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158 results on '"Rennhofer, Harald"'

6. Effect of Salts on Laccase‐Catalyzed Polymerization of Lignosulfonate.

Author

Mayr, Sebastian A., Rennhofer, Harald, Gille, Lars, Schwaiger, Nikolaus, Nyanhongo, Gibson S., Weiss, Renate, and Guebitz, Georg M.

Subjects
LACCASE, ELECTRON paramagnetic resonance, SUSTAINABLE chemistry, COUNTER-ions, SMALL-angle scattering, POLYMERIZATION
Abstract

Enzymatic polymerization of lignosulfonate (LS) has a high potential for various applications ranging from coatings to adhesives. Here, the effect of different ions in low concentrations on enzymatic polymerization of LS was investigated, including salt solutions consisting of mono‐ and dicarboxylic acids, sulfate, phosphate and chloride with sodium as counter ion. LS polymerization was followed by viscometry and size exclusion (SEC) chromatography. Interestingly, there was only a small effect of ions on the activity of the laccase on standard substrate ABTS, while the effect on polymerization of LS was substantially different. The presence of acetate led to a 39 % higher degree of polymerization (DP) for LS. Small angle X‐ray scattering (SAXS) revealed that the structure of the enzyme was largely unaffected by the ions, while the determination of the zeta potential showed that those ions conveying higher negative surface charges onto LS particles showed lower DPs, than those not affecting the surface charge. Further, electron paramagnetic resonance (EPR) spectroscopy showed 5‐times higher intensity in phenoxyl radicals for the monovalent ions compared to the divalent ones. It was concluded that the DPs of LS could be tuned in the presence of certain ions, by facilitating the interaction between the laccase substrate‐binding site and the LS molecules. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Glyphosate adsorption on synthetic allophanes and halloysite: Effects of pH and mineral properties.

Author

Remlinger, Vivian I., Lenhardt, Katharina R., Rechberger, Maria V., Rennert, Thilo, Rennhofer, Harald, Tunega, Daniel, Ottner, Franz, Willinger, Max, Zehetner, Franz, and Gerzabek, Martin H.

Subjects
GLYPHOSATE, MINERAL properties, HALLOYSITE, VOLCANIC soils, PH effect, CLAY minerals, ADSORPTION (Chemistry), SOIL mineralogy
Abstract

Background: Glyphosate (GLP) is a widely used herbicide with possible adverse effects on human health and the environment. In soils, GLP strongly adsorbs on clay‐sized minerals, depending on pH, the amount of organic carbon, as well as the contents and properties of Al and Fe oxyhydroxides and clay minerals. Many clay‐sized minerals have already been investigated regarding GLP adsorption behavior, but information on minerals commonly found in volcanic soils is still lacking. Aim: The aim of this study was to investigate for the first time the pH‐dependent adsorption of GLP on allophane and halloysite, typical minerals found in volcanic soils. Methods: GLP adsorption was studied in batch experiments at three pH values (5, 6, and 7). Synthetic allophanes with two different initial Al:Si ratios (1.4 and 1.8) and a halloysite were used as adsorbents. Results: The adsorption capacity (AC) increased with rising Al:Si ratio and decreasing pH. The AC of allophane was significantly higher than that of halloysite. GLP adsorption on allophane was larger than that reported for other clay minerals and Al and Fe oxyhydroxides, especially at low pH. The AC of halloysite was higher than reported for most other clay minerals. Conclusion: Different mineral formation pathways in volcanic soils, notably the formation of halloysite versus allophanes, strongly affect the soils' retention capacity for GLP. The high AC of allophanes may induce the low mobility of GLP in allophane‐containing soils. Long‐term use of GLP may accumulate the herbicide in these soils with potential effects on biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

Published
2023
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11. Glyphosate adsorption on allophane and halloysite

