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Chemoselective reduction of nitroarenes to corresponding arylamines is a significant reaction in the chemical industry. However, in the presence of other reducible groups, including halogenated nitrobenzene, nitrobiphenyl, and nitroquinoline in the same molecule of nitroaromatics, the control of chemoselectivity remains challenging. Here, a facile fabrication of a heterogeneous iron‐based catalyst is reported as a potential alternative to precious metal catalysts for the chemoselective reduction of nitroarenes. The pyrolysis of iron acetate/polyacrylonitrile (PAN) template under an inert atmosphere furnishes active Fe3O4 nanoparticles (NPs) encapsulated in nitrogen‐doped (N‐doped) carbon layers, which can provide more catalytic active sites (Fe3O4/PAN@800). Notably, non‐precious iron oxide NPs supported on N‐doped carbon support prevent aggregation, thereby enhancing the catalytic activity. The sustainable and reusable Fe3O4/PAN@800 catalyst, having only 0.8% metal content as demonstrated by x‐ray photoelectron spectroscopy, delivers excellent yields of corresponding amines from differently functionalized nitroarenes. Hydrogenation of a series of structurally functionalized nitroarenes produced excellent yields of anilines, which serve as building blocks and intermediates for fine and bulk chemicals. Hydrogenation of 2‐chloro‐3‐nitropyridine, 2‐nitro‐1,1′‐biphenyl, ortho‐nitroaniline, and 4‐aminophenyl acrylonitrile yielded respective anilines up to 99%. The active sites of Fe3O4 have magnetic performance, hence, the catalyst can be easily recovered using a magnet and reused for at least five cycles without significant loss of catalytic activity. Therefore, the easily prepared, cost‐effective, and reusable Fe3O4/PAN@800 catalyst presented in this study shows potential for applications in the selective reduction of aromatic nitro compounds. Consequently, this study potentially establishes a guideline for the facile preparation of abundant transition‐non‐noble metal‐based reusable supported catalysts for various applications in the chemical industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon nanofibrous membranes were prepared for adsorptive separation of VOCs. • The membranes showed hierarchical porous structures and functional surfaces. • The membranes possessed comparable adsorption quantities and fast kinetics. • The membranes exhibited good reusability and dynamic adsorption performance. Volatile organic compounds (VOCs) in the air pose great health risks to humans and the environment. Adsorptive separation technology has proven effective in mitigating VOC pollution, with the adsorbent being the critical component. Therefore, the development of highly efficient adsorbent materials is crucial. Carbon nanofibers, known for their physical–chemical stability and rapid adsorption kinetics, are promising candidates for removing VOCs from the air. However, the relatively simple porous structures and inert surface chemical properties of traditional carbon nanofibers present challenges in further enhancing their application performance further. Herein, a hierarchical porous carbon nanofibrous membrane was prepared using electrospinning technology and a one-step carbonization & activation method. Phenolic resin and polyacrylonitrile were used as co-precursors, with silica nanoparticles serving as the dopant. The resulting membrane exhibited a specific surface area of up to 1560.83 m2/g and surfaces rich in functional O-/N- groups. With a synergistic effect of developed micro- and meso -pores and active chemical surfaces, the carbon nanofibrous membrane demonstrated excellent adsorption separation performance for various VOCs, with comparable adsorption capacities and fast kinetics. Moreover, the membrane displayed remarkable reusability and dynamic adsorption performance for different VOCs, indicating its potential for practical applications. [ABSTRACT FROM AUTHOR]

The functional group distribution and skin–core structure of polyacrylonitrile (PAN) pre-oxidized fibers have been evaluated by solid-state 13C-NMR, electron probe micro-analysis, element analysis, nano-infrared spectroscopy atomic force microscopy, and optical microscopy. The pre-oxidized fibers exhibited a skin–core structure with high optical density (OD) values in the skin and low OD values in the core. As the heat treatment temperature was increased, the OD of the pre-oxidized fibers increased, which is because of the formation of C = O, C = N, C = C, and their conjugated structures of C = N with C = C. The difference in the OD values between the pre-oxidized fiber skin and core became increasingly apparent as the heat treatment temperature increased, with the OD difference increasing from 0.045 at 220 °C to 0.085 at 260 °C. The OD difference is closely related to the oxygen element and C = O functional groups in the fiber. The contents of the oxygen element and C = O in the pre-oxidized fiber skin were higher than those in the pre-oxidized fiber core. At a heat treatment temperature of 260 °C, the relative content of C = O in the skin was 0.454, whereas that in the core was 0.313, which was consistent with the trend of the OD value change. In comparison, C = C and C = N formed during pre-oxidation were not substantially distributed in the radial direction of the fibers. The radial inhomogeneity of the pre-oxidized fiber was mainly affected by the radial difference of the carbonyl content. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) are crucial for high‐performance energy storage, offering high power density, swift charge–discharge rates, and durability. The enhancement of their performance hinges on the development of advanced electrode materials. This study presents an innovative method involving polyacrylonitrile (PAN) nanofibers adorned with manganese dioxide (MnO₂) nanoparticles (NPs), created through electrospinning and subsequent thermal treatment. This synergy exploits the extensive surface area and electrical conductivity of PAN nanofibers along with the substantial capacitance of MnO₂. The MnO₂‐coated PAN nanofibers reached an impressive specific capacitance of 247 F g−1 at a scan rate of 10 mVs−1, markedly boosting the efficacy of all‐solid‐state asymmetric SCs. The SCs, incorporating a polyvinyl alcohol (PVA)/potassium hydroxide (KOH) gel electrolyte, exhibited an energy density of 8.2 Wh kg−1 at a power density of 700 W kg−1, preserving 80.4% of their original capacitance after 5000 cycles. This research is pioneering in combining MnO₂ with PAN nanofibers, marking a significant leap forward in supercapacitor technology with enhanced energy storage capacity and prolonged stability. These findings underscore the promise of these composite materials in future energy storage solutions. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The key to the modification of the properties of carbon fibers is to understand how to control the structure of polyacrylonitrile-based precursors. Results of a mesoscale modeling of the structure formation processes in a mixture of polyacrylonitrile, dimethyl sulfoxide, and water (good and poor solvents for polymers) are reported. The system′s composition is chosen using the composition of precursor fibers at the later formation stages under coagulation bath conditions. All calculations are performed using the dynamic density functional theory. The proposed model considers effects caused by changes in the system composition, carbon nanotube filler, temperature, and shear flow. It is shown that the polymer structure can be significantly changed by varying the amount of water in the system (determined by the coagulation bath composition) and by introducing a carbon filler. [ABSTRACT FROM AUTHOR]

