Xiaoyun Liu

The ultralow k porous polymer dielectrics have been widely explored for Integrated circuit (IC) interconnects, 5G/6G communications, and wearable devices. However, disordered pore structures and poor interfacial adhesion remain a major challenge, thus making it difficult to decouple the k ‐tanδ trade‐off. Here, we employ hollow covalent organic frameworks (H‐TD‐COF) as multifunctional molecular anchoring nodes to construct robust pore‐chain interlocked networks in polyimide nanofibrous films. The amino‐functionalized COF shells participate in the in situ growth of polyimide (PI) chains, thus enabling interlocked interfaces that fundamentally restrict segmental mobility and suppress dipolar relaxation. Subsequent electrospinning technique allows anchored chains to be stretched along the fiber axis and immobilizes them within an oriented fibrous architecture. This simultaneously disrupts long‐range charge migration pathways while preserving stress‐transfer and heat‐dissipation continuity. The resulting PI‐g‐COF ₍₄₎ nanocomposites with 4 wt% H‐TD‐COF loading achieve an ultralow dielectric constant of 1.50 and dielectric loss of 0.001 at 1 kHz, with highly stable dielectric properties up to 250°C. Notably, device‐level measurements further reveal a signal‐to‐noise‐and‐distortion ratio (SINAD) of 22.30 dB under 200 MHz crosstalk interference, showing a 52.2% improvement over commercial polyimide. This work lays solid foundations for nanoscale interfacial regulation in porous polymer nanocomposites towards ultralow k dielectrics.

Post-synthetic BF ₂ locking stabilizes the conformational chirality of a molecular cage and reprograms its excited states, enabling persistent CPL and TADF.

Polybenzoxazoles are promising high-performance materials for thermally stable dielectric components, microelectronic insulating layers, and aerospace-related applications owing to their exceptional thermal stability and mechanical properties; however, their poor solubility, high processing temperatures, and limited processability still restrict practical fabrication. This study presents the design and synthesis of two series of thermosetting benzoxazole monomers to address these limitations. These monomers incorporate cross-linkable arylethynyl and arylonitrile terminal groups, combined with either symmetric hexafluoroisopropylidene-bridged or asymmetric mono-benzoxazole architectures. The structure–property relationships governing solubility, curing behaviour, thermal stability, and dielectric properties are systematically investigated. The results show that incorporating hexafluoroisopropylidene units significantly enhances solubility and reduces dielectric constants, whereas nitrile-terminated systems exhibit superior thermal stability compared with their alkyne-terminated counterparts. Notably, the optimized asymmetric polybenzoxazole achieved a temperature at 5% mass loss of 602.2 °C, while the optimized symmetric polybenzoxazole exhibited an ultra-low dielectric constant of 1.83 at a frequency of 1 MHz. This work demonstrates a viable molecular design strategy for balancing solution processability, thermal stability, and dielectric performance in advanced polybenzoxazole thermosets.

The rational design of yolk–shell structured materials with integrated dielectric–magnetic synergy has emerged as a critical strategy for developing lightweight and high-performance electromagnetic wave (EMW) absorbers. Comparing to the conventional yolk–shell structures that typically rely on single cavity configuration, the air-induced dual-cavity yolk–shell structures offer both lightweight absorber design and substantial enhancements in interfacial polarization over wide frequency range. To this end, this study proposes a novel "coating-protected etching-high temperature carbonization" strategy to successfully construct an air-induced dual-cavity yolk-shell hollow Fe3O4@air@Co/C composite absorber. The unique nanostructure possesses two independent cavities: one within the inner hollow Fe3O4 core, and another between the inner Fe3O4 core and the Co/C shell. The dual cavities not only significantly reduce the material density but also optimize the impedance matching. Importantly, the synergistic effects of the air-induced dual-cavity interfaces (Fe3O4-air and Co/C-air) amplify multi-interfacial polarization and improve the adsorption ability via combined magnetic and dielectric loss mechanisms. Experimental results demonstrate that the optimized absorber achieves a remarkable reflection loss of –67.21 dB and a maximum EAB of 5.12 GHz (12.08–17.20 GHz) at an ultra-thin thickness of 2.0 mm and a low filler loading of 20 wt%. Collectively, our findings provide a new design approach for constructing high-efficiency, lightweight EMW absorption materials.

