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1.
Chem Rev ; 2024 Oct 25.
Artículo en Inglés | MEDLINE | ID: mdl-39454031

RESUMEN

The copolymerization of CO2 and epoxides presents a transformative approach to converting greenhouse gases into aliphatic polycarbonates (CO2-PCs), thereby reducing the polymer industry's dependence on fossil resources. Over the past 50 years, a wide array of metallic catalysts, both heterogeneous and homogeneous, have been developed to achieve precise control over polymer selectivity, sequence, regio-, and stereoselectivity. This review details the evolution of metal-based catalysts, with a particular focus on the emergence of organoborane catalysts, and explores how these catalysts effectively address kinetic and thermodynamic challenges in CO2/epoxides copoly2merization. Advances in the synthesis of CO2-PCs with varied sequence and chain architectures through diverse polymerization protocols are examined, alongside the applications of functional CO2-PCs produced by incorporating different epoxides. The review also underscores the contributions of computational techniques to our understanding of copolymerization mechanisms and highlights recent advances in the closed-loop chemical recycling of CO2-sourced polycarbonates. Finally, the industrialization efforts of CO2-PCs are discussed, offering readers a comprehensive understanding of the evolution and future potential of epoxide copolymerization with CO2.

2.
Chem Soc Rev ; 53(7): 3384-3456, 2024 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-38411207

RESUMEN

The scientific community has witnessed extensive developments and applications of organoboron compounds as synthetic elements and metal-free catalysts for the construction of small molecules, macromolecules, and functional materials over the last two decades. This review highlights the achievements of organoboron-mediated polymerizations in the past several decades alongside the mechanisms underlying these transformations from the standpoint of the polymerization mode. Emphasis is placed on free radical polymerization, Lewis pair polymerization, ionic (cationic and anionic) polymerization, and polyhomologation. Herein, alkylborane/O2 initiating systems mediate the radical polymerization under ambient conditions in a controlled/living manner by careful optimization of the alkylborane structure or additives; when combined with Lewis bases, the selected organoboron compounds can mediate the Lewis pair polymerization of polar monomers; the bicomponent organoboron-based Lewis pairs and bifunctional organoboron-onium catalysts catalyze ring opening (co)polymerization of cyclic monomers (with heteroallenes, such as epoxides, CO2, CO, COS, CS2, episulfides, anhydrides, and isocyanates) with well-defined structures and high reactivities; and organoboranes initiate the polyhomologation of sulfur ylides and arsonium ylides providing functional polyethylene with different topologies. The topological structures of the produced polymers via these organoboron-mediated polymerizations are also presented in this review mainly including linear polymers, block copolymers, cyclic polymers, and graft polymers. We hope the summary and understanding of how organoboron compounds mediate polymerizations can inspire chemists to apply these principles in the design of more advanced organoboron compounds, which may be beneficial for the polymer chemistry community and organometallics/organocatalysis community.

