Macromolecular Materials and Engineering最新文献

In materials science, the investigation of microstructures is of critical importance, as the macroscopic properties of materials are typically governed by their microstructural characteristics. This study establishes a direct correlation between microstructure and macroscopic properties in perfluorosulfonic acid (PFSA) ionomer membranes by preparing them in different cationic forms and through various processing methods. Utilizing tensile testing, dynamic mechanical analysis (DMA), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS), we reveal that proton-form PFSA-H-F membranes can form irreversible structural templates through directional hydrogen bonding. Notably, the sodium-form membrane (PFSA-Na-T) prepared via post-processing ion exchange retains the highly ordered microstructure templated by the precursor proton-form membrane (PFSA-H-F), resulting in retained tensile strength. In contrast, the sodium-form membrane (PFSA-Na-F) fabricated directly by slot-die coating exhibits significantly reduced microstructural order and an almost complete loss of mechanical strength, due to the absence of hydrogen bonding-driven crystallization during self-assembly. This strategy of decoupling structural templating from ionic functionality provides a potential paradigm for designing mechanically robust ion-exchange membranes via processing histories independent of cation type.

The creation of protein-based magnetic fibers is a strategic issue in the field of advanced biocompatible materials, particularly relevant for technological sectors such as soft robotics and smart medicine. Here, we endow artificial spider silk fibers, which outperform many man-made fibers in terms of mechanical properties, with magnetic functionality through the incorporation of magnetic nanoparticles. We present two novel composite fibers, containing magnetite nanoparticles coated with aminopropylsilane and dextran, and compare them with a third fiber type, which was made, following an approach previously developed by us, using magnetite nanoparticles coated with dimercaptosuccinic acid. The nanoparticles also differ in their mean size, varying between 9 and 32 nm. The fibers are produced by wet spinning, with a nominal magnetite concentration in the 0.2–20 wt.% range. However, the coating rules the colloidal stability of the nanoparticles in the spinning dope and their tendency to agglomerate. Therefore, the actual magnetite concentration and the degree of dispersion of the nanoparticles in the fibers are different in the different composites, as revealed by magnetic analyses. All fibers, even those with the highest magnetite content, remain ductile, whereas the mechanical strength is only slightly reduced compared to the fiber without nanoparticles, hence without magnetic functionality.

Peripheral nerve injuries result in significant functional impairment, and limited regenerative capacity within the central nervous system further complicates recovery. This study investigates the effects of graphene oxide-decorated bacterial cellulose (BC/GO) scaffolds, with or without mesenchymal stem cells (MSCs), on axonal regeneration following sciatic nerve injury in rats. Twenty-seven male rats were assigned to autograft, BC/GO, and BC/GO+MSCs. The sciatic functional index (SFI), electromyography (EMG), and histopathological analysis were evaluated at 8 weeks. Although SFI scores showed no significant differences, compound muscle action potential (CMAP) values at 4 weeks were significantly higher in both the BC/GO and BC/GO+MSCs groups compared to autografts. Macroscopic examination revealed extensive tissue adhesions in the BC/GO and BC/GO+MSCs groups. Histological analysis indicated regeneration across all groups. The autograft group showed no inflammation, whereas the BC/GO group demonstrated the highest levels of inflammation and degeneration. The BC/GO+MSCs group exhibited reduced inflammation, likely due to the immunomodulatory effects of MSCs. While BC/GO scaffolds promoted early regeneration, the inflammatory response compromised the long-term outcomes. These findings suggest BC/GO scaffolds can facilitate initial nerve repair but require further refinement to sustain long-term functional recovery.

3D printing of biodegradable scaffolds for drug delivery holds significant promise for patient-specific tissue engineering. Solvent-cast direct-writing (SCDW) is a versatile technique that produces intricate architectures by microextruding polymer solutions that solidify upon solvent evaporation. Unlike conventional 3D printing approaches, which often require high pressures, elevated temperatures, or photocurable resins, SCDW operates under gentle conditions, accommodating a wide variety of biodegradable polymers and thermosensitive agents. This study develops a specialized SCDW protocol to construct complex scaffold geometries using polycaprolactone (PCL) and polylactic acid (PLA) as the polymer matrices, with ibuprofen serving as the model thermosensitive drug. The thermal, physical, and mechanical properties of the PCL/PLA system are characterized, and in vitro dissolution studies assess the impact of polymer composition on drug release kinetics. Results reveal a strong correlation between the polymers’ physical state and release behavior: PCL to PLA ratio of 35:65 achieved the highest cumulative release in a sustained manner, releasing over 40% of the encapsulated drug within three weeks. Ratios richer in PCL triggered an initial burst release, while higher PLA contents decreased the release rate. This study establishes a versatile framework for expanding SCDW-processed biodegradable polymers in advanced drug delivery and tissue engineering applications.

