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  • 1. Acharya, Shravan S.
    et al.
    Easton, Christopher D.
    McCoy, Thomas M.
    Spiccia, Leone
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Chemistry, Monash University, Clayton, Australia.
    Winther-Jensen, Bjorn
    Diverse composites of metal-complexes and PEDOT facilitated by metal-free vapour phase polymerization2017In: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 116, p. 101-106Article in journal (Refereed)
    Abstract [en]

    Abstract Oxidative polymerization for the manufacture of conducting polymers such as poly(3,4-ethylenedioxy-thiophene) has traditionally employed iron(III) salts. Demonstrated in this study is vapour phase polymerization of 3,4-ethylenedio- xythiophene using a metal-free oxidant, ammonium persulfate, leading to films with an estimated conductivity of 75 S/cm. Additionally, a route for embedding active transition metal complexes into these poly(3,4-ethylenedioxythiophene)/-poly(styrene-4-sulfonate) (PEDOT/PSS) films via vapour assisted complexation is outlined. Here, the vapour pressure of solid ligands around their melting temperatures was exploited to ensure complexation to metal ions added into the oxidant mixture prior to polymerization of PEDOT. Four composite systems are discussed, viz. PEDOT/PSS embedded with tris(8-hydroxyquinolinato)cobalt(III), tris(2,2-bipyridine)cobalt(II), tris(1,10- phenanthroline)cobalt(II) and tris(8-hyd-roxyquinolinato)aluminium(III). Using these composites, electrochemical reduction of nitrite to ammonia with a faradaic efficiency of 61% was reported.

  • 2.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University.
    de Wit, Paul P.
    AkzoNobel Specialty Chemicals.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Variation of the alkalisation conditions during the synthesis of a cellulose etherManuscript (preprint) (Other academic)
    Abstract [en]

    We show the effect of simultaneous variation of i) the NaOH/AGU (anhydroglucose unit) stoichiometric ratio (r), ii) added [NaOH], and iii) mercerization time, on the degree of cellulose substitution (DS), and by-product formation including proportions of insoluble particles and unreacted chemicals, in the synthesis of carboxymethylcellulose (CMC), under conditions resembling those often used for production of non-ionic cellulose ethers and without the use of alcohols. The DS was found to increase when (r) was increased (range 1.0-1.3) and added [NaOH] was decreased (range 50-30%). However, such changes also favoured the formation of unwanted by-products. Decreased (r) and increased [NaOH] resulted in increased the quantities of insoluble particles and unreacted chemicals. In the CMC samples, DS of 0.18-0.7 was obtained. The measured solubility (46%-86%) was lower than expected for a given DS. This, along with a deviation of the substituent distribution from the statistical calculations, indicated a high heterogeneity in the samples. The substitution at hydroxyl positions within the AGU shows the order of < ≈ , and that substitution increases with (r). The relative importance of substitution at increases with an increased [NaOH].

  • 3.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Svedberg, Anna
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The influence of different parameters on the mercerisation of cellulose for viscose production2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 2, p. 1061-1072Article in journal (Refereed)
    Abstract [en]

    A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

  • 4.
    Bolivar, Juan M
    et al.
    Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica-CSIC, Cantoblanco, Madrid, Spain.
    Rocha-Martin, Javier
    Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica-CSIC, Cantoblanco, Madrid, Spain.
    Mateo, Cesar
    Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica-CSIC, Cantoblanco, Madrid, Spain.
    Cava, Felipe
    CBM ‘Severo Ochoa’ CSIC-UAM, Madrid, Spain.
    Berenguer, Jose
    CBM ‘Severo Ochoa’ CSIC-UAM, Madrid, Spain.
    Fernandez-Lafuente, Roberto
    Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica-CSIC, Cantoblanco, Madrid, Spain.
    Guisan, Jose M
    Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica-CSIC, Cantoblanco, Madrid, Spain.
    Coating of soluble and immobilized enzymes with ionic polymers: full stabilization of the quaternary structure of multimeric enzymes2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 4, p. 742-747Article in journal (Refereed)
    Abstract [en]

