Rheological Behavior of Amino-Functionalized Multi-Walled Carbon Nanotube/Polyacrylonitrile Concentrated Solutions and Crystal Structure of Composite Fibers

Polyacrylonitrile Based Triblock Copolymer Binder Enabling Excellent Performance toward LiNi0.5Mn1.5O4 and Sulfur Based Batteries

There is an urgent need for lithium-ion batteries with high energy density to meet the increasing demand for advanced devices and ecofriendly electric vehicles. Spinel LiNi0.5Mn1.5O4 (LNMO) is the most promising cathode material for achieving high energy density due to its high operating voltage (4.75 V vs Li/Li+) and impressive capacity of 147 mAh g-1. However, the binders conventionally used are prone to high potential and oxidation at the cathode side, resulting in a loss of the ability to bond active material and conductive agent integrity. This can lead to severe capacity fading and irreversible battery failure. This study demonstrates that incorporating acrylic anhydride and methyl methacrylate into conventional acrylonitrile through solution polymerization improves the binding energy and voltage resistance. The results indicate that the triblock poly(acrylonitrile-methyl methacrylate-acrylic anhydride) (PAMA) binder has a much higher peeling strength (0.506 N cm-1) compared to its polyvinylidene fluoride (PVDF) counterpart (0.3 N cm-1), making it a more feasible strategy. When assembled with LiNi0.5Mn1.5O4, the PAMA based electrode maintains a capacity retention of 70.7% after 800 cycles at 0.1 C, which is significantly higher than the 33.9% retention of the PVDFbased electrode. This is due to the large number of polar groups, including ─C≡N and ─C═O, on PAMA, which are conducive to adsorbing lithium polysulfide. The S@PAMA electrode is tested and maintained a capacity value of 628.7 mAh g-1 after long-term cycling, confirming its ability to effectively suppress the shuttle effect.

A Flexible Multifunctional PAN Piezoelectric Fiber with Hydrophobicity, Energy Storage, and Fluorescence

Lightweight, flexible, and hydrophobic multifunctional piezoelectric sensors have increasingly important research value in contemporary society. They can generate electrical signals under the action of pressure and can be applied in various complex scenarios. In this study, we prepared a polyacrylonitrile (PAN) composite fiber doped with imidazolium type ionic liquids (ILs) and europium nitrate hexahydrate (Eu (NO₃)₃·6H₂O) by a facile method. The results show that the PAN composite fibers had excellent mechanical properties (the elongation at break was 114% and the elastic modulus was 2.98 MPa), hydrophobic self-cleaning ability (water contact angle reached 127.99°), and can also emit light under UV light irradiation red fluorescence. In addition, thanks to the induction of the piezoelectric phase of PAN by the dual fillers, the composite fibers exhibited efficient energy storage capacity and excellent sensitivity. The energy density of PAN@Eu-6ILs reached a maximum of 44.02 mJ/cm³ and had an energy storage efficiency of 80%. More importantly, under low pressure detection, the sensitivity of the composite fiber was 0.69 kPa⁻¹. The research results show that this PAN composite fiber has the potential to act as wearable piezoelectric devices, energy storage devices, and other electronic devices.

An ultralight, elastic carbon nanofiber aerogel with efficient energy storage and sorption properties

The fabrication of ultralight strong carbon nanofiber aerogels with excellent elasticity is still a challenge. Herein, 3D mesoporous graphene/carbon nanofibers (G/CNF) were prepared for the first time from polyacrylonitrile/poly(4-vinyl phenol) (PAN/PVPh) electrospun fibers. Through hydrogen bonding interactions between PAN and PVPh polymer chains, traditional soft carbon nanofibers can be converted to form hard nanofiber aerogels with excellent mechanical, electrical, and sorption properties. The specific interactions among PAN/PVPh led to the formation of porous features on carbonized nanofiber foams. The 3D carbon foams are extremely elastic, strong, and light in weight, and they exhibited super oleophilic and fire-resistance properties. Electrochemical studies indicate that the G/CNF foam achieves a capacitance of up to 267 F g^-1 (at a scan rate of 1 mV s^-1), with an energy density of 37.04 W h kg^-1, exhibiting better electrochemical performance than other reported porous carbon devices. In addition, the G/CNF foam also exhibits sorption capacity towards various organic solvents and oils. This study paves the way toward a new class of lightweight and robust porous carbon nanocomposites for application in electrochemical energy storage systems and oil sorption devices.

Interlaminar Mechanical Properties and Toughening Mechanism of Highly Thermally Stable Composite Modified by Polyacrylonitrile Nanofiber Films

This work concentrated on the interlaminar mechanical properties and toughening mechanism of carbon fiber-reinforced bismaleimide resin (CF/BMI) composites modified by polyacrylonitrile (PAN) nanofiber films. The PAN nanofiber films were prepared by electrospinning. End-notched flexure (ENF) and short-beam strength tests were conducted to assess the mode II fracture toughness (G_IIc) and interlaminar shear strength (ILSS). The results showed that the G_IIc and ILSS of PAN-modified specimens are 1900.4 J/m² and 93.1 MPa, which was 21.4% and 5.4% higher than that of the virgin specimens (1565.5 J/m² and 88.3 MPa), respectively. The scanning electron microscopy (SEM) images of the fracture surface revealed that the PAN nanofiber films toughen the composite on two scales. On the mesoscopic scale, the composite laminates modified by PAN formed a resin-rich layer with high strength and toughness, which made the crack propagate across the layers. At the microscopic scale, the crack propagation between two-dimensional nanofiber films led to constant pull-out and breakage of the nanofibers. As a result, the interlaminar fracture toughness of the composite laminates improved.

