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1.
Neural Regen Res ; 18(4): 708-715, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36204826

RESUMO

Alzheimer's disease is characterized by sustained neuroinflammation leading to memory loss and cognitive decline. The past decade has witnessed tremendous efforts in Alzheimer's disease research; however, no effective treatment is available to prevent disease progression. An increasing body of evidence suggests that neuroinflammation plays an important role in Alzheimer's disease pathogenesis, alongside the classical pathological hallmarks such as misfolded and aggregated proteins (e.g., amyloid-beta and tau). Firstly, this review summarized the clinical and pathological characteristics of Alzheimer's disease. Secondly, we outlined key aspects of glial cell-associated inflammation in Alzheimer's disease pathogenesis and provided the latest evidence on the roles of microglia and astrocytes in Alzheimer's disease pathology. Then, we revealed the double-edged nature of inflammatory cytokines and inflammasomes in Alzheimer's disease. In addition, the potential therapeutic roles of innate immunity and neuroinflammation for Alzheimer's disease were also discussed through these mechanisms. In the final section, the remaining key problems according to the current research status were discussed.

2.
Mater Today Bio ; 17: 100468, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36340592

RESUMO

Uncontrolled bleeding remains as a leading cause of death in surgical, traumatic, and emergency situations. Management of the hemorrhage and development of hemostatic materials are paramount for patient survival. Owing to their inherent biocompatibility, biodegradability and bioactivity, biopolymers such as polysaccharides and polypeptides have been extensively researched and become a focus for the development of next-generation hemostatic materials. The construction of novel hemostatic materials requires in-depth understanding of the physiological hemostatic process, fundamental hemostatic mechanisms, and the effects of material chemistry/physics. Herein, we have recapitulated the common hemostatic strategies and development status of biopolymer-based hemostatic materials. Furthermore, the hemostatic mechanisms of various molecular structures (components and chemical modifications) are summarized from a microscopic perspective, and the design based on them are introduced. From a macroscopic perspective, the design of various forms of hemostatic materials, e.g., powder, sponge, hydrogel and gauze, is summarized and compared, which may provide an enlightenment for the optimization of hemostat design. It has also highlighted current challenges to the development of biopolymer-based hemostatic materials and proposed future directions in chemistry design, advanced form and clinical application.

3.
Artigo em Inglês | MEDLINE | ID: mdl-36369928

RESUMO

PURPOSE: Literature reports of Adverse Drug Events can replicate across multiple companies, resulting in extreme duplication (defined as a majority of reports being duplicates) and can escape legacy duplicate detection algorithms routinely deployed on the FAERS database. Literature Reference field, added to in 2014, could potentially be utilized to identify replicated reports. FAERS does not enforce adherence to the Vancouver referencing convention, thus the same article may be referenced differently leading to duplication. The objective of this analysis is to determine if variations of the same literature references observed in FAERS can be resolved with text normalization and fuzzy string matching. METHODS: We normalized the literature references recorded in the FAERS database through the first quarter of 2021 with a rule-based algorithm so that they better conform to the Vancouver Convention. Levenshtein distance is then utilized to merge sufficiently similar normalized literature references together. RESULTS: Normalization of literature references increases the percentage that can be parsed into Author, Title, and Journal from 61.74% to 93.93%. We observe that about 98% of pairs within groups do have a Levenshtein similarity of the title above the threshold. The extreme duplication ranged from 66% to 87% with a median of 72% of reports being duplicates and often involved addictovigilance scenarios. CONCLUSIONS: We have shown that these normalized references can be merged via fuzzy string matching to improve enumeration of all the ICSRs that refer to the same article. Inclusion of the PubMed ID and adherence to the Vancouver Convention could facilitate identification of duplicates in the FAERS dataset. Awareness of this phenomenon may improve disproportionality analysis, especially in areas such as addictovigilance.

