Abstract A necklace‐like supramolecular structure is constructed from 18‐crown ether‐6 (18CE6) as the host molecule and fluorinated polyimide (FPI) as the guest molecule to enhance the mechanical properties as well as to further lower the dielectric constant of FPI. The introduction of 18CE6 simultaneously enhances the stiffness and toughness of FPI films. In particular, the elongation at break is increased by over 200%. Furthermore, the dielectric constant of FPI films with 40 mol% 18CE6 is decreased to 2.74 from 3.15 of pure FPI, which is attributed to the enlarged free volume by the necklace‐like supramolecular structure of 18CE6/FPI. Accordingly, the glass transition temperature of 18CE6/FPI films is slightly reduced to 305 °C, which is still high enough during the soldering process for the preparation of flexible copper clad laminate. In addition, the water absorption of FPI films is gradually decreased to 0.52% as the loading of 18CE6 raises to 40 mol%, representing the excellent moisture resistance of 18CE6/FPI films.
Polyimine covalent adaptable networks (CANs) exhibit several dynamic characteristics (such as recyclability and reprocessability) that are beneficial for compensating for the disadvantages of traditional petroleum-based synthetic thermosetting resins, and are therefore suggested as potential substitutes for environmentally unfriendly resins. However, owing to the lack of sufficient stability of imine bonds and their linked molecular chains, most polyimine CANs do not exhibit superior properties in applications with high stability requirements, such as strong water resistance, high heat resistance, and excellent mechanical strength. In this study, we designed and synthesized a new class of fully aromatic polyimine CANs to improve the stability of imine bonds and molecular chains employing the conjugation effect of the two benzene rings to C=N and fully aromatic structures. In contrast, these CANs simultaneously demonstrate superior water resistance (water absorption: 0.14–0.15%) and heat resistance (5% weight loss ( T d5% ): 434–441 °C; glass transition temperature ( T g ): 217–239 °C) than that of previously reported polyimine CANs (water absorption: 0.90–90%; T d5% : 200–348 °C; T g : 47–215 °C). They have outstanding mechanical properties that are almost unaffected by adsorbed water. Meanwhile, the resins exhibited remarkable resistance to ordinary acids, bases, oxidants, salts, solvents, and oils, except for several special solvents. In addition, like other polyimine CANs, they maintain their dynamic behavior characteristics, including degradability, recyclability, malleability, reprocessability, and rehealability. This study provides a new method for improving the comprehensive performance of polyimine CANs.
Emerging research has suggested the anticancer potential of tanshinone IIA, the bioactive ingredient isolated from the traditional Chinese herb Salvia miltiorrhiza. However, the molecular mechanism of sodium tanshinone IIA sulfonate (STS) antilung cancer effect is not very clear. In this study, our purpose is to investigate the roles of STS and elongation factor-2 kinase (eEF-2K) in regulating the proliferation, migration, and invasion of A549 cells and explore the implicated pathways. We found that STS suppressed A549 cell survival and proliferation in a time- and xdose-dependent manner. Knockdown of eEF-2K and treatment with STS synergistically exerted antiproliferative, -migratory, and -invasive effects on A549 cells. These effects were caused by attenuation of the extracellular signal-regulated kinase (ERK) pathway via inhibition of tissue transglutaminase (TG2). In summary, the inhibition of eEF-2K synergizes with STS treatment, exerting anticancer effects on lung adenocarcinoma cells through the TG2/ERK signaling pathway, which provides a potential therapeutic target for treating lung adenocarcinoma.