    This paper shows a simple and effective way to avoid the dissociation of multimeric enzymes by coating their surface with a large cationic polymer (e.g., polyethylenimine (PEI)) by ionic exchange. As model enzymes, glutamate dehydrogenase (GDH) from Thermus thermophilus and formate dehydrogenase (FDH) from Pseudomonas sp. were used. Both enzymes are very unstable at acidic pH values due to the rapid dissociation of their subunits (half-life of diluted preparations is few minutes at pH 4 and 25 degrees C). GDH and FDH were incubated in the presence of PEI yielding an enzyme-PEI composite with full activity. To stabilize the enzyme-polymer composite, a treatment with glutaraldehyde was required. These enzyme-PEI composites can be crosslinked with glutaraldehyde by immobilizing previously the composite onto a weak cationic exchanger. The soluble GDH-PEI composite was much more stable than unmodified GDH at pH 4 and 30 degrees C (retaining over 90% activity after 24 h incubation) with no effect of the GDH concentration in the inactivation course. The composite could be very strongly, but reversibly, adsorbed on cationic exchangers. Similarly, FDH could be treated with PEI and glutaraldehyde after adsorption on cationic exchangers, This permitted a stabilized FDH preparation. In this way, the coating of the enzymes surfaces with PEI is used as a simple and efficient strategy to prevent enzyme dissociation of multimeric enzymes. These composites can be used as a soluble catalyst or reversibly immobilized onto a cationic exchanger (e.g., CM-agarose).

  • 5.
    Byström, Emil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Porous polymeric materials for chromatography: Synthesis, functionalization and characterization2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Separation science is heavily reliant on materials to fulfill ever more complicated demands raised by other areas of science, notably the rapidly expanding molecular biosciences and environmental monitoring. The key to successful separations lies in a combination of physical properties and surface chemistry of stationary phases used in liquid chromatographic separation, and this thesis address both aspects of novel separation materials.

    Methods: The thesis accounts for several approaches taken during the course of my graduate studies, and the main approaches have been i) to test a wild-grown variety of published methods for surface treatment of fused silica capillaries, to ascertain firm attachment of polymeric monoliths to the wall of microcolumns prepared in silica conduits; ii) developing a novel porogen scheme for organic monoliths including polymeric porogens and macromonomers; iii) evaluating a mesoporous styrenic monolith for characterization of telomers intended for use in surface modification schemes and; iv) to critically assess the validity of a common shortcut used for estimating the porosity of monoliths prepared in microconduits; and finally v) employing plasma chemistry for activating and subsequently modifying the surface of rigid, monodisperse particles prepared from divinylbenzene.

    Results: The efforts accounted for above have resulted in i) better knowledge of the etching and functionalization parameters that determine attachment of organic monoliths prepared by radical polymerization to the surface of silica; ii) polar methacrylic monoliths with a designed macroporosity that approaches the desired "connected rod" macropore morphology; iii) estab¬lishing the usefulness of monoliths prepared via nitroxide mediated polymerization in gradient polymer elution chromatography; iv) proving that scanning electron microscopy images are of limited value for assessing the macroporous properties of organic monoliths, and that pore measurements on externally polymerized monolith cocktails do not represent the porous properties of the same cocktail polymerized in narrow confinements; and v) showing that plasma bromination can be used as an activation step for rigid divinylbenzene particles to act as grafting handles for epoxy-containing telomers, that can be attached in a sufficiently dense layer and converted into carboxylate cation exchange layer that allows protein separations in fully aqueous eluents.

  • 6.
    Elhaj, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Porous Polymeric Monoliths by Less Common Pathways: Preparation and Characterization2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on my endeavors to prepare new porous polymeric monoliths that are viable to use as supports in flow-through processes. Polymer monoliths of various porous properties and different chemical properties have been prepared utilizing the thermally induced phase separation (TIPS) phenomenon and step-growth polymerization reactions. The aim has been to find appropriate synthesis routes to produce separation supports with fully controlled chemical, physical and surface properties. This thesis includes preparation of porous monolithic materials from several non-cross-linked commodity polymers and engineering plastics by dissolution/precipitation process (i.e. TIPS). Elevated temperatures, above the upper critical solution temperature (UCST), were used to dissolve the polymers in appropriate solvents that only dissolve the polymers above this critical temperature. After dissolution, the homogeneous and clear polymer-solvent solution is thermally quenched by cooling. A porous material, of three dimensional structure, is then obtained as the temperature crosses the UCST. More than 20 organic solvents were tested to find the most compatible one that can dissolve the polymer above the UCST and precipitate it back when the temperature is lowered. The effect of using a mixture of two solvents or additives (co-porogenic polymer or surfactant) in the polymer dissolution/precipitation process have been studied more in depth for poly(vinylidine difluoride) (PVDF) polymers of two different molecular weight grades. Monolithic materials showing different pore characteristics could be obtained by varying the composition of the PVDF-solvent mixture during the dissolute­ion/precipitation process. Step-growth polymerization (often called polycondensat­ion reaction) combined with sol-gel process with the aid of porogenic polymer and block copolymer surfactant have also been used as a new route of synthesis for production of porous melamine-formaldehyde (MF) monoliths. In general, the meso- and macro-porous support materials, for which the synthesis/preparation is discussed in this thesis, are useful to a wide variety of applications in separation science and heterogeneous reactions (catalysis).