Front Cover: This illustration depicts the integration of 3D printing and electrospinning to fabricate nanofiber-coated scaffolds. Incorporating hydroxyapatite-loaded nanofibers significantly boosts osteogenesis, hydrophilicity, and cell compatibility. This multifunctional surface engineering strategy offers a powerful route toward next-generation bone graft substitutes with tailored mechanical strength, improved bioactivity, and enhanced osteogenesis. More details can be found in article 2400286 by Norbert Radacsi and co-workers.

This study focuses on characterizing the crystallization kinetics of a PLA 4032D filament, specifically investigating the impact of the extrusion process and different thermal protocols. A principal finding reveals that the PLA filament exhibits a significantly faster crystallization rate compared to the original pellets. This acceleration is attributed to the thermomechanical stresses and potential partial degradation that the polymer experiences during filament extrusion. Two distinct calorimetric protocols, “melt” (erasing prior history) and “solid” (preserving nucleation seeds), were employed. The “solid” protocol demonstrated notably faster kinetics, approximately half the time of the “melt” protocol, underscoring the crucial role of pre-existing nuclei—a condition relevant to the short residence time in Fused Filament Fabrication (FFF) liquefiers. The research also confirmed the phase transition between α′ and α crystalline forms in PLA 4032D, which is highly dependent on crystallization temperature. A kinetic model was successfully developed to accurately predict the evolution of crystallinity for both phases, effective for crystallization from the melt and in the presence of nuclei. These results are crucial for optimizing PLA filament production and controlling the final properties of 3D-printed parts, contributing to a deeper understanding of PLA behavior under processing conditions and improving FFF efficiency.

Until now, most results on processing high molecular weight polyethylene (HMWPE) in laser sintering (PBF-LB/P) have been achieved using industrial machines with a CO₂ laser. The use of diode laser sintering machines could make new materials more accessible to a wider audience. In this study, the role of carbon black (CB) concentration and processing strategy in HMWPE processing using diode laser PBF-LB/P machines is investigated. This work reveals that the carbon black concentration strongly influences processing, as it affects both absorption and specific heat capacity. Changes of specific heat capacity impact thermal balance during processing. Due to its narrow sintering window, HMWPE exhibits a high tendency for curling, which can be mitigated by reducing the scanning area and layer thickness. A suitable CB concentration ranges from 0.25 to 0.5 wt.%. In general, mechanical properties improve with volume energy density. This effect is caused by a more pronounced particle coalescence and interlayer bonding. However, the absorption properties of carbon black have a stronger impact on the mechanical properties than the energy input for the tested parameters. Mechanical tests on fabricated tensile bars reveal brittle fracture, which results from the high melt viscosity of HMWPE and the resulting delayed coalescence of particles.

Cross-linked gel polymer electrolytes for lithium-ion batteries were prepared using a unique photocrosslinking technology. Hydroxyethyl cellulose was dissolved in N-vinylpyrrolidone and combined with polyethylene glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetrakis(3-mercaptopropionate), then subjected to UV irradiation to form a semi-interpenetrating network. This cross-linked structure enhanced stability and compatibility with liquid electrolytes and significantly improved ionic conductivity (2.14 × 10⁻³ S cm⁻¹) compared to hydroxyethyl cellulose-based GPEs. The hydrophilic hydroxyethyl cellulose blend and flexible pentaerythritol tetrakis(3-mercaptopropionate) contributed to improved mechanical and thermal stability, increased liquid retention, and reduced electrolyte leakage. The GHPT-3 electrolyte exhibited electrochemical stability up to 4.5 V and delivered excellent cycling performance in a lithium metal cell with a LiFePO₄ cathode, providing a high reversible capacity of 155.8 mAh g⁻¹ at 0.1 C with near-perfect coulombic efficiency. Remarkably, it retained 90.3% of its initial discharge capacity after 100 cycles. GHPT-3 effectively suppressed lithium dendrite formation for over 1000 h, outperforming a commercial liquid electrolyte, which failed within 895 h. These advancements highlighted GHPT-3's potential as a safer, high-performance electrolyte for lithium-ion batteries.