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Takeshi Endo - One of the best experts on this subject based on the ideXlab platform.

Richard Hoogenboom - One of the best experts on this subject based on the ideXlab platform.

  • Cation−π Interactions Accelerate the Living Cationic Ring-Opening Polymerization of Unsaturated 2-Alkyl-2-oxazolines
    Macromolecules, 2020
    Co-Authors: Elias Van Den Broeck, Bart Verbraeken, Karen Dedecker, Pieter Cnudde, Louis Vanduyfhuys, Toon Verstraelen, Kristof Van Hecke, Valentin Victor Jerca, Saron Catak, Richard Hoogenboom
    Abstract:

    Cation–dipole interactions were previously shown to have a rate-enhancing effect on the Cationic Ring-Opening Polymerization (CROP) of 2-oxazolines bearing a side-chain ester functionality. In line...

  • macropropagation rate coefficients and branching levels in Cationic ring opening Polymerization of 2 ethyl 2 oxazoline through prediction of size exclusion chromatography data
    Macromolecules, 2019
    Co-Authors: Francisco J Arraez, Richard Hoogenboom, Valentin Victor Jerca, Xiaowen Xu, Paul H M Van Steenberge, Dagmar R Dhooge
    Abstract:

    A systematic kinetic study of the isothermal Cationic Ring-Opening Polymerization of 2-ethyl-2-oxazoline (EtOx) in acetonitrile initiated by methyl tosylate under microwave irradiation (353–413 K) for a target degree of Polymerization of 100 is reported as a basis for kinetic Monte Carlo simulations with parameters tuned based on monomer conversion and chain length data. It is highlighted that the size-exclusion chromatography (SEC) trace is needed to properly tune the less known macropropagation rate coefficient, which is related to the incorporation of enamine-terminated polymer chains resulting from chain transfer to monomer and which determines the contribution of linear and branched chains. A model-based design is applied to identify the reaction temperatures that lead to an optimum between the reaction time and control over molecular properties. A linear relationship is derived, which can be used to reliably assess the mass fraction of branched chains at sufficiently high monomer conversions based o...

  • Fluorinated 2‑Alkyl-2-oxazolines of High Reactivity: Spacer-Length-Induced Acceleration for Cationic Ring-Opening Polymerization As a Basis for Triphilic Block Copolymer Synthesis
    2017
    Co-Authors: Leonid I. Kaberov, Richard Hoogenboom, Bart Verbraeken, Anna Riabtseva, Jiri Brus, Yeshayahu Talmon, Petr Stepanek, Sergey K. Filippov
    Abstract:

    The synthesis of defined triphilic terpolymers with hydrophilic, lyophilic, and fluorophilic blocks is an important challenge as a basis for the development of multicompartment self-assembled structures with potential for, e.g., cascade catalysis and multidrug loading. The synthesis of fluorophilic poly­(2-oxazoline)­s generally suffers from a very low reactivity of fluorinated 2-oxazoline monomers in Cationic Ring-Opening Polymerization (CROP). We report a systematic study on overcoming the extremely low reactivity of 2-perfluoroalkyl-2-oxazolines in CROP by the insertion of methyl and ethyl hydrocarbon spacers between the 2-oxazoline ring and the trifluoromethyl group. The kinetic studies showed the gradual increase of the rate of Polymerization with increasing of the hydrocarbon spacer length. The monomer with an ethyl spacer was found to have similar reactivity as 2-alkyl-2-oxazolines and allowed the synthesis of defined triphilic triblock copolymers

  • sulfolane as common rate accelerating solvent for the Cationic ring opening Polymerization of 2 oxazolines
    ACS Macro Letters, 2015
    Co-Authors: Maarten Vergaelen, Bart Verbraeken, Bryn D Monnery, Richard Hoogenboom
    Abstract:

    The search for alternative solvents for the Cationic Ring-Opening Polymerization (CROP) of 2-methyl-2-oxazoline (MeOx) is driven by the poor solubility of P(MeOx) in Polymerization solvents such as acetonitrile (CH3CN) and chlorobenzene as well as in MeOx itself. In this study, solvent screening has revealed that especially sulfolane is a good solvent for PMeOx. Unexpectedly, an increased propagation rate constant (kp) was found for the CROP of MeOx in sulfolane. Further extended kinetic studies at different temperatures (60–180 °C), revealed that the acceleration is due to an increase in frequency factor, while the activation energy (Ea) of the reaction is hardly affected. In order to explore the versatility of sulfolane as Polymerization solvent for the CROP of 2-oxazolines in general, also the Polymerization kinetics of other 2-oxazoline monomers, such as 2-ethyl-2-oxazoline (EtOx) and 2-phenyl-2-oxazoline (PhOx), have been studied, revealing a common acceleration of the CROP of 2-oxazoline monomers in...