Poly(acrylonitrile-co-styrene) microspheres are utilized in several applications due to their superior mechanical properties, excellent chemical stability, and tunable surface modification. In this work, poly(acrylonitrile-co-styrene) microspheres were synthesized in ethyl acetate usingreflux precipitation polymerization. The average particle size and morphology of microspheres were carefully measured to investigate the responding influencing factors. In the growth process of these microspheres, the average particle size of poly(AN-co-St) microspheres changed a little after 180 min. However, the yield of the microspheres continued to increase until 420 min. The properties of the solvents had a significant impact on both the average particle size and the morphology of the poly(AN-co-St) microspheres. The concentrations of the initiator and the cross-linker have minimal effect on the average particle size of poly(AN-co-St) microspheres. By controlling the monomer content at 25 wt%, the yield of these microspheres could reach 82%. The method is straightforward to operate andthe prepared microspheres exhibithigh sphericity and uniformity. As a result, it shows great promise for thepreparation of submicron poly(AN-co-St) microspheres. [ABSTRACT FROM AUTHOR]

Aqueous precipitation polymerization is commonly used in the industry due to its efficient heat dissipation, reaction stability and production flexibility. However, its mechanisms and kinetics are still partially unclear. The ammonium persulfate-ammonium sulfite monohydrate (APS-AS) initiated aqueous phase precipitation polymerization of acrylonitrile (AN) at low concentration was deeply investigated, with the APS initiation system as a control. The apparent kinetic equations for the APS and APS-AS initiation systems were determined to be Rp= K[AN]1.706[(NH4)2S2O8]0.704 and Rp= K[AN]3[(NH4)2S2O8]0.704[(NH4)2S2O3]−1.055, respectively. Monitoring AN distribution in the aqueous and polyacrylonitrile (PAN) phases revealed a rapid transition of the reaction site from the aqueous phase to the PAN phase following polymer precipitation. Zeta potential and primary particle number exposed that the nucleation site disparities between initiation systems led to different predominant factors affecting the polymerization rate. The change in molecular weight during polymerization had a maximum due to its dependence on the monomer concentration. The crystallinity of the product initially increased during polymerization, then decreased and eventually stabilized. Scanning electron microscopy (SEM) revealed that the diameter of the internal particles was larger, while the surface particles were smaller after coagulation. These findings offer crucial insights for optimizing aqueous precipitation polymerization and PAN particle property control. [ABSTRACT FROM AUTHOR]

We present a mesoscale model and the simulation results of a system composed of polyacrylonitrile (PAN), carbon nanotubes (CNTs), and a mixed solvent of dimethylsulfoxide (DMSO) and water. The model describes a fragment of a nascent PAN/CNT composite fiber during coagulation. This process represents one of the stages in the production of PAN composite fibers, which are considered as precursors for carbon fibers with improved properties. All calculations are based on dynamic density functional theory. The results obtained show that the greatest structural heterogeneity of the system is observed when water dominates in the composition of the mixed solvent, which is identified with the conditions of a non-solvent coagulation bath. The model also predicts that the introduction of CNTs can lead to an increase in structural heterogeneity in the polymer matrix with increasing water content in the system. In addition, it is shown that the presence of a surface modifier on the CNT surface, which increases the affinity of the filler to the polymer, can sufficiently reduce the inhomogeneity of the nascent fiber structure. [ABSTRACT FROM AUTHOR]

Adsorptive nanofiber electrospun membranes (ANEMs) show promise for heavy metal removal, particularly in dilute solutions. Nanofibrous polyacrylonitrile (PAN) membranes incorporating Cloisite 20A (C20) organoclay were fabricated via electrospinning for As(V) removal. The impact of C20 on structural properties and As(V) removal efficiency of the nanofiber membranes was investigated. The results indicated that the PAN‐C20 membranes morphology was uniform, with fiber diameters mostly falling within the 100–300 nm range. Incorporation of C20, especially in an exfoliated structure, led to increased hydrophilicity, mechanical strength, and roughness of the membranes. Batch adsorption results revealed that the adding C20 up to 1.5 wt.% significantly enhanced adsorption capacity due to the higher concentration and proper C20 dispersion. Dynamic filtration showed that the PAN‐C20(1.0) membrane achieved over 90% As(V) removal efficiency for 960 min and demonstrated excellent regeneration ability. Highlights: Cloisite 20A organoclay was incorporated into PAN by electrospinning to prepare adsorptive membrane.Adsorptive membranes were used for As(V) removal from water.Type of Cloisite 20A dispersion in PAN in dynamic filtration was more important than in static adsorptionPAN‐C20‐1.0 with exfoliated structure showed higher removal efficiency than PAN‐C20‐1.0 with intercalated structure.PAN‐C20‐1.0 membrane was usable for multiple adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

This work presents the results of an investigation on the physiochemical and structural characteristics of polyacrylonitrile (PAN) nanofiltration (NF) membranes prepared using a novel concept of binary solvents for nickel (Ni) removal from wastewater streams. The thermodynamic and kinetic aspects are emphasized aiming to optimize dope formulation, membrane performance, and durability. The fabricated membranes were characterized by scanning electron microscopy (SEM), porosimetry, tensile stress/strain, and flux and rejection. Results revealed that the use of an equal (1:1) mixture of n‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF) as dope solvents led to the formation of membranes with enhanced performance, offering pure water flux of 2.33 L·m−2·h−1·bar−1 and Ni rejection of 90.84%. Moreover, the incorporation of 0.5 wt.% PEG as a pore‐forming agent to the dope solution further boosted pure water flux to 4.97 L·m−2·h−1·bar−1 with negligible impact on Ni rejection. Besides attractive performance, the adopted strategy offered membranes of exceptionally high flexibility with no sign of defect or failure especially during module fabrication and testing enabling smooth and hassle‐free scale‐up and extension to other applications. Practitioner Points: Optimized solvent mixture: A 1:1 blend of n‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF) as solvents resulted in enhanced membrane performance.High flux and Ni rejection: The fabricated membranes exhibited a pure water flux of 2.33 L·m−2·h−1·bar−1 and a remarkable Ni rejection of 90.84%.PEG enhancement: Incorporating 0.5 wt.% PEG as a pore‐forming agent further improved the membrane's pure water flux to 4.97 L·m−2·h−1·bar−1, without compromising Ni rejection.Exceptional flexibility: The adopted strategy yielded membranes with exceptional flexibility, making them suitable for scale‐ups and other applications. [ABSTRACT FROM AUTHOR]

