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rss_1.0 Recursos de colección

Document Server@UHasselt (38,665 recursos)
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.

Dept. Chemistry-Biology-Geology (SBG) - Organic and Polymer Chemistry

Mostrando recursos 1 - 20 de 455

1. Solvent-Dependent Deprotonation of meso-Pyrimidinylcorroles: Absorption and Fluorescence Studies - Kruk, Mikalai; Ngo, Thien H.; Savva, Vadim; Starukhin, Aleksander; Dehaen, Wim; Maes, Wouter
The absorption spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in 15 solvents. The formation of deprotonated corrole species was found to account for the dramatic changes in the absorption spectra in several solvents. Careful analysis of the relationship between the formation of deprotonated species and solvent properties results in the conclusion that there is no single solvent parameter correlation, and either multiparameter correlations or specific solute-solvent interactions (preferential solvation of the most acidic NH tautomer or perturbation of intramolecular hydrogen bonding in the macrocycle core) should be considered. The fluorescence properties of the deprotonated pyrimidinylcorrole are also reported for the first...

2. Corrole NH Tautomers: Spectral Features and Individual Protonation - Ivanova, Yulia B.; Savva, Vadim A.; Mamardashvili, Nugzar Z.; Starukhin, Aleksander S.; Ngo, Thien H.; Dehaen, Wim; Maes, Wouter; Kruk, Mikalai M.
Protonation of a free-base meso-pyrimidinyl-substituted AB(2)-corrole (H(3)AB(2)) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the titration was undertaken. Two steps in the titration curve were identified at temperatures around 293-298 K, whereas one-step formation of protonated species was found to occur at temperatures above 308 K. The protonation product was the same in both cases, i.e., H(4)AB(2)(+) corrole, protonated at the macrocycle core nitrogen atoms. The two steps in the...

3. Unraveling the Fluorescence Features of Individual Corrole NH Tautomers - Kruk, Mikalai; Ngo, Thien H.; Verstappen, Pieter; Starukhin, Aleksander; Hofkens, Johan; Dehaen, Wim; Maes, Wouter
The fluorescence spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in the temperature range from 4.2 to 332 K. For the first time, the individual fluorescence profiles of the two corrole NH tautomers have been assigned over the whole temperature range. The pronounced temperature dependence of the fluorescence spectra of the meso-pyrimidinylcorrole under study was found to originate from switching between the fluorescence emissions of the two tautomers due to a reduced NH tautomerization rate with decreasing temperature. As a result, the long wavelength tautomer dominates the total emission spectrum at room temperature, whereas at low temperatures, the majority of the emission...

4. Charge transfer in the weak driving force limit in blends of MDMO-PPV and dithienylthiazolo[5,4-d]thiazoles towards organic photovoltaics with high V-OC - Nevil, Nissy; Ling, Yun; Van Mierloo, Sarah; Kesters, Jurgen; Piersimoni, Fortunato; Adriaensens, Peter; Lutsen, Laurence; Vanderzande, Dirk; Manca, Jean; Maes, Wouter; Van Doorslaer, Sabine; Goovaerts, Etienne
A series of three 5'-aryl-2,5-dithienylthiazolo[5,4-d]thiazole (DTTzTz) semiconducting molecules with different aryl substituents has been investigated as alternative acceptor materials in combination with the donor polymer poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) in order to evaluate the photoinduced charge transfer (CT) efficiency in the resulting blends, designed towards possible application in organic photovoltaics. Photoluminescence quenching together with polaron detection by electron paramagnetic resonance and photoinduced absorption (PIA) demonstrate an increasing charge transfer efficiency when the DTTzTz substituents are varied from thien-2-yl to 4-trifluoromethylphenyl and 4-cyanophenyl groups, correlating well with the increasing acceptor strength in this series of molecules. In line with this observation, there...

5. Single-pulse pulsed laser polymerization-electron paramagnetic resonance investigations into the termination kinetics of n-butyl acrylate macromonomers - Barth, Johannes; Buback, Michael; Barner-Kowollik, Christopher; Junkers, Thomas; Russell, Gregory T.
The termination of model mid-chain radicals (MCRs), which mimic radicals that occur in acrylate polymerization over a broad range of reaction conditions, has been studied by single-pulse pulsed laser polymerization (SP-PLP) in conjunction with electron paramagnetic resonance spectroscopy. The model radicals were generated by initiator-fragment addition to acrylic macromonomers that were preformed prior to the kinetic experiments, thus enabling separation of termination from the propagation reaction, for these model radicals propagate sparingly, if at all, on the timescale of SP-PLP experiments. Termination rate coefficients of the MCRs were determined in the temperature range of 060 degrees C in acetonitrile and...

