Recursos de colección

Document Server@UHasselt (59.068 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.

Organic and Bio-polymer Chemistry

Mostrando recursos 1 - 20 de 235

  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. 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...

  4. 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

  5. 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...

  6. 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.

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

    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.

  8. 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...

  9. 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...

  10. 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...

  11. Synthetic protocols towards homodithiacalix[n]arenes

    Thomas, Joice; Dobrzanska, Liliana; Sonawane, Mahendra Punjaji; Smet, Mario; MAES, Wouter; Dehaen, Wim
    Synthetic procedures towards homodithiacalix[n]arenes are developed, starting from simple and readily available bifunctional aryl building blocks, by a dynamic covalent chemistry approach. Reaction of 1,3-bis(mercaptomethyl)-5-tert-butyl-2-methoxybenzene under basic conditions leads to a mixture of trimeric, tetrameric and pentameric dimethylenedithia-bridged cyclooligomers, whereas reaction of 5-tert-butyl-2-methoxy-1,3-bis(thiocyanatomethyl) benzene under reducing conditions (and subsequent oxidation) affords the homodithiacalix[4]arene macrocycle in a very selective fashion through efficient disulphide exchange chemistry.

  12. Diamond functionalization with light-harvesting molecular wires: improved surface coverage by optimized Suzuki cross-coupling conditions

    YEAP, Weng Siang; BEVK, David; Liu, X.; Krysova, H.; Pasquarelli, A.; VANDERZANDE, Dirk; LUTSEN, Laurence; Kavan, L.; Fahlman, M.; MAES, Wouter; HAENEN, Ken
    Donor-acceptor type light-harvesting molecular wires are covalently attached to a boron-doped diamond surface via a combination of diazonium electrografting and Suzuki cross-coupling. For the Suzuki reaction, various catalytic systems are compared with respect to their imposed surface coverage. Combining 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos) and Pd(0), the diamond coverage improves considerably (by 98%) as compared to the standard tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)(4)) catalyst. As the energy levels between the molecular chromophores and the diamond film align well, the sophisticated functionalized diamond surfaces present a first step towards the development of fully carbon-based devices for light to electricity conversion.

  13. Thermal detection of histamine with a graphene oxide based molecularly imprinted polymer platform prepared by reversible addition-fragmentation chain transfer polymerization

    PEETERS, Marloes; KOBBEN, Stephan; Jimenez-Monroy, K. L.; Modesto, L.; Kraus, M.; VANDENRYT, Thijs; GAULKE, Andreas; VAN GRINSVEN, Bart; Ingebrandt, S.; JUNKERS, Thomas; WAGNER, Patrick
    Graphene oxide (GO), with its small dimension and high surface-to-volume ratio, can enhance the binding capacity and sensitivity of molecularly imprinted polymers ( MIPs). Therefore, a straightforward and fast method was developed to graft MIPs onto GO by reversible addition-fragmentation chain transfer (RAFT) polymerization. First, the initiator was linked to the GO in a simple two-step process which was verified via UV-vis spectroscopy. Subsequently, a MIP layer for histamine was grown onto the functionalized surface by RAFT crosslinking polymerization, enabling control over the imprint structure. The formation of a hybrid GO-MIP structure, particles surrounded with a polymer network of similar...

  14. Efficient [2+2] photocycloadditions under equimolar conditions by employing a continuous UV-flow reactor

    Conradi, Matthias; Junkers, Thomas
    The [2 + 2] photocycloaddition between maleimide and various alkenes was optimized in a simple custom-made UV flow reactor. While complete maleimide conversion is only achieved with excesses of at least 10 eq. of alkene and reaction times of 12-24 h in batch, complete reactions with yields in the range >98% could be obtained in 5 min in the flow reactor under strictly equimolar conditions. Functional alkenes carrying allyl, alcohol, amine and ether moieties were successfully conjugated in good yields under optimized reaction conditions. As is demonstrated, the reaction gains in flow most characteristics of a high-efficient reaction, making the...

  15. Functionalization of Boron-Doped Nanocrystalline Diamond with N3 Dye Molecules

    YEAP, Weng Siang; Liu, X.; BEVK, David; Pasquarelli, A.; LUTSEN, Laurence; Fahlman, M.; MAES, Wouter; HAENEN, Ken
    N3 dye molecules [cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II)] are covalently attached to boron-doped nanocrystalline diamond (B:NCD) thin films through a combination of coupling chemistries, i.e., diazonium, Suzuki, and EDC-NHS. X-ray and ultraviolet photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy are used to verify the covalent bonding of the dye on the B:NCD surface (compared to a hydrogen-terminated reference). The spectroscopic results confirm the presence of a dense N3 chromophore layer, and the positions of the frontier orbitals of the dye relative to the band edge of the B:NCD thin film are inferred as well. Proof-of-concept photoelectrochemical measurements show a strong increase in...

