chain walkinga new strategy to control polymer

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Chain Walking:A New Strategy to Control Polymer

Chain Walking:A New Strategy to Control Polymer Topology Zhibin Guan,* P. M. Cotts, E. F. McCord, S. J. McLain Ethylene pressure has been used to control the competition between isomer-ization (chain walking) and monomer insertion processes for ethylene coordi-nation polymerization catalyzed by a palladium-cx-diimine catalyst. The topol- Chain Walking:A New Strategy to Control Polymer Topology Mar 01, 1999 · adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A ERRATUM Control of Polymer Topology through Late aration of new functional materials. CHAIN WALKING:A NEW STRATEGY FOR CONTROLLING POLYMER TOPOLOGY In our second strategy,5456 we successfully con-trolled PE topology by regulating the competition between propagation and chain walking for eth-ylene polymerization with a chain-walking cata-lyst. Our work is based on the discovery of PdII- Synthesis of Necklace Polymers by Chain-Walking Polymer chain architecture is a critically important chain parameter governing intrinsically the properties and applications of polymers. Chain Walking:A New Strategy to Control Polymer Secondary Alkene Insertion and Precision Chain-Walking:A The desired process involves two relatively uncommon mechanistic steps:(1) a regioselective 2,1-olefin insertion and (2) controlled chain-walkinga series of sequential -hydride eliminations, alkene rotations, and reinsertions that relocates the active metal center along the growing polymer chain. Polymerization Catalysts Take a Walk on the Wild Side In olefin polymerization, polymer propagation and chain walking are promoted by:(i) catalyst coordination to the orbital of an olefin, and (ii) catalyst activation via -agostic interactions with hydrogen atoms on the polymer backbone. The ability to polymerize readily from unactivated olefins enables olefin polymerization to tolerate a wide variety of functional groups. Zhibin Guan - Google Scholar858. 2012. Chain walking:a new strategy to control polymer topology. Z Guan, PM Cotts, EF McCord, SJ McLain. Science 283 (5410), 2059-2062. , 1999. 746. 1999. Malleable and self-healing covalent polymer networks through tunable dynamic boronic ester bonds. interaction effect in insertion polymerization with Oct 01, 2019 · Recently, Chen et al. installed the sterically bulkier diarylmethyl moiety (CHAr 2) on the -diimine Pd(II) catalysts to improve thermal stabilities of catalysts as well as physical properties of polymer products, enabling slow-chain walking (co)polymerizations , , (Chart 1, IV). Most recently, Jian et al. reported the pentiptycenyl-based -diimine Pd(II) catalysts. Ligand-Enabled NiH-Catalyzed Migratory Hydroamination

  • IntroductionResults and DiscussionConclusionThe direct and site-selective functionalization of ubiquitous CH bonds has the potential to streamline synthetic routes substantially.1 Despite notable recent efforts in CH functionalization, the regioselective functionalization of alkyl chains, in particular, remains an important synthetic challenge. Many reported protocols for sp3CH functionalization require the assistance of specialized polar-directing groups to achieve the desired regiochemical outcome and to improve reactivity. This limits their generality and ap2001 Chemistry of Supramolecules and Assemblies Jul 29, 2001 · The 2001 Gordon Research Conference on Chemistry of Supramolecules and Assemblies will be held in New London, CT. Apply today to reserve your spot. Frontiers of Science. Templating of Micelles or Polymer/Surfactant Interactions Bjorn Lindman Chain Walking:A New Strategy to Control Polymer Topology Wednesday Morning 1 August 2001: Chain-topology-controlled hyperbranched polyethylene as Jan 02, 2008 · The hyperbranched polymer, HBPE, forms phase-separated droplets, which can migrate to the die surface and form a lubricating layer promoting extrudate slippage. By identifying the effect of chain topology on the polymers performance, this work may provide a chain-topology guideline for designing polymer-based processing aids. (PDF) Monte-Carlo simulation of branching distribution in In this process the active site moves from the terminal carbon in the polymer chain to the next carbon in the backbone. This chain-walking step can be repeated several times before monomer is added to the chain or the chain is terminated. A monomer insertion after a chain-walking step produces a branch. Facile synthesis and linker guided self-assembly of Mar 22, 2019 · For example, the cyclic polymers exhibit higher glass transition temperatures (T g), smaller hydrodynamic volumes, as well as lower degree of entanglement, Chain walking:a new strategy to control polymer topology. Science, 283 (5410) (1999), pp. 2059-2062. View Record in Scopus Google Scholar. Polymers Free Full-Text Direct Synthesis of Branched In this work, we studied propylene polymerization using some -diimine palladium catalysts with systematically varied ligand sterics. In propylene polymerization, the ligand steric effect exhibits significant variations on the catalytic activity, polymer molecular weight, and branching density. However, the regio control for the polymer microstructure is poor. Furthermore, copolymerization of UC Irvine - Faculty Profile System - Zhibin GuanMay 18, 2016 · Currently, we are pursuing two directions of biomedical studies with our new biomaterials. In one study, we are developing stimuli-responsive nanogels as vectors for efficient siRNA delivery. In another direction, we are designing saccharide-peptide based hydrogels as biomimetic extracellular matrices (ECMs) to control stem cell differentiation. Polymers Free Full-Text Influences of Alkyl and Aryl A series of alkyl- and aryl-substituted iminopyridine Fe(II) complexes 1a7a and Co(II) complexes 2b, 3b, 5b, and 6b were synthesized. The activator effect, influence of temperature, and, particularly, the alkyl and aryl substituents effect on catalytic activity, polymer molecular weight, and regio-/stereoselectivity were investigated when these complexes were applied in isoprene Ligand-Enabled NiH-Catalyzed Migratory Hydroamination Sep 01, 2021 · Create a new account. Email. Returning user Cotts P. M.; McCord E. F.; McLain S. J. Chain Walking:A New Strategy to Control Polymer Topology. Science 1999, 283, 2059 Kochi T. Chain Walking as a Strategy for CarbonCarbon Bond Formation at Unreactive Sites in Organic Synthesis:Catalytic Cycloisomerization of Various 1 Synergistic effect and fluorination effect in ethylene Nov 24, 2017 · A series of binuclear nickel phenoxyiminato catalysts with different linkers and fluorine substituents were efficiently synthesized. Binuclear nickel catalysts with rigid linkers showed higher catalytic activity and thermal stability in ethylene polymerization and produced polymers with higher molecular weight possibly due to the larger steric hindrance and metal-metal synergistic effect. The

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