In this study, p-morpholinomethylcalix[4]arene (p-MC4) was synthesized using Mannich reaction and utilized for the fabrication of polyacrylonitrile nanofibers impregnated with p-morpholinomethylcalix[4]arene (PAN/p-MC4) using electrospinning. The nanofibers were prepared by blending 12% solution of PAN with 20% solution of p-MC4. The PAN/p-MC4 NFs were thoroughly evaluated for their removal efficiency of Cu2+ from the aqueous media. The selectivity of PAN/-p-MC4 nanofibers was also examined by adsorbing a set of metal ions with same charge and similar ionic radius. The results of distribution ratio showed that PAN/p-MC4 nanofibers have superior selectivity for Cu2+ as compared to other heavy metal ions. The relative selectivity coefficients of PAN/p-MC4 nanofibers were found to be 25.2, 14.1, 8.9, and 4.03 for Cu2+/Ni2+, Cu2+/Co2+, Cu2+/Cd2+ and Cu2+/Pb2+, respectively. This indicates that PAN/p-MC4 nanofibers have a higher selectivity for Cu2+ ions. Numerous parameters such as pH, time, adsorbent dosage and analyte concentration were optimized to evaluate the maximum adsorption capacity of nanofibers for Cu2+. Adsorption isotherm models showed that the adsorption is promising and follows Langmuir adsorption isotherm. Whereas, PAN/p-MC4 nanofibers followed pseudo- second order kinetics during adsorption experiments. The PAN/p-MC4 nanofibers showed excellent adsorption capacity (qo) of 65.35 mg/g for Cu2+ at pH 5 in 60 min under shaking speed of 120 rpm. Moreover, PAN/p-MC4 nanofibers had been used to remove Cu2+ from real surface water samples. According to the results, PAN/p-MC4 nanofibers are more effective adsorbent for removing Cu2+ from contaminated water. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The conversion of polyacrylonitrile (PAN)-based precursors into high-performance carbon fibres requires careful control of treatment conditions. The stabilization process is a crucial step in this conversion process as the precursor undergoes chemical modifications that will substantially influence the properties of the final product. As the PAN fibre undergoes stabilization, its colour changes from white through various shades of orange and brown until an overall black appearance is achieved as a result of the imine-based chromophores generated from the underlining chemical reactions. In this work, we quantified the colour changes caused by a wide range of stabilization conditions on a reflectance spectrophotometer. Both CIELAB colour space and RGB colour space measurements correlated well with widely adopted stabilization indicators for oxidized PAN fibre (OPF), including fibre density and relative cyclization index. In particular, RGB colour component B showed very good linear and quadratic relationships with OPF density and relative cyclization index, respectively. The method used in this investigation may be further developed into a convenient tool for monitoring the progression of PAN fibre stabilization. [ABSTRACT FROM AUTHOR]

Graphene PAN based composite nanofibers have good flexibility and processability, and have shown significant importance and value in many fields, such as health care and textiles. In order to optimize the preparation method of graphene PAN based composite nanofibers and investigate the effect of graphene mass fraction on the antibacterial performance of composite nanofibers. Graphene PAN based composite nanofibers with different graphene mass fractions were prepared by electrospinning method. The macroscopic Properties and microstructure of the composite nanofibers were characterized by XRD, SEM, FT-IR, DSC, and mechanical properties analysis. The research results indicate that the addition of graphene reduces the crystallinity of composite nanofibers. Graphene PAN based composite nanofibers exhibit a three-dimensional network structure at the microscopic level, with disordered and staggered arrangement of nanofibers, with a fiber diameter of 170-230 rail. As the mass fraction of graphene increases, the tensile strength of composite nanofibers first increases and then decreases, and the fracture elongation continues to decrease. When the mass fraction of graphene increases to 0.9%, the tensile strength of composite fibers reaches its maximum value of 20. 61 MPa. The addition of graphene improved the thermal properties of composite nanofibers and increased the dehydration temperature. The bacteriostatic rates of Graphene PAN based composite nanofibers against E. coli and S. aureus were both over 95%, and the composite nanofiber membrane with 0.9% graphene mass fraction had the maximum bacteriostatic efficiency against the two strains, with bacteriostatic rates of 97.32% and 99.85%, respectively. The antibacterial efficiency of composite nanofiber membrane against Staphylococcus aureus was higher than that of Escherichia coli. [ABSTRACT FROM AUTHOR]

The separation and recovery of uranium from natural water is of great significance to the exploitation of unconventional uranium resources. In our paper, a novel polyacrylonitrile(PAN)/Hummers oxidized lotus seedpod carbon composite was prepared, and adsorption of U(Ⅵ) ion from U(Ⅵ)-CO3 solution under weakly alkaline condition was also studied. Batch adsorption experimental results show that at room temperature, pH=8.0, ρ(U(Ⅵ))=50 mg/L, cT(CO3)=2 mmol/L, the adsorption reaches equilibrium after 840 min, and the maximum adsorption capacity is about 51.92 mg/g. The increase of the pH values, calcium ion concentration, magnesium ion concentration and carbonate concentration inhibit the U(Ⅵ) adsorption. Thermodynamic results indicate that it is a spontaneous, endothermic chemical adsorption process. Characterization results show that the composite displays good structure stability during U(Ⅵ) adsorption process, meanwhile, the phenolic —OH and —COOH(C=O) are the main adsorption sites on the composite surfaces. In the presence of calcium/magnesium ions, the order of adsorption affinity of U(Ⅵ) on the composite material is as follows: Mg-U(Ⅵ)-CO3 system＞Ca-U(Ⅵ)-CO3 system. The results can provide the new materials for the separation and extraction of uranium from natural uranium-containing water.

Polymer electrolyte membranes with superior lithium‐ion (Li+) conductivity and sufficient electrochemical stability are desired for all‐solid‐state lithium‐ion batteries (ASS‐LIBs). This paper reports novel polymer composite membranes consisting of polyacrylonitrile (PAN) nanofibers (Nfs) containing lithium salts. It is first revealed that the lithium salt addition increases polar surface groups on the PAN nanofibers. Subsequently, the lithium salts‐containing PAN nanofiber (PAN/Li Nf) composite membrane affects the matrix poly(ethylene oxide) (PEO)/lithium bis(trifluoromethyl sulfonylimide) (LiTFSI) electrolyte to increase the numbers of Li+ with high mobility. Consequently, the PAN/Li Nf composite membrane shows relatively good ion conductivity (σ = 9.0 × 10−5 S cm−1) and a considerably large Li+ transference number (tLi+ = 0.41) at 60 °C, compared to the PEO/LiTFSI membrane without nanofibers. The 6Li solid‐state NMR study supports that the PAN/Li Nf bearing abundant polar nitrile groups at their surface enhances Li+ diffusion in the PEO‐based electrolyte membranes. The galvanostatic constant current cycling tests reveal that the PAN/Li Nf composite membrane possesses good electrochemical and mechanical stabilities. The ASS‐LIB consisting of the PAN/Li Nf composite membrane shows significantly improved charge and discharge cycling performances, promising future all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

