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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Chemistry

Mostrando recursos 1 - 20 de 441

  1. Direct Access to Dithiobenzoate RAFT Agent Fragmentation Rate Coefficients by ESR Spin-Trapping

    RANIERI, Kayte; Delaittre, Guillaume; Barner-Kowollik, Christopher; JUNKERS, Thomas
    The beta-scission rate coefficient of tert-butyl radicals fragmenting off the intermediate resulting from their addition to tert-butyl dithiobenzoate-a reversible addition-fragmentation chain transfer (RAFT) agent-is estimated via the recently introduced electron spin resonance (ESR)-trapping methodology as a function of temperature. The newly introduced ESR-trapping methodology is critically evaluated and found to be reliable. At 20 degrees C, a fragmentation rate coefficient of close to 0.042 s(-1) is observed, whereas the activation parameters for the fragmentation reaction-determined for the first time-read E-A = 82 +/- 13.3 kJ mol(-1) and A = (1.4 +/- 0.25) x 10(13) s(-1). The ESR spin-trapping methodology thus...

  2. Solvent Effects on Acrylate k(p) in Organic Media?-A Systematic PLP-SEC Study

    Haehnel, Alexander P.; WENN, Benjamin; Kockler, Katrin; Bantle, Tobias; Misske, Andrea M.; Fleischhaker, Friederike; JUNKERS, Thomas; Barner-Kowollik, Christopher
    The Arrhenius parameters of the propagation rate coefficient, k(p), are determined employing high-frequency pulsed laser polymerization-size exclusion chromatography (PLP-SEC) for the homologous series of five linear alkyl acrylates (i.e., methyl acrylate (MA), butyl acrylate (BA), dodecyl acrylate (DA), stearyl acrylate (SA), and behenyl acrylate (BeA)) in 1 M solution in butyl acetate (BuAc) as well as in toluene. The comparison of the obtained k(p) values with the literature known values for bulk demonstrates that no significant solvent influence neither in BuAc nor in toluene on the propagation reaction compared to bulk is detectable. Concomitantly, the k(p) values in toluene and...

  3. Exploring the rhizospheric and endophytic bacterial communities of Acer pseudoplatanus growing on a TNT-contaminated soil: towards the development of a rhizocompetent TNT-detoxifying plant growth promoting consortium

    THIJS, Sofie; Van Dillewijn, Pieter; SILLEN, Wouter; TRUYENS, Sascha; HOLTAPPELS, Michelle; D'HAEN, Jan; CARLEER, Robert; WEYENS, Nele; AMELOOT, Marcel; Ramos, Juan-Luis; VANGRONSVELD, Jaco
    Background and aims Numerous microorganisms have been isolated from trinitrotoluene (TNT)-contaminated soils, however TNT tends to persist, indicating that the microbial biomass or activity is insufficient for degradation. Deep-rooting trees at military sites have been found to take-up contaminants from groundwater, and the extensive root and endosphere provide ideal niches for microbial TNT-transformations. Methods We characterised the rhizosphere, root endosphere and endo-phyllosphere bacteria of Acer pseudoplatanus growing at a historically TNT-contaminated location, using 16S rRNA gene fingerprinting, bacteria isolation, oxidoreductase gene-cloning, in planta growth-promotion (PGP) tests, inoculation, plant physiology measurements and microscopy. Results Based on terminal-restriction-fragment-length-polymorphism analysis, bulk soil and...

  4. Evaluation of the Thickness and Oxygen Transmission Rate before and after Thermoforming Mono- and Multi-layer Sheets into Trays with Variable Depth

    BUNTINX, Mieke; WILLEMS, Gert; KNOCKAERT, Griet; Adons, Dimitri; YPERMAN, Jan; CARLEER, Robert; PEETERS, Roos
    During thermoforming, plastic sheets are heated and subsequently deformed through the application of mechanical stretching and/or pressure. This process directly impacts sheet properties such as material thickness in walls, corners, and bottom, crystallinity in the constituent layers, and particularly the oxygen gas permeability. The aim of this study was to quantify the impact of thermoforming on thickness and oxygen transmission rate (OTR) of selected packaging materials (polypropylene (PP); PP/ethylene-vinyl alcohol co-polymer/PP (PP/EVOH/PP); polystyrene/EVOH/polyethylene (PS/EVOH/PE); amorphous polyethylene terephtalate/PE (APET/PE); APET/PE/EVOH/PE; polyamide/PE (PA/PE); and (PE/)PA/EVOH/PA/PE). These materials were extruded in two different thicknesses and thermoformed into trays with the same top dimensions...

