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Haug I, Reitz J, Ziane C, Buchmeiser MR, Hansmann MM, Naumann S. Mesoionic N-Heterocyclic Olefins as Initiators for the Lewis Pair Polymerization of Epoxides. Macromol Rapid Commun 2024; 45:e2300716. [PMID: 38497903 DOI: 10.1002/marc.202300716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 03/14/2024] [Indexed: 03/19/2024]
Abstract
Mesoionic N-heterocyclic olefins (mNHOs) have recently emerged as a novel class of highly nucleophilic and super-basic σ-donor compounds. Making use of these properties in synthetic polymer chemistry, it is shown that a combination of a specific mNHO and a Mg-based Lewis acid (magnesium bis(hexamethyldisilazide), Mg(HMDS)2) delivers poly(propylene oxide) in quantitative yields from the polymerization of the corresponding epoxide (0.1 mol% mNHO loading). The initiation mechanism involves monomer activation by the Lewis acid and direct ring-opening of the monomer by nucleophilic attack of the mNHO, forming a zwitterionic propagating species. Modulation of the mNHO properties is thereby a direct tool to impact initiation efficiency, revealing a sterically unencumbered triazole-derivative as particularly useful. The joint application of mNHOs together with borane-type Lewis acids is also outlined, resulting in high conversions and fast polymerization kinetics. Importantly, while molar mass distributions remain relatively broad, indicating faster propagation than initiation, the overall molar masses are significantly lower than found in the case of regular NHOs, underlining the increased nucleophilicity and ensuing improved initiation efficiency of mNHOs.
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Affiliation(s)
- Iris Haug
- University of Stuttgart, Institute of Polymer Chemistry, 70569, Stuttgart, Germany
| | - Justus Reitz
- TU Dortmund, Faculty for Chemistry and Chemical Biology, 44227, Dortmund, Germany
| | - Célia Ziane
- University of Stuttgart, Institute of Polymer Chemistry, 70569, Stuttgart, Germany
| | - Michael R Buchmeiser
- University of Stuttgart, Institute of Polymer Chemistry, 70569, Stuttgart, Germany
| | - Max M Hansmann
- TU Dortmund, Faculty for Chemistry and Chemical Biology, 44227, Dortmund, Germany
| | - Stefan Naumann
- University of Stuttgart, Institute of Polymer Chemistry, 70569, Stuttgart, Germany
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Czysch C, Dinh T, Fröder Y, Bixenmann L, Komforth P, Balint A, Räder HJ, Naumann S, Nuhn L. Nontoxic N-Heterocyclic Olefin Catalyst Systems for Well-Defined Polymerization of Biocompatible Aliphatic Polycarbonates. ACS POLYMERS AU 2022; 2:371-379. [PMID: 36855582 PMCID: PMC9955374 DOI: 10.1021/acspolymersau.2c00017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 06/30/2022] [Accepted: 07/05/2022] [Indexed: 11/28/2022]
Abstract
Herein, N-heterocyclic olefins (NHOs) are utilized as catalysts for the ring-opening polymerization (ROP) of functional aliphatic carbonates. This emerging class of catalysts provides high reactivity and rapid conversion. Aiming for the polymerization of monomers with high side chain functionality, six-membered carbonates derived from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) served as model compounds. Tuning the reactivity of NHO from predominant side chain transesterification at room temperature toward ring-opening at lowered temperatures (-40 °C) enables controlled ROP. These refined conditions give narrowly distributed polymers of the hydrophobic carbonate 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MTC-OBn) (Đ < 1.30) at (pseudo)first-order kinetic polymerization progression. End group definition of these polymers demonstrated by mass spectrometry underlines the absence of side reactions. For the active ester monomer 5-methyl-5-pentafluorophenyloxycarbonyl-1,3-dioxane-2-one (MTC-PFP) with elevated side chain reactivity, a cocatalysis system consisting of NHO and the Lewis acid magnesium iodide is required to retune the reactivity from side chains toward controlled ROP. Excellent definition of the products (Đ < 1.30) and mass spectrometry data demonstrate the feasibility of this cocatalyst approach, since MTC-PFP has thus far only been polymerized successfully using acidic catalysts with moderate control. The broad feasibility of our findings was further demonstrated by the synthesis of block copolymers for bioapplications and their successful nanoparticular assembly. High tolerability of NHO in vitro with concentrations ranging up to 400 μM (equivalent to 0.056 mg/mL) further emphasize the suitability as a catalyst for the synthesis of bioapplicable materials. The polycarbonate block copolymer mPEG44-b-poly(MTC-OBn) enables physical entrapment of hydrophobic dyes in sub-20 nm micelles, whereas the active ester block copolymer mPEG44-b-poly(MTC-PFP) is postfunctionalizable by covalent dye attachment. Both block copolymers thereby serve as platforms for physical or covalent modification of nanocarriers for drug delivery.
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Affiliation(s)
- Christian Czysch
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Thi Dinh
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yannick Fröder
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Leon Bixenmann
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Patric Komforth
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Alexander Balint
- Institute
of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Hans-Joachim Räder
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Stefan Naumann
- Institute
of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Lutz Nuhn
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany,Chair
of Macromolecular Chemistry, Julius-Maximilians-Universität
Würzburg, Röntgenring
11, 97070 Würzburg, Germany,
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3
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Guthardt R, Mellin J, Bruhn C, Siemeling U. 1,1′‐Ferrocenylene‐Bridged Bis(N‐Heterocyclic Olefin) Derivatives. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Robin Guthardt
- Institut für Chemie Universität Kassel Heinrich-Plett-Straße 40 34132 Kassel Germany
| | - Johanna Mellin
- Institut für Chemie Universität Kassel Heinrich-Plett-Straße 40 34132 Kassel Germany
| | - Clemens Bruhn
- Institut für Chemie Universität Kassel Heinrich-Plett-Straße 40 34132 Kassel Germany
| | - Ulrich Siemeling
- Institut für Chemie Universität Kassel Heinrich-Plett-Straße 40 34132 Kassel Germany
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