6. Poly(3-alkylthiophene) nanofibers for photovoltaic energy conversion - Bertho, Sabine; Oosterbaan, Wibren D.; Vrindts, Veerle; Bolsee, Jean-Christophe; Piersimoni, Fortunato; Spoltore, Donato; D'Haen, Jan; Lutsen, Laurence; Vanderzande, Dirk; Manca, Jean V.
The use of nanostructured non-conventional semiconductors such as conjugated polymers and metal oxides (e.g. TiO2), opens promising perspectives towards a new generation of solar cells based on the concept of donor:acceptor bulk heterojunctions. In this concept donor material and acceptor material form interpenetrating networks allowing light absorption, charge transfer and charge transport throughout the entire bulk of the thin film. Since nanomorphology is of crucial importance for this type of solar cells, in this contribution the use of nanofibers in bulk heterojunction solar cells is explored in order to obtain highways for charge transport. We investigate in particular the use...

7. Synthesis and Spectroscopic Properties of a Novel Perylenediimide Derivative - Hakli-Birel, Ozgul; Dincalp, Haluk; Zafer, Ceylan; Demic, Serafettin; Colladet, Kristof; Vanderzande, Dirk; Yurum, Yuda; Icli, Siddik
A novel symmetric 3,4,9,10-perylenetetracarboxylic acid derivative (PDI1) dye based on thiophene donor group was synthesized and characterized by FT-IR and (1)H NMR. Cyclic Voltammetry analysis is performed to determine the energy levels of the perylene derivative. Optical characteristics were determined by visible absorption and fluorescence emission spectra. Spectral behavior and fluorescence quantum yield of PDI1 have been measured in different solvents. The dye exhibits high fluorescence quantum yield (Phi(f): 0.94-0.99). But the quantum yield PDI1 is very low in the n-butanol solution (Phi(f): 0.12). The photophysical properties have important implications for use in a variety of electroactive and photovoltaic applications....

8. MIP-based biomimetic sensor for the electronic detection of serotonin in human blood plasma - Peeters, M.; Troost, F. J.; van Grinsven, B.; Horemans, F.; Alenus, J.; Murib, M. S.; Keszthelyi, D.; Ethirajan, A.; Thoelen, R.; Cleij, T.J.; Wagner, P.
Serotonin is an important signaling molecule in the human body. The detection of serotonin is commonly performed by high performance liquid chromatography (HPLC), which is costly and time consuming due to extensive sample preparation. We will show that these problems can be overcome by using molecularly imprinted polymers (MIPs) as synthetic receptors in combination with impedance spectroscopy as readout technique. The MIPs were prepared with several blends of the underlying monomers and the best performing MIP material was selected by optical batch-rebinding experiments. MIP microparticles were then integrated in an impedimetric sensor cell and dose-response curves were measured in PBS...

9. Macromonomers from AGET Activation of Poly(n-butyl acrylate) Precursors: Radical Transfer Pathways and Midchain Radical Migration - Vandenbergh, Joke; Junkers, Thomas
Macromonomers are synthesized from AGET activation of poly(n-butyl acrylate), P(nBuA), synthesized via ATRP. Reactivation of the polymer chains is achieved at 140 degrees C using Sn(EH)(2) as reducing agent. Under such conditions, P(nBuA) macroradicals undergo fast chain transfer reactions forming midchain radicals, MCR, followed by beta-scission reactions leading to unsaturated macromonomers. Furthermore, intermolecular transfer-to-polymer reactions lead to considerable amounts of hydrogen-terminated products. Soft ionization mass spectrometry of product samples reveals that under very dilute conditions the macromonomer formation is predominant over the hydrogen transfer reaction of the macroradicals, and macromonomers with overall 80% end-group purity can be achieved, which is,...

10. Corrole-Porphyrin Conjugates with Interchangeable Metal Centers - Ngo, Thien H.; Nastasi, Francesco; Puntoriero, Fausto; Campagna, Sebastiano; Dehaen, Wim; Maes, Wouter
Oligoporphyrinoid materials composed of two or three tetrapyrrolic macrocycles have been synthesized by either mono- or disubstitution (SNAr) of a phenolic Zn-AB3-porphyrin on a meso-dichloropyrimidinyl-substituted Cu-AB2-corrole. Selective metallation/demetallation sequences were carried out on these mixed corroleporphyrin conjugates to afford multichromophoric systems with variable metal centers. The absorption spectra of the free-base corroleporphyrin systems were essentially additive, which demonstrates that only weak intercomponent interactions take place in these assemblies and therefore they can be regarded as supramolecular systems. Photophysical studies of the free-base conjugates showed that these species are highly fluorescent, with fluorescence occurring from the lowest-energy singlet state of the...