  5. Factors Influencing the Conductivity of Aqueous Sol(ution)-Gel-Processed Al-Doped ZnO Films

    DAMM, Hanne; ADRIAENSENS, Peter; DE DOBBELAERE, Christopher; Capon, Boris; ELEN, Ken; DRIJKONINGEN, Jeroen; CONINGS, Bert; MANCA, Jean; D'HAEN, Jan; Detavernier, Christophe; Magusin, Pieter C. M. M.; Hadermann, Joke; HARDY, An; VAN BAEL, Marlies
    Solution processing of Al-doped ZnO (AZO) is interesting from an economical point of view for reducing synthesis and deposition costs in comparison to that for vacuum methods. Several (aqueous) chemical solution deposition routes have been explored for AZO, but the question that has never been answered is how state-of-the-art conductivity is achieved. Here, we fine tune an aqueous solution precursor for AZO, resulting in resistivities within the 10???3 Ohm cm range after a reductive treatment. Profound insights are gained through the study of the density of the film, the crystal phase, the optimum Al doping, and the effect of Al...

  6. Nitrone-Mediated Radical Coupling of Polymers Derived from Reverse Iodine-Transfer Polymerization

    RANIERI, Kayte; VANDENBERGH, Joke; Barner-Kowollik, Christopher; JUNKERS, Thomas
    The current study describes the synthesis of iodine-end-capped polystyrene (PS) and poly(methyl methacrylate) (PMMA) precursors using reverse iodine-transfer polymerization, which, in a second step, are used in nitrone-mediated radical coupling (NMRC) reactions. Initially, the reverse iodine polymerization of both monomers is studied and optimized in order to obtain iodine-end-capped materials with controlled molecular weights and low dispersities. Subsequently, NMRC of both PS and PMMA precursors is carried out in the presence of CuCl as a halide-exchange agent. Coupling efficiencies of x(c) = 0.754 for PS-I and 0.84 for PMMA-I are observed; however, the addition of 10 equivalents of styrene is...

  7. Diamond functionalization with lighth-arvesting molecular wires: improved surface coverage by optimized Suzuki cross-coupling conditions (vol 4, pg 42044, 2014)

    YEAP, Weng Siang; BEVK, David; Liu, X.; Krysova, H.; Pasquarelli, A.; VANDERZANDE, Dirk; LUTSEN, Laurence; Kavan, L.; Fahlman, M.; MAES, Wouter; HAENEN, Ken

  8. Preparation and characterization of three dimensionally ordered macroporous Li5La3Ta2O12 by colloidal crystal templating for all-solid-state lithium-ion batteries

    Kokal, I.; VAN DEN HAM, Jonathan; Delsing, A.C.A.; Notten, P.H.L.; Hintzen, H.T.
    Three dimensionally ordered macroporous (3DOM) membranes of Li5La3Ta2O12 (LLTO) for all-solid-state lithium-ion batteries were prepared by using colloidal crystal templating of mono dispersed polystyrene (PS) spheres combined with sol???gel synthesis of LLTO precursor. During the sol???gel synthesis, the appropriate mixtures of CH3COOLi, La(NO3)3??6H2O and Ta(OC2H5)5 were dissolved in two different solvents to prepare garnet-type LLTO. Various sizes of mono dispersed (1, 3 and 5 ??m) PS beads were used as a template to investigate the size effect of template on the network formation of LLTO membranes. The transformation from precursor solutions, which are added onto the PS template, to crystalline...

