The Experts below are selected from a list of 20274 Experts worldwide ranked by ideXlab platform
Richard Hoogenboom - One of the best experts on this subject based on the ideXlab platform.
-
the chemistry of poly 2 Oxazoline s
European Polymer Journal, 2017Co-Authors: Bart Verbraeken, Bryn D Monnery, Kathleen Lava, Richard HoogenboomAbstract:Abstract As we celebrate the 50th birthday of the discovery of poly(2-alkyl/aryl-2-Oxazoline)s (PAOx) this year we see a research field that is rapidly expanding after some lesser academic activity in the nineties. This renewed interest in PAOx stems from the fact that this polymer class combines high synthetic versatility with good biocompatibility, opening up the way to highly functional (biocompatible) materials. PAOx are prepared by living cationic ring-opening polymerization (CROP) of 2-Oxazolines, which will be the in-depth focus off this review. The variety of 2-Oxazoline monomers that are readily available or can easily be synthesized, allows for tuning of polymer properties and introduction of diverse functionalities as well as provides access to different polymer architectures. Moreover, thanks to the living nature of the CROP, well-defined polymers with narrow molar mass distribution and high end-group fidelity can be obtained.
-
poly 2 ethyl 2 Oxazoline block polycarbonate block copolymers from improved end group control in poly 2 Oxazoline s to chain extension with aliphatic polycarbonate through a fully metal free ring opening polymerisation process
Polymer Chemistry, 2016Co-Authors: Victor Retamero De La Rosa, Richard Hoogenboom, Sarah Tempelaar, Philippe Dubois, Laetitia MespouilleAbstract:Block copolymer micelles hold great promise for developing next generation drug delivery vehicles to improve therapeutics. In this work, the biocompatibility of poly(2-alkyl-2-Oxazoline)s (PAOx) was combined with the biodegradability and biocompatibility of aliphatic polycarbonates through the preparation of block copolymers. These well-defined blocks were prepared via cationic ring-opening polymerisation (CROP) of 2-Oxazolines followed by the organocatalytic ring-opening polymerisation (ROP) of cyclic carbonate monomers. The improved synthesis of hydroxyl terminated poly(2-ethyl-2-Oxazoline)s (PEtOx-OH) is reported allowing high end-group fidelity. These polymers were used as macroinitiators in the controlled ROP of various cyclic carbonate monomers (TMC and benzyl, allyl, propargyl, bromide and morpholino functional monomers) resulting in well-defined amphiphilic block copolymers.
-
Microwave-assisted cationic ring-opening polymerization of 2-Oxazolines.
Advances in polymer science = Fortschritte der Hochpolymeren-Forschung, 2015Co-Authors: Klaus Peter Luef, Richard Hoogenboom, Ulrich S. Schubert, Frank WiesbrockAbstract:More than any other polymer class, the synthesis of (co-)poly(2-Oxazoline)s has benefited tremendously from the introduction of microwave reactors into chemical laboratories. This review focuses on research activities in the area of (co-)poly(2-Oxazoline)s prepared by microwave-assisted syntheses and summarizes the current state-of-the-art for microwave-assisted syntheses of 2-Oxazoline monomers, microwave-assisted ring-opening (co-)polymerizations of 2-Oxazolines, and prominent examples of post-polymerization modifications of (co-)poly(2-Oxazoline)s. Special attention is paid to kinetic analyses of the microwave-assisted polymerization of 2-Oxazolines and to the discussion of non-thermal microwave effects.
-
Model-Based Visualization and Understanding of Monomer Sequence Formation in Gradient Copoly(2-Oxazoline)s On the basis of 2-Methyl-2-Oxazoline and 2-Phenyl-2-Oxazoline
Macromolecules, 2015Co-Authors: Paul H. M. Van Steenberge, Richard Hoogenboom, Bart Verbraeken, Marie-françoise Reyniers, Dagmar R. D'hoogeAbstract:For the first time, the formation of monomer sequences of individual macromolecules during cationic ring-opening copolymerization (CROcoP) of 2-methyl-2-Oxazoline (MeOx) and 2-phenyl-2-Oxazoline (PhOx) in acetonitrile (3 mol L–1; 100–140 °C; target degree of polymerization (DP): 50–400) is visualized via kinetic Monte Carlo simulations with model parameters optimized based on experimental data. It is shown that chain transfer via β-elimination and branching reactions are required to describe the experimental data. At complete monomer conversion for target DPs below 200, at most 5% of the chains are macromonomers and the average number of branches per chain remains below 15%. A higher amount of chains with a defined, steeper MeOx to PhOx gradient is obtained by lowering the polymerization temperature albeit at the expense of polymerization time. The simulations results highlight the great potential of CROcoP of 2-Oxazolines for the direct synthesis of well-defined steep gradient copolymers.
