtotalMEK). The VtotalMEK for the materials with smaller pores (MCM-41) were comparable to those determined by nitrogen adsorption, whereas respective values for the solids with larger pores (SBA-15) were underestimated. The mechanism of adsorption of MEK onto the adsorbents was elucidated. The MEK molecules were adsorbed solely in the form of keto tautomer. The enhanced MEK adsorption capacity came from the beneficial textural features of the support and the presence of a ladder-type PAN structure containing O-groups.

Development of Surface-Modified Polyacrylonitrile Fibers and Their Selective Sorption Behavior of Precious Metals

The purpose of this study was to design a powerful fibrous sorbent for recovering precious metals such as Pd(II) and Pt(IV), and moreover for identifying its selectivity toward Pd(II) or Pt(IV) from a binary metal solution. For the development of the sorbent, polyacrylonitrile (PAN) was selected as a model textile because its morphological property (i.e., thin fiber form) is suitable for fast adsorption processes, and a high amount of PAN has been discharged from industrial textile factories. The PAN fiber was prepared by spinning a PAN–dimethylsulfoxide mixture into distilled water, and then its surface was activated through amidoximation so that the fiber surface could possess binding sites for Pd(II) and Pt(IV). Afterwards, by Fourier-transform infrared (FT-IR) and scanning electron microscopy (SEM) analyses, it was confirmed that the amidoximation reaction successfully occurred. The surface-activated fiber, designated as PAN–oxime fiber, was used to adsorb and recover precious metals. In the experiment results, it was clearly observed that adsorption capacity of PAN–oxime fiber was significantly enhanced compared to the raw material form. Actually, the raw material does not have sorption capacity for the metals. In a comparison study with commercial sorbent (Amberjet™ 4200), it was found that adsorption capacity of PAN–oxime was rather lower than that of Amberjet™ 4200, however, in the aspects of sorption kinetics and metal selectivity, the new sorbent has much faster and better selectivity.

Preparation and properties of highly branched sulfonated poly(arylene ether)/polyacrylonitrile composite materials as proton exchange membranes

Highly branched sulfonated poly(arylene ether ketone)s (BSPAEKs) exhibit excellent potential as proton exchange membranes (PEMs). However, the mechanical properties of the branched membranes must be further improved. In this work, a series of BSPAEK-based composite membranes containing different amounts of polyacrylonitrile (PAN) were fabricated as PEMs. The expected ionic cross-linking and hydrogen bonding between BSPAEK and PAN was confirmed by Fourier transform infrared spectroscopy. The tensile strengths of the composite membranes with PAN contents from 5 to 20 % ranged from 16.4 to 23.0 MPa, which were notably higher than that of the BSPAEK membrane (13.1 MPa). Furthermore, the oxidative stability of the composite membranes was enhanced significantly from 295 to 430 min (2 ppm FeSO4 in 3 % H2O2) with increased PAN doping. Although the proton conductivity of the composite membrane was lower than that of BSPAEK, the proton conductivity of the composite membranes was still above 10−2 S cm−1 and satisfied the requirement of the fuel cells. The results indicate that this material is a suitable candidate PEM for evaluation in fuel cell applications.

Materials design towards sport textiles with low-friction and moisture-wicking dual functions

In the field of sportswear, the structure and morphology of textiles are of great importance to achieve good moisture transport and low friction, which are two critical comfort-related properties. To improve these properties, dual-layer nanofibrous nonwoven mats were studied in this work. Core–shell nanofibers with a polyacrylonitrile (PAN)-rich core and a poly(vinylidene fluoride) (PVDF)-rich shell were fabricated by single-spinneret electrospinning and used as the inner layer of the dual-layer mats, while thick base-treated Cellulose Acetate (CA) nanofibrous mats were used as the outer layer. The core-located PAN and a small amount of PAN on the PAN/PVDF nanofiber surface ensure good moisture transport through the nanofibrous mats. The synergistic combination of a considerably hydrophobic PAN/PVDF inner layer and a highly hydrophilic CA outer layer induces a strong push–pull effect, resulting in efficient moisture transport from the inner to the outer layer. Furthermore, the fluorine-rich PVDF shell of the inner layer touches the human skin and provides a lubricating effect to enhance comfortability. This design provides a promising route for sports textiles with both good moisture-wicking and low friction.

Synthesis of carbon/α-Al2O3 composite adsorbents for the elimination of methyl-ethyl ketone vapour

α-Al 2 O 3 has been modified by the deposition of different amounts of polyacrylonitrile (PAN) via precipitation radical polymerization in an aqueous suspension. Carbonization of the product performed in an inert atmosphere at 350 °C resulted in obtaining of a carbon layer supported on the surface of α-Al 2 O 3 . The content of carbon in the composites was determined by temperature-programmed oxidation, whereas textural properties of the synthesized samples were studied by low-temperature sorption of N 2 (BET). The carbon/α-Al 2 O 3 composites appeared to be effective adsorbents of methyl ethyl ketone vapour.