3.
J Transl Med ; 22(1): 210, 2024 02 27.
Artículo en Inglés | MEDLINE | ID: mdl-38414015

RESUMEN

BACKGROUND: Clear cell renal cell carcinoma is a prototypical tumor characterized by metabolic reprogramming, which extends beyond tumor cells to encompass diverse cell types within the tumor microenvironment. Nonetheless, current research on metabolic reprogramming in renal cell carcinoma mostly focuses on either tumor cells alone or conducts analyses of all cells within the tumor microenvironment as a mixture, thereby failing to precisely identify metabolic changes in different cell types within the tumor microenvironment. METHODS: Gathering 9 major single-cell RNA sequencing databases of clear cell renal cell carcinoma, encompassing 195 samples. Spatial transcriptomics data were selected to conduct metabolic activity analysis with spatial localization. Developing scMet program to convert RNA-seq data into scRNA-seq data for downstream analysis. RESULTS: Diverse cellular entities within the tumor microenvironment exhibit distinct infiltration preferences across varying histological grades and tissue origins. Higher-grade tumors manifest pronounced immunosuppressive traits. The identification of tumor cells in the RNA splicing state reveals an association between the enrichment of this particular cellular population and an unfavorable prognostic outcome. The energy metabolism of CD8+ T cells is pivotal not only for their cytotoxic effector functions but also as a marker of impending cellular exhaustion. Sphingolipid metabolism evinces a correlation with diverse macrophage-specific traits, particularly M2 polarization. The tumor epicenter is characterized by heightened metabolic activity, prominently marked by elevated tricarboxylic acid cycle and glycolysis while the pericapsular milieu showcases a conspicuous enrichment of attributes associated with vasculogenesis, inflammatory responses, and epithelial-mesenchymal transition. The scMet facilitates the transformation of RNA sequencing datasets sourced from TCGA into scRNA sequencing data, maintaining a substantial degree of correlation. CONCLUSIONS: The tumor microenvironment of clear cell renal cell carcinoma demonstrates significant metabolic heterogeneity across various cell types and spatial dimensions. scMet exhibits a notable capability to transform RNA sequencing data into scRNA sequencing data with a high degree of correlation.


Asunto(s)
Carcinoma de Células Renales , Neoplasias Renales , Humanos , Carcinoma de Células Renales/genética , Linfocitos T CD8-positivos , Perfilación de la Expresión Génica , Metabolismo de los Lípidos , Neoplasias Renales/genética , Microambiente Tumoral/genética
4.
World J Urol ; 42(1): 208, 2024 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-38565733

RESUMEN

OBJECTIVES: To determine the relationship between renal tumor complexity and vascular complications after partial nephrectomy using PADUA, RENAL, and ZS scores. METHODS: Between January 2007 and December 2018, a total of 1917 patients with available cross-sectional imaging were enrolled in the study. Logistic regressions were used to identify independent predictors of vascular complications. RESULTS: Of 1917 patients, 31 (1.6%) developed vascular complications, including 10 females and 21 males. The high-complexity category was significantly associated with a decreased risk of vascular complication in PADUA (OR = 0.256; 95%CI = 0.086-0.762; P = 0.014) and ZS score (OR = 0.279; 95%CI = 0.083-0.946; P = 0.040). Laparoscopic partial nephrectomy and robot-assisted laparoscopic partial nephrectomy were independent risk factors for vascular complications. Meanwhile, the incidence was significantly reduced in the recent 4 years in the high score tumor group alone in PADUA (0.2% [1/474] vs. 2.2% [3/139], P = 0.038) and ZS score (0.2% [1/469] vs. 2.7% [3/112], P = 0.024). In the first 8 years, laparoscopic partial nephrectomy and robot-assisted laparoscopic partial nephrectomy were the only two independent risk factors for vascular complications. In the recent 4 years, only the high-complexity category was significantly associated with a decreased risk of vascular complication in the PADUA score (OR = 0.110; 95%CI = 0.013-0.938; P = 0.044). CONCLUSION: The renal anatomic classification system cannot predict the occurrence of vascular complications after partial nephrectomy.


Asunto(s)
Neoplasias Renales , Laparoscopía , Procedimientos Quirúrgicos Robotizados , Masculino , Femenino , Humanos , Riñón/cirugía , Nefrectomía/efectos adversos , Nefrectomía/métodos , Neoplasias Renales/patología , Procedimientos Quirúrgicos Robotizados/efectos adversos , Laparoscopía/efectos adversos , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/patología , Estudios Retrospectivos , Resultado del Tratamiento
5.
J Surg Oncol ; 129(8): 1407-1412, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38606525