AbstractIn this study, it was aimed to analyze the effects of liposomes on the dyeing of polyacrylonitrile fabrics. For this purpose, firstly liposome synthesis was carried out, and then liposome production was confirmed by Fourier transform infrared spectroscopy analysis. Additionally, zeta potential measurements were carried out to see whether stable structures were formed. Then, a selected basic dye was encapsulated with a liposome and the possibilities of using these capsules as alternative to retarders in the dyeing of polyacrylonitrile fabrics were examined. According to results obtained, it can be said that the 1% solution of synthesized liposomes creates a more stable suspension with a polydispersity index of 0.472 and the average particle size of 165.2 nm. On the other hand, it has been revealed that if 1% liposome is used in dyeing, a kind of retarder effect can be achieved in the dyeing of polyacrylonitrile fabrics. Moreover, it can be said that the decrease in color efficiency, that is, the loss of yield, caused by the use of liposome at the end of dyeing is lower compared to the retarder. This is also a very important issue, because a good retarder is expected to slow down the dye uptake, but not reduce the dye intake too much at the end of the dyeing. Dyeing levelness (%) was found to be 96.1, 97.4, and 97.1 for dyeings without auxiliary, with 1% cationic retarder and with 1% liposome, respectively. Beyond this, no significant difference was observed in terms of fastness of dyeing. [ABSTRACT FROM AUTHOR]

Thermo‐oxidative stabilization of polyacrylonitrile (PAN)‐copolymer and PAN/single‐walled carbon nanotube (SWCNT) composite films were studied in the presence of oxygenated entities which may act as an internal oxygen supplier. The oxygenated moiety exhibited dual behavior, enhancing the stabilization efficiency of PAN while also improving the dispersion of SWCNT. The addition of oxygenated moiety treated SWCNT to PAN resulted in a significant reduction in activation energy from 118 kJ/mol to 99 kJ/mol, owing to a more stable oxidation reaction. Thermogravimetric analysis showed weight loss due to stabilization, and polymer chain degradation was lower in treated SWCNT composite films, resulting in an approximate 6% increase in residual weight. Mechanical testing showed a significant increase in tensile strength to 54.15 MPa and tensile modulus to 2.53 GPa with elongation at break of 13.2%, which is attributed to the enhanced interfacial shear strength resulting from the improved dispersion of oxygenated moiety‐treated nanotubes. Furthermore, thermomechanical analysis studies showed improvement in dimension stability with oxygenated moiety treated SWCNT composite films, attributed to better dispersion and increased interfacial strength between the polymer and filler. Highlights: Oxygenated entities stabilize PAN and improve SWCNT dispersion.Activation energy was reduced from 118 to 99 kJ/mol with Tween‐80.Residual weight increased by 6% with treated SWCNT in TGA.Improved tensile strength (54.14 MPa), modulus (2.53 GPa) with modified SWCNT.Dimension stability is enhanced by interfacial strength with modified SWCNT. [ABSTRACT FROM AUTHOR]

Nanostructured porous materials are desirable sorbents for separating and removing oil spills from water. This work examines the performance of the prepared efficient sorbents in the oil sorption process. Polyacrylonitrile (PAN) fibers served as the skeleton matrix, while glutaraldehyde and poly(vinyl alcohol) (PVA) served as cross-linking agents. The prepared polymer sorbents showed high adsorption capacity (12.47 g/g), porosity (95.41%) and low density (0.069 g/cm3). The incorporation of carbon nanostructures (nanotubes or graphene oxide) in the sorbent increased the adsorption capacity to 14.85 g/g. The hydrophobic nature of carbon nanotubes significantly increases the contact angle of water with the surface of the nanocomposite absorber and reaches 137.5 degrees. The obtained sorbents showed good reusability in the adsorption process and maintained an adsorption capacity of about 10 g/g after 5 cycles. The optimal temperature range for using nanocomposite sorbents was 25°C to 35°C. The combination of high sorption capacity, low porosity and density in modified polyacrylonitrile, along with its reusability, makes this designed sorbent highly suitable for efficient removal of oil spills. [ABSTRACT FROM AUTHOR]

Coaxial composite fibers with a cortex of polyacrylonitrile (PAN) and a core layer of mesophase pitch (MP) and PAN were prepared by wet spinning, then heat‐treated in air. The effects of heat treatment on the thermal reaction characteristics, pre‐oxidation degree, radial structure, and thermal stability of coaxial composite fibers were studied by differential scanning calorometry, Raman, and thermogravimetric analysis. As the heat treatment temperature increases, the coaxial composite fibers only undergo cyclization without oxidation, the peak temperature of the thermal reaction increases from 258 to 270°C, and the enthalpy increases from 19.66 to 237.82 J g−1, the heat mainly arises from the PAN component. The Dr value of the coaxial fiber skin layer increases from 0.193 to 0.255 (330°C) and then decreases to 0.236; the core layer Dr value increases from 0.353 to 0.392 (310°C) and then decreases to 0.368. The pre‐oxidation reaction leads to an increase in sp2‐hybridized carbons and an increase in pre‐oxidation degree. When the heat treatment temperature <310°C, the pre‐oxidation degree of the composite fibers increases, leading to formation of a more stable structure compared with that at lower temperatures and an increase in the carbon residue rate. [ABSTRACT FROM AUTHOR]

In the pursuit of fabricating functional ceramic nanostructures, the design of preceramic functional polymers has garnered significant interest. With their easily adaptable chemical composition, molecular structure, and processing versatility, these polymers hold immense potential in this field. Our study succeeded in focusing on synthesizing ferrocene-containing block copolymers (BCPs) based on polyacrylonitrile (PAN). The synthesis is accomplished via different poly(acrylonitrile-block-methacrylate)s via atom transfer radical polymerization (ATRP) and activators regenerated by electron transfer ATRP (ARGET ATRP) for the PAN macroinitiators. The molecular weights of the BCPs range from 44 to 82 kDa with dispersities between 1.19 and 1.5 as determined by SEC measurements. The volume fraction of the PMMA block ranges from 0.16 to 0.75 as determined by NMR. The post-modification of the BCPs using 3-ferrocenyl propylamine has led to the creation of redox-responsive preceramic polymers. The thermal stabilization of the polymer film has resulted in stabilized morphologies based on the oxidative PAN chemistry. The final pyrolysis of the sacrificial block segment and conversion of the metallopolymer has led to the formation of a porous carbon network with an iron oxide functionalized surface, investigated by scanning electron microscopy (SEM), energy dispersive X-ray mapping (EDX), and powder X-ray diffraction (PXRD). These findings could have significant implications in various applications, demonstrating the practical value of our research in convenient ceramic material design. [ABSTRACT FROM AUTHOR]