-
sulfolane as common rate accelerating solvent for the cationic ring opening polymerization of 2 Oxazolines
ACS Macro Letters, 2015Co-Authors: Maarten Vergaelen, Bart Verbraeken, Bryn D Monnery, Richard HoogenboomAbstract: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...
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, 2016Co-Authors: Meike N Leiske, Helmar Görls, Matthias Hartlieb, Fabian H Sobotta, Renzo M Paulus, Peter Bellstedt, Ulrich S. SchubertAbstract: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.
-
Microwave-assisted cationic ring-opening polymerization of 2-Oxazolines.
Advances in polymer science = Fortschritte der Hochpolymeren-Forschung, 2015Co-Authors: Klaus Peter Luef, Richard Hoogenboom, Ulrich S. Schubert, Frank WiesbrockAbstract:More than any other polymer class, the synthesis of (co-)poly(2-Oxazoline)s has benefited tremendously from the introduction of microwave reactors into chemical laboratories. This review focuses on research activities in the area of (co-)poly(2-Oxazoline)s prepared by microwave-assisted syntheses and summarizes the current state-of-the-art for microwave-assisted syntheses of 2-Oxazoline monomers, microwave-assisted ring-opening (co-)polymerizations of 2-Oxazolines, and prominent examples of post-polymerization modifications of (co-)poly(2-Oxazoline)s. Special attention is paid to kinetic analyses of the microwave-assisted polymerization of 2-Oxazolines and to the discussion of non-thermal microwave effects.
-
One-pot synthesis of 2-phenyl-2-Oxazoline-containing quasi-diblock copoly(2-Oxazoline)s under microwave irradiation
Journal of Polymer Science Part A: Polymer Chemistry, 2006Co-Authors: Richard Hoogenboom, Hanneke M. L. Thijs, Martin W. M. Fijten, Bart M. Van Lankvelt, Ulrich S. SchubertAbstract:The microwave-assisted statistical copolymerization of 2-phenyl-2-Oxazoline with 2-methyl-2-Oxazoline or 2-ethyl-2-Oxazoline is discussed in this contribution. Kinetic studies of these statistical copolymerizations as well as reactivity ratio determinations were performed to investigate the monomer distribution in these copoly(2-Oxazoline)s, demonstrating the formation of quasi-diblock copolymers. In addition, the synthesis of copolymer series with monomer concentrations ranging from 0 to 100 mol % is described. These copolymer series were characterized with 1H NMR spectroscopy, gas chromatography, and gel permeation chromatography. Moreover, the glass-transition temperatures and solubility of these copolymers were studied, and this revealing better mixing of poly(2-methyl-2-Oxazoline) (pMeOx) with poly(2-phenyl-2-Oxazoline) (pPhOx) than poly(2-ethyl-2-Oxazoline) (pEtOx) with poly(2-phenyl-2-Oxazoline) (pPhOx). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 416–422, 2007.
-
Microwave Accelerated Polymerization of 2‐Phenyl‐2‐Oxazoline: Microwave or Temperature Effects?
Macromolecular Rapid Communications, 2005Co-Authors: Richard Hoogenboom, Mam Mark Leenen, Frank Wiesbrock, Ulrich S. SchubertAbstract:Summary: Investigations regarding the cationic ring-opening polymerization of 2-phenyl-2-Oxazoline under microwave irradiation and conventional heating are reported. This study was inspired by contradictory reports of the (non-)existence of non-thermal microwave effects that might accelerate the cationic ring-opening of 2-Oxazolines. The polymerization of 2-phenyl-2-Oxazoline was investigated under pressure in acetonitrile and under reflux (or at the boiling point of butyronitrile in a closed vessel) in butyronitrile utilizing a single-mode microwave reactor and automated synthesis robots with conventional heating.