RESUMEN

BACKGROUND: Retroperitoneal partial nephrectomy (RLPN) is the premier treatment for localized renal tumors despite narrow operation space. Many efforts have been taken to facilitate the operation of RLPN, but the optimal resolution remains debatable. OBJECTIVE: To explore the feasibility of using Mini-lap to improve workspace and surgical vision in RLPN. DESIGN, SETTING, AND PARTICIPANTS: A multicenter retrospective review of 51 patients who underwent RLPN with Mini-lap from January 2018 to December 2020 was conducted. SURGICAL PROCEDURE: Standard RLPN under three poles was performed in all cases. We highlighted the usage of Mini-lap (Teleflex Minilap percutaneous Surgical System) as a novel retractor in RLPN. OUTCOME AND MEASUREMENTS AND STATICAL ANALYSIS: Demographics, preoperative, intraoperative, and postoperative outcomes were assessed. RESULTS AND LIMITATIONS: All 51 cases completed RLPN with three ports successfully and no conversion to open surgery. The mean diameter of tumors was (3.53 ± 1.05) cm, in which 62.7% (32/51) were located anteriorly. The operation time and warm ischemic time (WIT) were (86.7 ± 15.9) min and (25.6 ± 5) min respectively. Minor complications (Clavien grade 1-2) occurred in 6 cases. The limitations were small sample size, retrospective design, and absence of control. CONCLUSIONS: Mini-lap could be used as a mini-retractor in RLPN, sparing extra assistant ports, expanding workspace, and optimizing vision. PATIENT SUMMARY: With highlights of larger workspace and less instrument interference, mini-lap could be applied in retroperitoneal laparoscopic partial nephrectomy.


Asunto(s)
Neoplasias Renales , Laparoscopía , Nefrectomía , Humanos , Nefrectomía/métodos , Laparoscopía/métodos , Estudios Retrospectivos , Femenino , Masculino , Persona de Mediana Edad , Espacio Retroperitoneal/cirugía , Neoplasias Renales/cirugía , Neoplasias Renales/patología , Anciano , Tempo Operativo , Estudios de Factibilidad , Adulto , Estudios de Seguimiento , Pronóstico
6.
Angew Chem Int Ed Engl ; 63(32): e202401850, 2024 Aug 05.
Artículo en Inglés | MEDLINE | ID: mdl-38706222

RESUMEN

Seeking high-performance photoresists is an important item for semiconductor industry due to the continuous miniaturization and intelligentization of integrated circuits. Polymer resin containing carbonate group has many desirable properties, such as high transmittance, acid sensitivity and chemical formulation, thus serving as promising photoresist material. In this work, a series of aqueous developable CO2-sourced polycarbonates (CO2-PCs) were produced via alternating copolymerization of CO2 and epoxides bearing acid-cleavable cyclic acetal groups in the presence of tetranuclear organoborane catalyst. The produced CO2-PCs were investigated as chemical amplification resists in deep ultraviolet (DUV) lithography. Under the catalysis of photogenerated acid, the acetal (ketal) groups in CO2-PC were hydrolysed into two equivalents of hydroxyl groups, which change the exposed area from hydrophobicity to hydrophilicity, thus enabling the exposed area to be developed with water. Through normalized remaining thickness analysis, the optimal CO2-derived resist achieved a remarkable sensitivity of 1.9 mJ/cm2, a contrast of 7.9, a favorable resolution (750 nm, half pitch), and a good etch resistance (38 % higher than poly(tert-butyl acrylate)). Such performances outperform commercial KrF and ArF chemical amplification resists (i.e., polyhydroxystyrene-derived and polymethacrylate-based resists), which endows broad application prospects in the field of DUV (KrF and ArF) and extreme ultraviolet (EUV) lithography for nanomanufacturing.