  • Systematic investigation of alkyl sulfonate initiators for the Cationic Ring-Opening Polymerization of 2-oxazolines revealing optimal combinations of monomers and initiators
    European Polymer Journal, 2015
    Co-Authors: Mathias Glassner, Bryn D Monnery, Dagmar R. D'hooge, Jin Young Park, Paul H. M. Van Steenberge, Marie-françoise Reyniers, Richard Hoogenboom
    Abstract:

    A systematic kinetic investigation of the living Cationic Ring-Opening Polymerization (CROP) involving 2-ethyl-2-oxazoline, 2-methyl-2-oxazoline, and 2-phenyl-2-oxazoline employing a series of alkyl sulfonate initiators with variation of the alkyl initiating fragment (methyl, ethyl, iso-propyl) and the leaving group/counterion (tosylate, nosylate, triflate) is reported. The study reveals that the initiation and propagation reactivity increases in the order tosylate < nosylate < triflate. Slow initiation is observed for EtOTs, while EtONs is a sufficiently fast initiator even for 2-phenyl-2-oxazoline. It is thus recommended to avoid the use of alkyl tosylates, except MeOTs, as initiators for the CROP of 2-alkyl-2-oxazolines. Although triflates are generally the best initiators, the use of the more stable and easier synthesizable nosylates provides a suitable alternative for the design of functional initiators for the CROP of 2-alkyl-2-oxazolines.

Ulrich S Schubert - One of the best experts on this subject based on the ideXlab platform.

  • Cationic ring opening Polymerization of protected oxazolidine imines resulting in gradient copolymers of poly 2 oxazoline and poly urea
    Polymer Chemistry, 2016
    Co-Authors: Meike N Leiske, Helmar Görls, Matthias Hartlieb, Fabian H Sobotta, Renzo M Paulus, Peter Bellstedt, Ulrich S Schubert
    Abstract:

    Poly(urea)s are a polymer class widely used in industry. Their utilization in biomedical applications is already described, however, the use of controlled Polymerization methods instead of polycondensation approaches would allow a better control over the degree of Polymerization and the dispersity of the resulting polymers, improving their suitability for this particular field of application. Cationic Ring-Opening Polymerization (CROP) as a chain growth Polymerization enables those requirements and, additionally, allows the coPolymerization with 2-oxazolines, which are generally known for their biocompatibility. In this report, a Boc protected oxazolidine imine monomer is synthesized and polymerized in a homoPolymerization, as well as in a coPolymerization with 2-ethyl-2-oxazoline (EtOx) via CROP. The synthesized polymers were analyzed regarding their chemical and physical properties, using NMR, GC, MALDI-MS, SEC, TGA and DSC. CoPolymerization kinetics revealed the formation of quasi-block copolymers, able to self-assemble in aqueous solution as indicated by DLS.

  • A Sugar Decorated Macromolecular Bottle Brush by Carbohydrate-Initiated Cationic Ring-Opening Polymerization
    Macromolecules, 2011
    Co-Authors: Christine Weber, Richard Hoogenboom, Justyna A. Czaplewska, Anja Baumgaertel, Esra Altuntaş, Michael Gottschaldt, Ulrich S Schubert
    Abstract:

    The capability of a range of protected glucose- (Glc), galactose- (Gal), and fructose- (Fru) based tosylates and triflates to initiate the living Cationic Ring-Opening Polymerization of 2-ethyl-2-oxazoline (EtOx) was investigated by detailed kinetic studies utilizing 1H and 19F NMR spectroscopy and SEC as well as MALDI and ESI TOF mass spectrometry. The Glc and Gal tosylates and a sterically hindered Fru triflate revealed slow and incomplete initiation, whereas the Glc and Gal triflates resulted in living Polymerizations. Well-defined Glc as well as Gal α-end-functionalized PEtOx was obtained after deprotection. Functionalization of the living oxazolinium chain ends with methacrylate anions resulted in a macromonomer that was applied for RAFT Polymerization. Deprotection resulted in a comb polymer that is selectively functionalized with Glc at the ends of all side chains (DPbackbone = 13, DPside chains = 10, PDI = 1.11).

