Polymers最新文献

Among the various contenders for next-generation sodium-ion battery anodes, hard carbons stand out for their notable reversible capacity, extended cycle life, and cost-effectiveness. Their economic advantage can be further enhanced by using inexpensive precursors, such as biomass waste. Lignin, one of the most abundant natural biopolymers on Earth, which can be readily obtained from wood, possesses a three-dimensional amorphous polymeric structure, making it a suitable candidate for producing carbonaceous materials through appropriate carbonization processes for energy storage applications. In this work, we synthesized hard carbon using lignin containing CaSO₄ to facilitate partial catalytic graphitization to improve the microstructural features, such as interlayer spacing, degree of disorder, and surface defects. Partial catalytic graphitization enables hard carbon to develop an ordered structure compared with hard carbon carbonized without CaSO₄ as analyzed by X-ray diffraction, Raman spectroscopy, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy. The CaSO₄-aided partially catalytic graphitized hard carbon (CCG-HC) exhibited improved electrochemical performance, showing a larger portion of the low-voltage plateau-an indicator typically associated with a highly ordered structure-compared to simply carbonized hard carbon (HC). Notably, CCG-HC delivered a reversible capacity of 237 mAh g^-1, retained 95.6% of its capacity over 100 cycles at 50 mA g^-1, and exhibited 127 mAh g^-1 at 1.0 A g^-1.

A rigid, high temperature-resistant aromatic polymer, poly(1,1'-biphenyl)-6,8a-dihydroacenaphthylene-1(2H)-one (BDA) comprising acenaphthenequinone and biphenyl was successfully synthesized by superacid catalyzed polymerization. BDA has a high decomposition temperature (T_d = 520 °C) that renders it a viable candidate for carbon molecular sieve membranes (CMSM) formation. BDA precursor pyrolysis at 600 °C (BDA-P600) leads to a carbon turbostratic structure formation with graphene-like amorphous strands in a matrix with micropores and ultramicropores, resulting in a carbon structure with higher diffusion and higher selectivity than dense BDA. When the BDA pyrolysis temperature is raised to 700 °C (BDA-P700), the average stacking number of carbon layers N increases, along with an increase in the crystallite thickness stacking L_c, and layer plane size L_a, leading to a more compact structure. Pure gas permeability coefficients P are between 3 and 5 times larger for BDA-P600 compared to the BDA precursors. On the other hand, there is a P decrease between 10 and 50% for O₂ and CO₂ between CMSM BDA-P600 and BDA-P700, while the large kinetic diameter gases N₂ and CH₄ show a large decrease in permeability of 44 and 67%, respectively. It was found that the BDA-P700 WAXD results show the emergence of a new peak at 2θ = 43.6° (2.1 Å), which effectively hinders the diffusion of gases such O₂, N₂, and CH₄. This behavior has been attributed to the formation of new micropores that become increasingly compact at higher pyrolysis temperatures. As a result, the CMSM derived from BDA precursors pyrolyzed at 700 °C (BDA-P700) show exceptional O₂/N₂ gas separation performance, significantly surpassing baseline trade-off limits.

Due to excellent chemical resistance and impermeability, high-density polyethylene (HDPE) is widely used in petrochemical transportation, product packaging, sports equipment, and marine applications. Yet, with the wide variety of service environments, its mechanical and thermal properties do not meet the demand. In the present study, a compounding cross-linker comprising di-tert-butyl peroxide (DTBP) and triallyl isocyanurate (TAIC) is employed by combining with a two-step preparation process. High-quality cross-linking reactions are achieved for HDPE. In this study, the cross-linking of DTBP is first examined separately. A peak cross-linking degree of 74.7% is achieved, and there is a large improvement in thermal resistance and mechanical properties. Subsequently, the composite cross-linking system of DTBP and TAIC is investigated. The peak cross-linking degree is 82.1% (10% increase compared to DTBP). The peak heat deformation temperature is 80.1 °C (22% increase compared to DTBP). The peak impact strength is 104.73 kJ/m² (207% increase compared to neat HDPE). The flexural strength is 33.6 MPa (22% increase compared to neat HDPE). The results show that this cross-linking system further improves the cross-linking degree, heat resistance, and mechanical properties of HDPE, indicating its potential application in engineering materials for high performance.

