2-Methyl-2-Oxazoline

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

  • Synthesis of defined high molar mass poly(2-Methyl-2-Oxazoline)
    Polymer Chemistry, 2019
    Co-Authors: Ondrej Sedlacek, Bryn D. Monnery, Richard Hoogenboom
    Abstract:

    In this communication, we report for the first time the synthesis of defined high molar mass poly(2-Methyl-2-Oxazoline) (PMeOx), a water-soluble polymer with excellent anti-fouling properties. So far, there has been no report on low dispersity (Đ < 1.2) PMeOx longer than 10 kg mol−1. Higher molar mass would be beneficial for synthesis of polymer–drug conjugates, excipients as well as for other biomedical applications. We report our attempts to prepare defined high molar mass PMeOx via living cationic ring-opening polymerization (CROP) of its monomer using our optimized method that failed due to extensive chain transfer and chain coupling side reactions. Therefore, we proposed an alternative strategy to high molar mass PMeOx based on acetylation of well-defined linear polyethyleneimine (PEI) prepared by controlled side-chain hydrolysis of defined high molar mass PEtOx. This method allowed us to synthesize a series of low-dispersity PMeOx up to 58 kg mol−1 (Đ = 1.07). Considering the biomedical potential of PMeOx, the synthesis of such polymers might open a way to a new class of effective polymer-based therapeutics.

  • Fluorophilic–Lipophilic–Hydrophilic Poly(2-oxazoline) Block Copolymers as MRI Contrast Agents: From Synthesis to Self-Assembly
    2018
    Co-Authors: Leonid I. Kaberov, Richard Hoogenboom, Bart Verbraeken, Anna Riabtseva, Jiri Brus, Yeshayahu Talmon, Petr Stepanek, Aurel Radulescu, Sergey K. Filippov
    Abstract:

    This work focuses on the synthesis and self-assembly of triphilic poly­(2-oxazoline) triblock copolymers with high fluorine content toward our future aim of developing poly­(2-oxazoline) magnetic resonance imaging (MRI) contrast agents. A highly fluorinated 2-substituted-2-oxazoline monomer, namely 2-(1H,1H,2H,2H-perfluorooctyl)-2-oxazoline, was synthesized using the Grignard reaction. The polymerization kinetics of the synthesized monomer was studied, and it was used for the preparation of triblock copolymers with hydrophilic 2-Methyl-2-Oxazoline, hydrophobic 2-octyl-2-oxazoline, and fluorophilic blocks by cationic ring-opening polymerization yielding polymers with low relatively dispersity (1.2–1.4). The presence of the blocks with the different nature in one copolymer structure facilitated self-assembly of the copolymers in water and dimethyl sulfoxide as observed by dynamic light scattering, cryo-transmission electron microscopy, and small-angle neutron scattering. The nanoparticle morphology is strongly influenced by the order and length of each block and the nature of solvent, leading to nanoparticles with core–shell structure as confirmed by small-angle neutron scattering. The reported poly­(2-oxazoline) block copolymers with high fluorine content have high potential for future development of MRI contrast agents

  • 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

  • side chain variations radically alter the diffusion of poly 2 alkyl 2 oxazoline functionalised nanoparticles through a mucosal barrier
    Biomaterials Science, 2016
    Co-Authors: Edward D H Mansfield, Richard Hoogenboom, Victor Retamero De La Rosa, Radoslaw M Kowalczyk, Isabelle Grillo, Katy Sillence, Patrick Hole, Adrian C Williams, Vitaliy V Khutoryanskiy
    Abstract:

    Functionalised nanomaterials are gaining popularity for use as drug delivery vehicles and, in particular, mucus penetrating nanoparticles may improve drug bioavailability via the oral route. To date, few polymers have been investigated for their muco-penetration, and the effects of systematic structural changes to polymer architectures on the penetration and diffusion of functionalised nanomaterials through mucosal tissue have not been reported. We investigated the influence of poly(2-oxazoline) alkyl side chain length on nanoparticle diffusion; poly(2-Methyl-2-Oxazoline), poly(2-ethyl-2-oxazoline), and poly(2-n-propyl-2-oxazoline) were grafted onto the surface of thiolated silica nanoparticles and characterised by FT-IR, Raman and NMR spectroscopy, thermogravimetric analysis, and small angle neutron scattering. Diffusion coefficients were determined in water and in a mucin dispersion (using Nanoparticle Tracking Analysis), and penetration through a mucosal barrier was assessed using an ex vivo fluorescence technique. The addition of a single methylene group in the side chain significantly altered the penetration and diffusion of the materials in both mucin dispersions and mucosal tissue. Nanoparticles functionalised with poly(2-Methyl-2-Oxazoline) were significantly more diffusive than particles with poly(2-ethyl-2-oxazoline) while particles with poly(2-n-propyl-2-oxazoline) showed no significant increase compared to the unfunctionalised particles. These data show that variations in the polymer structure can radically alter their diffusive properties with clear implications for the future design of mucus penetrating systems.

  • synthesis of poly 2 oxazoline s with side chain methyl ester functionalities detailed understanding of living copolymerization behavior of methyl ester containing monomers with 2 alkyl 2 oxazolines
    Journal of Polymer Science Part A, 2015
    Co-Authors: Petra J M Bouten, Bryn D. Monnery, Maarten Vergaelen, Dietmar Hertsen, Saron Catak, Veronique Van Speybroeck, Jan C M Van Hest, Richard Hoogenboom
    Abstract:

    Poly(2-oxazoline)s with methyl ester functionalized side chains are interesting as they can undergo a direct amidation reaction or can be hydrolyzed to the carboxylic acid, making them versatile functional polymers for conjugation. In this work, detailed studies on the homo- and copolymerization kinetics of two methyl ester functionalized 2-oxazoline monomers with 2-Methyl-2-Oxazoline, 2-ethyl-2-oxazoline, and 2-n-propyl-2-oxazoline are reported. The homopolymerization of the methyl ester functionalized monomers is found to be faster compared to the alkyl monomers, while copolymerization unexpectedly reveals that the methyl ester containing monomers significantly accelerate the polymerization. A computational study confirms that methyl ester groups increase the electrophilicity of the living chain end, even if they are not directly attached to the terminal residue. Moreover, the electrophilicity of the living chain end is found to be more important than the nucleophilicity of the monomer in determining the rate of propagation. However, the monomer nucleophilicity can be correlated with the different rates of incorporation when two monomers compete for the same chain end, that is, in copolymerizations. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2649–2661

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

  • in vitro hemocompatibility and cytotoxicity study of poly 2 methyl 2 oxazoline for biomedical applications
    Journal of Polymer Science Part A, 2013
    Co-Authors: Marius Bauer, Susann Schroeder, Lutz Tauhardt, Kristian Kempe, Ulrich S Schubert, Dagmar Fischer
    Abstract:

    Since poly(2-Methyl-2-Oxazolines) (PMeOx) attract high attention for the potential use in drug delivery, cytotoxicity, and hemocompatibility of a set of PMeOxs with molar masses in the range from 2 to 20 kDa are systematically investigated under standardized conditions in terms of molar mass, concentration and time dependency. PMeOx polymers are well tolerated in red blood cell aggregation and hemolysis assays without any damaging effects even at high concentrations up to 80 mg/mL. Only in long term cytotoxicity tests PMeOx polymers moderately influence cell viability in a time, concentration, and molar mass dependent manner. Referring to these results it can be concluded that PEtOx could be promising nonionic hydrophilic polymers for many biomedical applications without any cyto- and hemotoxic effects at typically used therapeutic doses. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

  • poly 2 oxazoline hydrogel monoliths via thiol ene coupling
    Macromolecular Rapid Communications, 2012
    Co-Authors: Tim R Dargaville, Kristian Kempe, Ulrich S Schubert, Rebecca Forster, Brooke L Farrugia, Lenny Voorhaar, Richard Hoogenboom
    Abstract:

    Copoly(2-oxazoline)s, prepared by the cationic ring-opening polymerization of 2-(dec-9-enyl)-2-oxazoline with either 2-Methyl-2-Oxazoline or 2-ethyl-2-oxazoline, are crosslinked with small dithiol molecules under UV irradiation to form homogeneous networks. In situ monitoring of the crosslinking reaction by photo-rheology reveals the formation of soft gels within minutes. The degree of swelling in water is tunable based on the hydrophilicity of the starting macromers and the proportion of alkene side arms present. Furthermore, degradable hydrogels are prepared based on incorporation of a hydrolytically cleavable dithiol crosslinker. The rapid synthesis of the macromers and mild crosslinking conditions make these materials ideal for future biomaterial applications.

  • unexpected radical polymerization behavior of oligo 2 ethyl 2 oxazoline macromonomers
    Polymer Chemistry, 2012
    Co-Authors: Christine Weber, Richard Hoogenboom, Krzysztof Babiuch, Sarah E Rogers, Igor Perevyazko, Ulrich S Schubert
    Abstract:

    A well-defined oligo(2-ethyl-2-oxazoline)acrylate (OEtOxA) macromonomer was obtained by direct end functionalization of the living cationic oxazolinium species from the cationic ring-opening polymerization of EtOx with in situ deprotonated acrylic acid. Kinetic studies during subsequent reversible addition–fragmentation chain transfer (RAFT) polymerization as well as nitroxide mediated polymerization (NMP) experiments revealed proceeding monomer consumption but no increase of the molar mass of the resulting comb polymers. The chain transfer during the radical polymerizations is proposed to result from backbiting and subsequent β-scission of the formed mid-chain radical and took place in a well-defined manner, so that POEtOxA could also be obtained by free radical polymerization with a PDI value below 1.2. A series of POEtOxA was synthesized by RAFT polymerization with varying [monomer]/[chain transfer agent] (M/CTA) ratios and analyzed in detail by means of analytical ultracentrifugation and small angle neutron scattering, indicating that the backbone DP does not exceed 25, which is in accordance with the thermal polymer properties in bulk and in aqueous solution (Tg = 32 °C, Tcp ≈ 73 °C).

  • block copolymers of poly 2 oxazoline s and poly meth acrylates a crossover between cationic ring opening polymerization crop and reversible addition fragmentation chain transfer raft
    ACS Macro Letters, 2012
    Co-Authors: Andreas Krieg, Remzi C Becer, Richard Hoogenboom, Christine Weber, Ulrich S Schubert
    Abstract:

    To combine the advantages of poly(2-oxazoline)s (POx) and controlled radical polymerization (CRP) techniques, the cationic ring-opening polymerization (CROP) of 2-Methyl-2-Oxazoline (MeOx), 2-ethyl-2-oxazoline (EtOx), and 2-n-nonyl-2-oxazoline (NonOx) were terminated with a carboxylic acid functionalized chain transfer agent (CTA). The obtained PEtOx with a high degree of functionalization (DF) was used as macro-CTA for the reversible addition–fragmentation chain transfer (RAFT) polymerization of various vinylic monomers (styrene (St), methyl acrylate (MA), tert-butyl acrylate (tBuA), acrylic acid (AA), N,N-dimethyl acrylamide (DMAAm), and N,N-dimethylaminoethylacrylate (DMAEA)) resulting in well-defined block copolymers. Thus, in this work we report a versatile route to combine poly(2-oxazoline)s prepared via CROP with RAFT polymerization for the synthesis of novel block copolymers.

  • 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.

Rainer Jordan - One of the best experts on this subject based on the ideXlab platform.

