Helmut Keul

Dr. Helmut Keul


Research Focus & Metrics

Academic Career Length

38Years (1989-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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20 May 2009 in Journal of Polymer Science Part A: Polymer Chemistry
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HKHelmut Keul
Helmut Keul
MMMartin Möller
Martin Möller
Linear and star shaped polyglycidols (synonym with polyglycerols) are prepared in a controlled ring opening polymerization of protected glycidols. Beside the molar mass and the polydispersity, the architecture of the polyglycidols is controlled by using mono‐ and multifunctional mono‐ and polydispers initiators. Copolymers of dissimilarly protected glycidols as well as copolymers with nonfunctional oxiranes were prepared by means of anionic polymerization while copolymers of protected glycidol with tetrahydrofuran were prepared by means of cationic polymerization. Polyethers with functional groups in the side chains (functional polyethers) with special emphasis on polyglycidols (containing hydroxymethyl groups in the side chains) were used to prepare multifunctional polymers and (hetero)grafted polymer brushes via chemical and enzyme catalyzed reaction. The potential of poly(glycidol‐graft‐ε‐caprolactone)‐co‐glycidol) prepared via enzyme catalyzed grafting of polyglycidols using ε‐caprolactone as a monomer and Lipase B from Candida antarctica as a catalyst is presented. Finally, comparative degradation studies of densely and loosely grafted polyglycidols are presented and discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3209–3231, 2009

21 September 2015 in Dalton Transactions
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JMJagadeesh Malineni
Jagadeesh Malineni
HKHelmut Keul
Helmut Keul
MMMartin Moeller
Martin Moeller
An efficient novel protocol is applied for direct synthesis of carboxylic acids from primary alcohols through catalytic dehydrogenation. This reaction occurs in water as the solvent and as the oxygen-atom source and no toxic oxidizing agent is involved.

23 May 2012 in Polymer International
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CHChristian Hahn
Christian Hahn
HKHelmut Keul
Helmut Keul
MMMartin Möller
Martin Möller

25 July 2012 in Macromolecular Bioscience
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ÉKÉva Kiss
Éva Kiss
EHElisabeth T. Heine
Elisabeth T. Heine
KHKatalin Hill
Katalin Hill
YHYing Chun He
Ying Chun He
NKNina Keusgen
Nina Keusgen
MMMartin Moeller
Martin Moeller

14 March 2006 in Green Chemistry
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GPGünter Prömpers
Günter Prömpers
HKHelmut Keul
Helmut Keul
HHHartwig Höcker
Hartwig Höcker
1,6-Bis-O-phenoxycarbonyl-2,3∶4,5-di-O-isopropylidenegalactitol (5) and 1,6-di-O-phenoxycarbonylgalactitol (6) were prepared from galactaric acid in four and five steps, with overall yields of 76% and 72%, respectively. These AA type monomers were reacted with α,ω-diamines (H2N–(CH2)x–NH2; x = 2–10 and 12) as BB type monomers in a polycondensation reaction to result in polyurethanes with four protected hydroxy groups PiG2-12 or polyurethanes with four free hydroxy groups PG2-6 per repeating unit. The polyurethanes of the PiG-series were transformed by hydrolysis into polyurethanes with four free hydroxy groups per repeating unit PaG2-6. As shown by 1H NMR spectroscopy, the polyurethanes of the PG series and of the PaG series differ in their microstructure: the polymers of the first series has urethane groups with primary and secondary carbon atoms adjacent to the urethane group, while the polymers of the second series have only primary carbon atoms adjacent to the urethane group. The molecular weights of the polyurethanes, as determined by means of gel permeation chromatography in dimethylacetamide–LiCl, are in the range of 15000 to 63000 for the PiG and the PaG series and 15000 to 36000 for the PG-series with polydispersity indices of about 1.6. The thermal stability of the polyurethanes was studied by means of TGA, the polyurethanes with protected hydroxyl groups being more stable than those with free hydroxy groups. The polyurethanes of the PiG series are semi-crystalline materials with melting points between 160 and 167 °C and glass transition temperatures between 59 and 78 °C. The polyurethanes of the PG and the PaG series show glass transition temperatures of 44 to 74 °C; no melting transition is observed before decomposition starts at about 180 °C.

18 October 2010 in Macromolecular Chemistry and Physics
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YHYingchun He
Yingchun He
VGVishal Goel
Vishal Goel
HKHelmut Keul
Helmut Keul
MMMartin Möller
Martin Möller