4.
Opt Lett ; 47(20): 5373-5376, 2022 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-36240366

RESUMO

We present and demonstrate a method based on a periodic phase noise estimation in an optical frequency domain reflectometry (OFDR) capable of a beyond 107 range-resolution-1 product (RRP) for the first time, which corresponds to 2.5 × improvement compared with the state-of-the-art. The moving average filter is employed to suppress the amplification of noise in the derivation process. Further, with the help of a third-order Taylor expansion, this method provides a highly precise estimation of periodic phase noise, which is the main factor impacting the performance of OFDR systems with medium-to-long measurement range combined with a submillimeter spatial resolution. A spatial resolution within 535 µm over the measurement range of 8 km is obtained. The proposed method offers a promising technique for fiber network monitoring and sensing applications.

5.
Cancer Lett ; 549: 215931, 2022 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-36216652

RESUMO

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief and authors. Following the publication of the above article, the Editor was notified by a concerned reader that the authors supplied duplicated images. Specifically, that in Fig. 5 A, both FACS panels are identical and in Fig 5E, two different proteins (HK2 and PDK1) have the same western blot. After checking the data in relation with Fig. 5A and E, the authors have confirmed that the two pictures indeed have the problems of duplication. The authors reported that this problem came from the authors' unintentional behavior, which may be due to a copy and paste error in the manner of image processing. The authors sincerely apologize for the inconvenience caused to our Editors and readers. Due to this duplication error, the authors and Editor have made the decision to retract this paper.

6.
J Am Chem Soc ; 144(40): 18470-18478, 2022 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-36164747

RESUMO

Despite recent encouraging developments, achieving efficient blue perovskite light-emitting diodes (PeLEDs) have been widely considered a critical challenge. The efficiency breakthrough only occurred in the sky-blue region, and the device performance of pure-blue and deep-blue PeLEDs lags far behind those of their sky-blue counterparts. To avoid the negative effects associated with dimensionality reduction and excess chloride typically needed to achieve deep-blue emission, here we demonstrate guanidine (GA+)-induced deep-blue (∼457 nm) perovskite emitters enabling spectrally stable PeLEDs with a record external quantum efficiency (EQE) over 3.41% through a combination of quasi-2D perovskites and halide engineering. Owing to the presence of GA+, even a small inclusion of chloride ions is sufficient for generating deep-blue electroluminescence (EL), in clear contrast to the previously reported deep-blue PeLEDs with significant chloride inclusion that negatively affects spectral stability. Based on the carrier dynamics analysis and theoretical calculation, GA+ is found to stabilize the low-dimensional species during annealing, retarding the cascade energy transfer and facilitating the deep-blue EL. Our findings open a potential third route to achieve deep-blue PeLEDs beyond the conventional methods of dimensionality reduction and excessive chloride incorporation.

7.
Opt Lett ; 47(18): 4810-4813, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36107096

RESUMO

We propose a common-path interferometer (CPI) method to suppress the ambient and laser phase noise in frequency sweeping interferometry. The CPI realizes the multiplexing of the main and auxiliary interferometer to ensure the common-mode characteristic of the interference phase noise, which can be eliminated by signal mixing. In experiments, we obtain a dynamic range of up to 110 dB. Compared with the compensation method using a separated auxiliary interferometer, the CPI method improves the dynamic range by 10 dB and is immune to ambient noise. The proposed method enables high-precision distributed polarization measurements of optical fibers and devices.

8.
J Oncol ; 2022: 7574458, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36016581

RESUMO

Oral squamous cell carcinoma (OSCC) is one of the most lethal cancers worldwide. The high morbidity and mortality of OSCC are a great burden to global health-care systems. Therefore it is important to understand the underlying molecular mechanisms of OSCC initiation and progression. This study aimed to investigate the role of circMAT2B in OSCC progression and its molecular mechanisms. First, the expression and circularization of circMAT2B in OSCC cells were verified. Subsequently, knockdown of circMAT2B was shown to inhibit OSCC cell proliferation, migration, invasion, and the Warburg effect. Bioinformatics prediction, RNA-pull down, and luciferase reporter gene assays led to the identification of a novel TEAD1/circMAT2B/miR-942-5p/HSPD1 axis in OSCC progression. In conclusion, the novel TEAD1/circMAT2B/miR-942-5p/HSPD1 axis is a potential target for OSCC.