  • 7.
    Gillgren, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Comparison of laccase-catalyzed cross-linking of organosolv lignin and lignosulfonates2017In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 105, no 1, p. 438-446Article in journal (Refereed)
    Abstract [en]

    Lignin, an underutilized by-product from chemical pulping of wood, can be modified enzymatically through oxidation by laccase. However, little is known about the molecular details surrounding the cross linking which is a result of the oxidation. To reduce this lack of knowledge, we used oxygen consumption rate data, phenolic content data and molecular weight data together with data from NMR and FTIR spectroscopy to.characterize laccase-catalyzed cross-linking of the industrial lignin preparations organosolv lignin and lignosulfonate. The organosolv lignin preparation had a M-n of 780 g/mol, a M-w of 5200 g/mol, and a phenolic content of 1.8 mmol/g. The lignosulfonate preparation had a M-n of 6000 g/mol, a M-w of 19800 g/mol, and a phenolic content of 1.1 mmol/g. Laccase-catalyzed oxidation of organosolv lignin was characterized by a relatively slow increase in molecular weight, decreased intensities for aromatic signals and p-hydroxycinnamyl groups, and increased intensity for beta-O-4' signals, whereas oxidation of lignosulfonates resulted in a very rapid increase in molecular weight, and strongly decreased intensities for aromatic signals. The data suggest that lignosulfonates cross-linked by couplings to the aromatic ring (e.g. 5-5' and 4-O-5'), whereas beta-O-4' coupling characterized cross-linking of organosolv lignin, probably involving cinnamyl alcohol end-groups. (C) 2017 Published by Elsevier B.V.

  • 8. Jilal, Issam
    et al.
    El Barkany, Soufian
    Bahari, Zahra
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    El Idrissi, Abderahmane
    Abou-Salama, Mohamed
    Romane, Abderrahmane
    Zannagui, Chahid
    Amhamdi, Hassan
    New quaternized cellulose based on hydroxyethyl cellulose (HEC) grafted EDTA: Synthesis, characterization and application for Pb (II) and Cu (II) removal2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 180, p. 156-167Article in journal (Refereed)
    Abstract [en]

    In this paper, new quaternized cellulose derivative based on Ethylenediaminetetraacetic acid (EDTA) and hydroxyethyl cellulose (HEC) is successfully prepared in homogeneous medium. The resulted product is characterized using spectroscopy techniques (FTIR, 1H NMR and 13C NMR). At the supramolecular level, the x-ray patterns show that a high hydrogen bond density occurs by grafting EDTA on the HEC fibers. The new adsorbent (HEC-EDTA) shows a high adsorption capacity of heavy metals (Pb (II) and Cu (II)) from aqueous metals solutions. The adsorption of the both metal ions follows the pseudo-second-order kinetic model, while the adsorption isotherms are well described by the Langmuir model. The qm values are determined for Pb (II) and Cu (II), respectively. For each metal, the equilibrium adsorption time is found to be 30 min. Moreover, the HEC-EDTA adsorption capacity is strongly dependent on the pH value; and the adsorption is favorable for pH values ​​between 4 and 6. Moreover, the results show a high affinity toward Cu (II) than Pb (II).

  • 9. Jogi, Ramakrishna
    et al.
    Mäki-Arvela, Päivi
    Virtanen, Pasi
    Kumar, Narendra
    Hemming, Jarl
    Smeds, Annika
    Lestander, Torbjörn A.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Biocrude production through hydro‐liquefaction of wood biomass in supercritical ethanol using iron silica and iron Beta zeolite catalysts2019In: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: In the production of biofuels from lignocellulosic material, biocrude plays a key role. The present work deals with the biocrude production through hydrothermal liquefaction (HTL) of birch wood in supercritical ethanol over 5 wt. % Fe‐H‐Beta‐150 (SiO2 to Al2O3 ratio of 150) or 5 wt. % Fe‐SiO2 catalyst.

    RESULTS: The liquid and solid products were characterized with various analytical techniques such as GC‐MS, GC‐FID, SEC, ICP‐MS, p‐XRD, SEM, and solid‐state 13C MAS NMR respectively. The results revealed that 5 wt. % Fe‐H‐Beta‐150, a strongly Brønsted acidic catalyst, enhanced the biocrude formation when compared with a non‐acidic 5 wt. % Fe‐SiO2 catalyst. Hemicellulose and lignin degradation occurred resulting in formation of mainly sugars, acids‐esters and phenolic compounds in liquid phase. The gaseous atmosphere of hydrogen also enhanced the degradation of biomass. The biocrude yield from birch was 25 wt. % over 5 wt. % Fe‐H‐Beta‐150. The Brønsted acidic catalyst gave higher dissolution efficiency and its clear catalytic effect was observed in comparison to non‐acidic 5 wt. % Fe‐SiO2. The degradation level of lignin in presence of 5 wt. % Fe‐H‐Beta‐150 was high 68 wt. % aromatic products were formed, while only 38 wt. % was obtained with 5 wt. % Fe‐SiO2.