Graphene oxide incorporated waste wool/PAN hybrid fibres

This work aims to evaluate the potential of using textile waste in smart textile applications in the form of a hybrid fibre with electrical properties. The bio-based electrically conductive fibres were fabricated from waste wool and polyacrylonitrile (PAN) via wet spinning with different wool content. The control PAN and hybrid fibre produced with the highest amount of wool content (25% w/v) were coated with graphene oxide (GO) using the "brushing and drying" technique. The GO nanosheets coated control PAN and wool/PAN hybrid fibres were chemically reduced through hydrazine vapour exposure. The Fourier transform infrared spectroscopy showed the presence of both protein and nitrile peaks in the wool/PAN hybrid fibres, although the amide I and amide A groups had disappeared, due to the dissolution of wool. The morphological and structural analysis revealed effective coating and reduction of the fibres through GO nanosheets and hydrazine, respectively. The hybrid fibre showed higher electrical conductivity (~ 180 S/cm) compared to the control PAN fibres (~ 95 S/cm), confirming an effective bonding between the hydroxyl and carboxylic groups of the GO sheets and the amino groups of wool evidenced by chemical analysis. Hence, the graphene oxide incorporated wool/PAN hybrid fibres may provide a promising solution for eco-friendly smart textile applications.

Rheological Behavior of Polymer/Carbon Nanotube Composites: An Overview

This paper reviews the current achievements regarding the rheological behavior of polymer-based nanocomposites containing carbon nanotubes (CNTs). These systems have been the subject of a very large number of scientific investigations in the last decades, due to the outstanding characteristics of CNTs that have allowed the formulation of nanostructured polymer-based materials with superior properties. However, the exploitation of the theoretical nanocomposite properties is strictly dependent on the complete dispersion of CNTs within the host matrix and on the consequent development of a huge interfacial region. In this context, a deep knowledge of the rheological behavior of CNT-containing systems is of fundamental importance, since the evaluation of the material's viscoelastic properties allows the gaining of fundamental information as far as the microstructure of nanofilled polymers is concerned. More specifically, the understanding of the rheological response of polymer/CNT nanocomposites reveals important details about the characteristics of the interface and the extent of interaction between the two components, hence allowing the optimization of the final properties in the resulting nanocomposites. As the literature contains plenty of reviews concerning the rheological behavior of polymer/CNT nanocomposites, this review paper will summarize the most significant thermoplastic matrices in terms of availability and relevant industrial applications.

Thermal Analysis and Crystal Structure of Poly(Acrylonitrile-Co-Itaconic Acid) Copolymers Synthesized in Water

The composition and structure of polyacrylonitrile (PAN) precursors play an important role during thermal stabilization, which influences the properties of the resulting carbon fibers. In this paper, PAN homopolymer and PAN-itaconic (IA) copolymers with different IA contents were synthesized by aqueous phase precipitation polymerization. The effects of IA content on the structure and thermal properties were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology of PAN polymers showed that the average size of the PAN particles increased with the increase of IA content in the feed. The content of the IA comonomer on the copolymers was quantitatively characterized by the relative absorbance intensity (A₁₇₃₅/A₂₂₄₃) in FTIR spectrum. With the increase of IA content in the feed, PAN-IA copolymers exhibited lower degree of crystallinity and crystal size than the control PAN homopolymer. The results from DSC curves indicated that PAN-IA1.0 copolymers had lower initial exothermic temperature (192.4 °C) and velocity of evolving heat (6.33 J g⁻¹ °C⁻¹) in comparison with PAN homopolymer (T_i = 238.1 °C and ΔH/ΔT = 34.6 J g⁻¹ °C⁻¹) in an air atmosphere. TGA results suggested that PAN-IA1.0 copolymers had higher thermal stability than PAN homopolymer, which can form a ladder structure easier during thermal processing. Therefore, PAN-IA1.0 copolymers would be a suitable candidate for preparing high performance PAN based carbon fibers.

The Structure and Properties of Polyacrylonitrile Nascent Composite Fibers with Grafted Multi Walled Carbon Nanotubes Prepared by Wet Spinning Method

Polyacrylonitrile (PAN) grafted amino-functionalized multi walled carbon nanotubes (amino-MWCNTs) were synthesized by in situ polymerization under aqueous solvent. The grafted MWCNT/PAN nascent composite fibers were prepared by the wet spinning method. Fourier transform infrared spectroscopy and Raman spectroscopy indicated that the amino-MWCNTs and PAN macromolecular chains had interfacial interactions and formed chemical bonds. The grafting content of the PAN polymer on the amino-MWCNTs was up to 73.2% by thermo gravimetric analysis. The incorporation of the grafted MWCNTs improved the degree of crystallization and crystal size of PAN nascent fibers, and changed the thermal properties during exothermic processing in an air atmosphere. Morphology analysis and testing of mechanical properties showed that the grafted MWCNT/PAN nascent composite fibers with a more uniform diameter distribution and larger diameter had higher tensile strength and tensile modulus than the control PAN nascent fibers.