Anti-fouling ultrafiltration membranes containing polyacrylonitrile- graft-poly(ethylene oxide) comb copolymer additives

Membrane fouling is one of the most important challenges faced in membrane ultrafiltration (UF) operations. In this study, polyacrylonitrile- graft-poly(ethylene oxide) (PAN- g-PEO), an amphiphilic comb copolymer with a water-insoluble polyacrylonitrile (PAN) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains, was used as an additive in the manufacture of novel PAN UF membranes. During casting, the PAN- g-PEO additive segregates to form a PEO brush layer on all membrane surfaces, including internal pores. Wettability, pure water permeability, and resistance to irreversible fouling increased when either the amount of PAN- g-PEO added to the membrane or the PEO content of the comb copolymer was increased. These trends were consistent with measured adhesion forces between the membranes and a carboxylated latex particle probe in an atomic force microscopy (AFM) analysis, and with the near-surface PEO coverage as determined by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) revealed further effects of additive incorporation on membrane morphology. In 24-h dead-end filtration studies, blend membranes prepared with 20 wt% PAN- g-PEO (comb PEO content: 39 wt%) were found to resist irreversible fouling by 1000 ppm solutions of bovine serum albumin (BSA), sodium alginate, and humic acid, recovering the initial pure water flux completely by a pure water rinse, or a backwash in the case of humic acid. This exceptional anti-fouling performance holds promise for extending UF membrane lifetimes without need for aggressive cleaning procedures.

Preparation of a microporous gel polymer electrolyte with a novel preferential polymer dissolution process for Li‐ion batteries

AbstractA special type of polyacrylonitrile (PAN)‐based microporous polymer electrolyte was prepared by the dissolution of poly(vinyl chloride) (PVC) with a novel preferential polymer dissolution process from cast polymer films containing various amounts of PAN and PVC. PVC, dissolved from a 50 : 50 (w/w) PAN/PVC blended polymer film, had a high ionic conductivity of 5.01 × 10−3 S/cm at the ambient temperature when soaked in a 1M solution of LiClO4 in ethylene carbonate and diethyl carbonate. The amorphosity, surface morphology, and thermal stability of the microporous gel polymer electrolyte were characterized by X‐ray diffraction, scanning electron microscopy, and differential scanning calorimetry studies. Chronoamperometry and linear‐sweep voltammetry studies were performed to determine the lithium transference number and stability of the microporous polymer electrolyte membrane, respectively. Finally, a Li‐ion polymer cell was assembled with the prepared microporous gel polymer electrolyte, and its compatibility with electrode materials was studied by cyclic voltammetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1891–1896, 2005

Characterization of the surface properties of nitrogen-enriched carbons by inverse gas chromatography methods

The characterization of the surface properties of carbonaceous materials by inverse gas chromatography (IGC) techniques is described. The cokes investigated were produced by the co-pyrolysis of a coal-tar pitch (CTP) with different amounts of polyacrylonitrile (PAN) as a possible method to synthesize carbonaceous materials enriched in nitrogen. IGC at infinite dilution and LSER (linear solvation energy relationship) techniques were used to determine the physical and chemical surface properties of the cokes. In general, the surface free energy of adsorption is due to both dispersive and specific interactions. The dispersive component of the surface free energy was determined using n-alkane probes. For the specific component, which is primarily due to acid–base interactions, different polar probes were used. The LSER method was applied to improve our understanding of the adsorption process in terms of molecular interactions. We show that, to characterize dispersive interactions using n-alkanes, the LSER and IGC methods are equivalent. On the other hand, with both methods we find that all the samples present acidic and basic characteristics. However, the sensitivity of the LSER method does not allow us to discriminate between the three samples in terms of specific interactions.

Studies on Composite Electrolytes Composed of Thermoplastic Polyurethane and Polyacrylonitrile

Composite electrolytes comprised of thermoplastic polyurethane (TPU) with polyacrylonitrile (PAN) were investigated. Differential scanning calorimetry (DSC) and impedance spectroscopy were used to monitor the changes in the thermal characteristics and bulk conductivity of the composites due to the amounts of PAN in the composite. Fourier transform infrared spectroscopy (FTIR) was employed to identify the modifications in molecular interactions associated with TPU. The deconvolution of spectral bands associated with CO and the NH group of TPU and the C⋮N group of PAN was utilized to obtain such information. The bulk conductivity of the composites with different PAN content was determined, and the influence of PAN on that was brought out. The effects of temperature and lithium salt concentration on conductivity of the composites were analyzed with respect to TPU. The conductivity changes were correlated through DSC and FTIR results.