ABSTRACT Lipid droplets (LDs) can interact with other organelles to regulate cell death, and it has also been reported to play an important role in virus replication. However, the interplay among LDs, cell death, and viral replication remains unclear. Neuroinvasive viruses, such as Japanese encephalitis virus (JEV), rabies virus (RABV), and encephalomyocarditis virus (EMCV) still threaten global public health and raise intensive concerns. Here, we reveal that neuroinvasive virus infection enhances cellular triglyceride biosynthesis by upregulating the expression of diacylglycerol O-acyltransferase 2 (DGAT2) to promote LD formation and increase the expression of Perilipin 2 (PLIN2), an LD surface protein, which consequently facilitates neuroinvasive virus replication. Furthermore, PLIN2 could reduce mitochondrial damage and suppress apoptosis by restoring mitochondrial potential and interacting with anti-apoptotic protein Bcl-2, specifically the 136–209 amino acid region, to interrupt the BAX-Cytc-caspase-3 apoptotic pathway by decreasing the K48-linked ubiquitination of Bcl-2 at the 17th lysine. Together, we elucidate that neuroinvasive virus utilizes an LD surface protein to restrict the apoptosis of infected cells, providing a fresh insight into the pathogenesis and antiviral therapeutics development of neuroinvasive viruses. IMPORTANCE The neuroinvasive virus is a kind of pathogen that is capable of infiltrating and infecting the central nervous system to potentially induce severe neurological damage and disorders, which pose a significant threat to public health. Here, we found that neuroinvasive viruses can utilize an LD surface protein PLIN2 to facilitate viral replication. Notably, PLIN2 could reduce mitochondrial damage and suppress apoptosis by restoring mitochondrial potential and interacting with anti-apoptotic protein Bcl-2, specifically the 136-209 amino acid region, to interrupt the BAX-Cytc-caspase-3 apoptotic pathway by decreasing the K48-linked ubiquitination of Bcl-2 at the 17th lysine. This study reveals a common strategy for neuroinvasive viruses to avoid apoptosis of infected cells by employing LDs, which extends the important role of LDs in viral pathogenesis and may inspire further research in this field.
A way to suppress the deterioration in mechanical properties of polyamide 6 (PA6) is required, especially with high loading of flame retardants in the matrix. In this study, a novel aromatic Schiff base diepoxide (DES) was synthesized. It exhibited an efficient chain extension effect on PA6 and a synergistic flame-retardant effect with aluminum diethylphosphinate (AlPi) for PA6. The PA6 composite with 16 wt.% AlPi only passed UL-94 V-0 rating at 1.6 mm thickness, while the combination of 1.5 wt.% DES with 13 wt.% AlPi induced PA6 to achieve a UL-94 V-0 rating at 0.8 mm thickness. The tensile, flexural, and Izod notched impact strengths were increased by 16.2%, 16.5%, and 24.9%, respectively, compared with those of V-0 flame-retarded PA6 composites with 16 wt.% AlPi. The flame-retarded mechanism of PA6/AlPi/DES was investigated by cone calorimetry and infrared characterization of the char residues and pyrolysis products. These results showed that DES had a synergistic effect with AlPi in condensed-phase flame retardation by promoting the production of aluminum phosphorus oxides and polyphosphates in the char residues.
Black phosphorus (BP) nanosheets are widely used in flame retardant polymers, but the challenge of poor dispersion in polymers increases their additions as well as raises the cost of BP-based flame retardant materials. Here, for the first time, we propose an iterative dispersion strategy, which continuously approaches the homogeneous dispersion state by separating the BP dispersion solution and aggregates in multiple cycles. A Fe and F synergistic functionalized BP (BFF) is utilized for the flame retardant and reinforcing modification of epoxy matrix (DGEBA) to verify the reliability of this strategy, noting that the F element in BFF can achieve dynamic hydrogen bonds with the epoxy-amine system during the curing process, further promoting dispersion. Therefore, epoxy thermosets with only 0.2 wt% BFF loading achieve UL-94 V-0 level with an LOI of 29.2% through the synergistic effect of iterative dispersion and dynamic hydrogen bond. The formation of hydrogen bonds between BFF and epoxy matrix also contributes to a significant increase in the mechanical properties. This work provides a reasonable and facile concept to achieve sufficient dispersion of inorganic nanosheets in polymer or organic matrices and also promote the process of industrial large-scale manufacturing of BP-based fire retardant materials.
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