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  High-Speed Living Polymerization of Polar Vinyl Monomers by Self-Healing Silylium Catalysts

Zhang, Y., Lay, F., García-García, P., List, B., & Chen, E.-Y.-X. (2010). High-Speed Living Polymerization of Polar Vinyl Monomers by Self-Healing Silylium Catalysts. Chemistry – A European Journal, 16(34), 10462-10473. doi:10.1002/chem.201000961.

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 Creators:
Zhang, Yuetao1, Author
Lay, Frank2, Author              
García-García, Pilar2, Author              
List, Benjamin2, Author              
Chen, Eugene Y.-X.1, Author
Affiliations:
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523‐1872 (USA), ou_persistent22              
2Research Department List, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445585              

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Free keywords: anions; Bronsted acids; polar vinyl monomers; polymerization; silicon
 Abstract: This contribution describes the development and demonstration of the ambient‐temperature, high‐speed living polymerization of polar vinyl monomers (M) with a low silylium catalyst loading (≤ 0.05 mol % relative to M). The catalyst is generated in situ by protonation of a trialkylsilyl ketene acetal (RSKA) initiator (I) with a strong Brønsted acid. The living character of the polymerization system has been demonstrated by several key lines of evidence, including the observed linear growth of the chain length as a function of monomer conversion at a given [M]/[I] ratio, near‐precise polymer number‐average molecular weight (Mn, controlled by the [M]/[I] ratio) with narrow molecular weight distributions (MWD), absence of an induction period and chain‐termination reactions (as revealed by kinetics), readily achievable chain extension, and the successful synthesis of well‐defined block copolymers. Fundamental steps of activation, initiation, propagation, and catalyst “self‐repair” involved in this living polymerization system have been elucidated, chiefly featuring a propagation “catalysis” cycle consisting of a rate‐limiting C-C bond formation step and fast release of the silylium catalyst to the incoming monomer. Effects of acid activator, catalyst and monomer structure, and reaction temperature on polymerization characteristics have also been examined. Among the three strong acids incorporating a weakly coordinating borate or a chiral disulfonimide anion, the oxonium acid [H(Et2O)2]+[B(C6F5)4] is the most effective activator, which spontaneously delivers the most active R3Si+, reaching a high catalyst turn‐over frequency (TOF) of 6.0×103 h−1 for methyl methacrylate polymerization by Me3Si+ or an exceptionally high TOF of 2.4×105 h−1 for n‐butyl acrylate polymerization by iBu3Si+, in addition to its high (>90 %) to quantitative efficiencies and a high degree of control over Mn and MWD (1.07–1.12). An intriguing catalyst “self‐repair” feature has also been demonstrated for the current living polymerization system.

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Language(s): eng - English
 Dates: 2010-04-152010-07-212010-09-10
 Publication Status: Published in print
 Pages: 12
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1002/chem.201000961
 Degree: -

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Title: Chemistry – A European Journal
  Other : Chem. – Eur. J.
  Other : Chem. Eur. J.
Source Genre: Journal
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Publ. Info: Weinheim : Wiley-VCH
Pages: - Volume / Issue: 16 (34) Sequence Number: - Start / End Page: 10462 - 10473 Identifier: ISSN: 0947-6539
CoNE: https://pure.mpg.de/cone/journals/resource/954926979058