Effect of the fabrication method on the electrical properties of poly(acrylonitrile-co-butadiene-co-styrene)/carbon black composites

Poly(acrylonitrile-co-butadiene-co-styrene) (ABS), an engineering plastic, was combined with carbon black (CB) to increase its conductivity. The ABS/CB composites were prepared using two different methods: dissolution of ABS in Butan-2-one and manual mixing of the constituent materials. These fabrication methods led to different microstructures, which led to vastly different electrical properties. The microstructures were acquired using scanning electron microscopy (SEM) and optical microscopy, while the electrical conductivity was obtained using impedance spectroscopy. The percolation threshold of the composites fabricated using the manual mixing method was found to be much lower (0.0054 vol.% CB) than that of the composites fabricated using the dissolution method (2.7 vol.% CB).     

Asymmetric Trilayer All-Polymer Dielectric Composites with Simultaneous High Efficiency and High Energy Density: A Novel Design Targeting Advanced Energy Storage Capacitors

Polymeric dielectrics have attracted intensive attention worldwide because of their huge potential for advanced energy storage capacitors. Thus far, various effective strategies have been developed to improve the inherent low energy densities of polymer dielectrics. However, enhanced energy density is always accompanied by suppressed discharge efficiency, which is detrimental to practical applications and deserves considerable concern. Targeting at achieving simultaneous high energy density and high discharge efficiency, the unique design of asymmetric all-polymer trilayer composite consisting of a transition layer sandwiched by a linear dielectric layer and a nonlinear dielectric layer is herein reported. It is demonstrated that the nonlinear dielectric layer offers high energy density, while the linear dielectric layer provides high discharge efficiency. Especially, the transition layer can effectively homogenize the electric field distribution, resulting in greatly elevated breakdown strength and improved energy density. In particular, a high efficiency of 89.9% along with a high energy density of 12.15 J cm⁻³ are concurrently obtained. The asymmetric trilayer all-polymer design strategy represents a new way to achieve high-performance dielectric energy storage materials.     

Mixed-Metal MOF-74 Templated Catalysts for Efficient Carbon Dioxide Capture and Methanation

The vast chemical and structural tunability of metal–organic frameworks (MOFs) are beginning to be harnessed as functional supports for catalytic nanoparticles spanning a range of applications. However, a lack of straightforward methods for producing nanoparticle-encapsulated MOFs as efficient heterogeneous catalysts limits their usage. Herein, a mixed-metal MOF, NiMg-MOF-74, is utilized as a template to disperse small Ni nanoclusters throughout the parent MOF. By exploiting the difference in Ni O and Mg O coordination bond strength, Ni²⁺ is selectively reduced to form highly dispersed Ni nanoclusters constrained by the parent MOF pore diameter, while Mg²⁺ remains coordinated in the framework. By varying the ratio of Ni to Mg in the parent MOF, accessible surface area and crystallinity can be tuned upon thermal treatment, influencing CO₂ adsorption capacity and hydrogenation selectivity. The resulting Ni nanoclusters prove to be an active catalyst for CO₂ methanation and are examined using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy. By preserving a segment of the Mg²⁺-containing MOF framework, the composite system retains a portion of its CO₂ adsorption capacity while continuing to deliver catalytic activity. The approach is thus critical for designing materials that can bridge the gap between carbon capture and CO₂ utilization.     

A Path Beyond Metal and Silicon:Polymer/Nanomaterial Composites for Stretchable Strain Sensors

Conventional strain sensors based on metals and semiconductors are rigid and cannot measure soft and stretchable objects. Thus, new strain sensors based on polymer/nanomaterial composites are attracting more interest. Although much effort has been dedicated to achieve high values of both sensitivity and stretchability with linearity, this work endeavors to search and establish guidelines for the development of stretchable strain sensors, by critically reviewing conventional sensors and examining recent progress. It starts from introducing key parameters for conventional strain sensors; these parameters are further discussed for their potential impact on new polymer/nanomaterial strain sensors. The work concludes that there are no general benchmarks for conventional strain sensors utilized in industry. From the findings, the authors suggest that stretchable strain sensors should be custom designed and developed to meet particular measurement requirements, in comparison with a generic aim of yielding a sensor with high degrees of stretchability, sensitivity, and linearity. Challenges are discussed, including reliability, calibration to be used as proper gauges, and soft data acquisition systems.     

Highly Stretchable Conducting SIBS‐P3HT Fibers

Poly(styrene‐β‐isobutylene‐β‐styrene)‐poly(3‐hexylthiophene) (SIBS‐P3HT) conducting composite fibers are successfully produced using a continuous flow approach. Composite fibers are stiffer than SIBS fibers and able to withstand strains of up 975% before breaking. These composite fibers exhibit interesting reversible mechanical and electrical characteristics, which are applied to demonstrate their strain gauging capabilities. This will facilitate their potential applications in strain sensing or elastic electrodes. Here, the fabrication and characterization of highly stretchable electrically conducting SIBS‐P3HT fibers using a solvent/non‐solvent wet‐spinning technique is reported. This fabrication method combines the processability of conducting SIBS‐P3HT blends with wet‐spinning, resulting in fibers that could be easily spun up to several meters long. The resulting composite fiber materials exhibit an increased stiffness (higher Young’s modulus) but lower ductility compared to SIBS fibers. The fibers’ reversible mechanical and electrical characteristics are applied to demonstrate their strain gauging capabilities.     

