Living polymerization by suppressing chain transfer is a very useful method for achieving precise molecular weight and structure control. However, the suppression of chain transfer at high temperatures is extremely challenging in any catalytic polymerization. This has been a severe limitation for catalytic olefin polymerization, which is one of the most important chemical reactions. Here, we report the unprecedented living polymerization of ethylene at 130 °C, with a narrow molecular weight distribution range of 1.04 to 1.08. This is a significant increase in the reaction temperature. Tailor-made α-diimine nickel catalysts that exhibit both the steric shielding and fluorine effects play an essential role in this breakthrough. These nickel catalysts are even active at 200 °C, and enable the formation of semi-crystalline, ultrahigh-molecular-weight polyethylene at 150 °C. Mechanistic insights into the key chain transfer reaction are elucidated by density functional theory calculations.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1002/anie.202207363 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Silicone Composites with Electrically Oriented Boron Nitride Platelets and Carbon Microfibers for Thermal Management of Electronics.
Polymers (Basel)
January 2025
Faculty of Mechanics, University Politehnica of Timisoara, Piata Victoriei 2, 300006 Timisoara, Romania.
This study investigated silicone composites with distributed boron nitride platelets and carbon microfibers that are oriented electrically. The process involved homogenizing and dispersing nano/microparticles in the liquid polymer, aligning the particles with DC and AC electric fields, and curing the composite with IR radiation to trap particles within chains. This innovative concept utilized two fields to align particles, improving the even distribution of carbon microfibers among BN in the chains.
View Article and Find Full Text PDFElectrochemical Switching of Laser-Induced Graphene/Polymer Composites for Tunable Electronics.
Polymers (Basel)
January 2025
Research School of Chemical and Biomedical Technologies, Tomsk Polytechnic University, Lenin Ave. 30, 634050 Tomsk, Russia.
Laser reduction of graphene oxide (GO) is a promising approach for achieving flexible, robust, and electrically conductive graphene/polymer composites. Resulting composite materials show significant technological potential for energy storage, sensing, and bioelectronics. However, in the case of insulating polymers, the properties of electrodes show severely limited performance.
View Article and Find Full Text PDFAchieving a Near-Infrared Absorption by A-DA'D-A Type Isoindigo-Based Small Molecular Acceptors for Organic Photovoltaics.
Molecules
January 2025
School of Metallurgical and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China.
Isoindigo (IID)-based non-fullerene acceptors, known for their broad absorption spectra and high charge carrier mobilities, play a crucial role in organic photovoltaics. In this study, two A-DA'D-A type unfused ring acceptors (URAs), IDC8CP-IC and IDC6CP-IC, were designed and synthesized using cyclopentadithiophene (CPDT) and IID core units, each functionalized with different alkyl chains (2-hexyldecyl and 2-octyldodecyl), through an atom- and step-efficient direct C-H arylation (DACH) method. Both URAs, despite the absence of non-covalent conformation locking between CPDT and IID, demonstrated favorable molecular planarity, broad absorption ranges, low band gaps, and high molar absorption coefficients.
View Article and Find Full Text PDFExploring the Gating Mechanism of the Human Copper Transporter, hCtr1, Using EPR Spectroscopy.
Biomolecules
January 2025
Department of Chemistry and Institute of Nanotechnology and Advanced Materials, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
Ctr1 is a membrane-spanning homotrimer that facilitates copper uptake in eukaryotic cells with high affinity. While structural details of the transmembrane domain of human Ctr1 have been elucidated using X-ray crystallography and cryo-EM, the transfer mechanisms of copper and the conformational changes that control the gating mechanism remain poorly understood. The role of the extracellular N-terminal domains is particularly unclear due to the absence of a high-resolution structure of the full-length hCtr1 protein and limited biochemical and biophysical characterization of the transporter in solution and in cell.
View Article and Find Full Text PDFEvaluating Ecosystem Characteristics and Ecological Carrying Capacity for Marine Fauna Stock Enhancement Within a Marine Ranching System.
Animals (Basel)
January 2025
Laboratory for Marine Science and Technology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China.
China has recently launched extensive marine ranching projects, highlighting the need for scientific evaluation of ecosystem structure and function to guide their development. This study established two energy flow models and an evaluation index system to assess the structure, function, carrying capacity, and ecological status of both a marine ranching ecosystem and a nearby control site in the Beibu Gulf. The results show that the ranching ecosystem outperformed the control ecosystem in terms of food chain length, system size, and ecological carrying capacity of economically important species.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!