Cross-linked Polyacrylonitrile Research Articles

SIS-Based Electrostatic Spinning High-Safety Lithium-Ion Battery Separators.

As an important component, the properties of separators directly affect the capacity, life, and safety performance of lithium-ion batteries (LIBs). The high thermal stability and safety application value of the thermoplastic elastomer poly(styrene-b-isoprene-b-styrene) block copolymer (SIS) with different block ratios were explored to enhance the thermal stability and mechanical strength of the cross-linked polyacrylonitrile (PAN) membranes by vulcanization cross-linking and heat treatment. Among these membranes, the sample named the S/PAN/SIS-4019 separator was confirmed to be a self-closing separator that can cope with the thermal runaway, attributing to the continued fusion of the SIS soft and hard segments in the cross-linked structure under high-temperature heat treatment. Moreover, the tensile strength of S/PAN/SIS-4019 separator increased to 17.49 MPa, which was better than that of Celgard 2400, PAN, and other inlay separators. Using S/PAN/SIS-4019 as a battery separator, lithium-ion batteries showed a superior electrochemical performance compared to the usage of Celgard 2400. Owing to the stable pore structure and thermally protected self-shutdown mechanism, the overall properties of the obtained cross-linked separator were improved in terms of higher thermal stability, high ionic conductivity, and electrochemical properties.

Development and characterisation of MMT-reinforced polyacrylonitrile-pullulan nanofibers for controlled permeation of isotretinoin

Drug nanofibers play a crucial role in ameliorating therapeutic effects, reducing toxicity, and increasing the bioavailability of drugs. This study was aimed at the fabrication of isotretinoin-loaded MMT-reinforced bi-polymeric (PAN/PU) nanofibers with varying concentrations of isotretinoin. In this study, montmorillonite (MMT)-reinforced cross-linked polyacrylonitrile and pullulan nanofibers combined with varying amounts of isotretinoin were fabricated through an electrospinning approach and investigated for their drug permeation potential. PAN-PU nanofibers were successfully integrated with the isotretinoin. The incorporation of isotretinoin into the nanofibrous structure was confirmed by FTIR and XRD. TGA study indicated the stability of the fabricated nanoparticles. The SEM results showed the beaded and smooth morphology of nanofibers. Formulation with a higher drug concentration had a non-significantly (p > 0.05) higher swelling ratio. Drug-loaded polymeric nanofiber erodes at a slower rate as compared to drug-free nanofibers. The ex-vivo permeation study of nanofibers revealed that the drug was not released all at once, but rather gradually and consistently over the period of 24 h, indicating a controlled release of the drug. In addition, the drug concentration in the nanofibers affected the permeation of the drug. According to the findings, isotretinoin-loaded MMT-reinforced bi-polymeric (PAN/PU) nanofibers with varying concentrations of isotretinoin were successfully fabricated. The fabricated nanofibers (PAN/PU) showed a promising potential for controlled permeation of drugs through rabbit skin.

Sulfurized Polyacrylonitrile Cathode Derived from Intermolecular Cross-Linked Polyacrylonitrile for a Rechargeable Lithium Battery

Sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) has become one of the most promising cathodes for rechargeable batteries because of its high compressed density, low E/S ratio, no self-discharge, and stable cycling. However, it suffers from low sulfur content (<45 wt %), which limits the composite capacity and thereby the energy density. Herein, we prepared cross-linked PAN precursor with porous structure and high specific area via an intermolecular cross-linking method. The prepared cross-linked PAN offers more space to accommodate sulfur molecules, rendering the effective sulfur content up to 53.63 wt %. It realizes a remarkable reversible specific capacity of 829 mAh g–1composites at 0.2 C. As a result, it provides a way to prepare the S@pPAN cathodes for a lithium–sulfur battery with high energy density and good electrochemical performances.

WS2 deposition on cross-linked polyacrylonitrile with synergistic transformation to yield organic solvent nanofiltration membranes

Using liquid phase exfoliation (LPE) methods established in literature, several different tungsten (IV) disulfide (WS2) dispersions were prepared in solvents ranging from NMP, ethanol/water to pure water via sonication under ambient conditions. These various dispersions were then deposited directly onto cross-linked ultrafiltration-level polyacrylonitrile (PAN) flat sheet membranes through a pressure-assisted filtration process to produce ready-to-use membranes without any additional modifications. To evaluate and compare the performances of the various membranes produced, organic solvent nanofiltration (OSN) was utilized as the testing method while also representing a potential application of these fabricated membranes. After observing and comparing the outcomes of depositing different WS2 dispersions, deposition of the NMP dispersion was found to yield a promising membrane due to a concurrent synergistic densification effect with positive impacts on membrane performance. Thus, further emphases were placed on studying the use of different initial WS2 concentrations and longer sonication times in NMP dispersions. After the optimization, the composite membrane consisting of WS2 on cross-linked PAN substrates shows impressive performance with a high pure ethanol permeance of 43.35 L m−2 h−1 bar−1, a rejection of 86% towards Remazol Brilliant Blue R (Mw = 626.54 g/mol) and a long-term sustained rejection of 99% towards Evans Blue (Mw = 960.81 g/mol) in ethanol.