9.
ACS Nano ; 16(8): 12253-12261, 2022 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-35913128

RESUMO

The instability of perovskite nanocrystals (NCs) to moisture, heat, and blue light severely hinders their commercial applications in quantum dot displays. Here, organic semiconducting molecules are introduced onto CsPbBr3 NCs, and the as-obtained CsPbBr3 NCs have a high photoluminescent quantum yield (PLQY) of 82% and extremely high stability in harsh commercial accelerated operational stability tests (such as high temperature (85 °C) and high humidity (85%)). The products can survive and maintain more than 80% of the initial PL intensity value under high temperature, high humidity, and long-term blue light irradiation for hundreds to thousands of hours. They are among the most stable perovskite NCs and even superior to those encapsulated by inert shells and commercial green-emissive CdSe@ZnS quantum dots (QDs). The mechanism of the exceptional stability has been proposed, mainly including the strong interaction and moderate photocarrier transfer between the quasi type II heterostructure formed by the molecule and CsPbBr3. By using these stable CsPbBr3 NCs, a QD-enhanced liquid crystal display prototype has been successfully fabricated with a wide color gamut. This work provides understandings on the functionality of ligands in perovskite fields and a promising prospect in perovskite-based display technologies.

10.
BMC Ophthalmol ; 22(1): 301, 2022 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-35820855

RESUMO

BACKGROUND: To discussed the risk factor and the management of vitrectomy for long-term endophthalmitis developing after intraocular lens (IOL) implantation in children. METHODS: We retrospectively investigated the clinical characteristics and surgical outcomes of long-term endophthalmitis developing after IOL implantation in children. RESULTS: Four eyes of four children were included in the study. The mean time to endophthalmitis development after IOL implantation was 3.0 ± 0.8 years. The corneal or scleral sutures may have been caused the infection. All 4 patients underwent vitrectomy and received intravitreal antibiotics with or without IOL removal. At the last follow-up, the outcomes were satisfactory; the fundus was clear, the retina remained attached, the visual acuity improved, and there were no severe complications. CONCLUSIONS: The use of scleral sutures and the exposure of conceal sutures may induce the onset of long-term endophthalmitis after IOL implantation. Complete vitrectomy and appropriate use of antibiotics are effective in the treatment of long-term endophthalmitis developing after IOL implantation in children.


Assuntos
Endoftalmite , Implante de Lente Intraocular , Antibacterianos/uso terapêutico , Criança , Endoftalmite/epidemiologia , Endoftalmite/etiologia , Endoftalmite/terapia , Humanos , Implante de Lente Intraocular/efeitos adversos , Estudos Retrospectivos , Vitrectomia/efeitos adversos
11.
Nat Commun ; 13(1): 3845, 2022 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-35788132

RESUMO

For a light-emitting diode (LED) to generate light, the minimum voltage required is widely considered to be the emitter's bandgap divided by the elementary charge. Here we show for many classes of LEDs, including those based on perovskite, organic, quantum-dot and III-V semiconductors, light emission can be observed at record-low voltages of 36-60% of their bandgaps, exhibiting a large apparent energy gain of 0.6-1.4 eV per photon. For 17 types of LEDs with different modes of charge injection and recombination (dark saturation currents of ~10-39-10-15 mA cm-2), their emission intensity-voltage curves under low voltages show similar behaviours. These observations and their consistency with the diode simulations suggest the ultralow-voltage electroluminescence arises from a universal origin-the radiative recombination of non-thermal-equilibrium band-edge carriers whose populations are determined by the Fermi-Dirac function perturbed by a small external bias. These results indicate the potential of low-voltage LEDs for communications, computational and energy applications.