    CONCLUSIONS: Hydrogen atmosphere enhances the fractionation of birch wood when compared to argon atmosphere. 5 wt. % Fe‐H‐Beta‐150 catalyst enhanced very strongly the degradation of hemicellulose and lignin in biomass to sugars and acid‐esters as well as phenolic compounds, respectively compared to the non‐acidic 5 wt. % Fe‐SiO2 catalyst.

  • 10. Li, Xin
    et al.
    Lu, Xue Min
    Lu, Qing Hua
    Ohlin, C. André
    Re-writable multi-domain liquid crystal alignment layers through laser-induced micropatterning2006In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 45, no 20-23, p. L591-L594Article in journal (Refereed)
    Abstract [en]

    We report a method for the preparation of multi-domain liquid crystal (LC) alignment layers on polyimide surfaces with laser-induced periodic surface structures. Atomic force microscopy confirmed that the laser-induced microstructures could be easily erased and re-constructed by repeated laser exposure. The microstructures demonstrated excellent abilities to align LCs in a multi-domain way. The intricate micropatterning of LCs with high resolution was obtained. The opto-electric properties of the LC cells were also determined. In addition, the method is available to a wide range of polymeric substrates, including flexible ones such as poly(ethylene terephthalate).

  • 11.
    Mindemark, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kaihovirta, Nikolai
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brandell, Daniel
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-Performance Light-Emitting Electrochemical Cells by Electrolyte Design2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 8, p. 2618-2623Article in journal (Refereed)
    Abstract [en]

    Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m(-2) and a record-high power conversion efficiency of 18.1 lm W-1, when equipped with an external outcoupling film.

  • 12. Murto, Petri
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Xu, Xiaofeng
    Sandström, Andreas
    LunaLEC AB, Umeå University, Umeå, Sweden.
    Pietarinen, Juuso
    Bagemihl, Benedikt
    Abdulahi, Birhan A.
    Mammo, Wendimagegn
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell2018In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 4, p. 1753-1761Article in journal (Refereed)
    Abstract [en]

    Cost-efficient thin-film devices that emit in the near infrared (NIR) range promise a wide range of important applications. Here, the synthesis and NIR application of a series of copolymers comprising poly[indacenodithieno[3,2-b]thiophene-2,8-diyl] (PIDTT) as the host and different donor acceptor donor (DAD) segments as the guest are reported. We find that a key design criterion for efficient solid-state host-to-guest energy transfer is that the DAD conformation is compatible with the conformation of the host. Such host guest copolymers are evaluated as the emitter in light-emitting electrochemical cells (LECs) and organic light-emitting diodes, and the best performance is invariably attained from the LEC devices because of the observed balanced electrochemical doping that alleviates issues with a noncentered emission zone. An LEC device comprising a host guest copolymer with 4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene as the donor and benzo[c][1,2,5]thiadiazole as the acceptor delivers an impressive near-infrared (NIR) performance in the form of a high radiance of 1458 mu W/cm(2) at a peak wavelength of 725 nm when driven by a current density of 500 mA/cm(2), a second-fast turn-on, and a good stress stability as manifested in a constant radiance output during 3 days of uninterrupted operation. The high-molecular-weight copolymer features excellent processability, and the potential for low-cost and scalable NIR applications is verified through a spray-coating fabrication of a >40 cm(2) large-area device, which emits intense and uniform NIR light at a low drive voltage of 4.5 V.

  • 13. Ng, Chun Hin
    et al.
    Winther-Jensen, Orawan
    Kolodziejczyk, Bartlomiej
    Ohlin, C. Andre
    Winther-Jensen, Bjorn
    Photo-electrocatalytic H-2 evolution on poly(2,2 ‘-bithiophene) at neutral pH2014In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 32, p. 18230-18234Article in journal (Refereed)
    Abstract [en]

    Vapour phase polymerised (VPP) polybithiophene (PBTh) on glassy carbon is revealed to be an efficient photo-electrocatalytic electrode for the hydrogen evolution reaction (HER). An onset potential of -0.03 V vs SCE for the HER is observed on illumination using visible light in 0.1 mol L-1 phosphate buffer at pH 6.9, 600 mV lower in energy than E-o. Hydrogen evolution is confirmed using gas chromatography with a calculated faradaic efficiency of 34% when holding at a potential of -0.5 V. Importantly, this process occurs without platinum and under neutral aqueous conditions thus revealing a significant but overlooked application for PBTh: a potential low-cost cathode material for the splitting of water. 