Dendrite Suppression Membranes for Rechargeable Zinc Batteries.

Aqueous batteries with zinc metal anodes are promising alternatives to Li-ion batteries for grid storage because of their abundance and benefits in cost, safety, and nontoxicity. However, short cyclability due to zinc dendrite growth remains a major obstacle. Here, we report a cross-linked polyacrylonitrile (PAN)-based cation exchange membrane that is low cost and mechanically robust. Li2S3 reacts with PAN, simultaneously leading to cross-linking and formation of sulfur-containing functional groups. Hydrolysis of the membrane results in the formation of a membrane that achieves preferred cation transport and homogeneous ionic flux distribution. The separator is thin (30 μm-thick), almost 9 times stronger than hydrated Nafion, and made of low-cost materials. The membrane separator enables exceptionally long cyclability (>350 cycles) of Zn/Zn symmetric cells with low polarization and effective dendrite suppression. Our work demonstrates that the design of new separators is a fruitful pathway to enhancing the cyclability of aqueous batteries.

Experimental survey of temperature, time and cross-linking agent effects on polydimethylsiloxane composite membranes performances in sulfur removal

Four types of the multi composite membranes were fabricated to decrease the sulfur content in diesel fuel, which the investigated polymers are polydimethylsiloxane (PDMS), polyethyleneglycol (PEG), polyethersulfonic (PES) and cross-linked polyacrylonitrile (PAN) with tetra-ethyl-ortho-silicate (TEOS). The effects of the operating parameters such as the cross-linking temperature (65–85 °C) and cross-linking time (0.5–2.5 h) were studied on the membranes performances. The results showed that the sulfur selectivity of PDMS/PEG/PES/PAN membranes were improved through increasing temperature and time. In addition, most of the total flux and the lowest amount of sulfur in the back flow is related to composite membranes of PEG + PDMS.

Brain-like manganese monoxide microspheres as anode materials for lithium ion battery

Brain-like manganese monoxide (MnO) microspheres were synthesized by simple precipitation method with subsequent heat treatment. MnO with polyacrylonitrile (PAN) as a binder delivers an initial reversible specific capacity of 976.1mAhg−1 and it remains at 912.3mAhg−1 after 30 cycles. The excellent cyclic performance is attributed to the effective conductive network of cross-linked PAN that formed during the thermal treatment. FTIR, ex situ XRD and XAS were performed to investigate the excess reversible capacity of MnO. The results show that the excess capacity is partially ascribed to the interfacial lithium storage between nanosized Li2O and Mn which is formed during the conversion reaction. The porous microspheres with large surface area also provide some active sites for lithium storage.

Effect of microgel content on the shear and extensional rheology of polyacrylonitrile solution

Crosslinked polyacrylonitrile (cPAN) particles with uniform size were synthesized through precipitation polymerization. The as-formed cPAN nanoparticles were dispersed in polyacrylonitrile (PAN) solutions to form microgels with various contents, which were used as model to study the influence of the microgels on the shear and extensional rheology of PAN solutions. Flow curves of steady shear viscosity displayed shear thinning and followed time–temperature superposition principle. The dependency of activation energy on the content of cPAN microgels indicated that introduction of microgels weakened the temperature sensitivity of PAN solutions. For extensional rheology study, we utilized the capillary thinning rheometry to characterize the elongation relaxation time and apparent extensional viscosity. Study of filament thinning dynamics with a series of system strains confirmed that the higher content of cPAN microgels the lower extensional strength and worse spinnability of the PAN solution.

In situ thermally cross-linked polyacrylonitrile as binder for high-performance silicon as lithium ion battery anode.

Electrode integrity and electric contact between particles and between particle and current collector are critical for electrochemical performance, especially for that of electrode materials with large volume change during cycling and with poor electric conductivity. We report on the in situ thermally cross-linked polyacrylonitrile (PAN) as a binder for silicon-based anodes of lithium-ion batteries. The electrode delivers excellent cycle life and rate capability with a reversible capacity of about 1450 mA h g(-1) even after 100 cycles. The improved electrochemical performance of such silicon electrodes is attributed to heat-treatment-induced cross-linking and the formation of conjugated PAN. These findings open new avenues to explore other polymers for both anode and cathode electrodes of rechargeable batteries.