  • co delivery of paclitaxel and cisplatin in poly 2 oxazoline polymeric micelles implications for drug loading release pharmacokinetics and outcome of ovarian and breast cancer treatments
    Biomaterials, 2019
    Co-Authors: Xiaomeng Wan, Rainer Jordan, Herdis Bludau, Marina Sokolsky, James J Beaudoin, Natasha Vinod, Yuanzeng Min, Naoki Makita, Andrew Z Wang, Alexander V Kabanov
    Abstract:

    Abstract Concurrent delivery of multiple drugs using nanoformulations can improve outcomes of cancer treatments. Here we demonstrate that this approach can be used to improve the paclitaxel (PTX) and alkylated cisplatin prodrug combination therapy of ovarian and breast cancer. The drugs are co-loaded in the polymeric micelle system based on amphiphilic block copolymer poly(2-Methyl-2-Oxazoline-block-2-butyl-2-oxazoline-block-2-Methyl-2-Oxazoline) (P(MeOx-b-BuOx-b-MeOx). A broad range of drug mixing ratios and exceptionally high two-drug loading of over 50 wt.% drug in a stable micellar solution is demonstrated. The drugs co-loading in the micelles result in a slowed-down release to serum, improved pharmacokinetics and increased tumor distribution for both drugs. A superior anti-tumor activity of co-loaded PTX/CP drug micelles compared to single drug micelles or their mixture was demonstrated in cisplatin-resistant human ovarian carcinoma A2780/CisR xenograft tumor and multidrug resistant breast cancer LCC-6-MDR orthotopic tumor models. The improved tumor delivery of co-loaded drugs was related to decreased drug release rates as confirmed by simulation for micelle, serum and tumor compartments in a three-compartmental model. Overall, the results provide support for the use of PTX and cisplatin co-loaded micelles as a strategy for improved chemotherapy of ovarian and breast cancer and potential for the clinical translation.

  • poly 2 oxazoline block copolymer based formulations of taxanes effect of copolymer and drug structure concentration and environmental factors
    Polymers for Advanced Technologies, 2015
    Co-Authors: Youn Gee Seo, Robert Luxenhofer, Anita Schulz, Yingchao Han, Herdis Bludau, Xiaomeng Wan, Jing Tong, Tatiana K Bronich, Marina Sokolsky, Rainer Jordan
    Abstract:

    Many current nanoformulations of taxanes are hampered by low drug-loading capacity and unfavorable physicochemical characteristics such a sl arge particles size (>100nm) and/or low size uniformity. We have previously reported on taxane nanoformulations, based on poly(2-oxazoline) polymeric micelles that display an extremely high taxane loading capacity (>40%w/w) and particle size below 50nm. Previous work was based on a triblock copolymer having poly(2-butyl-2oxazoline) as the hydrophobic block and poly(2-Methyl-2-Oxazoline) as the hydrophilic blocks. This paper explores the effects of various formulation parameters such as (i) the drug and polymer structure; (ii) the drug and polymer concentration; and (iii) the composition of aqueous medium on the solubilization behavior and physicochemical properties of the resulting formulations. In addition, in vitro anticancer activity is reported. Despite numerous variations of the hydrophobicity, polarity or additionofaromaticresiduesinthehydrophobiccore,thetriblockcopolymerwiththepoly(2-butyl-2-oxazoline)blockremains the polymer with the highest drug-loading capacity. Notably, the formulationwas easily scalablewith uncompromisedencapsulation efficacy, loading capacity, and physicochemical properties. The taxane formulations were stable upon storage (water, saline, and dextrose solution) for1–2weeks andcouldbelyophilizedandre-dispersedwithoutcompromisingthe formulation properties.Furthermore,the micelles remained stable upondilution. The drug-loaded poly(2-oxazoline) micelles showed high toxicityagainstseveralcancercell lines.Takentogether,theseresultsunderscorethepotentialof poly(2-oxazoline)micellesas formulation excipient for taxanes and possibly other hydrophobic drugs. Copyright © 2015 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper.