Bart Verbraeken - One of the best experts on this subject based on the ideXlab platform.
-
the chemistry of poly 2 Oxazoline s
European Polymer Journal, 2017Co-Authors: Bart Verbraeken, Bryn D Monnery, Kathleen Lava, Richard HoogenboomAbstract:Abstract As we celebrate the 50th birthday of the discovery of poly(2-alkyl/aryl-2-Oxazoline)s (PAOx) this year we see a research field that is rapidly expanding after some lesser academic activity in the nineties. This renewed interest in PAOx stems from the fact that this polymer class combines high synthetic versatility with good biocompatibility, opening up the way to highly functional (biocompatible) materials. PAOx are prepared by living cationic ring-opening polymerization (CROP) of 2-Oxazolines, which will be the in-depth focus off this review. The variety of 2-Oxazoline monomers that are readily available or can easily be synthesized, allows for tuning of polymer properties and introduction of diverse functionalities as well as provides access to different polymer architectures. Moreover, thanks to the living nature of the CROP, well-defined polymers with narrow molar mass distribution and high end-group fidelity can be obtained.
-
Model-Based Visualization and Understanding of Monomer Sequence Formation in Gradient Copoly(2-Oxazoline)s On the basis of 2-Methyl-2-Oxazoline and 2-Phenyl-2-Oxazoline
Macromolecules, 2015Co-Authors: Paul H. M. Van Steenberge, Richard Hoogenboom, Bart Verbraeken, Marie-françoise Reyniers, Dagmar R. D'hoogeAbstract:For the first time, the formation of monomer sequences of individual macromolecules during cationic ring-opening copolymerization (CROcoP) of 2-methyl-2-Oxazoline (MeOx) and 2-phenyl-2-Oxazoline (PhOx) in acetonitrile (3 mol L–1; 100–140 °C; target degree of polymerization (DP): 50–400) is visualized via kinetic Monte Carlo simulations with model parameters optimized based on experimental data. It is shown that chain transfer via β-elimination and branching reactions are required to describe the experimental data. At complete monomer conversion for target DPs below 200, at most 5% of the chains are macromonomers and the average number of branches per chain remains below 15%. A higher amount of chains with a defined, steeper MeOx to PhOx gradient is obtained by lowering the polymerization temperature albeit at the expense of polymerization time. The simulations results highlight the great potential of CROcoP of 2-Oxazolines for the direct synthesis of well-defined steep gradient copolymers.
-
sulfolane as common rate accelerating solvent for the cationic ring opening polymerization of 2 Oxazolines
ACS Macro Letters, 2015Co-Authors: Maarten Vergaelen, Bart Verbraeken, Bryn D Monnery, Richard HoogenboomAbstract: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...
-
poly 2 Oxazoline s and click chemistry a versatile toolbox toward multi functional polymers
European Polymer Journal, 2015Co-Authors: Kathleen Lava, Bart Verbraeken, Richard HoogenboomAbstract:Abstract Poly(2-alkyl/aryl-2-Oxazoline)s (PAOx) have been gaining increasing attention because they combine biocompatibility with so-called stealth behavior, making them ideal candidates for use in a wide variety of biomedical applications. Especially, the possibility of side-chain modification makes them a valuable alternative to poly(ethylene glycol), currently the gold standard amongst biocompatible polymers. Nevertheless, the cationic ring opening polymerization of 2-Oxazolines is not compatible with nucleophilic entities, for example hydroxyl and amine moieties. Therefore, the modular approach of ‘click chemistry’ offers an elegant strategy toward functional PAOx by post-polymerization modification of PAOx that contain clickable groups. This feature describes the synthesis of PAOx with such clickable entities at the chain-end or in the side-chain, as well as their potential (bio)materials applications.