7.
Angew Chem Int Ed Engl ; 63(27): e202404207, 2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38647637

RESUMEN

Alkyl borane compounds-mediated polymerizations have expanded to Lewis pair polymerization, free radical polymerization, ionic ring-opening polymerization, and polyhomologation. The bifunctional organoborane catalysts that contain the Lewis acid and ammonium or phosphonium salt in one molecule have demonstrated superior catalytic performance for ring-opening polymerization of epoxides and ring-opening copolymerization of epoxides and CO2 than their two-component analogues, i.e., the blend of organoborane and ammonium or phosphonium salt. To explore the origin of the differences of the one-component and two-component organoborane catalysts, here we conducted a systematic investigation on the catalytic performances of these two kinds of organoborane catalysts via terpolymerization of epoxide, carbon dioxide and anhydride. The resultant terpolymers produced independently by bifunctional and binary organoborane catalyst exhibited distinct microstructures, where a series of gradient polyester-polycarbonate terpolymers with varying polyester content were afforded using the bifunctional catalyst, while tapering diblock terpolymers were obtained using the binary system. The bifunctional catalyst enhances the competitiveness of CO2 insertion than anhydride, which leads to the premature incorporation of CO2 into the polymer chains and ultimately results in the formation of gradient terpolymers. DFT calculations revealed the role of electrostatic interaction and charge distribution caused by intramolecular synergistic effect for bifunctional organoborane catalyst.

8.
Angew Chem Int Ed Engl ; 62(48): e202312376, 2023 Nov 27.
Artículo en Inglés | MEDLINE | ID: mdl-37847123

RESUMEN

This work reported that a silicon-centered alkyl borane/ammonium salt binary (two-component) catalyst exhibits much higher activity than its bifunctional analogue (one-component) for the ring-opening polymerization of propylene oxide, showing 7.3 times the activity of its bifunctional analogue at a low catalyst loading of 0.01 mol %, and even 15.3 times the activity at an extremely low loading of 0.002 mol %. By using 19 F NMR spectroscopy, control experiments, and theoretical calculation we discovered that the central silicon atom displays appropriate electron density and a larger intramolecular cavity, which is useful to co-activate the monomer and to deliver propagating chains, thus leading to a better intramolecular synergic effect than its bifunctional analogue. A unique two-pathway initiation mode was proposed to explain the unusual high activity of the binary catalytic system. This study breaks the traditional impression of the binary Lewis acid/nucleophilic catalyst with poor activity because of the increase in entropy.

9.
J Am Chem Soc ; 144(43): 19896-19909, 2022 11 02.
Artículo en Inglés | MEDLINE | ID: mdl-36256447

RESUMEN

Switchable catalysis, in combination with epoxide-involved ring-opening (co)polymerization, is a powerful technique that can be used to synthesize various oxygen-rich block copolymers. Despite intense research in this field, the sequence-controlled polymerization from epoxide congeners has never been realized due to their similar ring-strain which exerts a decisive influence on the reaction process. Recently, quaternary ammonium (or phosphonium)-containing bifunctional organoboron catalysts have been developed by our group, showing high efficiency for various epoxide conversions. Herein, we, for the first time, report an operationally simple pathway to access well-defined polyether-block-polycarbonate copolymers from mixtures of epoxides by switchable catalysis, which was enabled through thermodynamically and kinetically preferential ring-opening of terminal epoxides or internal epoxides under different atmospheres (CO2 or N2) using one representative bifunctional organoboron catalyst. This strategy shows a broad substrate scope as it is suitable for various combinations of terminal epoxides and internal epoxides, delivering corresponding well-defined block copolymers. NMR, MALDI-TOF, and gel permeation chromatography analyses confirmed the successful construction of polyether-block-polycarbonate copolymers. Kinetic studies and density functional theory calculations elucidate the reversible selectivity between different epoxides in the presence/absence of CO2. Moreover, by replacing comonomer CO2 with cyclic anhydride, the well-defined polyether-block-polyester copolymers can also be synthesized. This work provides a rare example of sequence-controlled polymerization from epoxide mixtures, broadening the arsenal of switchable catalysis that can produce oxygen-rich polymers in a controlled manner.