  • 14. Ng, Chun Hin
    et al.
    Winther-Jensen, Orawan
    Ohlin, C. Andre
    Winther-Jensen, Bjorn
    Exploration and optimisation of poly(2,2 ‘-bithiophene) as a stable photo-electrocatalyst for hydrogen production2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 21, p. 11358-11366Article in journal (Refereed)
    Abstract [en]

    An organic photo-electrochemical catalyst for the hydrogen evolution reaction (HER) based on the conducting polymer, poly(2,2 ‘-bithiophene) (PBTh), is further explored. Long-term stability testing shows the successful operation of the catalyst over a period of 12 days at neutral pH with corresponding turnover numbers exceeding 6 x 10(4). Experimental parameters such as substrate type, electrolyte, pH and thickness of the film are explored and their subsequent effects on catalytic behaviour and performance discussed. Significant findings include the four-fold increase in performance by the reduction of thickness to better facilitate charge transfer and the successful photo-catalysis of the HER at pH 11, with an onset that is 0.14 V below E-0. Faradaic efficiency was also determined with a maximum recorded efficiency of 80% despite known losses such as crossover reactions and H-2 escape from within the system.

  • 15.
    Nordborg, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Byström, Emil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gradient polymer elution chromatography of methacrylate Telomers on monolithic capillary columns prepared by nitroxide-mediated polymerizationManuscript (preprint) (Other academic)
    Abstract [en]

    Linear methacrylate telomers prepared by isopropylxanthic disulfide photoiniferted polymerization of 2-hydroxyethyl methacrylate, methyl methacrylate, and ethyl methacrylate have been separated from their precursor monomers using gradient polymer elution chromatography (GPEC) on a monolithic capillary column. The capillary monoliths were prepared by thermally initiated radical polymerization of styrene and divinylbenzene controlled by 1-carboxy-PROXYL stable free radicals, and characterized by nitrogen adsorption and mercury intrusion porosimetry. The separations in GPEC mode were performed using a mobile phase gradient from water to methanol, where water is the non-solvent and methanol the good solvent with respect to the telomers. Successful separation of telomers from their monomer was achieved for all tested telomers. In addition, it was observed that the retention times of the intact telomers were different from those of telechelic oligomers produced by hydrolysing the isopropylxanthic terminals. The current set-up is therefore promising both for monitoring of the progress of photoiniferted polymerizations and to monitor the hydrolysis of resulting polymerized oligomers into thiol-terminated telechelics.

  • 16.
    Nordborg, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A Library of Thiol-Terminated Methacrylate Telomers Prepared by Photoinitiated Iniferter Mediated Polymerization for Use in Modifications of Chromatographic Surfaces by the "Grafting to" Approach2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 117, no 5, p. 2781-2789Article in journal (Refereed)
    Abstract [en]

    A library of thiol-terminated methacrylate telomers aimed for use in surface modifications of chromatographic support materials has been prepared by iniferter mediated polymerization, using isopropylxanthic disulfide as a photoiniferter. The telomers range from hydrophobic to hydrophilic and were prepared in different lengths, with the length being adjusted by the ratio of monomer to iniferter used in the polymerization mixture. The telomers were characterized by size-exclusion chromatography and MALDI-TOF-MS. In initial surface characterization experiments, the prepared telomers were attached to the inner surface of fused silica capillaries by radical initiated addition to vinyl groups, and the electro-osmotic flow (EOF) in the prepared capillaries was determined in a capillary electrophoresis set-up. The EOF measurements verified surface grafting.

  • 17.
    Ortuno, Nuria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundin, Lisa
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Emissions of PBDD/Fs, PCDD/Fs and PBDEs from flame-retarded high-impact polystyrene under thermal stress2015In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 123, p. 64-70Article in journal (Refereed)
    Abstract [en]

    The emissions of polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) and their chlorinated analogues (PCDD/Fs) during the thermal treatment of a high impact polystyrene (HIPS) TV casing were investigated. The halogenated compounds were analyzed in the original material and in the gases emitted during its treatment at temperatures between 50 degrees C and 250 degrees C. DecaBDE was the primary PBDE in the TV casing, which also contained high levels of PBDFs (ppm range). At the lower treatment temperatures, non-modified PBDEs evaporated from the samples. Conversely, at 200 degrees C or above, debromination reactions led to the formation of additional tri- through nonaBDE. The formation of new PBDD/Fs was also detected in the gas phase when the plastic was heated to 200 degrees C or 250 degrees C, with higher yields of furans than dioxins. This appreciably increased the toxic equivalent (TEQ) levels of the gas phase relative to those seen in the untreated sample. In all cases, the levels and TEQ contributions from PCDD/Fs were negligible compared to those for brominated analogues. (C) 2014 Elsevier Ltd. All rights reserved.