12.
Front Nutr ; 9: 903293, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35811972

RESUMO

Background: Conflicting results have been reported on the value of the Geriatric Nutritional Risk Index (GNRI) in predicting adverse outcomes in patients with peripheral artery disease (PAD). The objective of this meta-analysis was to evaluate the association of GNRI with adverse outcomes in patients with lower extremity PAD. Methods: Relevant studies were comprehensively searched in PubMed and Embase databases until December 31, 2021. Eligible studies should evaluate the value of GNRI in predicting major adverse cardiovascular and leg events (MACLEs), all-cause mortality, and amputation in patients with lower extremity PAD. Results: Eight studies reporting on 9 articles involving 5,541 patients were included. A fixed-effect model meta-analysis showed that patients with PAD with low GNRI had an increased risk of MACLEs [adjusted risk ratio (RR) 2.26; 95% confidence interval (CI) 1.54-3.31] and all-cause mortality (RR 2.38; 95% CI 1.71-3.31) compared with those with high GNRI. When analysis of GNRI is by continuous data, 10 units of GNRI decrease was associated with 36% and 44% higher risk of MACLEs and all-cause mortality, respectively. However, per 10 units GNRI score decrease was not significantly associated with a higher risk of amputation (p = 0.051). Conclusion: Low GNRI may be an independent predictor of adverse outcomes in patients with lower extremity PAD. Routine screening of nutritional status using the GNRI may provide important prognostic information in patients with PAD.

13.
Front Cell Dev Biol ; 10: 888598, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35663398

RESUMO

Objective: To explore the repair effect of the prepared drug-loaded AM1241 poly(ethylene glycol)-dithiothreitol (PEG-DTT) hydrogel on cranial bone defects in SD rats. Methods: The PEG-DTT hydrogel under borax catalysis was quickly prepared, and the characterization of the material was observed by a scanning electron microscope. The effect of AM1241 on cell activity and bone tissue differentiation was tested. The SD rat model of cranial bone defect was established, and the defect was repaired by injecting the prepared hydrogel into the defect. The defect was divided into four groups, namely, sham group, blank group, PEG-DTT group, and PEG-DTT + AM1241 group. The rats were euthanized, and whole cranial bone was taken out for micro-CT and histological observation. Results: The prepared hydrogel is porous; it is liquid when heated to 80°C and a hydrogel when cooled to 25°C. 5-10 µM AM1241 increased osteoblast activity. A moderate amount of AM1241 can promote osteogenic differentiation. Both the PEG-DTT group and PEG-DTT + AM1241 group showed obvious new bone tissue formation, but the PEG-DTT + AM1241 group had a better effect. In addition, the new bone tissue in the PEG-DTT + AM1241 group was significantly more than that in the other groups. Conclusion: The prepared AM1241-loaded PEG-DTT hydrogel showed a good repair effect on SD rats with cranial bone defects. It can be used as materials for cranial bone repair in SD rats with cranial bone defects, but the repair effect is weaker than that of normal bone. These results provide a theoretical and practical basis for its further clinical application.

14.
Front Med (Lausanne) ; 9: 776855, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35721061

RESUMO

Proliferative diabetic retinopathy (PDR) accounts for severe impact on vision, its mechanism is still poorly understood. To compare the differences of vitreous protein profiles in PDR patients before and after a complete anti-vascular endothelial growth factor (VEGF) loading dose with ranibizumab treatment. Twelve vitreous humor (VH) samples were collected from six PDR patients before (set as pre group) and after (set as post group) intravitreal injection of ranibizumab (IVR) treatment. LC-MS/MS and bioinformatics analysis were performed to identify differentially expressed proteins. Proteins were validated with targeted proteomics using parallel reaction monitoring (PRM) in a validation set consisting of samples from the above patients. A total of 2680 vitreous proteins were identified. Differentially expressed proteins were filtrated with fold change ≥2.0 (post group/ pre group protein abundance ratio ≥2 or ≤ 0.5) and p-value <0.05. 11 proteins were up-regulated and 17 proteins were down-regulated, while consistent presence/absence expression profile group contains one elevated protein and nine reduced proteins, among which seven proteins were identified as potential biomarkers for IVR treatment through PRM assays. Bioinformatics analysis indicated the up-regulated proteins were significantly enriched in "GnRH secretion" and "Circadian rhythm" signaling pathway. This report represents the first description of combined label-free quantitative proteomics and PRM analysis of targeted proteins for discovery of different proteins before and after IVR treatment in the same patient. IVR treatment may protect against PDR by promoting SPP1 expression through "GnRH secretion" and "Circadian rhythm" signaling pathway.