Intelligent hydrophilic nanoparticles fabricated via alkaline hydrolysis of crosslinked polyacrylonitrile nanoparticles

Crosslinked polyacrylonitrile (PAN) nanolatex, with an average hydrodynamic diameter of 84 nm and a polydispersity index of 0.06, was successfully synthesized at a high monomer concentration and low surfactant content via a modified emulsion polymerization. Three measurements were adopted to control the nucleation and growth processes. Taking advantage of the chemical activity of nitrile groups, intelligent hydrophilic polymeric nanoparticles were fabricated via simple alkaline hydrolysis treatment of the crosslinked PAN nanolatex. Dynamic light scattering, electrophoretic light scattering, FT-IR spectroscopy, elemental analysis, and TEM observations were used to monitor the changes in the composition, structure, and morphology of the nanoparticles during the hydrolysis process. The sizes, chemical composition, morphology, and pH-responsive behavior of the intelligent hydrophilic nanoparticles could be adjusted by simply changing the hydrolysis time. As the hydrolysis was prolonged, the following nanoparticles could be obtained, crosslinked PAN nanoparticles with hydrophilic surfaces, amphiphilic nanoparticles with a hydrophobic PAN core and a hydrophilic polymeric shell composed of acrylamide and acrylic acid units, or carboxylic polyacrylamide nanoparticles. These modified nanoparticles all display good hydrophilicity, good biocompatibility, pH-sensitivity, as well as carboxyl functional groups, and thus are ideal candidates for various biomedical applications.

히드라진 가교 PAN 입자의 가수분해 및 흡습발열 특성

Polyacrylonitrile (PAN) particles synthesized by dispersion/emulsion polymerization of acrylonitrile monomer were cross-linked with hydrazine in order to prevent its dissolution in water when they were subjected to hydrolysis. Hydrazine-crosslinked PAN (cPAN) particles were hydrolyzed with NaOH solution in order to impart them with high hydrophilicity. The effects of the cross-linking degree, i.e., the hydrazine concentration during the cross-linking of PAN, NaOH concentration on the hydrolysis behavior of cPAN particles and their particle shapes were analyzed. Results revealed that cross-linking of PAN with 5% hydrazine solution at <TEX>$110^{\circ}C$</TEX> for 3 hours and hydrolysis of cPAN with 5% NaOH solution at <TEX>$80^{\circ}C$</TEX> for 3 hours is suitable for the preparation of highly hydrophilic and water-insoluble PAN particles. Then, hydrophilicity and the heat release property of the hydrolyzed, cross-linked PAN (h-cPAN) particles were examined. The h-cPAN particles exhibited a temperature rise of up to <TEX>$11^{\circ}C$</TEX> by water absorption and a moisture regain of up to 23% at <TEX>$20^{\circ}C$</TEX> and 65% RH, depending on the hydrazine cross-linking and NaOH hydrolysis conditions. Cotton fabrics were treated with h-cPAN dispersion solutions of different concentrations by a normal pad-dry process. The temperature changes of the treated fabrics by water absorption were measured. The h-cPAN treated fabrics showed higher temperature rise by moisture absorption compared to untreated one. It indicates that the particles can be used as a potential moisture-absorbing heat release finishing agent for textiles.

Adsorption Behavior of Lead(Ⅱ) by Crosslinked Polyacrylonitrile and Its Application in Trace Analysis

采用火焰原子吸收光谱法（FAAS）研究了交联聚丙烯腈螯合树脂对环境样品中Pb2＋的吸附分离/富集行为,并考察了共存离子的干扰。结果表明,该树脂对Pb2＋的吸附率在溶液pH=5.4、静态吸附时间1.5 h时室温下可达90%。在最佳吸附条件下,树脂对单一Pb2＋的饱和吸附容量可达49.6 mg/g。以0.1 mol/L盐酸溶液作为解吸剂,可将吸附在树脂上的Pb2＋定量洗脱,富集倍数和解吸率可分别达到50和97%。富集50倍后,方法的检出限（3σ10）为5.3μg/L;相对标准偏差（RSD）为2.1%;加标回收率为92.9%～97.6%。

Cross-Linked Polyacrylonitrile Prepared by Radiation-Induced Polymerization Technique

Cross-linked polyacrylonitrile PAN granules were prepared at ambient temperature by γ-rays at a constant dose rate of 8.5 kGy/h. It was found that the rate of polymerization was linear with the radiation dose at the initial stage of polymerization, and then, at high conversion, it tends to level off above 35 kGy. Cross-linking of PAN is accompanied simultaneously with the polymerization process at high energy radiation. Characterizations of the cross-linked PAN prepared at different radiation doses were investigated by FT-IR, XRD, DSC, and TGA analysis. The appearance of an IR band at 1670 cm-1 confirmed the cross-linking of PAN via nitrile groups. The original crystal lattice and the entropy of melting ΔSm did not change significantly at high radiation doses.