  • 18.
    Reyes Forsberg, Diana Carolina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Experimental study of alkalinisation of cellulose in industrial relevant conditions2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mercerisation of cellulose pulp with a solution of NaOH is the first step of manufacturing cellulose-based value-added products, e.g. viscose fibres and cellulose ethers. During this process, cellulose transforms into a swollen crystalline structure, alkali cellulose (Na-Cell). This increases the reactivity of the cellulose and makes it more accessible for reagents to penetrate and react with the hydroxyl groups. The mercerisation conditions are known to affect the degree of alkalinisation of cellulose as well as the final products. The main objective of this thesis is to investigate how the alkalinisation of softwood sulphite dissolving cellulose pulp is influenced by the co-variation of process variables in the mercerisation in industrial relevant conditions, for both viscose and cellulose ether production. This objective was achieved by quantitative analysis of the effect of simultaneous variation of a set of key parameters on the degree of alkalinisation (i.e. degree of activation, DoA) of the chosen dissolving pulp. Quantitative measurements were performed using Raman spectroscopy data, evaluated by partial least squares (PLS) regression. For mercerisation at viscose production conditions, the effect of studied variables on mass yield was also considered. In the case of mercerisation at ether processing conditions, formation of alkali cellulose at a fixed temperature was included. The knowledge obtained on mercerisation under ether processing conditions was then applied for preparation of the ionic cellulose ether carboxymethylcellulose (CMC).

    The overall results show that temperature has a strong effect on DoA and mass yield for mercerised samples under steeping conditions. Measured DoA decreases as the temperature increases from 20 to 70 °C. Mass yield correlates positively with the temperature up to 45-50 °C in the PLS model, after which the relation is negative. The [NaOH] and reaction time show a complex dependence of other variables. At mercerisation conditions for cellulose ether production, the NaOH/AGU stoichiometric ratio, denoted as (r), shows to be very important for DoA, with a positive correlation. At these mercerisation conditions, temperature shows no effect on DoA. The influence of the [NaOH] (which also refers to the concentration of water) shows a complex dependence on (r). As (r) increases and [NaOH] decreases, the measured DoA increases. Prolonged mercerisation time shows no significance in the modelled DoA. However, a gradual increase of the DoA over time was seen when mercerisation was performed with 30% and 40% [NaOH] at (r) = 0.8, suggesting a slow diffusion of NaOH and Na-Cell formation. 13C CP-MAS NMR measurements of samples produced at room temperature show that formation of the Na-Cell allomorph is mainly determined by the [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, (r) also seems to be of importance.  An increase of DS in the produced CMC samples also shows to be consistent at such conditions with the increase in the measured DoA and with increased (r) and decreased [NaOH]. However, these conditions also favour the formation of by-products. In the synthesised CMC samples, a DS of up to 0.7 was achieved. Measured solubility was lower than expected for any given DS. This, along with the non-statistical distribution of monomer units in the polymer chains, indicates high heterogeneity in the synthesised samples. The distribution of substituents within the AGU shows attachment to hydroxyl oxygens in the order O3 < O2 ≈ O6. The relative importance of the substitution at O3 indicates an increase at this position when [NaOH] increases.

    The models presented in this thesis will hopefully serve as a basis for predicting the effects of the studied variables on the DoA, as well as on the mass yield of cellulose pulp when mercerisation conditions are adjusted. Moreover, it is believed that the presented studies can give a better understanding of mercerisation at cellulose ether conditions, hence enabling further development of this process step.

  • 19. Santos, Denys E. S.
    et al.
    Li, Danyang
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gautrot, Julien E.
    Soares, Tereza A.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, Brazil.
    Conformational Dynamics and Responsiveness of Weak and Strong Polyelectrolyte Brushes: Atomistic Simulations of Poly(dimethyl aminoethyl methacrylate) and Poly(2-(methacryloyloxy)ethyl trimethylammonium chloride)2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 14, p. 5037-5049Article in journal (Refereed)
    Abstract [en]

    The complex solution behavior of polymer brushes is key to control their properties, including for biomedical applications and catalysis. The swelling behavior of poly(dimethyl aminoethyl methacrylate) (PDMAEMA) and poly(2-(methacryloyloxy)ethyl trimethylammonium chloride) (PMETAC) in response to changes in pH, solvent, and salt types has been investigated using atomistic molecular dynamics simulations. PDMAEMA and PMETAC have been selected as canonical models for weak and strong polyelectrolytes whose complex conformational behavior is particularly challenging for the development and validation of atomistic models. The GROMOS-derived atomic parameters reproduce the experimental swelling coefficients obtained from ellipsometry measurements for brushes of 5–15 nm thickness. The present atomistic models capture the protonated morphology of PDMAEMA, the swollen and collapsed conformations of PDMAEMA and PMETAC in good and bad solvents, and the salt-selective response of PMETAC. The modular nature of the molecular models allows for the simple extension of atomic parameters to a variety of polymers or copolymers.

