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Nathaniel A Lynd - One of the best experts on this subject based on the ideXlab platform.

  • statistical copolymerization of epoxides and lactones to high molecular weight
    Macromolecules, 2017
    Co-Authors: Malgorzata Chwatko, Nathaniel A Lynd
    Abstract:

    Copolymerization provides a modular strategy for compositional control of structure–property relationships in polymeric materials. However, this versatility is typically limited to structurally homologous comonomers. To further expand the scope of copolymerization in heterocyclic systems, we explored the copolymerization of structurally distinct lactones and epoxides utilizing the classical Vandenberg catalyst. Copolymerizations were conducted between monomer pairs selected from among two common lactones (dl-lactide, e-caprolactone) and four epoxides (epichlorohydrin, butylene oxide, propylene oxide, ethylene oxide). The resultant materials had molecular weights of up to 16 Mg/mol. Reactivity ratios were determined for the copolymerization of dl-lactide and propylene oxide, which were consistent with a gradient copolymer with propylene oxide (PO) being the preferred monomer: rPO = 2.81 ± 0.27 and rLA = 0.36 ± 0.02. The copolymerization between e-caprolactone and propylene oxide was also monitored by 1H NM...

  • reactivity ratios and mechanistic insight for anionic ring opening copolymerization of epoxides
    Macromolecules, 2012
    Co-Authors: Martin Wolffs, Kris T Delaney, Johannes K Sprafke, Frank A Leibfarth, Craig J Hawker, Nathaniel A Lynd
    Abstract:

    Reactivity ratios were evaluated for anionic ring-opening Copolymerizations of ethylene oxide (EO) with either allyl glycidyl ether (AGE) or ethylene glycol vinyl glycidyl ether (EGVGE) using a benzyl alkoxide initiator. The chemical shift for the benzylic protons of the initiator, as measured by 1H NMR spectroscopy, were observed to be sensitive to the sequence of the first two monomers added to the initiator during polymer growth. Using a simple kinetic model for initiation and the first propagation step, reactivity ratios for the copolymerization of AGE and EGVGE with EO could be determined by analysis of the 1H NMR spectroscopy for the resulting copolymer. For the copolymerization between EO and AGE, the reactivity ratios were determined to be rAGE = 1.31 ± 0.26 and rEO = 0.54 ± 0.03, while for EO and EGVGE, the reactivity ratios were rEGVGE = 3.50 ± 0.90 and rEO = 0.32 ± 0.10. These ratios were consistent with the compositional drift observed in the copolymerization between EO and EGVGE, with EGVGE b...

  • Reactivity Ratios and Mechanistic Insight for Anionic Ring-Opening Copolymerization of Epoxides
    Macromolecules, 2012
    Co-Authors: Bongjae F. Lee, Martin Wolffs, Kris T Delaney, Johannes K Sprafke, Frank A Leibfarth, Craig J Hawker, Nathaniel A Lynd
    Abstract:

    Reactivity ratios were evaluated for anionic ring-opening Copolymerizations of ethylene oxide (EO) with either allyl glycidyl ether (AGE) or ethylene glycol vinyl glycidyl ether (EGVGE) using a benzyl alkoxide initiator. The chemical shift for the benzylic protons of the initiator, as measured by 1H NMR spectroscopy, were observed to be sensitive to the sequence of the first two monomers added to the initiator during polymer growth. Using a simple kinetic model for initiation and the first propagation step, reactivity ratios for the copolymerization of AGE and EGVGE with EO could be determined by analysis of the 1H NMR spectroscopy for the resulting copolymer. For the copolymerization between EO and AGE, the reactivity ratios were determined to be rAGE = 1.31 ± 0.26 and rEO = 0.54 ± 0.03, while for EO and EGVGE, the reactivity ratios were rEGVGE = 3.50 ± 0.90 and rEO = 0.32 ± 0.10. These ratios were consistent with the compositional drift observed in the copolymerization between EO and EGVGE, with EGVGE b...

Holger Frey - One of the best experts on this subject based on the ideXlab platform.

  • The poly(propylene oxide-co-ethylene oxide) gradient is controlled by the polymerization method: determination of reactivity ratios by direct comparison of different copolymerization models
    Polymer Chemistry, 2019
    Co-Authors: Jan Blankenburg, Manfred Wagner, Erik Kersten, Kamil Maciol, Sirus Zarbakhsh, Holger Frey
    Abstract:

    An investigation of the highly relevant copolymerization of ethylene oxide (EO) and propylene oxide (PO) by in situ1H NMR spectroscopy shows striking differences in the copolymerization kinetics, depending on the polymerization method. Examination of the EO/PO copolymerization kinetics using iBu3Al for the monomer-activated anionic ring opening polymerization (AROP) confirmed a strong monomer gradient of the microstructure (rEO = 6.4, rPO = 0.16) in contrast to the known weak gradient in the conventional AROP (rEO = 2.8, rPO = 0.25). The first study via in situ1H-NMR kinetics of the copolymerization of PO and EO under heterogeneous double metal cyanide (DMC) catalysis, a method that produces megatons of polyether polyols in industry, revealed a reversal of the monomer gradient (rEO = 0.42, rPO = 2.4). Thus, the copolymer microstructure of these polyether copolymers can be specifically adjusted depending on the choice of the polymerization method. The in situ1H NMR kinetics data were fitted to both the non-terminal and terminal copolymerization models. To directly compare the fits of both models, a new copolymerization equation for the non-terminal model was derived by solving the Skeist-relation analytically in analogy to the Meyer–Lowry equation. This newly derived equation allows the direct comparison of both models without transformation of the in situ data for the first time. Thus, the ideal integrated equation can help to recognize overfitting of copolymerization data. Furthermore, the equation was proven to give good estimates for reactivity ratios of ideal Copolymerizations, even when systematic errors were introduced. Additionally, the obtained reactivity ratios were used to perform kinetic Monte Carlo simulations to visualize the EO/PO copolymer microstructure and to determine the nature of the terminal monomer unit.

  • monomer sequence distribution monitoring in living carbanionic copolymerization by real time h 1 nmr spectroscopy
    Macromolecules, 2013
    Co-Authors: Adrian Natalello, Mathias Werre, Arda Alkan, Holger Frey
    Abstract:

    Detailed understanding of the monomer sequence distribution in carbanionic copolymerization was achieved by direct online monitoring of Copolymerizations in an NMR tube. Obtaining detailed knowledge of the changing monomer concentration in stock during the reaction, this technique permits to determine the incorporation probability for each monomer at every position of the polymer chain. An in situ kinetic study of two different carbanionic Copolymerizations has been carried out. On the one hand, the copolymerization of the structurally similar, protected hydroxystyrene derivatives, p-(1-ethoxy ethoxy)styrene (pEES) and 4-tert-butoxystyrene (tBuOS), and on the other hand the copolymerization of the chemically different monomers, styrene (S) and pEES, have been studied. Whereas in the first case a slight deviation from an ideal random copolymerization was observed, the latter copolymerization leads to gradient copolymers. Real-time 1H NMR spectroscopy gave detailed insight into the reaction behavior at ever...

  • Monomer Sequence Distribution Monitoring in Living Carbanionic Copolymerization by Real-Time 1H NMR Spectroscopy
    2013
    Co-Authors: Adrian Natalello, Mathias Werre, Arda Alkan, Holger Frey
    Abstract:

    Detailed understanding of the monomer sequence distribution in carbanionic copolymerization was achieved by direct online monitoring of Copolymerizations in an NMR tube. Obtaining detailed knowledge of the changing monomer concentration in stock during the reaction, this technique permits to determine the incorporation probability for each monomer at every position of the polymer chain. An in situ kinetic study of two different carbanionic Copolymerizations has been carried out. On the one hand, the copolymerization of the structurally similar, protected hydroxystyrene derivatives, p-(1-ethoxy ethoxy)­styrene (pEES) and 4-tert-butoxystyrene (tBuOS), and on the other hand the copolymerization of the chemically different monomers, styrene (S) and pEES, have been studied. Whereas in the first case a slight deviation from an ideal random copolymerization was observed, the latter copolymerization leads to gradient copolymers. Real-time 1H NMR spectroscopy gave detailed insight into the reaction behavior at every stage of the copolymerization and leads to precise understanding of the resulting gradient structures

Shengyu Dai - One of the best experts on this subject based on the ideXlab platform.

  • palladium catalyzed direct synthesis of various branched carboxylic acid functionalized polyolefins characterization derivatization and properties
    Macromolecules, 2018
    Co-Authors: Shengyu Dai, Changle Chen
    Abstract:

    Ethylene-co-acrylic acid (E–AA) copolymers are typically produced via high-pressure free radical copolymerization and have great industrial importance because of their many applications. The radical polymerization mechanism usually leads to highly branched products with poor mechanical properties. Transition-metal-catalyzed E–AA copolymerization represents a direct and economical route to access these copolymers with potentially better control over their microstructures and material properties. However, this is highly challenging due to catalyst poisoning from both the oxygen and carboxylic acid moieties in the monomers. In this contribution, we demonstrate that a series of α-diimine-based palladium catalysts can mediate efficient Copolymerizations of ethylene with AA, allylacetic acid, and 10-undecenoic acid, leading to the formation of various branched, carboxylic acid-functionalized polyolefin materials. These comonomers exist as carboxylic acid-based dimeric species at ambient temperatures, which is p...

  • Palladium-Catalyzed Direct Synthesis of Various Branched, Carboxylic Acid-Functionalized Polyolefins: Characterization, Derivatization, and Properties
    2018
    Co-Authors: Shengyu Dai, Changle Chen
    Abstract:

    Ethylene-co-acrylic acid (E–AA) copolymers are typically produced via high-pressure free radical copolymerization and have great industrial importance because of their many applications. The radical polymerization mechanism usually leads to highly branched products with poor mechanical properties. Transition-metal-catalyzed E–AA copolymerization represents a direct and economical route to access these copolymers with potentially better control over their microstructures and material properties. However, this is highly challenging due to catalyst poisoning from both the oxygen and carboxylic acid moieties in the monomers. In this contribution, we demonstrate that a series of α-diimine-based palladium catalysts can mediate efficient Copolymerizations of ethylene with AA, allylacetic acid, and 10-undecenoic acid, leading to the formation of various branched, carboxylic acid-functionalized polyolefin materials. These comonomers exist as carboxylic acid-based dimeric species at ambient temperatures, which is proposed as the key reason for the successful Copolymerizations. These polar, functionalized polyolefins demonstrate greatly improved surface properties based on water contact angle measurements and dyeing experiments. Furthermore, these copolymers can be converted to sodium-, zinc-, and iron-based ionomers. The metal ions can act as physical cross-links and dramatically improve the mechanical properties of these copolymers

Stefan Mecking - One of the best experts on this subject based on the ideXlab platform.