The multilayer composite film system was designed in this study. The multilayer composite film was constructed by alternating electrospinning of MXene doped with polyacrylonitrile (PAN) nanofilm and thermoplastic polyurethane (TPU) nanofilm as piezoelectric functional layer. After utilizing nanofilm material, the piezoelectric sensor was prepared and subsequently examined for its piezoelectric sensitivity, piezoelectric output, and mechanical characteristics. MXene/PAN/TPU multilayer composite films showed good piezoelectric output performance. The final experimental data showed that the piezoelectric sensor of the MXene/PAN/TPU-based system achieved 0.16 kPa−1 piezoelectric sensitivity, 150ms/140ms response time and recovery time, good output voltage and output current, and good output stability. In human biological motion detection, the generator produced a maximum output voltage of 30 V when pressed by the palm. Tests such as palm pressing, finger tapping, and footstomping demonstrated the potential of piezoelectric sensors in human energy harvesting and motion monitoring. Multilayer composite films had flexible mechanical properties and sensitive piezoelectric response and had broad application prospects in piezoelectric sensors and piezoelectric nanogenerators. [ABSTRACT FROM AUTHOR]

C-rich SiCN(O) ceramic nonwovens with thermo-oxidation resistance up to 600 °C were developed from electrospinning of polyacrylonitrile in combination with different ratios of an oligomeric or polymeric silazane and subsequent pyrolysis. The influence of the selective pre-polymerization of the oligosilazane and the respective amount on the electrospinning, pyrolysis, phase formation and the properties of the resulting C-rich ceramic nonwovens was evaluated. The fiber diameter after pyrolysis at 1000 °C ranges from 0.26 to 0.63 µm. The oligosilazane/PAN-derived ceramic nonwovens contain high oxygen and carbon content because of high reactivity leading to a high ceramic yield due to additional crosslinking. A higher initial oxidation temperature compared to pure carbon was confirmed for all samples. However, the best result was achieved with a sample based on a high proportion of polysilazane in combination with PAN, as a dense passivating layer to protect the free carbon regions was obviously better able to form. [ABSTRACT FROM AUTHOR]

Phytic acid (PA) modified polyacrylonitrile (PAN) nanofiber membranes for heavy metal adsorption were fabricated using electrospinning for the first time, and its mechanical properties and heavy metal adsorption under various conditions were tested. The results demonstrated that PA modification improved the mechanical properties of PAN nanofiber membranes at low modification ratio due to increased intermolecular hydrogen bonds and cross‐linking. The highest breaking strength and elongation at break were 70.1% and 31.5% over PAN without modification when the PA:PAN ratio was close to 1:5. The Pb2+ absorption tests in the water solutions demonstrated that the optimal PA:PAN ratio was 1:1, the optimal temperature was 30°C, and the optimal pH was 7. With the optimal parameters, the adsorption capacity reached the maximum and equilibrium after 4 h. The adsorption capacities increased with higher initial Pb2+ concentrations. The highest adsorption capacity in this study was approximately 240.1 mg g−1 at the initial Pb2+ concentration of 750.72 mg L−1. In addition, after de‐adsorption process, the 1:1 PA modified membranes maintained 91.9% re‐adsorption capacities compared to primary adsorption. Consequently, the PA‐modified PAN nanofiber membranes showed promising potentials of metal ion adsorption in wastewater treatment. Highlights: Phytic acid modified polyacrylonitrile nanofiber membranes were fabricated.Low ratio modification improved the mechanical properties.The optimal modification ratio for Pb2+ adsorption is 1:1.The maximum Pb2+ adsorption capacity was 240.1 mg g−1 in this study.The membranes maintained 91.9% capacities at re‐adsorption tests. [ABSTRACT FROM AUTHOR]

[Display omitted] The polyacrylonitrile (PAN) is an attractive matrix of polymer electrolytes owing to its wide electrochemical window and strong coordination with Li salts. However, the PAN-based electrolytes undergo severe interfacial problems from both cathode and anode sides, including uneven ionic transfer induced by high rigidity of dry PAN-based polymer, as well as inferior stability against Li-metal anode. Herein, the composition regulation of PAN-based electrolytes is proposed by introducing succinonitrile (SN) plastic crystal and LiNO 3 salt for the construction of interfacially stable solid-state lithium batteries. The plastic nature of SN enables the rapid ionic transfer in electrolytes, along with the establishment of conformally interfacial contacts. Meanwhile, a stable solid-electrolyte-interface (SEI) layer consisting of Li 3 N and LiNO 2 is in-situ formed at Li/electrolyte interface, contributing to the inhibition of uncontrol reactions between PAN and Li-metal. Consequently, the resultant Li symmetric cell delivers an extended critical current density of 1.7 mA cm−2 and an outstanding cycling lifespan of 700 h at 0.1 mA cm−2. Moreover, the corresponding solid-state LiNi 0.6 Co 0.2 Mn 0.2 O 2 /Li full cell shows an initial discharge capacity of 161 mAh/g followed by an outstanding capacity retention of 88.7 % after 100 cycles at 0.1C. This work paves the way for application of PAN-based electrolytes in the field of solid-state batteries by facile composition regulation. [ABSTRACT FROM AUTHOR]

Thermal analysis of polyacrylonitrile (PAN) fibers is commonly employed to assess the chemical and physical changes occurring during the pre-oxidation stage. However, in actual pre-oxidation processes, PAN fibers are stretched to a certain extent (approximately 5%) to prevent fiber shrinkage. Consequently, the pre-oxidation process of PAN fiber is influenced not only by temperature and atmosphere but also by the stretching tension. In this study, two types of PAN fiber samples with different crystal structures were utilized alongside four different processing methods (PAN powder, unfixation, physical fixation, and chemical fixation) to generate three degrees of fixed stretching. These included PAN powder and unfixed PAN fiber samples (without fixation tension), physically fixed PAN fiber with relatively weak fixation tension, and chemically fixed PAN fiber with strong fixation. Through a comparison of these samples, it was observed that the fixation tension aided in preserving the crystal structure during the heating process, significantly reducing the cyclization rate of the PAN fibers. The cyclization reaction rate of PAN fiber A, initially at 85% without any fixation, decreased to 66% after physical fixation and dropped to 56% after chemical fixation. For PAN fibers with distinct crystal morphologies, the impact of the fixation tension was more prominent for PAN fibers with larger crystal sizes and lower orientation. Additionally, the presence of crystal orientation facilitated the occurrence of the cyclization reactions. [ABSTRACT FROM AUTHOR]