A General Strategy for Antimony-Based Alloy Nanocomposite Embedded in Swiss-Cheese-Like Nitrogen-Doped Porous Carbon for Energy Storage

Due to its suitable working voltage and high theoretical storage capacity, antimony is considered a promising negative electrode material for lithium-ion batteries (LIBs) and has attracted widespread attention. The volume effect during cycling, however, will cause the antimony anode to undergo a severe structural collapse and a rapid decrease in capacity. Here, a general in situ self-template-assisted strategy is proposed for the rational design and preparation of a series of M Sb (M = Ni, Co, or Fe) nanocomposites with M N C coordination, which are firmly anchored on Swiss-cheese-like nitrogen-doped porous carbon as anodes for LIBs. The large interface pore network structure, the introduction of heteroatoms, and the formation of strong metal N C bonds effectively enhance their electronic conductivity and structural integrity, and provide abundant interfacial lithium storage. The experimental results have proved the high rate performance and excellent cycling stability of antimony-based composite materials. Electrochemical kinetics studies have demonstrated that the increase in capacity during cycling is mainly controlled by the diffusion mechanism rather than the pseudocapacitance contribution. This facile strategy can provide a new pathway for low-cost and high-yield synthesis of Sb-based composites with high performance, and is expected to be applied in other energy-related fields such as sodium-/potassium-ion batteries or electrocatalysis.     

Probing the Effects of Nanoscale Architecture on the Mechanical Properties of Hexagonal Silica/Polymer Composite Thin Films

We examine the effects of controlling nanoscale architecture on the tensile properties of honeycomb‐structured silica/polymer composite films. The hexagonal films are produced using evaporation‐induced self‐assembly and uniaxially strained using a home‐built tensile testing apparatus. Significant differences in the yield strain, failure strain, and tensile moduli between the axes parallel and perpendicular to the film‐deposition direction are observed for the thinnest films examined and are attributed to anisotropy in the film nanostructure that is further characterized with transmission electron microscopy and atomic force microscopy. For properly oriented composites, these films have tensile moduli comparable to the Young's modulus of bulk silica but exhibit failure strains that are about an order of magnitude larger than those seen in typical bulk‐silica systems. The yielding and failure processes are explored using X‐ray diffraction and optical microscopy and are characterized by irreversible changes in the nanoscale architecture. We show that tuning the nanoscale architecture can provide control over the tensile properties of composites, allowing for materials with combinations of stiffness and elasticity unachievable in the analogous bulk systems.     

A Facile Strategy for Preparing Self‐Healing Polymer Composites by Incorporation of Cationic Catalyst‐Loaded Vegetable Fibers

A two‐component healing agent, consisting of epoxy‐loaded microcapsules and an extremely active catalyst (boron trifluoride diethyl etherate, (C₂H₅)₂O · BF₃)), is incorporated into epoxy composites to provide the latter with rapid self‐healing capability. To avoid deactivation of the catalyst during composite manufacturing, (C₂H₅)₂O · BF₃ is firstly absorbed by fibrous carriers (i.e., short sisal fibers), and then the fibers are coated with polystyrene and embedded in the epoxy matrix together with the encapsulated epoxy monomer. Because of gradual diffusion of the absorbed (C₂H₅)₂O · BF₃ from the sisal into the surrounding matrix, the catalyst is eventually distributed throughout the composites and acts as a latent hardener. Upon cracking of the composites, the epoxy monomer is released from the broken capsules, spreading over the cracked planes. As a result, polymerization, triggered by the dispersed (C₂H₅)₂O · BF₃, takes place and the damaged sites are rebonded. Since the epoxy–BF₃ cure belongs to a cationic chain polymerization, the exact stoichiometric ratio of the reaction components required by other healing chemistries is no longer necessary. Only a small amount of (C₂H₅)₂O · BF₃ is sufficient to initiate very fast healing (e.g., a 76% recovery of impact strength is observed within 30 min at 20 °C).     

Modifying the Electronic Character of Single‐Walled Carbon Nanotubes Through Anisotropic Polymer Interaction: A Raman Study

Using Raman spectroscopy, we demonstrate that the anisotropic interaction between single‐walled carbon nanotubes (SWNTs) and poly(methyl methacrylate) (PMMA) causes significant changes in the electronic properties of their composites. Two different procedures were used to prepare the composites: melt blending and in‐situ UV polymerization. Resonant Raman studies relate the electronic density of states (DOS) of the SWNTs to the corresponding vibration symmetry changes of both the PMMA and the SWNTs. Our results show that, in the melt‐blended sample, the SWNTs—originally semiconducting—became predominantly metallic. The changes in the electronic properties were also confirmed by dielectric constant measurements. We propose that the anisotropic interaction between PMMA and SWNTs in the melt‐blended composite is the dominant reason for the observed electronic character change.     

Single‐Walled Carbon Nanotube Dispersions in Poly(ethylene oxide)

Dispersions of single‐walled carbon nanotubes (SWNTs) in poly(ethylene oxide) (PEO) assisted by a lithium‐based anionic surfactant demonstrate an electrical percolation of 0.03 wt.‐% and a geometrical percolation, inferred from melt rheometry, of 0.09 wt.‐%. Both the melting temperature and the extent of crystallinity of the PEO crystals decrease with increasing SWNT loading. Raman spectroscopy of the nanocomposites indicates a down‐shift of the SWNT G‐modes and suggests that the nanotubes are subjected to tensile stress transfer from the polymer at room temperature.