  • 20. Sindiku, O
    et al.
    Babayemi, J. O
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Osibanjo, O.
    Weber, R
    Watson, A
    Schlummer, M
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs)in e-waste plastic in Nigeria2015In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 22, no 19, p. 14515-14529Article in journal (Refereed)
    Abstract [en]

    Plastics from cathode ray tube (CRT) casings weresampled in Nigeria and analysed for their polybrominateddibenzo-p-dioxin and dibenzofuran (PBDD/F) content.PBDD/Fs, consisting mainly of PBDFs, were detected inBFR containing plastic with a median (mean) concentrationof 18,000 ng/g (41,000 ng/g). The PBDD/Fs levels werehighest in samples containing PBDEs, but the levels ofPBDFs were two orders of magnitude higher than the levelsreported in the technical PBDE mixtures and where frequentlyexceeding 1000 μg/g of PBDE content. These higher levelsare likely to arise from additional transformation of PBDEsduring production, use, recycling, or storage, but the processesresponsible were not identified in this study. PBDD/Fs in CRTcasings containing1,2-bistribromophenoxyethane (TBPE)were dominated by tetrabrominated dibenzo-p-dioxin(TBDDs) with concentrations around 10 μg/g of the TBPEcontent. The PBDD/Fs in CRT casings containingtetrabromobisphenol A (TBBPA) were found at concentrationsaround 0.1 μg/g of TBBPA levels. Casings treated withTBPE or TBBPA often contained PBDEs (and PBDF) as impurities—probably originating from recycled e-waste plastics.It was estimated that the 237,000 t of CRT casings stockpiledin Nigeria contain between 2 and 8 t of PBDD/Fs. The totalPBDD/F contamination in polymers arising from total historicPBDE production/use is estimated in the order of 1000 t. TEQvalues of CRT samples frequently exceeded the Basel Convention’sprovisional low POPs content of 15 ng TEQ/g. Dueto the significant risks to health associated with PBDD/Fs,more detailed studies on the exposure routes from PBDD/Fsin stockpiles are needed.

  • 21. Tan, Khooi Y.
    et al.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Colak, Burcu
    Huck, Wilhelm T. S.
    Gautrot, Julien E.
    Study of thiol-ene chemistry on polymer brushes and application to surface patterning and protein adsorption2016In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 7, no 4, p. 979-990Article in journal (Refereed)
    Abstract [en]

    Polymer brushes are attractive polymeric coatings for biomedical applications such as tissue engineering, biosensor design and the purification of biological samples. In order to confer bioactivity to these coatings, their functionalisation with biomolecules, proteins and peptides, is required. In this respect, thiol-ene coupling offers interesting features as it is regioselective, efficient and can be controlled by photo-irradiation to allow surface patterning. The efficiency of thiol-ene and the related thiol-yne couplings to poly(glycidyl methacrylate) brushes was quantified. The impact of the structure of thiols to be tethered and reaction conditions on the brush loading and the kinetics of reaction were investigated. Thiol-ene reactions were then used to pattern brushes via direct irradiation through a mask or via reactive micro-contact printing. The resulting patterns were used to control albumin adsorption and the formation of protein patterns.

  • 22. Trojer, Markus Andersson
    et al.
    Gabul-Zada, Asvad A.
    Ananievskaia, Anna
    Nordstierna, Lars
    Östman, Marcus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Blanck, Hans
    Use of anchoring amphiphilic diblock copolymers for encapsulation of hydrophilic actives in polymeric microcapsules: methodology and encapsulation efficiency2019In: Colloid and Polymer Science, ISSN 0303-402X, E-ISSN 1435-1536, Vol. 297, no 2, p. 307-313Article in journal (Refereed)
    Abstract [en]

    Aqueous core-shell particles based on polystyrene, poly(methyl methacrylate) or polycaprolactone have been formulated using a facile double emulsion-based solvent evaporation method. The size distribution is narrow, and the morphology control is remarkable given the simple characteristics of the encapsulation method. The inner droplets are stabilized by oil-soluble poly(ethylene oxide)-based block copolymers which are anchored in the polymeric shell by using hydrophobic blocks of the same type as that of the shell-forming polymer. This facilitates the efficient encapsulation of dyes and hydrophilic biocides.