  • tailored poly 2 oxazoline polymer brushes to control protein adsorption and cell adhesion
    Macromolecular Bioscience, 2012
    Co-Authors: Ning Zhang, Robert Luxenhofer, Rainer Jordan, Tilo Pompe, Ihsan Amin, Carsten Werner
    Abstract:

    POx bottle-brush brushes (BBBs) are synthesized by SIPGP of 2-isopropenyl-2-oxazoline and consecutive LCROP of 2-oxazolines on 3-aminopropyltrimethoxysilane-modified silicon substrates. The side chain hydrophilicity and polarity are varied. The impact of the chemical composition and architecture of the BBB upon protein (fibronectin) adsorption and endothelial cell adhesion are investigated and prove extremely low protein adsorption and cell adhesion on BBBs with hydrophilic side chains such as poly(2methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline). The influence of the POx side chain terminal function upon adsorption and adhesion is minor but the side chain length has a significant effect on bioadsorption.

  • effect of end group polarity upon the lower critical solution temperature of poly 2 isopropyl 2 oxazoline
    Colloid and Polymer Science, 2008
    Co-Authors: Stephan Huber, Naima A Hutter, Rainer Jordan
    Abstract:

    Thermo-sensitive poly(2-isopropyl-2-oxazoline)s (PiPrOx) were functionalized with end groups of different polarity by living cationic ring-opening polymerization using the initiator and/or termination method as well as sequential block copolymerization with 2-Methyl-2-Oxazoline. As end groups, methyl, n-nonyl, piperidine, piperazine as well as oligo(ethylenglygol) and oligo(2-Methyl-2-Oxazoline) were introduced quantitatively. The lower critical solution temperature (LCST) of the aqueous solutions was investigated. The introduction of hydrophobic end groups decreases the LCST, while hydrophilic polymer tails raise the cloud point. In comparison to poly(N-isopropyl acrylamide), the impact of the end group polarity upon the modulation of the LCST was found to be significantly stronger. Surprisingly, terminal oligoethylenegycol units also decrease the LCST of PiPrOx, thus acting as moieties of higher hydrophobicity as compared to the poly(2-oxazoline) main chain. Together with the possible variation of the side group polarity, this allows a broad modulation of the LCST of poly(2-oxazoline)s.

  • synthesis biodistribution and excretion of radiolabeled poly 2 alkyl 2 oxazoline s
    Journal of Controlled Release, 2007
    Co-Authors: Florian C Gaertner, Robert Luxenhofer, Rainer Jordan, Birgit Blechert, Markus Essler
    Abstract:

    Here we report on the preparation of well defined water-soluble poly(2-Methyl-2-Oxazoline) and poly(2-ethyl-2-oxazoline) terminally equipped with a chelator (N,N',N'',N'''-tetraazacylododecane-1,4,7,10-tetraacetic acid (DOTA)) for radionuclide labeling. The tissue distribution and excretion of (111)In-labeled poly(2-alkyl-2-oxazoline)s were studied in mice. We found that the hydrophilic polymers do not accumulate in tissues and are rapidly cleared from the blood pool, predominantly by glomerular filtration in the kidneys. In contrast only a small fraction is excreted via the hepatobiliary tract. Only minimal amounts of poly(2-alkyl-2-oxazoline)s are taken up by the reticuloendothelial system (RES). Scintigraphic studies revealed the feasibility of in vivo imaging of (111)In-labeled poly(2-oxazoline)s. Since additional functionalities for targeting can readily be introduced into poly(2-oxazoline)s via functional monomer units, these compounds fulfill fundamental requirements for an application as carrier molecules in radionuclide therapy.

Christine Weber - One of the best experts on this subject based on the ideXlab platform.

  • unexpected radical polymerization behavior of oligo 2 ethyl 2 oxazoline macromonomers
    Polymer Chemistry, 2012
    Co-Authors: Christine Weber, Richard Hoogenboom, Krzysztof Babiuch, Sarah E Rogers, Igor Perevyazko, Ulrich S Schubert
    Abstract:

    A well-defined oligo(2-ethyl-2-oxazoline)acrylate (OEtOxA) macromonomer was obtained by direct end functionalization of the living cationic oxazolinium species from the cationic ring-opening polymerization of EtOx with in situ deprotonated acrylic acid. Kinetic studies during subsequent reversible addition–fragmentation chain transfer (RAFT) polymerization as well as nitroxide mediated polymerization (NMP) experiments revealed proceeding monomer consumption but no increase of the molar mass of the resulting comb polymers. The chain transfer during the radical polymerizations is proposed to result from backbiting and subsequent β-scission of the formed mid-chain radical and took place in a well-defined manner, so that POEtOxA could also be obtained by free radical polymerization with a PDI value below 1.2. A series of POEtOxA was synthesized by RAFT polymerization with varying [monomer]/[chain transfer agent] (M/CTA) ratios and analyzed in detail by means of analytical ultracentrifugation and small angle neutron scattering, indicating that the backbone DP does not exceed 25, which is in accordance with the thermal polymer properties in bulk and in aqueous solution (Tg = 32 °C, Tcp ≈ 73 °C).

  • block copolymers of poly 2 oxazoline s and poly meth acrylates a crossover between cationic ring opening polymerization crop and reversible addition fragmentation chain transfer raft
    ACS Macro Letters, 2012
    Co-Authors: Andreas Krieg, Remzi C Becer, Richard Hoogenboom, Christine Weber, Ulrich S Schubert
    Abstract:

    To combine the advantages of poly(2-oxazoline)s (POx) and controlled radical polymerization (CRP) techniques, the cationic ring-opening polymerization (CROP) of 2-Methyl-2-Oxazoline (MeOx), 2-ethyl-2-oxazoline (EtOx), and 2-n-nonyl-2-oxazoline (NonOx) were terminated with a carboxylic acid functionalized chain transfer agent (CTA). The obtained PEtOx with a high degree of functionalization (DF) was used as macro-CTA for the reversible addition–fragmentation chain transfer (RAFT) polymerization of various vinylic monomers (styrene (St), methyl acrylate (MA), tert-butyl acrylate (tBuA), acrylic acid (AA), N,N-dimethyl acrylamide (DMAAm), and N,N-dimethylaminoethylacrylate (DMAEA)) resulting in well-defined block copolymers. Thus, in this work we report a versatile route to combine poly(2-oxazoline)s prepared via CROP with RAFT polymerization for the synthesis of novel block copolymers.

  • dual responsive methacrylic acid and oligo 2 ethyl 2 oxazoline containing graft copolymers
    Macromolecules, 2010
    Co-Authors: Christine Weber, Remzi C Becer, Richard Hoogenboom, Ulrich S Schubert, Wolfgang Guenther
    Abstract:

    Graft copolymers containing a poly(methacrylic acid) (PMAA) backbone and oligo(2-ethyl-2- oxazoline) (OEtOx) sidechains weresynthesizedbyreversibleaddition-fragmentationchaintransfer (RAFT) polymerization of methacrylic acid (MAA) and OEtOx methacrylate macromonomers. In order to achieve a constant backbone length of the graft copolymer, living OEtOx chains were also directly grafted onto a deprotonated PMAA backbone in grafting densities from 7% to 92%. Both methods resulted in graft copolymers which were characterized by SEC (Mn = 5500 to 18700 g mol -1 , PDI < 1.3), 1 H NMR spectro- scopy, and acid/base titrations. The solubility behavior of the graft copolymers in aqueous media was investigated using turbidity measurements revealing a lower critical solution temperature (LCST) behavior of the polymers with a grafting density above 35%. The cloud points of the solutions can be varied in a temperature range from 8 to 90 C by adjustment of the polymer composition and the pH of the solution. 1 H NMR measurements in D2O at varying temperatures revealed a collapse of the polymer backbone above the cloud point of the solution whereas parts of the OEtOx side chains remained mobile.