Evidence for Second-Order Optical Nonlinearity in γ-Ray Induced Partially Cross-Linked Polyacrylonitrile

The first direct evidence for second-order nonlinearity in partially cross-linked polyacrylonitrile is reported. The cross-linking in γ-ray-induced polymerized neat acrylonitrile is well supported by UV−vis spectroscopy, FTIR, and 13C CP/MAS solid-state NMR. The second harmonic generation (SHG) powder test was employed to access the preliminary information about the occurrence of second-order nonlinear effect. The second harmonic generation is accomplished without the application of an external electric field, thus illustrating the importance of structural changes imparted by high-energy photon flux. Second-order nonlinearity in the present case is expected due to the small π conjugation imparted by cross-linking through −CN across polymeric chains coupled with the noncentrosymmetric molecular structure. Second harmonic intensity as high as 80% of that for powder urea has been observed.

Photopolymerization of acrylonitrile in concentrated aqueous zinc halide solutions

Crosslinked polyacrylonitrile (PAN) was obtained with a high yield from the photoinduced polymerization of acrylonitrile (AN) in concentrated aqueous zinc chloride solution. It was found that the presence of zinc chloride results in the promotion of the radical generation in the photoinitiation process as well as an increase in the rate of propagation. Any attempt to isolate the polymer from the reaction mixture was not successful due to the insolubility of the polymer to any conventional solvents to polyacrylonitrile (PAN); therefore, the reaction mixtures, consisting of PAN, zinc chloride, and water—which are referred to as the polymer hybrid system—was used without further purification. The effect of other zinc halides on the polymerization such as zinc bromide and zinc iodide was also investigated in connection with the photoinitiation mechanism, which reveals that the complex (Zn++(AN)x(OH−)yCl) is the species that is responsible for the photoinitiation. It was found that the transparent, stretchable polymer hybrid systems are electric conductive and turn to black upon heating to 160°C due to the conversion of the nitrile group of PAN to tetrahydronaphthyridine rings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2588–2594, 2000

高速液体クロマトグラフィー（ＨＰＬＣ）によるスチレン（Ｓｔ）‐メタクリル酸メチル（ＭＭＡ）‐アクリロニトリル（ＡＮ）三元共重合体の組成分布解析

Separation of styrene-methyl methacrylate-acrylonitrile terpolymers by chemical composition was studied using high-performance liquid chromatography(HPLC). Cross-linked polyacrylonitrile gel or polyacrylamide gel as a stationary phase and mixture of chloroform, acetonitrile and n-hexane as an eluent were used in the normal phase HPLC. For the reversed-phase HPLC, polystyrene gel and a mixture of chloroform and acetonitrile were used as a stationary phase and an eluent, respectively. Solvent gradient of increasing chloroform content was utilized. In the case of normal phase HPLC terpolymer was eluted from the non-polar polymer, while from the polar polymer in the case of reversed-phase HPLC. Individual terpolymers were completely separated from a mixture of nine terpolymers by cross-fractionation using the combination of HPLC with acrylonitrile and acrylamide column or acrylonitrile and styrene column system.

Separation of Stereoisomers of Poly(methyl methacrylate) by High Performance Liquid Chromatography

Poly(methyl methacrylate) (PMMA) was separated by stereoisomerism using high performance liquid chromatography (HPLC). Using a cross-linked polyacrylonitrile gel as the stationary phase and a mixture of dichloromethane and n-hexane, ethyl ether, or benzene as the eluent, isotactic PMMA eluted faster than syndiotactic PMMA. With a cross-linked polystyrene gel and a mixture of dichloromethane and nitromethane, syndiotactic PMMA eluted earlier. With some eluent forming stereocomplex of PMMA after injecting a mixture of isotactic and syndiotactic polymers, the sample did not elute or eluted at a different elution time from that expected from an experiment of a separate injection. From the cloud point it was found that the separation was done by an adsorption mechanism rather than phase separation.

Preparation and analytical properties of a chelating resin containing cysteine groups

A macroporous, cross-linked polyacrylonitrile copolymer was synthesized, the nitrile groups were converted to carboxylic acid by hydrolysis, and these carboxylic acid groups were treated with L-cysteine and 1,6-hexanediol (binding agent). Studies of the basic characteristics of this resin showed that it was highly selective for silver(I), mercury(II), gold(III) and platinum(IV) in aqueous acidic solution, the maximum capacities being 0.97, 0.65, 1.22 and 0.39 mmol g -1 of dry resin, respectively. These four metal ions can be separated from each other, or concentrated from very dilute solutions, on a short column of the resin. The effects of different acids and of various common metal ions are reported.