15.
Angew Chem Int Ed Engl ; 61(29): e202204126, 2022 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-35575978

RESUMO

Transition-metal-catalyzed copolymerization of ethylene with carbon monoxide affords polyketones materials with excellent mechanical strength, photodegradability, surface and barrier properties. Unlike the widely used and rather expensive Pd catalysts, Ni-catalyzed carbonylative polymerization is very difficult since the strong binding affinity of CO to Ni deactivates the highly electrophilic metal center easily. In this study, various cationic P,O-coordinated Ni complexes were synthesized using the electronic modulation strategy, and the catalyst with strong electron-donating substituents exhibits an excellent productivity of 104  g polymer (g Ni)-1 , which represents a rare discovery that a Ni complex could operate with such exceptional efficiency in comparison with Pd catalysts. Notably, those Ni catalysts were also efficient for terpolymerization of ethylene, propylene with CO for producing commercial polyketone materials with low melting temperatures and easy processibility.

16.
Bioact Mater ; 16: 388-402, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35415284

RESUMO

Bio-adhesive polysaccharide-based hydrogels have attracted much attention in first-aid hemostasis and wound healing for excellent biocompatibility, antibacterial property and pro-healing bioactivity. Yet, the inadequate mechanical properties and bio-adhesion limit their applications. Herein, based on dynamic covalent bonds, photo-triggered covalent bonds and hydrogen bonds, multifunctional bio-adhesive hydrogels comprising modified carboxymethyl chitosan, modified sodium alginate and tannic acid are developed. Multi-crosslinking strategy endows hydrogels with improved strength and flexibility simultaneously. Owing to cohesion enhancement strategy and self-healing ability, considerable bio-adhesion is presented by the hydrogel with a maximal adhesion strength of 162.6 kPa, 12.3-fold that of commercial fibrin glue. Based on bio-adhesion and pro-coagulant activity (e.g., the stimulative aggregation and adhesion of erythrocytes and platelets), the hydrogel reveals superior hemostatic performance in rabbit liver injury model with blood loss of 0.32 g, only 54.2% of that in fibrin glue. The healing efficiency of hydrogel for infected wounds is markedly better than commercial EGF Gel and Ag+ Gel due to the enhanced antibacterial and antioxidant properties. Through the multi-crosslinking strategy, the hydrogels show enhanced mechanical properties, fabulous bio-adhesion, superior hemostatic performance and promoting healing ability, thereby have an appealing application value for the first-aid hemostasis and infected wound healing.

17.
Bioengineered ; 13(4): 11012-11025, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35481460

RESUMO

Circular RNAs, which are a novel subclass of noncoding RNAs, are reported to be involved in various biological processes. Aberrant expression of circular RNAs may promote cancer progression. The function of circular GOLPH3 RNA (circGOLPH3) in oral squamous cell carcinoma (OSCC) is unclear. In this study, the circGOLPH3 levels in OSCC cell lines were determined using quantitative real-time polymerase chain reaction (qRT-PCR). Gain-of-function and loss-of-function experiments were performed to evaluate the roles of circGOLPH3 in OSCC. Cell counting kit 8, migration, and invasion assays were performed to determine the functions of circGOLPH3. The mechanism of circGOLPH3 in OSCC was investigated using qRT-PCR, western blotting, luciferase activity, and RNA pull-down analyses. Furthermore, the function of circGOLPH3 in vivo was evaluated. circGOLPH3 derived from GOLPH3 was mainly localized to the cytoplasm and exhibited high stability. The expression of circGOLPH3 was upregulated in OSCC cells. circGOLPH3 promoted the growth of OSCC in vitro and in vivo. Additionally, circGOLPH3 upregulated OSCC cell migration and invasion. Mechanistically, circGOLPH3 functioned as a microRNA sponge and downregulated miR-1299 expression. miR-1299 downregulated the expression of LIF by targeting its 3'-untranslated region. Inhibition of the circGOLPH3/miR-1299/LIF axis suppressed the growth, migration, and invasion of OSCC cells. These findings indicate that the circGOLPH3/miR-1299/LIF axis promotes OSCC cell growth, migration, and invasion and that this axis is a potential therapeutic target for OSCC.