  • lower critical solution temperature behavior of comb and graft shaped poly oligo 2 ethyl 2 oxazoline methacrylate s
    Macromolecules, 2009
    Co-Authors: Christine Weber, Remzi C Becer, Richard Hoogenboom, Ulrich S Schubert
    Abstract:

    Comb and graft polymers with lower critical solution temperature (LCST) behavior based on hydrophilic oligo(2-ethyl-2-oxazoline) side chains and a hydrophobic methacrylate backbone were synthesized using the macromonomer method. Well-defined oligo(2-ethyl-2-oxazoline) methacrylate (OEtOxMA) macromonomers were obtained by direct end-capping of living oligo(2-ethyl-2-oxazoline) chains with in situ formed triethylammonium methacrylate. The macromonomers were subsequently polymerized in a controlled manner using the reversible addition−fragmentation chain transfer (RAFT) polymerization technique yielding a series of comb polymers with varying side chain length and backbone length. In addition, a series of graft copolymers were prepared by copolymerizing OEtOxMA with methyl methacrylate (MMA, 40−80 mol %). The copolymers were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and, partially, by matrix-assisted laser desorption ionization (MALDI-TOF) mass spectrometry. The LCST behavior ...

Remzi C Becer - One of the best experts on this subject based on the ideXlab platform.

  • investigations on the combination of cationic ring opening polymerization and single electron transfer living radical polymerization to synthesize 2 ethyl 2 oxazoline block copolymers
    Australian Journal of Chemistry, 2012
    Co-Authors: Robert A Young, Edward L Malins, Remzi C Becer
    Abstract:

    Cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) has been performed using α–bromoisobutyryl bromide (tertiary) and 2-bromopropionyl bromide (secondary) as initiators in acetonitrile. The reaction kinetics have been followed and selected P(EtOx) polymers have been used as macroinitiators for the single electron transfer living radical polymerization (SET-LRP) of methyl acrylate (MA), ethylene glycol methyl ether acrylate and 2-(dimethylamino)ethyl methacrylate. Moreover, the effect of solvent and catalyst concentration have been investigated on the SET-LRP of P(EtOx) initiated MA.

  • block copolymers of poly 2 oxazoline s and poly meth acrylates a crossover between cationic ring opening polymerization crop and reversible addition fragmentation chain transfer raft
    ACS Macro Letters, 2012
    Co-Authors: Andreas Krieg, Remzi C Becer, Richard Hoogenboom, Christine Weber, Ulrich S Schubert
    Abstract:

    To combine the advantages of poly(2-oxazoline)s (POx) and controlled radical polymerization (CRP) techniques, the cationic ring-opening polymerization (CROP) of 2-Methyl-2-Oxazoline (MeOx), 2-ethyl-2-oxazoline (EtOx), and 2-n-nonyl-2-oxazoline (NonOx) were terminated with a carboxylic acid functionalized chain transfer agent (CTA). The obtained PEtOx with a high degree of functionalization (DF) was used as macro-CTA for the reversible addition–fragmentation chain transfer (RAFT) polymerization of various vinylic monomers (styrene (St), methyl acrylate (MA), tert-butyl acrylate (tBuA), acrylic acid (AA), N,N-dimethyl acrylamide (DMAAm), and N,N-dimethylaminoethylacrylate (DMAEA)) resulting in well-defined block copolymers. Thus, in this work we report a versatile route to combine poly(2-oxazoline)s prepared via CROP with RAFT polymerization for the synthesis of novel block copolymers.

  • dual responsive methacrylic acid and oligo 2 ethyl 2 oxazoline containing graft copolymers
    Macromolecules, 2010
    Co-Authors: Christine Weber, Remzi C Becer, Richard Hoogenboom, Ulrich S Schubert, Wolfgang Guenther
    Abstract:

    Graft copolymers containing a poly(methacrylic acid) (PMAA) backbone and oligo(2-ethyl-2- oxazoline) (OEtOx) sidechains weresynthesizedbyreversibleaddition-fragmentationchaintransfer (RAFT) polymerization of methacrylic acid (MAA) and OEtOx methacrylate macromonomers. In order to achieve a constant backbone length of the graft copolymer, living OEtOx chains were also directly grafted onto a deprotonated PMAA backbone in grafting densities from 7% to 92%. Both methods resulted in graft copolymers which were characterized by SEC (Mn = 5500 to 18700 g mol -1 , PDI < 1.3), 1 H NMR spectro- scopy, and acid/base titrations. The solubility behavior of the graft copolymers in aqueous media was investigated using turbidity measurements revealing a lower critical solution temperature (LCST) behavior of the polymers with a grafting density above 35%. The cloud points of the solutions can be varied in a temperature range from 8 to 90 C by adjustment of the polymer composition and the pH of the solution. 1 H NMR measurements in D2O at varying temperatures revealed a collapse of the polymer backbone above the cloud point of the solution whereas parts of the OEtOx side chains remained mobile.