11. Enhanced Spin-capturing Polymerization and Radical Coupling Mediated by Cyclic Nitrones - Ranieri, Kayte; Conradi, Matthias; Chavant, Pierre-Yves; Blandin, Veronique; Barner-Kowollik, Christopher; Junkers, Thomas
A series of cyclic nitrones have been tested for their spin-trapping activity in the enhanced spin-capturing polymerization of styrene and in nitrone-mediated radical coupling reactions. rac-2-Isopropyl-2,3-dimethyl-1-oxy-2,3-dihydro-imidazol-4-one was found to be the most efficient nitrone. The specific polystyrene macroradical addition rate to this nitrone was determined to be 8.0 x 10(3) L mol(-1) s(-1), which is by a factor of 10 higher than for previously studied compounds. Via enhanced spin-capturing polymerization, polymers in the range of oligomers to 30000 g mol(-1) were obtained. A strong dependence of molecular weight on monomer conversion was observed, which can be explained by the high...

12. Use of a continuous-flow microreactor for thiol-ene functionalization of RAFT-derived poly(butyl acrylate) - VANDENBERGH, Joke; JUNKERS, Thomas
This study describes the synthesis of functionalized RAFT-derived poly(n-butyl acrylate) polymers via the use of a continuous-flow microreactor, in which aminolysis as well as thiol-ene reactions are executed in reaction times of just 20 minutes. Poly(n-butyl acrylate) (M-n = 3800 g mol(-1), PDI = 1.10) with a trithiocarbonate end group was prepared via a conventional RAFT process. The polymer was then functionalized via aminolysis/thiol-ene reactions in the micro-flow reactor with isobornyl acrylate, propargyl acrylate, poly(ethylene glycol) methyl ether acrylate and pentaerythritol tetraacrylate. To optimize the reaction time and reaction temperature of the micro-flow reactor, freshly collected samples were studied with...

13. On the stability of a variety of organic photovoltaic devices by IPCE and in situ IPCE analyses - the ISOS-3 inter-laboratory collaboration - Teran-Escobar, Gerardo; Tanenbaum, David M.; Voroshazi, Eszter; Hermenau, Martin; Norrman, Kion; Lloyd, Matthew T.; Galagan, Yulia; Zimmermann, Birger; Hosel, Markus; Dam, Henrik F.; Jorgensen, Mikkel; Gevorgyan, Suren; Kudret, Suleyman; Maes, Wouter; Lutsen, Laurence; Vanderzande, Dirk; Wuerfel, Uli; Andriessen, Ronn; Roesch, Roland; Hoppe, Harald; Rivaton, Agnes; Uzunoglu, Gulsah Y.; Germack, David; Andreasen, Birgitta; Madsen, Morten V.; Bundgaard, Eva; Krebs, Frederik C.; Lira-Cantu, Monica
This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RISempty set-DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work, we apply the Incident Photon-to-Electron Conversion Efficiency (IPCE) and the in situ IPCE techniques to determine the relation between solar cell performance and solar cell stability. Different ageing conditions were considered: accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices...

14. TOF-SIMS investigation of degradation pathways occurring in a variety of organic photovoltaic devices - the ISOS-3 inter-laboratory collaboration - Andreasen, Birgitta; Tanenbaum, David M.; Hermenau, Martin; Voroshazi, Eszter; Lloyd, Matthew T.; Galagan, Yulia; Zimmernann, Birger; Kudret, Suleyman; Maes, Wouter; Lutsen, Laurence; Vanderzande, Dirk; Wuerfel, Uli; Andriessen, Ronn; Roesch, Roland; Hoppe, Harald; Teran-Escobar, Gerardo; Lira-Cantu, Monica; Rivaton, Agnes; Uzunoglu, Guelsah Y.; Germack, David S.; Hosel, Markus; Dam, Henrik F.; Jorgensen, Mikkel; Gevorgyan, Suren A.; Madsen, Morten V.; Bundgaard, Eva; Krebs, Frederik C.; Norrman, Kion
The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible...