  16. The Heat-Transfer Method: A Versatile Low-Cost, Label-Free, Fast, and User-Friendly Readout Platform for Biosensor Applications

    VAN GRINSVEN, Bart; EERSELS, Kasper; PEETERS, Marloes; LOSADA-PEREZ, Patricia; VANDENRYT, Thijs; CLEIJ, Thomas; WAGNER, Patrick
    In recent years, biosensors have become increasingly important in various scientific domains including medicine, biology, and pharmacology, resulting in an increased demand for fast and effective readout techniques. In this Spotlight on Applications, we report on the recently developed heat-transfer method (HTM) and illustrate the use of the technique by zooming in on four established bio(mimetic) sensor applications: (i) mutation analysis in DNA sequences, (ii) cancer cell identification through surface-imprinted polymers, (iii) detection of neurotransmitters with molecularly imprinted polymers, and (iv) phase-transition analysis in lipid vesicle layers. The methodology is based on changes in heat-transfer resistance at a functionalized solid...

  17. Boron-Doped Diamond Functionalization by an Electrografting/Alkyne-Azide Click Chemistry Sequence

    YEAP, Weng Siang; MURIB, Mohammed Sharif; Cuypers, Wim; Liu, Xianjie; VAN GRINSVEN, Bart; AMELOOT, Marcel; Fahlman, Mats; WAGNER, Patrick; MAES, Wouter; HAENEN, Ken
    A straightforward protocol for the covalent functionalization of boron-doped diamond electrodes with either ferrocene or single-stranded deoxyribonucleic acid (DNA) is reported. The functionalization method is based on a combination of diazonium salt electrografting and click chemistry. An azide-terminated organic layer is first electrografted onto the diamond surface by electrochemical reduction of 4-azidophenyldiazonium chloride. The azidophenyl-modified surface then reacts rapidly and efficiently with molecules bearing a terminal alkyne moiety by means of Cu-1-catalyzed alkyne-azide cycloaddition. Covalent attachment of ferrocene moieties was analyzed by X-ray photoelectron spectroscopy and cyclic voltammetry, whereas impedance spectroscopy was applied for the characterization of the immobilized DNA.

  18. Alpha and Omega: Importance of the Nonliving Chain End in RAFT Multiblock Copolymerization

    Consecutive chain extensions via the RAFT process have been carried out, and polymers were investigated via ESI-MS to elucidate for the first time the chain end distributions in high detail. In this manner, the number of chains carrying living chain ends is assessed as well as the number of polymers carrying both RAFT typical R and Z groups. Polymerizations were carried out to practically full conversion, and two subsequent chain extensions have been carried out for each obtained material under systematic variation of the AIBN concentration between 1 and 10 mol 96 with regards to RAFT agent. Generally, very high...

  19. Poly(3-alkylthiophene) nanofibers for optoelectronic devices

    DIERCKX, Wouter; OOSTERBAAN, Wibren; BOLSEE, Jean-Christophe; MAES, Wouter; VANDERZANDE, Dirk; MANCA, Jean
    Semiconducting poly(3-alkylthiophene) nanofibers show remarkable optical and electrical properties, and because of their high aspect ratios they are perfectly suited to serve as organic quasi one-dimensional charge carriers. Hence, they offer interesting perspectives for next generation printable optoelectronic applications. This feature article provides an overview of the current state of the art regarding the preparation and characterization of poly(3-alkylthiophene) nanofibers, and a discussion on nanofiber-based optoelectronic applications, i.e. organic field-effect transistors and bulk heterojunction organic solar cells. In addition, current shortcomings and points of attention for future development are identified.

  20. An easy-to-fabricate low-temperature TiO2 electron collection layer for high efficiency planar heterojunction perovskite solar cells

    CONINGS, Bert; BAETEN, Linny; JACOBS, Tanya; DERA, Rafael; Jan D'HAEN; MANCA, Jean; BOYEN, Hans-Gerhard
    Organometal trihalide perovskite solar cells arguably represent the most auspicious new photovoltaic technology so far, as they possess an astonishing combination of properties. The impressive and brisk advances achieved so far bring forth highly efficient and solution processable solar cells, holding great promise to grow into a mature technology that is ready to be embedded on a large scale. However, the vast majority of state-of-the-art perovskite solar cells contains a dense TiO2 elec- tron collection layer that requires a high temperature treatment (>450◦C), which obstructs the road towards roll-to-roll processing on flexible foils that can with- stand no more than...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.