Asunto(s)
Dióxido de Carbono , Compuestos Epoxi , Compuestos Epoxi/química , Cinética , Dióxido de Carbono/química , Oxígeno , Catálisis , Polímeros/química , Carbonatos
10.
Acc Chem Res ; 54(23): 4434-4448, 2021 Dec 07.
Artículo en Inglés | MEDLINE | ID: mdl-34806374

RESUMEN

ConspectusElectron-deficient boron-based catalysts with metal-free but metallomimetic characteristics provide a versatile platform for chemical transformations. However, their catalytic performance is usually lower than that of the corresponding metal-based catalysts. Furthermore, many elaborate organoboron compounds are produced via time-consuming multistep syntheses with low yields, presenting a formidable challenge for large-scale applications of these catalysts. Given this context, the development of organoboron catalysts with the combined advantages of high efficiency and easy preparation is of critical importance.Therefore, we envisioned that the construction of a dynamic Lewis multicore system (DLMCS) by integrating the Lewis acidic boron center(s) and a Lewis basic ammonium salt in one molecule would be particularly efficient for on-demand applications because of the intramolecular synergistic effect. This Account summarizes our recent efforts in developing modular organoboron catalysts with unprecedented activities for several chemical transformations. A series of mono-, di-, tri-, and tetranuclear organoboron catalysts was readily designed and prepared in nearly quantitative yields over two steps using commercially available feedstocks. Notably, these catalysts can be modularly tailored by fine control over the electrophilic property of the Lewis acidic boron center(s), electronic and steric effects of the electropositive ammonium cation, linker length between the boron center and the ammonium cation, the number of boron centers, and the nucleophilic anion. This modular design allows systematic manipulation of the reactivity and efficacy of the catalysts, thus optimizing suitable catalysts for versatile chemical transformations. These include the coupling of CO2 and epoxides, copolymerization of CO2 and epoxides, ring-opening polymerization (ROP) of epoxides, and ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides.The utilization of mononuclear organoboron catalysts provided a turnover frequency of 11050 h-1 for the CO2/propylene oxide coupling reaction, an unprecedented efficiency of 5.0 kg of polymer/g of catalyst for the copolymerization of CO2 and cyclohexene oxide, and a record-breaking catalytic efficiency of 7.4 kg of polymer/g of catalyst for the ROCOP of epoxides with cyclic anhydrides. A turnover number of 56500 was observed at a catalyst loading of 10 ppm for the ROP of epoxides using the dinuclear catalysts. The tetranuclear organoboron catalysts realized the previously intractable task of the copolymerization of CO2 and epichlorohydrin, producing poly(chloropropylene carbonate) with the highest molecular weight of 36.5 kg/mol reported to date.Furthermore, the study revealed that the interaction between the dynamic Lewis multicore, that is, the intramolecular synergistic effect between the boron center(s) and the quaternary ammonium salt, plays a key role in mediating the catalytic activity and selectivity. This was based on investigations of the crystal structures of the catalysts, key intermediates, reaction kinetics, and density functional theory calculations. The modular tactics for the construction of organoboron catalysts presented in this Account should inspire more advanced catalyst designs.

11.
Angew Chem Int Ed Engl ; 61(7): e202115189, 2022 Feb 07.
Artículo en Inglés | MEDLINE | ID: mdl-34866295

RESUMEN

Construction of well-defined sulfur-rich macromolecules in a facile manner is an interesting but challenging topic. Herein, we disclose how to readily construct well-defined triblock sulfur-rich thermoplastic elastomers via a self-switchable isothiocyanate/episulfide copolymerization and air-assisted oxidative coupling strategy. During self-switchable polymerization, alternating copolymerization of isothiocyanate and episulfide occurs initially due to the lower energy barrier for isothiocyanate insertion with respect to successive episulfide ring-opening. After exhaustion of isothiocyanate, ring-opening polymerization of episulfide begins, providing diblock polymers. Subsequent exposure of the reaction to air leads to a transformation of diblock copolymers into triblock thermoplastic elastomers. This protocol can be extended to diverse isothiocyanates and episulfides, allowing fine-tuning of the performance of the produced sulfur-rich thermoplastic elastomers.