A polyacrylonitrile (PAN) / Methylene blue (MB) thin film was prepared using casting method at laboratory temperature and characterized using XRD and FTIR method. The optical properties of thin films were characterized using transmission and absorption spectra at the wavelengths from 200 to 900 nm. The optical bandgap Eg was calculated using Tauc's equation and found that equal to 1.79eV for direct band gap. The dispersion relation of the refractive index was quantified using the Wemple-Didomenico Single Oscillator model. [ABSTRACT FROM AUTHOR]

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BACKGROUND: The study of removing heavy metals from water through the use of chelating adsorbents is an emerging and critical area of research. However, the challenge lies in the lack of specificity that these adsorbents often exhibit towards individual metals. RESULTS: In addressing this challenge, we have synthesized a novel chelating polymer, thiosalicylichydrazidine‐modified poly(acrylonitrile‐co‐divinylbenzene) copolymer (TSH‐P), demonstrating a high affinity for Hg2+ ions. The crosslinking of the Hg2+/TSH‐P complex with a glyoxal crosslinking agent effectively encapsulates Hg2+ ions, stabilizing the functional chelating groups within the coordination geometry of Hg2+. The ions were subsequently removed with EDTA/HNO3, producing a sorbent imprinted with Hg2+ ions (Hg‐IIP). Analytical techniques were employed for a detailed examination of each synthesis step, confirming the successful chelation of Hg2+. Notably, the synthesized Hg‐IIP showed significant selectivity for Hg2+ over other metal cations, with an optimal adsorption pH of 5 and a maximum capacity of 350 mg g−1. The adsorption process was found to closely follow the Langmuir isotherm model, with kinetics that adhered to the pseudo‐second‐order model. Conclusion: This study introduces a highly selective chelating polymer for the removal of Hg2+ ions from water, highlighting its effectiveness and potential for specificity in heavy metal remediation. The use of analytical techniques to confirm the successful synthesis and chelation process, alongside the demonstrated selectivity and high capacity of the sorbent, underscores the polymer's utility in addressing the challenge of removing heavy metals from aqueous solutions. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Carbon-carbon (C-C) fiber composites are a new class of materials that are used in various industries due to their exceptional chemical, thermal and electrical conductivities properties. In this study, carbon-carbon fiber composites were manufactured where polyacrylonitrile (PAN) powder was dissolved in dimethylformamide (DMF) solution, and carbon fibers with desired concentrations (20–80 wt%) were immersed into this solution as reinforcement through evaporation and solidification. The PAN-fiber systems were then stabilized at 250–270°C for 120 min in the air and subsequently carbonized at 650, 750, and 850°C for 60 min in the presence of argon gas to obtain the desired C-C fiber composites. Thermogravimetric analysis (TGA) results showed that the carbonized samples had a small weight loss of 2.5%, while actual and oxidized samples had more weight loss. Moreover, the carbonized sample surface was more hydrophobic compared to other samples due to the carbon presence and surface texture changes. Fourier-Transform Infrared (FTIR) spectroscopy peaks showed the presence of different functional groups of PAN before oxidation and carbonization, but those peaks disappeared after oxidation and carbonization. The developed carbon-carbon composite passed the UL94 vertical flame retardancy testing with a V-0 rating. Surface smoothness, proper matrix and reinforcements bonding were confirmed by scanning electron microscopy (SEM) results and the manufactured composite properties changes were validated by the confocal microscopy images. The carbon-carbon fiber composite achieved an electrical conductivity value up to 4.75 × 103 S/m after the carbonization process. The excellent thermal, chemical, and electrical properties of these composites can be useful for numerous industrial applications in different extreme environments. [ABSTRACT FROM AUTHOR]

Because of their tunable porosity and specific surface area, porous materials are of high interest for the purification of wastewater by adsorption as well as in electrocatalysis, where, in particular, developing metal‐free carbon‐based catalysts for the oxygen reduction reaction (ORR) is researched. The carbon spheres presented here can meet these two requirements simultaneously. Porous polyacrylonitrile (PAN) spheres were firstly prepared by droplet shaping cum nonsolvent induced phase separation. Then, they were converted to nitrogen‐doped carbon spheres by two‐step carbonization via preoxidation and pyrolysis. During the pyrolysis step, carbon dioxide was used to reopen the pores of the materials that had been blocked after the preoxidation step. By this way, specific surface area values of carbon spheres of more than 1000 m2/g could be obtained. Best performing carbon materials (C#3) showed high adsorption capacity (e.g., 296 mg/g for methyl orange at solute equilibrium concentration of 24 mg/L in water). The XPS analysis revealed that only quaternary (N‐Q) and pyridinic (N‐6) nitrogen sites were found in these carbon spheres. The best ORR performance was found also for C#3 carbon spheres, with a potential of 0.81 V versus reversible hydrogen electrode (RHE) at −1 mA/cm2 and electron transfer number of 3.5 at 0.6–0.8 V versus RHE, as determined by rotating disk or rotating ring disk electrode tests. In conclusion, all results confirm that these PAN‐derived carbon spheres are potentially valuable materials for both wastewater treatment by adsorption and electrocatalytic oxygen reduction. [ABSTRACT FROM AUTHOR]

In this work, pre-oxidized polyacrylonitrile fibers are treated with ultrasonic etching and solution etching to produce ultra-thin sections. The evolution of the fibers' microstructure in the pre-oxidation process is observed, and the transformation model of the microstructure of the pre-oxidized fibers is proposed. Scanning electron microscopy and high-resolution transmission electron microscopy were used to observe the microstructure changes of the fibers. Fourier transform infrared spectroscopy and X-ray diffraction were used to observe the chemical structure transformation and crystallization degree of the fibers in the pre-oxidation process. The results revealed that pre-oxidized fibers exhibited a smooth surface, while their interior consisted of fibrils. The longitudinal microfibrils were connected by the transverse microfibrils and amorphous regions. The fracture morphology of the fibers shifted from ductile to brittle, and the cross-section gradually became smoother. The linear molecular chain of PAN transformed into a ring structure as pre-oxidation progressed, subsequently leading to the cross-linking of this ring structure into an orderly trapezoidal configuration. The connection between the fibrils was enhanced, and the fiber structure became more compact and stable. [ABSTRACT FROM AUTHOR]