15. Homoselenacalix[4]arenes: synthetic exploration and metallosupramolecular chemistry - Thomas, Joice; Dobrzanska, Liliana; Van Hecke, Kristof; Sonawane, Mahendra P.; Robeyns, Koen; Van Meervelt, Luc; Wozniak, Krzysztof; Smet, Mario; Maes, Wouter; Dehaen, Wim
Homoselenacalix[4]arenes were synthesized by a [2 + 2] reductive coupling protocol favouring the cyclotetramers. The inner and outer-rim decoration was varied and a bicyclic derivative was prepared by a similar one-pot procedure. Conformational analysis in solution and the solid state showed noticeable differences between the homoselenacalix[4]arenes and the analogous homothiacalix[4]arenes and provided insight into the metal binding potential of the Se-bridged macrocycles. The homoselenacalix[4]arenes were found to bind Ag(I). Complexation was visualized in the solid state and different packing networks were formed depending on the counter ions applied.

16. Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization - Debuigne, Antoine; Hurtgen, Marie; Detrembleur, Christophe; Jerome, Christine; Barner-Kowollik, Christopher; Junkers, Thomas
The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second...

17. Tuning the Dimensions of ZnO Nanorod Arrays for Application in Hybrid Photovoltaics - Baeten, Linny; Conings, Bert; D'Haen, Jan; De Dobbelaere, Christopher; Hardy, An; Manca, Jean V.; Van Bael, Marlies K.
ZnO nanorod arrays are a very eligible option as electron acceptor material in hybrid solar cells, owing to their favorable electrical properties and abundance of available, easy, and low-cost synthesis methods. To become truly effective in this field, a major prerequisite is the ability to tune the nanorod dimensions towards optimal compatibility with electron-donating absorber materials. In this work, a water-based seeding and growth procedure is used to synthesize ZnO nanorods. The nanorod diameter is tuned either by modifying the zinc concentration of the seeding solution or by changing the concentration of the hydrothermal growth solution. The consequences of this...

18. Investigation of the End Group Fidelity at High Conversion during Nitroxide-Mediated Acrylate Polymerizations - Guillaneuf, Yohann; Gigmes, Didier; Junkers, Thomas
The impact of formation of midchain radicals-and more specifically the follow up reactions of beta-scission and macromonomer addition to propagating macroradicals stemming from this process-on the nitroxide-mediated polymerization of acrylates have been studied via kinetic modeling with the software package Predici on the example of butyl acrylate polymerization at 120 degrees C. Only small influences of the midchain radical formation on the livingness of the process is observed, however, large effects must be envisaged by the (reverse) scission reaction at high monomer-to-polymer conversions. A significant loss of livingness, depending on the temperature, monomer and initiator concentration must be expected at...

19. Thermally responsive core-shell microparticles and cross-linked networks based on nitrone chemistry - Barner, Leonie; Quick, Alexander S.; Vogt, Andrew P.; Winkler, Volker; Junkers, Thomas; Barner-Kowollik, Christopher
Complex cross-linked soluble architectures with molecular weights ranging from 25 000 to 71 000 g mol(-1) and polydispersities (PDIs) ranging from 2.5 to 8.1 are generated using nitrone mediated chemistry. These cross-linked architectures are subsequently cleaved into their constituting fragments, i.e. linear chains with molecular weights ranging from 36 000 to 40 000 g mol(-1) and a PDI of 2.0 or network fragments with molecular weights ranging from 28 000 to 30 000 g mol(-1) and PDIs from 2.5 to 3.7, respectively. The cleavage into linear chains or network fragments depends on the pathway of network formation. Nitrone mediated reactions...

20. Relation between Morphology and Recombination Kinetics in Nanostructured Hybrid Solar Cells - Conings, Bert; Baeten, Linny; Boyen, Hans-Gerd; D'Haen, Jan; Van Bael, Marlies K.; Manca, Jean
Systematic performance improvement of excitonic solar cells hinges on thorough knowledge of their main loss mechanisms. Accordingly, the study of recombination kinetics is indispensable, enabling to identify and quantify what is considered the most important loss pathway for such devices. In contrast to the advances made in controlling the morphology of organic bulk heterojunction solar cells, it remains challengin to establish a robust correlation between morphology and recombination kinetics. Most obvious culpritsare the rather disordered nature of most heterojunctions and the absence of phase purity. In that respect, hybrid solar cells based on ZnO nanorod arrays and poly(3- hexylthiophene) can o???er a convenient...

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