The Experts below are selected from a list of 43305 Experts worldwide ranked by ideXlab platform
O. Max Ekiner - One of the best experts on this subject based on the ideXlab platform.
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Gas permeation properties of poly(urethane-urea)s containing different Polyethers
Journal of Membrane Science, 2011Co-Authors: Hua Li, Benny D. Freeman, O. Max EkinerAbstract:Abstract A series of poly(urethane-urea)s were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI), various Polyether diols, and ethylene diamine (EDA). The Polyethers were poly(ethylene glycol) (PEG) 2000, poly(propylene glycol) (PPG) 2700, poly(tetramethylene ether glycol) (Terathane®) 2000, Terathane® 2900, and a mixture of PEG 2000 and Terathane® 2000. The polymer based on PEG 2000 is semi-crystalline at room temperature, and the others are amorphous. The fractional free volume (FFV) increases as Polyether molecular weight and soft segment content increase. The permeability of these materials to He, H2, O2, N2, CO2 and CH4 was measured at 35 °C, and gas permeability increased with increasing FFV. The physical properties and gas transport characteristics of these poly(urethane-urea)s were compared with those of rubbery networks based on crosslinked PEG and PPG.
Giorgio Montaudo - One of the best experts on this subject based on the ideXlab platform.
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Pyrolysis pathways of Polyethers and a method for the interpretation of the pyrolysis mass spectra of Polyethers
Polymer Degradation and Stability, 1998Co-Authors: Costas Georgakopoulos, M. Statheropoulos, Giorgio MontaudoAbstract:The pyrolysis pathways of Polyethers are described. A method, which is based on these pathways, is proposed for the interpretation of pyrolysis mass spectra of Polyethers. The method makes use of pyrolysis data organised in tables, which relate Polyether structures with specific masses and mass series. The proposed method can be applied for most types of pyrolysis spectra, such as electron impact, chemical ionisation, field desorption and direct chemical ionisation. Examples of application of the method are presented and discussed.
Hua Li - One of the best experts on this subject based on the ideXlab platform.
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Gas permeation properties of poly(urethane-urea)s containing different Polyethers
Journal of Membrane Science, 2011Co-Authors: Hua Li, Benny D. Freeman, O. Max EkinerAbstract:Abstract A series of poly(urethane-urea)s were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI), various Polyether diols, and ethylene diamine (EDA). The Polyethers were poly(ethylene glycol) (PEG) 2000, poly(propylene glycol) (PPG) 2700, poly(tetramethylene ether glycol) (Terathane®) 2000, Terathane® 2900, and a mixture of PEG 2000 and Terathane® 2000. The polymer based on PEG 2000 is semi-crystalline at room temperature, and the others are amorphous. The fractional free volume (FFV) increases as Polyether molecular weight and soft segment content increase. The permeability of these materials to He, H2, O2, N2, CO2 and CH4 was measured at 35 °C, and gas permeability increased with increasing FFV. The physical properties and gas transport characteristics of these poly(urethane-urea)s were compared with those of rubbery networks based on crosslinked PEG and PPG.
Costas Georgakopoulos - One of the best experts on this subject based on the ideXlab platform.
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Pyrolysis pathways of Polyethers and a method for the interpretation of the pyrolysis mass spectra of Polyethers
Polymer Degradation and Stability, 1998Co-Authors: Costas Georgakopoulos, M. Statheropoulos, Giorgio MontaudoAbstract:The pyrolysis pathways of Polyethers are described. A method, which is based on these pathways, is proposed for the interpretation of pyrolysis mass spectra of Polyethers. The method makes use of pyrolysis data organised in tables, which relate Polyether structures with specific masses and mass series. The proposed method can be applied for most types of pyrolysis spectra, such as electron impact, chemical ionisation, field desorption and direct chemical ionisation. Examples of application of the method are presented and discussed.
Holger Frey - One of the best experts on this subject based on the ideXlab platform.