  • efficient Cationic ring opening Polymerization of diverse cyclic imino ethers unexpected coPolymerization behavior
    Macromolecules, 2011
    Co-Authors: Hanneke M L Lambermontthijs, Ulrich S Schubert, Martin W M Fijten, A J Van Der Linden, Bart M Van Lankvelt, Meta M Bloksma, Richard Hoogenboom
    Abstract:

    The recently developed fast microwave-assisted Cationic Ring-Opening Polymerization procedure for 2-oxazolines seems to be ideally suited for slower polymerizing cyclic imino ether monomers. In this study we report the effect of the cyclic imino ether structure on the Polymerization rate under exactly the same microwave-assisted conditions revealing that indeed less reactive cyclic imino ethers, including 2-oxazines as well as 4- and 5-substituted 2-oxazolines, can be polymerized to at least 50% conversion for the slowest monomer, namely 5-methyl-2-butyl-2-oxazoline, within 10 h. In addition, the coPolymerization behavior of 4-ethyl-2-butyl-2-oxazoline with 2-methyl-2-oxazoline and 2-phenyl-2-oxazoline unexpectedly revealed faster incorporation of the less reactive 4-ethyl-2-butyl-2-oxazoline monomer compared to 2-phenyl-2-oxazoline due to the increased bulk of the latter monomer amplifying the sterical hindrance for Polymerization onto the 4-ethyl-2-butyl-2-oxazolinium propagating species.

  • synthesis of poly 2 ethyl 2 oxazoline b poly styrene copolymers via a dual initiator route combining Cationic ring opening Polymerization and atom transfer radical Polymerization
    Macromolecules, 2008
    Co-Authors: Remzi C Becer, Richard Hoogenboom, Renzo M Paulus, Charlesandre Fustin, Jeanfrancois Gohy, Stephanie Hoppener, Ulrich S Schubert
    Abstract:

    Block copolymers of 2-ethyl-2-oxazoline (EtOx) and styrene were synthesized by a combination of Cationic Ring-Opening Polymerization (CROP) and atom transfer radical Polymerization (ATRP). Initially, a detailed kinetic investigation for the alpha-bromoisobutyrylbromide (BrEBBr) initiated CROP of EtOx was performed in acetonitrile at different Polymerization temperatures ranging from 100 to 180 degrees C under microwave irradiation. Poly(2-ethyl-2-oxazoline) (PEtOx) homopolymers with controlled molecular weights and narrow polydispersity indices were synthesized in short reaction times. Polymers with relatively high molar masses and low polydispersity indices (M-n,M-SEC = 48 500 g/mol, PDI = 1.29) could also be obtained. Following the synthesis of a PEtOx macroinitiator (M-n,M-SEC = 3700 g/mol, PDI = 1.09), the ATRP of styrene was performed with CuBr and tris[2-(dimethylamino)ethyl]amine (Me(6)Tren) as catalytic system. The micellization behavior of the obtained amphiphilic block copolymers was further investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM).

  • Acetyl Halide Initiator Screening for the Cationic Ring‐Opening Polymerization of 2‐Ethyl‐2‐Oxazoline
    Macromolecular Chemistry and Physics, 2008
    Co-Authors: Renzo M Paulus, Richard Hoogenboom, C. Remzi Becer, Ulrich S Schubert
    Abstract:

    Kinetic investigations on the Cationic Ring-Opening Polymerization of 2-ethyl-2-oxazoline were conducted using acetyl chloride, acetyl bromide, and acetyl iodide as initiators. Various Polymerization temperatures ranging from 80 to 220 °C were applied under microwave irradiation. The resulting Polymerization mixtures were characterized with GC and GPC for the determination of monomer conversion and molecular weight distribution, respectively. Well defined polymers with narrow molecular weight distributions ( = 6 000 Dalton, PDI ≈ 1.10) were obtained with all three initiators.

Cai-yuan Pan - One of the best experts on this subject based on the ideXlab platform.

Valentin Victor Jerca - One of the best experts on this subject based on the ideXlab platform.