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a coaxial tubular braiding technique to coat a high-conductivity carbon nanotube (CNT) yarn with a high-strength insulation layer made of ultra-high-molecular-weight polyethylene (UHMWPE) multifilaments, resulting in a core-sheath-structure CNT yarn with excellent electrothermal performance. By adjusting the number of UHMWPE multifilaments and the sheath braiding angle, we achieve high flexibility, high tensile strength, and abrasion and wash resistance, as well as improved electrical stability for the CNT yarns. Additionally, the CNT yarns with an insulation layer effectively prevent short-circuiting during use and achieve superior thermal management, with a significant increase in steady-state temperature under operational conditions, exhibiting significant potential for applications in wearable electronic devices.

Self-healing technology is an effective method for enhancing the crack resistance of cement-based composites. This study focuses on the impact of the environmentally friendly diluent C12-14 alkyl glycidyl ether (AGE) on the performance of the epoxy resin-polythiol (rimethylolpropane tris (3-mercaptopropionate), TMPMP) self-healing system, examining core fluidity, microcapsule properties, molecular dynamics, and the mechanical properties of cured products. The results show that as the AGE dosage increases, the particle size distribution of microcapsules becomes more concentrated, and the dispersion of particles is improved. Fourier-transform infrared spectroscopy confirms the successful encapsulation of E-51 and AGE. Microcapsules maintain structural integrity at high temperatures of 423.15 K. The onset thermal degradation temperature of the mixture shows an increasing trend with reduced AGE dosage. Specifically, TMPMP_35% exhibits an onset degradation temperature of 370.95 K, while that of TMPMP_20% is increased by 57.57% compared to TMPMP_35%. Conversely, the initial and peak temperatures of the curing reaction decrease with less AGE incorporation. Thermodynamic analysis reveals that activation energy (E) initially increases and then decreases with increasing AGE. The frequency factor (A) correlates positively with the heating rate, indicating that the curing reaction's reactivity is closely linked to heating rate. Minor variations in the reaction rate constant (k) indicate that the self-healing system maintains stable reactive activity at low temperatures. Notably, the AGE dosage significantly affects the rigidity of the self-healing system; the average Young's modulus inversely correlates with AGE dosage, with the most substantial decrease of 5.88% occurring when AGE increases from 30% to 35%. This study offers insights into optimizing diluent ratios to balance self-healing and mechanical properties, essential for developing high-performance self-healing cement materials.

Laser micro-machining is a rapidly growing technique to create, manufacture and fabricate microstructures on different materials ranging from metals and ceramics to polymers. Micro- and nano-machining on different materials has been helpful and useful for various biomedical applications. This study focuses on the micro-machining of innovative barbed sutures using an ultrashort pulse laser, specifically a femtosecond (fs) laser system. Two bioresorbable polymeric materials, namely, catgut and poly (4-hydroxybutyrate) (P4HB), were studied and micro-machined using the femtosecond (fs) laser system. The optimized laser parameter was used to fabricate two different barb geometries, namely, straight and curved barbs. The mechanical properties were evaluated via tensile testing, and the anchoring performance was studied by means of a suture-tissue pull-out protocol using porcine dermis tissue which was harvested from the medial dorsal site. Along with the evaluation of the mechanical and anchoring properties, the thermal characteristics and degradation profiles were assessed and compared against mechanically cut barbed sutures using a flat blade. The mechanical properties of laser-fabricated barbed sutures were significantly improved when compared to the mechanical properties of the traditionally/mechanically cut barbed sutures, while there was not any significant difference in the anchoring properties of the barbed sutures fabricated through either of the fabrication techniques. Based on the differential scanning calorimetry (DSC) results for thermal transitions, there was no major impact on the inherent material properties due to the laser treatment. This was also observed in the degradation results, where both the mechanically cut and laser-fabricated barbed sutures exhibited similar profiles throughout the evaluation time period. It was concluded that switching the fabrication technique from mechanical cutting to laser fabrication would be beneficial in producing a more reproducible and consistent barb geometry with more precision and accuracy.

Although crystalline nanocellulose (CNCs) can be extracted from different resources, the employed pretreatments, which disrupt the inter- and intramolecular physical interactions, depend on the biomass sources. This study aims to valorize Aloe Vera (AV) rinds into cellulose and crystalline nanocellulose (CNC) employing two approaches during hydrolysis: sulfuric acid (CNC_SA) and citric acid (CNC_CA) after 30, 60, and 90 min of reaction. The effects of pretreatments and hydrolysis time on the functional groups and hydrogen bonding in biomass are discussed. Crystalline structure (polymorph type), crystallinity, thermal stability, morphology, particle size, and metal presence are also analyzed. A transformation from type I into II polymorph was achieved, where the intermolecular interactions governing cellulose were increased in CNC_SA and were almost maintained in CNC_CA. Properties based on the structure, thermal properties, particle size, and metal presence indicate that the CNC_SA30 and CNC_CA90 samples displayed potential application as reinforcement agents for other types of polymers having no more melting points of 160 and 220 °C, respectively.