The aim of manufacturing silicon‐carbon (Si/C) composites for lithium‐ion batteries is to embed silicon particles into a carbon matrix or shell, which results in improved electrical conductivities and cycling stability by avoiding the direct solid electrolyte interphase (SEI) formation on the silicon surfaces. In this study, we explore the production of Si/C composites containing one (single) and two (multiple) carbon shells, achieved through the carbonization of polyacrylonitrile. We thoroughly analyze the carbonization process of polyacrylonitrile and investigate the structural, physical, and electrochemical properties of the resulting Si/C composites. Our findings indicate that the increase of the carbon fraction and the second thermal treatment during the manufacturing of multiple carbon shells (MCS) have a significant impact on the conductivity of the powders, increasing it by one order of magnitude. We also discover that the MCS cover the silicon surface more effectively, as revealed through etching in a NaOH solution and subsequent elemental analysis. The MCS composite, containing 30 wt.% silicon, exhibits the best cycling performance in half‐cells at 0.5 C, with an initial capacity of 776 mAh g−1 and a capacity retention of 83.0 % after 100 cycles. [ABSTRACT FROM AUTHOR]

MXenes consisting of thin layers of transition metal carbides or nitrides are good candidates for electrode materials due to their excellent electrical conductivity and fast ion transfer. Electrospun carbon nanofibers are highly porous and electrically conductive, making them attractive for electrode materials. In this study, free-standing electrodes were prepared by the dip-coating of carbon nanofibers (CNFs) in the MXene (Ti3C2) colloidal solution, which was synthesized via the wet-etching of MAX (Ti3AlC2) phase, and their chemical structures were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. In addition, scanning and transmission electron microscopy were used to investigate the morphological and crystallographic features of MXene-coated CNFs. Surface area and pore volumes were investigated by nitrogen adsorption/desorption measurements. Supercapacitor performance was studied by assembling a 3-electrode system with 1M aqueous sodium sulfate solution as an electrolyte. MXene-coated CNFs exhibited a maximum specific capacitance of 514 F/g at 0.5 A/g, with energy and power densities of 71.4 Wh/kg at 0.5 A/g and 2.3 kW/kg at 5 A/g, respectively, which are relevantly higher compared to the pristine CNFs due to the pseudocapacitive behavior of MXenes. They also showed comparable cyclic stability during 5000 cycles with the CNFs. This result indicates that MXene-coated carbon nanofibers can be effective electrode materials for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

The processes occurring on the contact surface during friction of experimental carbon–carbon composite materials reinforced with a carbon fabric based on polyacrylonitrile (PAN) and a viscose precursor were studied. Tribological tests of the composites were carried out on a tribometer using a ring–disk contact scheme. Two materials were used as counterbodies: hardened steel and silicon carbide ceramics. It has been established that the wear rate and friction coefficient under the load-speed modes used in operation mainly depend on the choice of the counterbody material. Heat treatment (carbonization or graphitization) and precursor material (PAN or viscose) also have an effect, but depending on the selected counterbody. It is shown that when tested with a ceramic counterbody, the tribological characteristics (friction coefficient and wear resistance) are better compared to friction paired with a steel counterbody. The surfaces of counterbodies and composites were studied before and after tribological tests by scanning electron microscopy, X-ray spectral analysis, and optical profilometry. It is shown that during friction a film of secondary structures is formed on the surface of carbon composites from wear products. This is the determining factor that affects tribological characteristics. After testing with a steel counterbody, a significant amount of iron was found on the surface of the composites in the film, which indicated wear of the counterbody. This process negatively affects the tribological properties of the composites. At the same time, the ceramic counterbody practically does not wear out, which makes it a more preferable material for working in friction units paired with a carbon composite. [ABSTRACT FROM AUTHOR]

While carbon fibers (CFs) are still the most attractive reinforcement material for lightweight structures, they are mostly manufactured using crude oil-based process chains. To achieve a higher eco-efficiency, the partial substitution of polyacrylonitrile (PAN) by renewable materials, such as lignin, is investigated. So far, this investigation has only been carried out for batch manufacturing studies, neglecting the transfer and validation to continuous CF manufacturing. Therefore, this work is the first to investigate the possibility of partial substituting lignin for PAN in a continuous process. Lignin/PAN-blended CFs with up to 15 wt.-% lignin were able to attain mechanical properties comparable to unmodified PAN-based carbon fibers, achieving tensile strengths of up to 2466 MPa and a Young's Modulus of 200 Pa. In summary, this study provides the basis for continuous Lignin/PAN-blended CF manufacturing. [ABSTRACT FROM AUTHOR]

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[Display omitted] A series of linear high molecular weight acrylonitrile homopolymers have been synthesized using controlled anionic polymerization. The possibility of producing polyacrylonitrile with a wide range of molecular weights by controlling the concentrations of metal-free initiator and water has been demonstrated. The resulting homopolymers exhibit excellent spinnability. [ABSTRACT FROM AUTHOR]

This article provides information on the synthesis of esterified derivatives of hydrolyzed polyacrylonitrile (EPAN) based on the polymer waste “Nitron” for use as an encapsulating reagent. The elemental and structural compositions of potassium humate and the organic polymer were determined using a scanning electron microscope (Jeol JSM-6490l V) and an IR Fourier spectrometer (Zhimadzu IR Prestige-21). A method is presented for determining the strength of the encapsulated granules of potassium humates using an IPG-1M device and a TAXTplus texture analyzer (Stable Microsystems). The scientific novelty of the article lies in the synthesis of EPAN from “Nitron” polymer waste using sodium hydroxide in the presence of ethylene glycol at a temperature of 370 K for 4 h, followed by the use of 0.5% synthesized solution for encapsulating the granular potassium humate produced from humic acid to give a strength of up to 17.3 kg and prolonged action to the granules. The effect of EPAN concentration on the encapsulation process of granular potassium humates was investigated and studied. The mechanism for the formation of a protective layer of granular potassium humates in the form of a transparent film has been established. The results of the experimental work were processed using the integrated program Statistica-10, which showed a 3D simulation of the process. Microscopic, IR spectral, X-ray phase and thermogravimetric analyses of the encapsulated potassium humate were carried out using modern instrumental devices (MicroXRF Analysis Report, monochromator D878-PC75-17.0, TGA/DSC 1HT/319). The encapsulated durable potassium humate granules provide longer-term nutrition, i.e., a slow, gradual release of plant nutrients in the soil. The use of the produced high-strength encapsulated potassium humate granules allows for restoring soil fertility and increasing the yield of agricultural plants. The encapsulated granules can withstand numerous transshipments and long-term transportation while maintaining the commercial and consumer properties of the product.

Electrospun membranes exhibit very promising properties, such as high surface area, high surface area-to-pore volume ratio, high pore interconnectivity, and uniform pore distribution. Nanoparticles are a promising alternative for improving the properties of the electrospun membranes. Titania nanoparticles, which are stable, resistant, and non-toxic, have various applications including water treatment, sensors, food additive and cosmetics. Due to the high hydrophilicity of titania nanoparticles, membrane fouling is reduced in titania nanoparticles doped membranes. Titania nanoparticle doped polyacrylonitrile (PAN) nanocomposite electrospun membranes were prepared by electrospinning method in this work. Compared to bare PAN electrospun membranes 0.05% titania nanoparticles doped electrospun membranes have thinner nanofibers, higher hydrophilicity and almost 2 times lower bovine serum albumin adsorption, which shows lower fouling tendency.