  9. A UV-absorber bismuth(III)-N-methyldiethanolamine complex as a low-temperature precursor for bismuth-based oxide thin films

    Perez-Mezcua, Dulce; Sirera, Rafael; Jimenez, Ricardo; Bretos, Inigo; DE DOBBELAERE, Christopher; HARDY, An; VAN BAEL, Marlies; Lourdes Calzada, M.
    Novel synthetic methods in solution that reduce the formation temperature of bismuth-based electronic oxides are essential for their successful integration with substrates of low thermal stability within micro- and flexible-electronic devices. This has become crucial for these oxides, since they appear as promising low-toxic functional materials alternative to other electronic oxides containing heavy metals. However, this is a challenge, since the crystallization of bismuth oxides occurs at high temperatures. To overcome these problems, we synthesize here a UV-absorber charge transfer metal complex in solution between the Bi(III) ion and an alkanolamine, N-methyldiethanolamine (Bi(III)-mdea). We take advantage of the photoreactivity of...

  10. Differential response of Arabidopsis leaves and roots to cadmium: Glutathione-related chelating capacity vs antioxidant capacity

    JOZEFCZAK, Marijke; KEUNEN, Els; Schat, Henk; Bliek, Mattijs; Hernandez, Luis E.; CARLEER, Robert; REMANS, Tony; BOHLER, Sacha; VANGRONSVELD, Jaco; CUYPERS, Ann
    This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mechanisms of cadmium (Cd)-induced detoxification (i.e. chelation and antioxidative defence). A kinetic study was conducted on hydroponically grown Arabidopsis thaliana (L Heyhn) to gain insight into the early events after exposure to Cd. Cadmium detoxification was investigated at different levels, including gene transcripts, enzyme activities and metabolite content. Data indicate a time-dependent response both within roots and between plant organs. Early on in roots, GSH was preferentially allocated to phytochelatin (PC) synthesis destined for Cd chelation. This led to decreased GSH levels, without alternative pathways activated...

  11. Worldwide outdoor round robin study of organic photovoltaic devices and modules

    Madsen, Morten V.; Gevorgyan, Suren A.; Pacios, R.; Ajuria, J.; Etxebarria, I.; Kettle, Jeff; Bristow, Noel D.; Neophytou, Marios; Choulis, Stelios A.; Roman, Lucimara Stolz; Yohannes, Teketel; Cester, Andrea; Cheng, Pei; Zhan, Xiaowei; Wu, Jiang; Xie, Zhiyuan; Tu, Wei-Chen; He, Jr-Hau; Fell, Christopher J.; Anderson, Kenrick; Hermenau, Martin; Bartesaghi, Davide; Koster, L. Jan Anton; Machui, Florian; Gonzalez-Valls, Irene; Lira-Cantu, Monica; Khlyabich, Petr P.; Thompson, Barry C.; Gupta, Ritu; Shanmugam, Kiruthika; Kulkarni, Giridhar U.; Galagan, Yulia; Urbina, Antonio; Abad, Jose; Roesch, Roland; Hoppe, Harald; Morvillo, P.; Bobeico, E.; Panaitescu, Eugen; Menon, Latika; Luo, Qun; Wu, Zhenwu; Ma, Changqi; Hambarian, Artak; Melikyan, Varuzhan; Hambsch, M.; Burn, Paul L.; Meredith, Paul; Rath, Thomas; Dunst, Sebastian; Trimmel, Gregor; Bardizza, Giorgio; Muellejans, Harald; Goryachev, A. E.; Misra, Ravi K.; Katz, Eugene A.; Takagi, Katsuhiko; Magaino, Shinichi; Saito, Hidenori; Aoki, Daisuke; Sommeling, Paul M.; Kroon, Jan M.; VANGERVEN, Tim; MANCA, Jean; KESTERS, Jurgen; MAES, Wouter; Bobkova, Olga D.; Trukhanov, Vasily A.; Paraschuk, Dmitry Yu.; Castro, Fernando A.; Blakesley, James; Tuladhar, Sachetan M.; Roehr, Jason Alexander; Nelson, Jenny; Xia, Jiangbin; Parlak, Elif Alturk; Tumay, Tulay Ash; Egelhaaf, Hans-Joachim; Tanenbaum, David M.; Ferguson, Gretta Mae; Carpenter, Robert; Chen, Hongzheng; Zimmermann, Birger; Hirsch, Lionel; Wantz, Guillaume; Sun, Ziqi; Singh, Pradeep; Bapat, Chaitnya; Offermans, Ton; Krebs, Frederik C.
    Accurate characterization and reporting of organic photovoltaic (OPV) device performance reniains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using "suitcase sample" approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where...