Author

Tunega, Daniel, primary, Rechberger, Maria, additional, Remlinger, Vivian, additional, Lenhardt, Katharina, additional, Rennert, Thilo, additional, Rennhofer, Harald, additional, Willinger, Max, additional, Zehetner, Franz, additional, and Gerzabek, Martin, additional

Published
2023
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16. OP10: Elucidating the Reasons Behind Hydrogel Induced Cell Elongation and Directed Migration in Schwann Cells

Author

Millesi, Flavia, primary, Mero, Sascha, additional, Semmler, Lorenz, additional, Mann, Anda, additional, Supper, Paul, additional, Haertinger, Maximilian, additional, Stadlmayr, Sarah, additional, Windberger, Ursula, additional, Rennhofer, Harald, additional, Ploszczanski, Leon, additional, Weiss, Tamara, additional, Naghilou, Aida, additional, and Radtke, Christine, additional

Published
2022
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19. Polymers / Solvent-free Ultrasonic Dispersion of Nanofillers in Epoxy Matrix

Author

Zanghellini, Benjamin, Knaack, Patrick, Schörpf, Sebastian, Semlitsch, Karl-Heinz, Lichtenegger, Helga C., Praher, Bernhard, Omastova, Maria, and Rennhofer, Harald

Subjects
carbon nanotubes, functionalization, Rheologie, dispersion, rheology, Ultraschall, ultrasonication, Funktionalisierung
Abstract

Dispersion of carbon nanotubes and carbon nanofibers is a crucial processing step in the production of polymer-based nanocomposites and poses a great challenge due to the tendency of nanofillers to agglomerate. One of the most effective methods for dispersion is the use of a three-roll mill, which is a well-established method and results in agglomerates below 5 m. Nevertheless, this process is time-consuming and thus a limiting factor for industrial applications. Our aim was to establish an easy and efficient ultrasonic dispersion process, characterize the dispersion parameters, and compare both methods, ultrasonication and the three-roll mill. We applied rheological tests and analyzed the agglomerate sizes by an image fit of the microscopy images. All these analyses combined deliver a valuable set of information about the dispersions quality and, therefore, allows the improvement and further adaptation of the dispersion process. (VLID)5734995

Published
2021

22. Poly(ester amide)s from poly(alkylene succinate)s and rapid crystallizing amido diols

Author

Kluge, Marcel, Rennhofer, Harald, Lichtenegger, Helga C., Liebner, Falk W., Robert, Tobias, and Publica

Subjects
bio-based polymers, thermal properties, microstructure, poly(ester amide), succinic acid, amido diol
Abstract

Random poly(ester amide)s are synthesized from succinic acid, ethylene glycol or 1,4-butanediol and different aliphatic amido diols - symmetric a,o-diols containing two amide moieties. The formation of chain-terminating N-succinimide end groups, which limit the molecular weight attainable by common synthetic strategies, is effectively suppressed. Poly(ester amide)s crystallize in a suprastructure similar to that of even-even polyamides. The thermal properties of both types of poly(ester amide)s synthesized are considerably improved and transition temperatures are tunable by changing the ratio of aliphatic diol to rapidly crystallizing amido diol in the feed. Using ethylene glycol as diol component, Tg and Tm of the material could be enhanced from −12 to −2 °C and 97 to 157 °C, respectively, while an increase from −33 to −8 °C and 115-153 °C was observed for their 1,4-butanediol derived counterparts. Furthermore, the slow crystallization rate of poly(ethylene succinate) from molten state could be significantly accelerated by the introduction of amide moieties into the polymer backbone.