Nanohybrid assemblies provide an effective platform for integrating the intrinsic properties of individual components into microscale fibers. In this study, a novel approach for creating mechanically and environmentally stable MXene fibers through the synergistic assembly of MXene and polyacrylonitrile (PAN), is introduced. Unlike fibers generated via a conventional stabilization process, which relies on air‐based stabilization to transform the PAN molecules into ring structures fundamental to carbon fibers, the hybrid fibers are annealed in an Ar atmosphere. This unique approach suggests MXene can serve as an oxygen provider that is essential for stabilizing PAN. As a result, significantly improved interfiber compactness is achieved and the oxidation stability of MXene is enhanced under atmospheric conditions. The resulting fibers exhibit exceptional stability, even after extended exposure to high humidity and elevated temperatures. This highlights the suitability of the thermally annealed MXene‐PAN (T‐MX‐PAN) fibers as robust electric heating elements. Notably, these fibers consistently generate heat over 1800 bending cycles. When integrated into fabrics, they demonstrate the capability to generate sufficient heat for melting ice and rapid evaporation. This study highlights the potential of T‐MX‐PAN fibers as next‐generation wearable heaters and offers valuable insights into advancing wearable technology in demanding environments. [ABSTRACT FROM AUTHOR]

Addressing the pressing and significant issue of reducing greenhouse gas emissions in our society, it is crucial to develop environmentally sustainable materials for carbon dioxide adsorption. In this work, we propose a straightforward and effective method, that is, in situ growth of covalent organic frameworks (COFs) on a polyacrylonitrile (PAN) nanofiber substrate using a reversible polycondensation termination technique and successfully prepare flexible COF nanofiber membranes (PANm@BTCA-TPB and APANm@BTCA-TPB COF) for highly efficient capture of CO2. The resulting composite of PAN@COFs comprises numerous nanofibers enveloped by well-defined porous COFs spheres (∼500 nm) that possess a stable crystal structure, abundant functional groups, and excellent stability. Additionally, these composites demonstrate promising capabilities in efficient carbon dioxide capture and have potential for the separation of carbon dioxide and methane. The proposed approach of in situ growth of COFs on nanofibrous membranes is not only applicable to other COF materials derived from Schiff bases but also provides an effective strategy for constructing flexible COF-based membranes that can meet the requirements of various application scenarios. [ABSTRACT FROM AUTHOR]

This paper reports the successful fabrication of a new nanofibrous membrane, F-PI/PAN, through electrospinning of polyacrylonitrile (PAN) and fluorinated polyimide (F-PI). The nanofibrous membrane exhibits comprehensive properties for high-temperature filtration and robust PM2.5 (particulate matter with an aerodynamic equivalent diameter of 2.5 microns or less) removal. The introduction of F enhances the hydrophobicity of the PI. The relationship between the hydrophobic performance and the filtration performance of particles is investigated. The chemical group of the composite membrane was demonstrated using FITR, while the surface morphology was investigated using field emission scanning electron microscopy. The TGA results indicated good thermal stability at 300 °C. Various ratios of F-PI membranes were prepared to characterize the change in properties, with the optimal mass ratio of F-PI being 20 wt%. As the proportion of F-PI increases, its mechanical and filtration efficiency properties and hydrophobicity become stronger. The contact angle reaches its maximum of 128 ± 5.2° when PAN:F-PI = 6:4. Meanwhile, when PAN:F-PI = 8:2, the filtration efficiency reaches 99.4 ± 0.3%, and the elongation at break can reach 76%. The fracture strength can also reach 7.1 MPa, 1.63 times that of the pure PAN membrane. [ABSTRACT FROM AUTHOR]

The rheological properties, spinnability, and thermal–oxidative stabilization of high-molecular-weight linear polyacrylonitrile (PAN) homopolymers (molecular weights Mη = 90–500 kg/mol), synthesized via a novel metal-free anionic polymerization method, were investigated to reduce coagulant use, enable solvent recycling, and increase the carbon yield of the resulting carbon fibers. This approach enabled the application of the mechanotropic (non-coagulating) spinning method for homopolymer PAN solutions in a wide range of molecular weights and demonstrated the possibility of achieving a high degree of fiber orientation and reasonable mechanical properties. Rheological analysis revealed a significant increase in solution elasticity (G′) with increasing molecular weight, facilitating the choice of optimal deformation rates for effective chain stretching prior to strain-induced phase separation during the eco-friendly spinning of concentrated solutions without using coagulation baths. The possibility of collecting ~80 wt% of the solvent at the first stage of spinning from the as-spun fibers was shown. Transparent, defect-free fibers with a tensile strength of up to 800 MPa and elongation at break of about 20% were spun. Thermal treatment up to 1500 °C yielded carbon fibers with a carbon residue of ~50 wt%, in contrast to ~35 wt% for industrial radically polymerized PAN carbonized under the same conditions. [ABSTRACT FROM AUTHOR]

In the present study, poly acrylonitrile (PAN) nanofiltration membrane has been tailored for applying in forward osmosis (FO) process via the combination of two modification approaches including blending and layer-by-layer (LBL)-surface modification techniques. Firstly, dopamine was embedded in PAN nanofiltration membrane to improve its hydrophilicity and antifouling features so that at the optimal loading rate (0.1 wt%) water contact angle (WCA) of the bare membrane declined from 62.7° to 54.5°, its pure water flux augmented from 3.59 to 7.2 kg/m2 h, and its flux recovery ratio (FRR) increased from 70.6 to 92.3%. Secondly, LBL technique has been performed on the optimal MM membrane's surface (with 0.1 wt%) by using poly diallyl dimethyl ammonium and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt as poly cation and poly anion, respectively. From the obtained results, the insertion of 5 bilayers on the optimally dopamine–incorporated membrane's surface showed an outperformance compared to the others with FRR and WCA of 99.2% and 34.5°, respectively. Finally, the performances of the synthesized membranes were evaluated in a FO setup containing NaCl (1M) as a draw solution and deionized water as a feed solution. Pursuant to the obtained results, the optimally tailored membrane by using both the modification methods revealed the lowest reverse solute flux (3.9 g/m2 h) and a moderate pure water flux (3 l/m2 h), corroborating its potential to be used in an effectual FO process. [ABSTRACT FROM AUTHOR]

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