  12. Valorisatie van varkensmest door pyrolyse - Cleantech business case in Limburg

    KUPPENS, Tom; MAGGEN, Jens; CARLEER, Robert; YPERMAN, Jan; VAN DAEL, Miet; VAN PASSEL, Steven
    i-Cleantech Vlaanderen

  13. Factors Influencing the Conductivity of Aqueous Sol(ution)−Gel- Processed Al-Doped ZnO Films

    DAMM, Hanne; Adriaensens, P.; De Dobbelaere, Christopher; Capon, Boris; ELEN, Ken; DRIJKONINGEN, Jeroen; CONINGS, Bert; MANCA, Jean; D'Haen, Jan; Detavernier, Christophe; Magusin, Pieter C. M. M.; Hadermann, Joke; HARDY, An; VAN BAEL, Marlies
    Solution processing of Al-doped ZnO (AZO) is interesting from an economical point of view for reducing synthesis and deposition costs in comparison to that for vacuum methods. Several (aqueous) chemical solution deposition routes have been explored for AZO, but the question that has never been answered is how state-of-the-art conductivity is achieved. Here, we fine tune an aqueous solution precursor for AZO, resulting in resistivities within the 10−3 Ohm cm range after a reductive treatment. Profound insights are gained through the study of the density of the film, the crystal phase, the optimum Al doping, and the effect of Al...

  14. Momentum space analysis of the electronic structure of biphenyl

    MORINI, Filippo; SHOJAEIKOHNEHSHAHRI, Reza; DELEUZE, Michael
    The results of a yet to come experimental study of the electronic structure of biphenyl employing electron momentum spectroscopy (EMS) have been theoretically predicted, taking into account complications such as structural mobility in the electronic ground state, electronic correlation and relaxation, and a dispersion of the inner-valence ionization intensity to electronically excited (shake-up) configurations in the cation. The main purpose of this work is to explore the current limits of EMS in unraveling details of the molecular structure, namely the torsional characteristics of large and floppy aromatic molecules. At the benchmark ADC(3)/cc-pVDZ level of theory, the influence of the twist...

  15. One pot synthesis of higher order quasi-block copolymer libraries via sequential RAFT polymerization in an automated synthesizer

    HAVEN, Joris; Guerrero-Sanchez, Carlos; Keddie, Daniel J.; Moad, Graeme; Thang, San H.; Schubert, Ulrich S.
    Recently developed sequential reversible addition-fragmentation chain transfer (RAFT) polymerization protocols allow the rapid, fully unattended preparation of quasi-block copolymer libraries that cover a wide range of copolymer compositions in an automated synthesizer. This contribution explores the scope and limitations of this sequential approach for the synthesis of higher order quasi-multiblock copolymers (including copolymer sequences of BAB, CBABC, ABC and ABCD). These syntheses illustrate the utility of this high-throughput approach for the one pot synthesis of functional polymers of increased complexity. Additionally, the use of this experimental technique for method development is highlighted.

  16. Formulation of itraconazole nanococrystals and evaluation of their bioavailability in dogs

    De Smet, Lieselotte; Saerens, Lien; De Beer, Thomas; CARLEER, Robert; ADRIAENSENS, Peter; Van Bocxlaer, Jan; Vervaet, Chris; Remon, Jean Paul
    The aim of the study is to increase the bioavailability of itraconazole (ITRA) using nanosized cocrystals prepared via wet milling of ITRA in combination with dicarboxylic acids. Wet milling was used in order to create a nanosuspension of ITRA in combination with dicarboxylic acids. After spray-drying and bead layering, solid state was characterized by MDSC, XRD, Raman and FT-IR. The release profiles and bioavailability of the nanococrystalline suspension, the spray-dried and bead layered formulation were evaluated. A monodisperse nanosuspension (549 +/- 51 nm) of ITRA was developed using adipic acid and Tween (R) 80. Solid state characterization indicated the formation...