Assuntos
Carcinoma de Células Escamosas , Neoplasias de Cabeça e Pescoço , MicroRNAs , Neoplasias Bucais , Regiões 3' não Traduzidas , Carcinogênese/genética , Carcinoma de Células Escamosas/metabolismo , Linhagem Celular Tumoral , Movimento Celular/genética , Regulação Neoplásica da Expressão Gênica/genética , Neoplasias de Cabeça e Pescoço/genética , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismo , Neoplasias Bucais/metabolismo , RNA Circular/genética , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética
18.
Nat Commun ; 13(1): 1954, 2022 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-35414067

RESUMO

The heterogenization of homogeneous metal complexes on solid supports presents an efficient strategy for bridging homogeneous catalysts with industrially-preferred heterogeneous catalysts; however, a series of drawbacks restrict their implementation in olefin polymerization, particularly for copolymerization with polar comonomers. In this contribution, we report an ionic anchoring strategy that is highly versatile, generally applicable to different systems, and enables strong catalyst-support interactions while tolerating various polar functional groups. In addition to greatly enhanced polymerization properties, the supported catalysts achieved higher comonomer incorporation than their unsupported counterparts. This strategy enabled efficient polymerization at high temperatures at large scale and great control over product morphology, and the facile synthesis of polyolefin composites. More importantly, the dispersion of different fillers in the polyolefin matrix produced great material properties even at low composite loadings. It is expected that this strategy will find applications in different catalytic systems and the synthesis of advanced engineering materials.

19.
Bioengineered ; 13(3): 6371-6382, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-35240924

RESUMO

Emerging studies indicate that long non-coding RNAs play important roles in oral squamous cell carcinoma (OSCC). However, the function of the majority of long non-coding RNAs is still unclear. Recently, LINC00472 has been reported to play crucial roles in multiple cancers. However, the role of LINC00472 in oral squamous cell carcinoma (OSCC) is still not clear. This study found that LncRNA LINC00472 was significantly down-regulated in several squamous cell carcinoma cancer tissues and OSCC cell lines. Over-expression of LINC00472 in OSCC cells inhibited OSCC progression and alleviated OSCC immune responses. Additionally, we confirmed that LINC00472 functioned as an hsa-miR-4311 sponge and regulated the expression of GNG7 (guanine nucleotide-binding protein, gamma 7). Also, we found that LINC00472 over-expression could suppress xenograft tumor growth in vivo. Our study provides evidence that LINC00472 plays an essential role in inhibiting oral squamous cell carcinoma progression and affecting immune responses by directly binding to hsa-miR-4311 to regulate the expression of GNG7 positively.


Assuntos
Carcinoma de Células Escamosas , Neoplasias de Cabeça e Pescoço , MicroRNAs , Neoplasias Bucais , RNA Longo não Codificante , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/genética , Subunidades gama da Proteína de Ligação ao GTP , Regulação Neoplásica da Expressão Gênica , Neoplasias de Cabeça e Pescoço/genética , Humanos , MicroRNAs/genética , MicroRNAs/metabolismo , Neoplasias Bucais/metabolismo , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética
20.
J Am Chem Soc ; 144(5): 2245-2254, 2022 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-35073070

RESUMO

Product morphology control represents a critical challenge for polyolefin production, but it has remained largely unexplored in the field of ethylene-polar monomer copolymerization. Herein, an ionic cluster strategy was designed to control the product morphology during the synthesis of polar-functionalized polyolefins via precipitation polymerization. In addition to product morphology control, simultaneous improvements in the catalytic copolymerization performance (activities, copolymer molecular weights, and comonomer incorporation ratios) were achieved. These results were due to less poisoning of the metal-salt-based comonomers compared with their ester counterparts and the high local concentration of the alkene comonomers induced by ionic cluster formation. Moreover, the ionic cluster strategy is generally applicable to various comonomers and catalytic systems, greatly enhances the catalyst's thermal stability at high temperatures (90-150 °C), and enables the homopolymerization of both terminal and internal polar-functionalized olefins. Finally, polar-functionalized polyolefins and polyolefin composites (generated from a tandem process combining a prepolymerization step and subsequent polymerization) were developed, which showed tunable mechanical properties and great potential as compatibilizing agents for mixtures of polyolefins and other types of polymers.

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