-
Encyclopedia Of Polymer Science and Technology - Poly(2-Oxazoline)s
Encyclopedia of Polymer Science and Technology, 2014Co-Authors: Bart Verbraeken, Kathleen Lava, Richard HoogenboomAbstract:Research in the field of poly(2-Oxazoline)s (PAOx) is rapidly expanding as this polymer class combines high synthetic versatility and biocompatibility, opening up the way to highly functional (biocompatible) materials. PAOx are prepared by living cationic ring-opening polymerization (CROP) of 2-Oxazolines. The variety of 2-Oxazoline monomers that are readily available or can easily be synthesized allows for tuning of polymer properties and introduction of diverse functionalities. Moreover, thanks to the living nature of CROP, well-defined polymers with narrow molar mass distribution and high end group fidelity can be obtained. This article covers all aspects of PAOx ranging from the synthesis of 2-Oxazoline monomers, via in-depth discussion on the CROP mechanism to the synthesis and properties of functional PAOx (co)polymers. The presented research demonstrates that owing to their structural adaptability and the so-called “stealth” behavior, PAOx are well suited for a range of biomedical applications, including polymer therapeutics, scaffolds for three-dimensional cell culture, surface modification, matrix excipient for solid dispersions, and antimicrobial agents. Keywords: poly(2-Oxazoline); 2-Oxazoline; biocompatible; cationic ring-opening polymerization; living polymerization
John C Walton - One of the best experts on this subject based on the ideXlab platform.
-
effect of chain length on radical to carbanion cyclo coupling of bromoaryl alkyl linked Oxazolines 1 3 areneotropic migration of Oxazolines
Journal of Organic Chemistry, 2007Co-Authors: Laura J Marshall, Mark D Roydhouse, And Alexandra M Z Slawin, John C WaltonAbstract:2-Halophenylalkyl-2-Oxazolines with alkyl chain spacers of two to six C atoms (n = 0−4) were prepared and their SRN1-type reactions with several base systems examined. The best conditions to promote cyclo-coupling to the corresponding benzocycloalkane derivatives involved use of LDA in THF. The precursors with 3-C-atom and 4-C-atom spacers gave good yields of 2-(1‘-phenylindan-1‘-yl)-2-Oxazolines and 2-(1-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)-2-Oxazoline, respectively. The major products from the precursor with a 5-C-atom spacer were derivatives of benzocycloheptane in which the Oxazoline group had undergone a novel areneotropic migration from the end of the spacer to the benzo ring. The product from reaction of the corresponding 2-C-atom precursor was a 9-oxazolinophenanthrene derivative. EPR spectroscopy showed the intermediates of the LDA-promoted reactions to be radical anions of the product benzocycloalkanes. This supported an SRN1-type chain mechanism involving initial production of aryl radical...
-
Radical-carbanion cyclo-coupling in armed aromatics: overriding steric hindrance to ring closure.
Chemical Communications, 2005Co-Authors: Mark D Roydhouse, John C WaltonAbstract:ω-(2-Halophenyl)alkyl-2-Oxazolines were prepared and reacted via base promoted intramolecular coupling of radical with carbanionic centres to yield 1-phenyl-1-oxazolino-indan and -tetralin derivatives containing quaternary C-atoms.
Yong-min Liang - One of the best experts on this subject based on the ideXlab platform.
-
Palladium-Catalyzed Cascade Difluoroalkylation/Cyclization of N-Propargylamides: Synthesis of Oxazoles and Oxazolines.
Journal of Organic Chemistry, 2018Co-Authors: Qiang Wang, Xin-gang Wang, Yong-min LiangAbstract:A palladium-catalyzed process to construct oxazoles and Oxazolines with broad functional-group tolerance has been developed, and the method introduces difluoromethyl groups into heterocycles in a one-pot fashion. This system uses a carbonyl oxygen as the acceptor for the addition of a vinylpalladium intermediate to achieve the cyclization. Oxazoline derivatives are generated as the Z-isomer with high stereoselectivity. Additionally, we validated the tentative mechanism of this reaction.
-
Palladium-Catalyzed Cascade Difluoroalkylation/Cyclization of N‑Propargylamides: Synthesis of Oxazoles and Oxazolines
2018Co-Authors: Qiang Wang, Xin-gang Wang, Yong-min LiangAbstract:A palladium-catalyzed process to construct oxazoles and Oxazolines with broad functional-group tolerance has been developed, and the method introduces difluoromethyl groups into heterocycles in a one-pot fashion. This system uses a carbonyl oxygen as the acceptor for the addition of a vinylpalladium intermediate to achieve the cyclization. Oxazoline derivatives are generated as the Z-isomer with high stereoselectivity. Additionally, we validated the tentative mechanism of this reaction