  17. Electronic Structure of the Positive Radical of C-13-Labeled Poly(3-Octylthienylene Vinylene) Polymer

    Ling, Yun; DILIEN, Hanne; VANDERZANDE, Dirk; ADRIAENSENS, Peter; VAN DOORSLAER, Sabine
    Poly(3-octylthienylene vinylene) (O-PTV) has a great potential as low-bandgap p-type semiconductor for photovoltaic applications. Here, the positive radical state (positive polaron) is induced chemically in the O-PTV polymer in which the vinylene sites are selectively C-13-labeled. Using multi-frequency continuous wave and pulsed electron paramagnetic resonance, the g tensor and maximum H-1 and C-13 hyperfine couplings are determined. A comparative density functional theory (DFT) analysis of PTV-like oligomers is performed. The experimental parameters suggest a larger localization of the positive polaron than follows from the DFT analysis. The counter anion may play a crucial role in localizing the polaron.

  18. Photoinduced Sequence-Controlled Copper-Mediated Polymerization: Synthesis of Decablock Copolymers

    CHUANG, Ya-Mi; ETHIRAJAN, Anitha; JUNKERS, Thomas
    Photoinitiated copper-mediated radical polymerization offers an one-pot and time efficient method of preparing a decablock copolymer PMA-PtBA-PMA-PDEGA-PMA-PtBA-PMA-PDEGA-PnBA-PDEGA with an overall molecular weight of 8500 g.mol(-1). The molecular weight is in close agreement with theoretical expectations and significantly narrow dispersities (D = 1.1-1.17) are achieved for the various block extensions. The tert-butyl group of the decadeblock was deprotected to form PMA-PAA-PMA-PDEGA-PMA-PAA-PMA-PDEGA-PnBA-PDEGA. The deprotection is confirmed by the disappearance of tert-butyl signal and the loss of molecular weight investigated by H-1 NMR and SEC, respectively. The carboxylic group of PAA is protonated in acidic solution (water insoluble) and deprotonated in basic solution...

  19. Cross-linked degradable poly(beta-thioester) networks via amine-catalyzed thiol-ene click polymerization

    VANDENBERGH, Joke; PEETERS, Marloes; Kretschmer, Tobias; WAGNER, Patrick; JUNKERS, Thomas
    A set of binary and ternary biodegradable cross-linked poly(beta-thioester) networks have been synthesized via thiol-ene Michael additions, by reacting combinations of dithiols, diacrylates and multifunctional cross-linkers. Insoluble binary thermoset networks and soluble ternary branched polymers with broad molar mass distributions are obtained in a facile manner after polymerization at room temperature for only few minutes. The networks display excellent thermal stability up to 250 degrees C and exhibit low glass transition temperatures. The soluble branched polymers show degradation of the polyester backbone upon chemical degradation by acidic and basic solutions. Finally, the (bio)degradability of ternary PBT polymer films is examined...

  20. Fast and Efficient [2+2] UV Cycloaddition for Polymer Modification via Flow Synthesis

    CONRADI, Matthias Horst; JUNKERS, Thomas
    The alkene enone [2 + 2] photocycloaddition reaction between polymer-bound maleimide and functional alkenes has been tested in a UV-flow reactor, demonstrating a very high efficiency of the reaction. As a test reaction, polymer end group modifications were carried out on maleimide-functional poly(butyl acrylate). The polymer was prepared by atom transfer radical polymerization (ATRP) using a N-hydroxysuccinimide-functionalized initiator, followed by exchange reaction of the activated ester with a maleimide amine linker. Good control over the polymerization and successful exchange of the end group under mild reaction conditions was confirmed by electrospray ionization mass spectrometry (ESI-MS). The terminal maleimide group was...

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