Characterization of Some Polyacrylonitrile-Based Electrolytes

Polyacrylonitrile (PAN)-based electrolytes have been prepared by encapsulating Li salt solutions. The conductivity of these electrolytes is governed by a combination of factors including the relative amounts of PAN, EC, PC and the Li salt, and temperature. A conductivity of about 4.5 x 10{sup -3}{Omega}{sup -1} cm{sup -1} at 30 {degrees}C was exhibited by EC-rich electrolytes containing both LiN(SO{sub 2}CF{sub 3}){sub 2} and LiPF{sub 6}. The cationic transference numbers, measured using a dc polarization method coupled with impedance spectroscopy, were found to be between 0.2 and 0.3 for electrolytes containing LiN(CF{sub 3}SO{sub 2}){sub 2} and LiPF{sub 6}. The tensile strength of the electrolytes was observed to increase from 60 to 140 lb/in.{sup 2} upon incorporation of the thermally activated cross-linking agent ethylene glycol dimethacrylate. Cyclic voltammetry on Pt electrodes has shown that these electrolytes have an inherent oxidation stability window extending up to about 5 V versus Li{sup +}/Li. On Al, Ni, and Cu electrodes, however, oxidation was observed at lower potentials because of metal corrosion reactions. Copper was reversibly oxidized at 3.5 V, irrespective of the Li salt present in the electrolyte. On the other hand, the nature of the Li salt influenced the corrosion potentials of Al andmore » Ni. Nickel was found to be stable up to 4.2 V in the presence of LiAsF{sub 6}, whereas it was oxidized at about 3.5 and 4 V when the electrolyte contained LiN(SO{sub 2}CF{sub 3}){sub 2} and LiSO{sub 3}CF{sub 3} showing oxidation at {le}4 V. The electrochemical stability of the electrolytes was further verified in Li/LiMn{sub 2}O{sub 4} cells. 10 refs., 15 figs., 9 tabs.« less

Raman Spectroscopic Investigation of the Dissociation of Dimethylsulphoxide Induced by Polyacrylonitrile

The complex species of dimethylsulphoxide (DMSO) containing various amounts of polyacrylonitrile (PAN) have been studied by Raman spectroscopy. By systematically studying the Raman spectra of the C=O stretching region, it has been found that the addition of PAN to DMSO breaks down the linear dimer and/or higher polymer, leading to the dissociation of DMSO molecules. It seems that the cyclic dimers of self-associated DMSO molecules are less affected by the introduction of PAN. Although the spectral changes of PAN are not as obvious as those of DMSO, it can still be seen that the scattering cross-section of the C&24XXXw;N stretching mode decreases above a PAN molar ratio of 0.8. It seems that DMSO and PAN interact through the dipoles of their respective S=O and C&24XXXw;N groups, which makes DMSO a suitable plasticizer in PAN-based electrolytes.

Investigation on the preconcentration of trace elements on polyacrylonitrile

Trace amounts of Co, Ni, and Mn have been enriched from aqueous solutions by retention of their ions on polyacrylonitrile (PAN). The recovery has been determined as a function of the amount of PAN, pH, the concentration of eluent (HCl) and the volume of sample solution. The elements were removed with 100% efficiency by means of conc. HCl. Recoveries were up to 95% depending on the elements. The resin has been used in combination with atomic absorption spectrophotometry for the determination.

Graft polymerization of acrylonitrile onto wheat straw

Acrylonitrile was graft polymerized onto ground, water-washed wheat straw using Fe2+-H2O2 as initiator. Reaction conditions were selected to minimize homopolymer formation and maximize the amount of polyacrylonitrile (PAN) grafted to straw. Polymerizations typically yielded straw-g-PAN containing 30–35% PAN. A two-step fractionation scheme was developed for determining the relative amounts of PAN grafted to cellulose, hemicellulose, and lignin. This scheme involved (1) delignification of straw-g-PAN with sodium chlorite followed by removal of lignin-grafted PAN by extraction with dimethylformamide (DMF), and (2) hydrolysis of the hemicellulose component with 1 N trifluoroacetic acid followed by DMF extraction of hemicellulose-grafted PAN. Product remaining after these two treatments was assumed to be cellulose-g-PAN. When relative amounts of PAN grafted to cellulose, hemicellulose, and lignin were compared with relative percentages of these components present in wheat straw, the percentage of total PAN grafted to lignin was less than its relative percentage in straw, whereas that grafted to hemicellulose was considerably more. Although the use of Ce4+ as initiator gave little or no polymer with whole, water-washed straw, grafted polymerization occurred when delignified straw was used as substrate. Relative amounts of PAN grafted to cellulose and hemicellulose were not greatly different from those observed with Fe2+-H2O2 initiation onto whole straw.

Anionic synthesis of poly[ethylene methylene bis(4‐phenyl‐carbamate)‐g‐acrylonitrile

AbstractA relatively high‐molecular‐weight polyurethane based on MDI and ethylene glycol was prepared and characterized. This polymer was metalated with sodium hydride in N,N‐dimethylformamide (DMF) at about 0°C. Metalation was confirmed principally by spectroscopic identification of the N‐methyl derivative obtained by coupling the metalated polymer with methyl iodide. Under appropriate reaction conditions the metalated polyurethane was used for the anionic graft polymerization of the reactive monomers acrylonitrile and ethylene and propylene sulfides. Attempted anionic graft polymerizations with other monomers, including styrene and ethylene and propylene oxides, were unsuccessful. The polyurethane grafted with acrylonitrile was separated by fractionation from accompanying small amounts of polyacrylonitrile, a low‐molecular‐weight homopolymer. One sample of polyurethane grafted with acrylonitrile was identified by microanalysis, IR, NMR, and increase in weight and was also characterized by differential thermal analysis.