Background: Obstructive sleep apnea (OSA) has been recognized as a potential risk factor for stroke. Among the pathophysiological mechanisms involved in stroke, neuroinflammatory response has gained increasing attention. However, the influence of OSA and inflammation on stroke prognosis remains insufficiently clarified. Methods: A retrospective analysis was conducted using clinical data from patients diagnosed with acute ischemic stroke (AIS) due to non-Large Artery Occlusion (LAO) in anterior circulation who were admitted between May 2018 and October 2021. Patients were stratified based on documented pre-stroke history of OSA. Multiple linear regression was employed to examine associations among hematological parameters, vascular risk factors, and clinical outcomes of AIS. Results: No statistically significant differences were observed between the OSA and non-OSA groups in terms of National Institutes of Health Stroke Scale (NIHSS) scores at admission, modified Rankin Scale (mRS) scores at discharge, or mRS scores at the 3-month follow-up (all p > 0.05). However, the multiple linear regression analysis revealed that a pre-stroke history of OSA was significantly associated with lower discharge NIHSS scores ( p = 0.005), lower discharge mRS scores ( p = 0.001), and lower 3-month mRS scores ( p = 0.004). Platelet distribution width (PDW) was positively associated with higher discharge mRS scores ( p = 0.018) and 3-month mRS scores ( p = 0.006). Elevated white blood cell (WBC) counts were positively associated with discharge NIHSS ( p = 0.001), discharge mRS ( p < 0.001), and 3-month mRS ( p = 0.001). Conclusion: Lower WBC count and the presence of a pre-stroke OSA history may be associated with less severe stroke presentation and more favorable functional outcomes both at discharge and at 3 months post-stroke. Additionally, a lower PDW might associated with better short-term and 3-month outcomes. In cases of anterior circulation AIS without LAO, our findings did not reveal an association between pre-stroke history of OSA with increased stroke severity or poorer prognosis.

Currently, the effective therapeutic strategies for acute ischemic stroke (AIS) remain revascularization therapies, including intravenous thrombolysis and endovascular thrombectomy. However, the narrow time window and reperfusion injury associated with reperfusion therapy limit favorable outcomes in some patients. As adjuncts to revascularization, certain neuroprotective agents have demonstrated robust preclinical results, but only a few have achieved successful clinical translation due to challenges in dosing and safety concerns. In recent years, convenient and relatively safe non-pharmacological neuroprotective interventions—such as hypothermia, remote ischemic conditioning (RIC), and normobaric hyperoxia (NBO)—have gained increasing research attention. These approaches offer advantages including high safety profiles, excellent tolerability, low cost, and the potential to synergize with reperfusion therapy, underscoring their broad clinical applicability. Numerous clinical trials have validated their potential to improve neurological functional outcomes, and this review explores the mechanisms and clinical applications of non-pharmacological neuroprotective therapies in ischemic stroke.

As integrated circuits have developed towards the direction of complexity and miniaturization, there is an urgent need for low dielectric constant materials to effectively realize high-fidelity signal transmission. However, there remains a challenge to achieve ultralow dielectric constant and ultralow dielectric loss over a wide temperature range, not to mention having excellent thermal conductivity and processability concurrently. We herein prepare dual-linker freestanding covalent organic framework films with tailorable fluorine content via interfacial polymerization. The covalent organic framework possesses an ultralow dielectric constant (1.25 at 1 kHz, ≈1.2 at 6 G band), ultralow dielectric loss (0.0015 at 1 kHz) with a thermal conductivity of 0.48 Wm⁻¹K⁻¹. We show high-fidelity signal transmission based on the large-sized (>15 cm²) COF films, far exceeding the most commercially available polyimide-based printed circuit board. In addition, the covalent organic framework also features excellent electret properties, which allows for active high-temperature electromechanical sensing. The electrode nanogenerator maintains 90% of the output voltage at 120 °C, outperforming the traditional fluorinated ethylene propylene electret. Collectively, this work paves the way for scalable application of ultralow dielectric constant covalent organic framework thin films in signal transmission and electromechanical sensing.