  • lower critical solution temperature behavior of comb and graft shaped poly oligo 2 ethyl 2 oxazoline methacrylate s
    Macromolecules, 2009
    Co-Authors: Christine Weber, Remzi C Becer, Richard Hoogenboom, Ulrich S Schubert
    Abstract:

    Comb and graft polymers with lower critical solution temperature (LCST) behavior based on hydrophilic oligo(2-ethyl-2-oxazoline) side chains and a hydrophobic methacrylate backbone were synthesized using the macromonomer method. Well-defined oligo(2-ethyl-2-oxazoline) methacrylate (OEtOxMA) macromonomers were obtained by direct end-capping of living oligo(2-ethyl-2-oxazoline) chains with in situ formed triethylammonium methacrylate. The macromonomers were subsequently polymerized in a controlled manner using the reversible addition−fragmentation chain transfer (RAFT) polymerization technique yielding a series of comb polymers with varying side chain length and backbone length. In addition, a series of graft copolymers were prepared by copolymerizing OEtOxMA with methyl methacrylate (MMA, 40−80 mol %). The copolymers were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and, partially, by matrix-assisted laser desorption ionization (MALDI-TOF) mass spectrometry. The LCST behavior ...

  • water uptake of hydrophilic polymers determined by a thermal gravimetric analyzer with a controlled humidity chamber
    Journal of Materials Chemistry, 2007
    Co-Authors: Hanneke M L Thijs, Remzi C Becer, Richard Hoogenboom, Ulrich S Schubert, Carlos Guerrerosanchez, David Fournier
    Abstract:

    The moisture uptake of several water-soluble polymers at different humidities was investigated with a thermal gravimetric analyzer equipped with a controlled humidity chamber. The water sorption of poly(acrylic acid) sodium salt, poly(ethylene glycol) and silica, which are known as super absorbers, were examined. In addition, various hydrophilic polymeric materials were selected according to their structural features. These included hydroxyl functions on the side chains (e.g. poly(2-hydroxyethyl methacrylate)), as well as acidic or basic functionalities (e.g. poly (dimethylaminoethyl methacrylate) or poly(vinylimidazole)). In addition, poly(2-Methyl-2-Oxazoline) (P(MeOx)) and poly(2-ethyl-2-oxazoline) (P(EtOx)), which are well-known hydrophilic polymers, were also investigated in this context. More significant weight percent changes were obtained for P(MeOx) (60% at 90% relative humidity (RH)) in comparison to P(EtOx) (35% at 90% RH) as a result of the slight difference in hydrophilicity of the structures. The effect of the chain length on the ability for water uptake was also investigated for both poly(oxazolines). Finally, thermoresponsive polymers with a lower critical solution temperature (LCST) behavior (e.g. poly(N-isopropylacrylamide) and poly(dimethylaminoethyl methacrylate)) were also examined. The measurements for the latter polymers were performed below and above the LCST of each polymer whereby the humidities are varied from 0 to 90% with steps of 10%. Upon increasing humidity, the results revealed relatively high water uptake values (8% and 22% for P(NIPAM) and for P(DMAEMA), respectively) below the LCSTs of the polymers and, contrastingly, a small weight loss above their LCSTs. The present results allow a deeper insight into important structure–property relationships (e.g. the influence of the polymer backbone, functional groups, LCST behavior, etc. on the water-uptake properties), and will in subsequent steps permit the directed design of tailor-made polymers for selected applications.