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epicyanohydrin polymerization by monomer activation gives access to nitrile amino and carboxyl functional poly ethylene glycol
Macromolecules, 2015Co-Authors: Jana Herzberger, Holger FreyAbstract:Both homo- and copolymerization of the hitherto nonpolymerizable epoxide monomer epicyanohydrin (EPICH) with ethylene oxide (EO) have been studied, employing the monomer activation technique. Tetraoctylammonium bromide or tetrabutylammonium iodide was used as initiator combined with i-Bu3Al to activate the EPICH monomer. The EPICH content was varied from 4 to 16 mol %, yielding well-defined PEG-co-PEPICH copolymers with molecular weights Mn (SEC) ranging from 3700 to 8800 g mol–1. The nitrile groups of the resulting Polyethers were further reduced or hydrolyzed to introduce amino, amide, or carboxyl groups at the Polyether backbone, circumventing protecting group chemistry. Successful transformation of the functional groups was proven by SEC measurements, 1H NMR, 13C NMR, and FT-IR spectroscopy. These carboxyl-functional PEG copolymers are anionic polyelectrolytes consisting only of purely aliphatic Polyether structures with carboxyl groups. The hydrolyzed PEPICH homopolymers represent the first Polyether...
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Hyperbranched aliphatic Polyether polyols
Journal of Polymer Science Part A, 2012Co-Authors: Martina Schömer, Christoph Schüll, Holger FreyAbstract:Hyperbranched polymers, dendritic macromolecules with branch-on-branch structures, have become an important polymer class since the early 1990s. They combine several advantages of the perfectly branched dendrimers with easy accessibility, typically in a one-step synthesis. Hyperbranched Polyethers are a particularly interesting class of chemically stable and often biocompatible materials. Multifunctional hyperbranched Polyethers with controllable molar mass and comparably low polydispersities can been prepared using hydroxyl-functional epoxides or oxetanes for polymerization via anionic and cationic polymerization mechanisms. Here, we review the progress in the preparation, characterization, and application of these uniquely versatile aliphatic Polyether polyols. Their unusual mechanical, thermal, and solution properties render them useful for a variety of applications, for example, as building blocks for various complex macromolecular architectures or in biomedical applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
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Hyperbranched Polyether−Polyols Based on Polyglycerol: Polarity Design by Block Copolymerization with Propylene Oxide
Macromolecules, 2000Co-Authors: Alexander Sunder, Rolf Mülhaupt, Holger FreyAbstract:Multiarm block copolymers were synthesized via anionic ring-opening multibranching polymerization (ROMBP) of glycidol followed by addition of propylene oxide. The resulting Polyether−polyols with molecular weights in the range 5000−12 000 g/mol possessed up to five propylene oxide units per end group and showed narrow molecular weight distributions (MWD < 1.7). Via propoxylation the polarity of the highly hydrophilic polyglycerols can be varied, resulting in versatile, highly functional branched Polyether polyols. The hyperbranched polyglycerols with oligo(propylene oxide) segments were characterized by 13C and 1H NMR, demonstrating complete propoxylation of all end groups. 1H NMR, SEC, vapor pressure osmometry, and hydroxyl number titration were used to determine molecular weights. The effect of the short poly(propylene oxide) blocks on the flexibility of the Polyethers was studied by DSC. The Tg varied between −37 and −71 °C, depending on the length of the propylene oxide segments attached.
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hyperbranched Polyether polyols based on polyglycerol polarity design by block copolymerization with propylene oxide
Macromolecules, 2000Co-Authors: Alexander Sunder, Rolf Mülhaupt, Holger FreyAbstract:Multiarm block copolymers were synthesized via anionic ring-opening multibranching polymerization (ROMBP) of glycidol followed by addition of propylene oxide. The resulting Polyether−polyols with molecular weights in the range 5000−12 000 g/mol possessed up to five propylene oxide units per end group and showed narrow molecular weight distributions (MWD < 1.7). Via propoxylation the polarity of the highly hydrophilic polyglycerols can be varied, resulting in versatile, highly functional branched Polyether polyols. The hyperbranched polyglycerols with oligo(propylene oxide) segments were characterized by 13C and 1H NMR, demonstrating complete propoxylation of all end groups. 1H NMR, SEC, vapor pressure osmometry, and hydroxyl number titration were used to determine molecular weights. The effect of the short poly(propylene oxide) blocks on the flexibility of the Polyethers was studied by DSC. The Tg varied between −37 and −71 °C, depending on the length of the propylene oxide segments attached.