12.
Angew Chem Int Ed Engl ; 61(46): e202210243, 2022 Nov 14.
Artículo en Inglés | MEDLINE | ID: mdl-36131491

RESUMEN

Poly(cyclopentene carbonate) (PCPC) produced by copolymerization of CO2 and cyclopentene oxide (CPO) is a promising but challenging chemical recyclable polymer that has high potential in minimizing plastic pollution and maximizing CO2 utilization. Currently, problems remain to be solved, include low reactivity of toxic metal catalysts, inevitable byproducts, and especially the ambiguous mechanism understanding. Herein, we present the first metal-free access to PCPC by using a series of modular dinuclear organoboron catalysts. PCPC was afforded in an unprecedented catalytic efficiency of 1.0 kg of PCPC/g of catalyst; while the depolymerization of PCPC abides by a combination pathway of random chain scission and chain unzipping, returning CPO in near-quantitative yield (>99 %). The preparation and depolymerization of PCPC along with in depth understanding of related mechanisms would be helpful for further development of advanced catalysts and recyclable plastics.

13.
J Am Chem Soc ; 143(9): 3455-3465, 2021 Mar 10.
Artículo en Inglés | MEDLINE | ID: mdl-33591738

RESUMEN

The copolymerization of carbon dioxide (CO2) and epoxides to produce aliphatic polycarbonates is a burgeoning technology for the large-scale utilization of CO2 and degradable polymeric materials. Even with the wealth of advancements achieved over the past 50 years on this green technology, many challenges remain, including the use of metal-containing catalysts for polymerization, the removal of the chromatic metal residue after polymerization, and the limited practicable epoxides, especially for those containing electron-withdrawing groups. Herein, we provide kinds of pinwheel-shaped tetranuclear organoboron catalysts for epichlorohydrin/CO2 copolymerization with >99% polymer selectivity and quantitative CO2 uptake (>99% carbonate linkages) under mild conditions (25-40 °C, 25 bar of CO2). The produced poly(chloropropylene carbonate) has the highest molecular weight of 36.5 kg/mol and glass transition temperature of 45.4 °C reported to date. The energy difference (ΔEa = 60.7 kJ/mol) between the cyclic carbonate and polycarbonate sheds light on the robust performance of our metal-free catalyst. Control experiments and density functional theory (DFT) calculations revealed a cyclically sequential copolymerization mechanism. The metal-free feature, high catalytic performance under mild conditions, and no trouble with chromaticity for the produced polymers imply that our catalysts are practical candidates to advance the CO2-based polycarbonates.

14.
Angew Chem Int Ed Engl ; 60(35): 19253-19261, 2021 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-34109722

RESUMEN

Producing polyesters with high molecular weight (Mn ) through ring-opening copolymerization (ROCOP) of epoxides with cyclic anhydrides remains a major challenge. Herein, we communicate a metal-free, highly active, and high thermoresistance system for the ROCOP of epoxides with cyclic anhydrides to prepare polyesters (13 examples). The organoboron catalysts can endure a reaction temperature as high as 180 °C for the ROCOP of cyclohexane oxide (CHO) with phthalic anhydride (PA) without the observation of any side reactions. The average Mn of the produced poly(CHO-alt-PA) climbed to 94.5 kDa with low polydispersity (Ð=1.19). Furthermore, an unprecedented turnover number of 9900, equivalent to an efficiency of 7.4 kg of polyester/g of catalyst, was achieved at a feed ratio of CHO/PA/catalyst=20000:10000:1 at 150 °C. Kinetic studies, crystal structure analysis, 11 B NMR spectra, and DFT calculations provided mechanistic justification for the effectiveness of the catalyst system.