Published
2020

33. Strain Hardening and Pore Size Harmonization by Uniaxial Densification: A Facile Approach toward Superinsulating Aerogels from Nematic Nanofibrillated 2,3-Dicarboxyl Cellulose

Author

Plappert, Sven, Nedelec, J.-M., Rennhofer, Harald, Lichtenegger, Helga, Liebner, Falk, Department of Chemistry, Division of Chemistry of Renewables, University of Natural Resources and Life Sciences Vienna, Vienna, Institut de Chimie de Clermont-Ferrand (ICCF), SIGMA Clermont (SIGMA Clermont)-Institut de Chimie du CNRS (INC)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), University of Natural Resources and Life Sciences (BOKU), Institute of Physics and Materials Science, University of Natural Resources and Life Sciences Vienna, Department of Chemistry, Universität für Bodenkultur Wien [Vienne, Autriche] (BOKU), Nedelec, Jean-Marie, and Universität für Bodenkultur Wien = University of Natural Resources and Life [Vienne, Autriche] (BOKU)

Subjects
[CHIM.MATE] Chemical Sciences/Material chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017

34. Acid Free Oxidation and Simple Dispersion Method of MWCNT for High-Performance CFRP

Author

Singer, Gerald, primary, Siedlaczek, Philipp, additional, Sinn, Gerhard, additional, Rennhofer, Harald, additional, Mičušík, Matej, additional, Omastová, Maria, additional, Unterlass, Miriam, additional, Wendrinsky, Josef, additional, Milotti, Valeria, additional, Fedi, Filippo, additional, Pichler, Thomas, additional, and Lichtenegger, Helga, additional

Published
2018
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35. Impact of Pyrolysis Temperature on Charcoal Characteristics

Author

Tintner, Johannes, primary, Preimesberger, Christoph, additional, Pfeifer, Christoph, additional, Soldo, Denis, additional, Ottner, Franz, additional, Wriessnig, Karin, additional, Rennhofer, Harald, additional, Lichtenegger, Helga, additional, Novotny, Etelvino H., additional, and Smidt, Ena, additional

Published
2018
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40. Electrically Conducting Carbon Microparticles by Direct Carbonization of Spent Wood Pulping Liquor

Author

Köhnke, Janea, primary, Rennhofer, Harald, additional, Lichtenegger, Helga, additional, Mahendran, Arunjunai raj, additional, Unterweger, Christoph, additional, Prats-Mateu, Batirtze, additional, Gierlinger, Notburga, additional, Schwaiger, Elisabeth, additional, Mahler, Arnulf-Kai, additional, Potthast, Antje, additional, and Gindl-Altmutter, Wolfgang, additional

Published
2018
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43. Strain Hardening and Pore Size Harmonization by Uniaxial Densification: A Facile Approach toward Superinsulating Aerogels from Nematic Nanofibrillated 2,3-Dicarboxyl Cellulose

Author

Plappert, Sven F., Nedelec, Jean-Marie, Rennhofer, Harald, Lichtenegger, Helga C., and Liebner, Falk W.

Abstract

Dissolving pulp has been subjected to consecutive periodate/chlorite treatments to afford 2,3-dicarboxyl cellulose (DCC, 1.02 mmol g–1COOH). Subsequent nanofibrillation afforded stable nematic nf-DCC dispersions (average particle size 2.1 nm × 525 nm) at significantly lower energy input compared to TEMPO-oxidation. Acid-induced gelation triggered by extensive hydrogen bonding sets the ordered state and affords free-standing hydrogels that can be converted to highly transparent birefringent aerogels by scCO2drying. Uniaxial compression of the obtained ultra-lightweight ductile nf-DCC aerogels down to 5% of their original volume intriguingly preserves nematic orientation and transparence. Simultaneously, strain hardening translates into exceptionally good mechanical properties, such as toughness at nearly zero Poisson’s ratio. Uniaxial compression has been furthermore demonstrated to be a facile and efficient means for converting nf-DCC aerogels of broad, multiscale pore size distribution into entirely micro/mesoporous scaffolds of narrow size distribution at far-reaching preservation of porosity. Following this approach, thermally superinsulating nf-DCC aerogels (λ = 0.018 W m–1K–1) have been prepared, whose intriguing mechanical properties, transparence, and nematic ordering bear great potential for other applications as well.

Published
2024
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