Silicone structural adhesives (SSAs) play a critical role in load transfer within glass curtain wall systems. With the increasing service life of existing glass curtain walls in recent years, their structural safety has become a significant concern across various societal sectors. Accurate characterization of the stress-strain relationship of SSAs is fundamental for evaluating the safety and performance of curtain wall structures. While most existing studies rely on hyperelastic constitutive models derived from rubber materials, employing parameter fitting to describe the constitutive behavior of SSAs, there remains a notable lack of research directly addressing constitutive models tailored specifically for SSAs. Although SSAs share similar chemical compositions with rubber after curing, their mechanical properties exhibit substantial differences. As a result, conventional hyperelastic constitutive models often fail to adequately capture the diverse mechanical responses of SSAs. To address this gap, this study begins with a comprehensive market survey to identify and select representative SSAs. Tensile and shear mechanical experiments are then conducted, with the stress-strain relationships during loading processes accurately captured using advanced techniques, such as Digital Image Correlation (DIC). Building on the Acoustic Emission (AE) algorithm, an intelligent algorithm is developed to optimize the fitting of hyperelastic constitutive parameters, enabling a critical evaluation of the applicability of existing phenomenological hyperelastic models to SSAs. Furthermore, in response to the limitations of current models, a novel and universally applicable constitutive model for SSAs is proposed. The robustness of this model is rigorously validated through comparative analysis with experimental data. The findings of this study provide a universal phenomenological constitutive model for SSAs, significantly enhancing the efficiency and accuracy of constitutive relationship fitting for these materials. This advancement contributes to the improved design, assessment, and maintenance of glass curtain wall systems.

Nanocomposite hydrogels are gaining significant attention for biomedical applications in soft tissue engineering due to the increasing demand for highly flexible and durable soft polymer materials. This research paper focused on investigating and optimizing a procedure for the development of novel nanocomposite hydrogels based on poly(2-hydroxyethyl methacrylate)-co-(2-acrylamido-2-methylpropane sulfonic acid) (HEMA/AMPSA) copolymers. These hydrogels were synthesized through a grafting-through process, where the polymer network was formed using a modified clay crosslinker. The layered double hydroxide (LDH) clay modified with 3-(trimethoxysilyl)propyl methacrylate (ATPM) was synthesized using a novel recipe through a two-step procedure. The nanocomposite hydrogel compositions were optimized to achieve soft hydrogels with high flexibility. The developed materials were analyzed for their mechanical and morphological properties using tensile and compressive tests, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and micro-computed tomography (micro-CT). The swelling behavior, network density, and kinetic diffusion mechanism demonstrated the specific characteristics of the materials. The modified LDH-ATPM was further characterized using Thermogravimetry (TGA), FTIR-ATR and X-ray diffraction (XRD). Biological assessments on human adipose-derived stem cells (hASCs) were essential to evaluate the biocompatibility of the nanocomposite hydrogels and their potential for soft tissue applications.

Flexible sensors are revolutionizing wearable and implantable devices, with conductive hydrogels emerging as key materials due to their biomimetic structure, biocompatibility, tunable transparency, and stimuli-responsive electrical properties. However, their fragility and limited durability pose significant challenges for broader applications. Drawing inspiration from the self-healing capabilities of natural organisms like mussels, researchers are embedding self-repair mechanisms into hydrogels to improve their reliability and lifespan. This review highlights recent advances in self-healing (SH) conductive hydrogels, focusing on synthesis methods, healing mechanisms, and strategies to enhance multifunctionality. It also explores their wide-ranging applications, including in vivo signal monitoring, wearable biochemical sensors, supercapacitors, flexible displays, triboelectric nanogenerators, and implantable bioelectronics. While progress has been made, challenges remain in balancing self-healing efficiency, mechanical strength, and sensing performance. This review offers insights into overcoming these obstacles and discusses future research directions for advancing SH hydrogel-based bioelectronics, aiming to pave the way for durable, high-performance devices in next-generation wearable and implantable technologies.