15.
J Am Chem Soc ; 142(28): 12245-12255, 2020 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-32538080

RESUMEN

The metallic catalyst-dominated alternating copolymerization of CO2 and epoxides has flourished for 50 years; however, the involved multistep preparation of the catalysts and the necessity to remove the colored metal residue in the final product present significant challenges in scalability. Herein, we report a series of highly active metal-free catalysts featured with an electrophilic boron center and a nucleophilic quaternary ammonium halide in one molecule for copolymerization of epoxides and CO2. The organocatalysts are easily scaled up to kilogram scale with nearly quantitative yield via two steps using commercially available stocks. The organocatalyst-mediated copolymerization of cyclohexane oxide and CO2 displays high activity (turnover frequency up to 4900 h-1) and >99% polycarbonate selectivity in a broad temperature range (25-150 °C) at mild CO2 pressure (15 bar). At a feed ratio of cyclohexane oxide/catalyst = 20 000/1, an efficiency of 5.0 kg of product/g of catalyst was achieved, which is the highest record achieved to date. The unprecedented activity toward CO2/epoxide copolymerization for our catalyst is a consequence of an intramolecular synergistic effect between the electrophilic boron center and the quaternary ammonium salt, which was experimentally ascertained by reaction kinetics studies, multiple control experiments, 11B NMR investigation, and the crystal structure of the catalyst. Density functional theory calculations further corroborated experimental conclusions and provided a deeper understanding of the catalysis process. The metal-free characteristic, scalable preparation, outstanding catalytic performances along with long-term thermostability demonstrate that the catalyst could be a promising candidate for large-scale production of CO2-based polymer.

16.
Angew Chem Int Ed Engl ; 59(39): 16910-16917, 2020 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-32562445

RESUMEN

This manuscript describes a kind of bifunctional organocatalyst with unprecedented reactivity for the synthesis of polyethers via ring-opening polymerization (ROP) of epoxides under mild conditions. The bifunctional catalyst incorporates two 9-borabicyclo[3.3.1]nonane centers on the two ends as Lewis acidic sites for epoxide activation and a quaternary ammonium halide in the middle as the initiating site. The catalyst could be easily prepared in two steps from commercially available stocks on up to kilogram scale with ≈100 % yield. The organoboron catalyst mediated ROP of epoxides displays living behavior with low catalyst loading (5 ppm) and enables the synthesis of polyethers with molecular weights of over a million grams per mole (>106  g mol-1 ). Based on the investigations on crystal structure of catalyst, MALDI-TOF, and 11 B NMR spectroscopy, an intramolecular ammonium cation assisted SN 2 mechanism is proposed and verified by DFT calculations.

17.
Angew Chem Int Ed Engl ; 59(51): 23291-23298, 2020 Dec 14.
Artículo en Inglés | MEDLINE | ID: mdl-32869449

RESUMEN

A series of highly active organoboron catalysts for the coupling of CO2 and epoxides with the advantages of scalable preparation, thermostability, and recyclability is reported. The metal-free catalysts show high reactivity towards a wide scope of cyclic carbonates (14 examples) and can withstand a high temperature up to 150 °C. Compared with the current metal-free catalytic systems that use mol % catalyst loading, the catalytic capacity of the catalyst described herein can be enhanced by three orders of magnitude (epoxide/cat.=200 000/1, mole ratio) in the presence of a cocatalyst. This feature greatly narrows the gap between metal-free catalysts and state-of-the-art metallic systems. An intramolecular cooperative mechanism is proposed and certified on the basis of investigations on crystal structures, structure-performance relationships, kinetic studies, and key reaction intermediates.