  • Long-Spaced Polyketones from ADMET Copolymerizations as Ideal Models for Ethylene/CO Copolymers
    ACS Macro Letters, 2015
    Co-Authors: Patrick Ortmann, Florian P. Wimmer, Stefan Mecking
    Abstract:

    Long-spaced polyketones containing 0–52.6 ketone groups per 1000 methylene units were prepared by ADMET copolymerization of docosa-1,21-dien-11-one (1) with undeca-1,10-diene (2), followed by exhaustive hydrogenation. Melting point differences of 5–10 °C were found between these polyketones and their reported congeners from ethylene/CO Copolymerizations with comparable CO contents, which were related to additional methyl branching occurring in insertion copolymerization. Consequently, ADMET-derived polyketones can act as defect-free model polyketones. Comparison with polymers containing the same degrees of other carbonyl functionalities (esters, carbonates) shows that the partial compensation of the disturbance of polyethylene crystallization goes along with the groups’ polarity.

  • long spaced polyketones from admet Copolymerizations as ideal models for ethylene co copolymers
    ACS Macro Letters, 2015
    Co-Authors: Patrick Ortmann, Florian P. Wimmer, Stefan Mecking
    Abstract:

    Long-spaced polyketones containing 0–52.6 ketone groups per 1000 methylene units were prepared by ADMET copolymerization of docosa-1,21-dien-11-one (1) with undeca-1,10-diene (2), followed by exhaustive hydrogenation. Melting point differences of 5–10 °C were found between these polyketones and their reported congeners from ethylene/CO Copolymerizations with comparable CO contents, which were related to additional methyl branching occurring in insertion copolymerization. Consequently, ADMET-derived polyketones can act as defect-free model polyketones. Comparison with polymers containing the same degrees of other carbonyl functionalities (esters, carbonates) shows that the partial compensation of the disturbance of polyethylene crystallization goes along with the groups’ polarity.

Changle Chen - One of the best experts on this subject based on the ideXlab platform.

  • palladium catalyzed direct synthesis of various branched carboxylic acid functionalized polyolefins characterization derivatization and properties
    Macromolecules, 2018
    Co-Authors: Shengyu Dai, Changle Chen
    Abstract:

    Ethylene-co-acrylic acid (E–AA) copolymers are typically produced via high-pressure free radical copolymerization and have great industrial importance because of their many applications. The radical polymerization mechanism usually leads to highly branched products with poor mechanical properties. Transition-metal-catalyzed E–AA copolymerization represents a direct and economical route to access these copolymers with potentially better control over their microstructures and material properties. However, this is highly challenging due to catalyst poisoning from both the oxygen and carboxylic acid moieties in the monomers. In this contribution, we demonstrate that a series of α-diimine-based palladium catalysts can mediate efficient Copolymerizations of ethylene with AA, allylacetic acid, and 10-undecenoic acid, leading to the formation of various branched, carboxylic acid-functionalized polyolefin materials. These comonomers exist as carboxylic acid-based dimeric species at ambient temperatures, which is p...

  • Palladium-Catalyzed Direct Synthesis of Various Branched, Carboxylic Acid-Functionalized Polyolefins: Characterization, Derivatization, and Properties
    2018
    Co-Authors: Shengyu Dai, Changle Chen
    Abstract:

    Ethylene-co-acrylic acid (E–AA) copolymers are typically produced via high-pressure free radical copolymerization and have great industrial importance because of their many applications. The radical polymerization mechanism usually leads to highly branched products with poor mechanical properties. Transition-metal-catalyzed E–AA copolymerization represents a direct and economical route to access these copolymers with potentially better control over their microstructures and material properties. However, this is highly challenging due to catalyst poisoning from both the oxygen and carboxylic acid moieties in the monomers. In this contribution, we demonstrate that a series of α-diimine-based palladium catalysts can mediate efficient Copolymerizations of ethylene with AA, allylacetic acid, and 10-undecenoic acid, leading to the formation of various branched, carboxylic acid-functionalized polyolefin materials. These comonomers exist as carboxylic acid-based dimeric species at ambient temperatures, which is proposed as the key reason for the successful Copolymerizations. These polar, functionalized polyolefins demonstrate greatly improved surface properties based on water contact angle measurements and dyeing experiments. Furthermore, these copolymers can be converted to sodium-, zinc-, and iron-based ionomers. The metal ions can act as physical cross-links and dramatically improve the mechanical properties of these copolymers