18.
Nano Lett ; 17(2): 1233-1239, 2017 02 08.
Artículo en Inglés | MEDLINE | ID: mdl-28068100

RESUMEN

Directed self-assembly (DSA) of block copolymers (BCPs) combines advantages of conventional photolithography and polymeric materials and shows competence in semiconductors and data storage applications. Driven by the more integrated, much smaller and higher performance of the electronics, however, the industry standard polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) in DSA strategy cannot meet the rapid development of lithography technology because its intrinsic limited Flory-Huggins interaction parameter (χ). Despite hundreds of block copolymers have been developed, these BCPs systems are usually subject to a trade-off between high χ and thermal treatment, resulting in incompatibility with the current nanomanufacturing fab processes. Here we discover that polystyrene-b-poly(propylene carbonate) (PS-b-PPC) is well qualified to fill key positions on DSA strategy for the next-generation lithography. The estimated χ-value for PS-b-PPC is 0.079, that is, two times greater than PS-b-PMMA (χ = 0.029 at 150 °C), while processing the ability to form perpendicular sub-10 nm morphologies (cylinder and lamellae) via the industry preferred thermal-treatment. DSA of lamellae forming PS-b-PPC on chemoepitaxial density multiplication demonstrates successful sub-10 nm long-range order features on large-area patterning for nanofabrication. Pattern transfer to the silicon substrate through industrial sequential infiltration synthesis is also implemented successfully. Compared with the previously reported methods to orientation control BCPs with high χ-value (including solvent annealing, neutral top-coats, and chemical modification), the easy preparation, high χ value, and etch selectivity while enduring thermal treatment demonstrates PS-b-PPC as a rare and valuable candidate for advancing the field of nanolithography.

19.
Inorg Chem ; 52(6): 2802-8, 2013 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-23458186

RESUMEN

NCN-pincer (S,S)-2,6-bis(4'-isopropyl-2'-oxazolinyl)phenyl-ligated rare-earth-metal dichlorides [(S,S)-Phebox-(i)Pr]LnCl2(THF)2 (Ln = Sc (1); Y (2); Dy (3); Ho (4); Tm (5); Lu (6)) were synthesized via transmetalation between [(S,S)-Phebox-(i)Pr]Li and LnCl3 in THF solvent. Interestingly, treatment of LaCl3 by the same method generated tris(ligand) lanthanum complex [(S,S)-Phebox-(i)Pr]3La (7). Molecular structures of complexes 1, 2, 3, and 7 were established by single-crystal X-ray diffraction study. Pincer ligand (S,S)-Phebox-(i)Pr adopts a κC:κN:κN' tridentate coordination mode to the central metal ion. Upon activation with [PhNHMe2][B(C6F5)4] and Al(i)Bu3, complexes 2-5 exhibited highly catalytic activities and more than 98% cis-1,4-selectivity for isoprene polymerization while complexes 1 and 6 were inactive for this reaction. When use of the catalyst system consisted of complex 2, [PhNHMe2][B(C6F5)4], and Al(i)Bu3 for isoprene polymerization, the resultant polymer has a high cis-1,4-selectivity up to 99.5%. The reaction temperature had little effect on the regioselectivity, and high cis-1,4-selectivity almost remained even at 80 °C.

20.
ACS Macro Lett ; 10(1): 135-140, 2021 Jan 19.
Artículo en Inglés | MEDLINE | ID: mdl-35548986

RESUMEN

The development of a controlled and reliable method to construct well-defined sulfur-containing polymers has sparked great interest in polymer science. Herein, we present the trial on the copolymerization of isothiocyanates with episulfides in the presence of organic onium salts, which provides direct access to a class of sulfur-rich polymers. This methodology has combined advantages of simple operation, no metals, mild conditions (25-100 °C), controlled polymerization performance (Mn > 105 g mol-1, D < 1.3), and high reactivity (turnover frequency over 1000 h-1). The metal-free feature and versatility of the easily accessible monomers, along with fine adjustment of the final properties enable this strategy to be a feasible approach to produce sulfur-rich polymers (16 examples).

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