  • 23. Wang, Xuefeng
    et al.
    Ohlin, C. André
    Lu, Qinghua
    Hu, Jun
    Influence of physicochemical properties of laser-modified polystyrene on bovine serum albumin adsorption and rat C6 glioma cell behavior2006In: Journal of Biomedical Materials Research. Part A, ISSN 1549-3296, E-ISSN 1552-4965, Vol. 78A, no 4, p. 746-754Article in journal (Refereed)
    Abstract [en]

    Biomaterial surface modification is an efficient way of improving cell-material interactions. In this study, sub-micrometer laser-induced periodic surface structures (LIPSS) were produced on polystyrene by laser irradiation. FT-IR analysis confirmed that this treatment also led to surface oxidation and anisotropic orientation of the produced carbonyl groups. As a consequence, the surface energy of the laser-treated polystyrene was 1.45 times that of the untreated polystyrene, as measured by contact-angle goniometry. Protein adsorption and rat C6 glioma cell behavior on the two substrates were investigated, showing that the changed physicochemical properties of laser-modified polystyrene surface led to an increase in the quantity of adsorbed bovine serum albumin and significantly affected the behavior of rat C6 glioma cells. In the early stages of cell spreading, cells explored their microenvironment using filopodium as the main sensor. Moreover, cells actively aligned themselves along the direction of LIPSS gradually and cell attachment and proliferation were significantly enhanced. 

  • 24. Wang, Xuefeng
    et al.
    Ohlin, Christian A.
    Lu, Qinghua
    Hu, Jun
    Cell directional migration and oriented division on three-dimensional laser-induced periodic surface structures on polystyrene2008In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 29, no 13, p. 2049-2059Article in journal (Refereed)
    Abstract [en]

    The extracellular matrix in animal tissues usually provides a three-dimensional structural support to cells in addition to performing various other important functions. In the present study, wavy submicrometer laser-irradiated periodic surface structures (LIPSS) were produced on a smooth polystyrene film by polarized laser irradiation with a wavelength of 266 nm. Rat C6 glioma cells exhibited directional migration and oriented division on laser-irradiated polystyrene, which was parallel to the direction of LIPSS. However, rat C6 glioma cells on smooth polystyrene moved in a three-step invasion cycle, with faster migation speed than that on laser-irradiated polystyrene. In addition, focal adhesions examined by immunostaining focal adhesion kinase in human epithelial carcinoma HeLa cells were punctuated on smooth polystyrene, whereas dash-like on laser-irradiated polystyrene. We hypothesized that LIPSS on laser-irradiated polystyrene acted as an anisotropic and persistent mechanical stimulus to guide cell anisotropic spreading, migration and division through focal adhesions.

  • 25. Wierzbicka, Celina
    et al.
    Liu, Mingquan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bauer, David
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sellergren, Borje
    Cationic pTyr/pSer imprinted polymers based on a bis-imidazolium host monomer: phosphopeptide recognition in aqueous buffers demonstrated by mu-liquid chromatography and monolithic columns2017In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 5, no 5, p. 953-960Article in journal (Refereed)
    Abstract [en]

    We report on the design and characterization of imprinted cationic host polymers for selective trapping of phosphoserine and phosphotyrosine peptides. A series of imidazolium host monomers were synthesized and characterized with respect to binding affinity and stoichiometry of interaction with salts of phenylphosphonic acid. The strongest binders were subsequently used for the preparation of imprinted polymers in the form of crushed monoliths, using Fmoc-phosphotyrosine-ethyl ester or Fmoc-phosphoserine-ethyl ester as templates in combination with a hydrophilic crosslinking monomer. The polymers were compared with respect to binding and its dependence on solvent, and whether charged or uncharged host monomers were used. The recipes were subsequently implemented in the capillary monolith format for evaluation by micro-liquid chromatography in both buffered and organic media. Results from both tested formats reveal that the cationic host polymers displayed enhanced recognition in polar and buffered media, in contrast to neutral urea-based hosts which showed best results in acetonitrile rich mobile phases.

  • 26.
    Yu, Junchun
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tonpheng, Bounphanh
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Thermal conductivity of highly crystallized polyethylene2014In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 55, no 1, p. 195-200Article in journal (Refereed)
    Abstract [en]

    We report thermal conductivity (kappa) of low-density, high-density and ultra-high density polyethylene (PE) with different crystallinity and microstructures. PE was crystallized under high-pressure and high-temperature conditions which produce extended chain crystals. By applying a two-phase model, we estimate kappa of 100% crystallized PE as a function of pressure and temperature. The increased crystallinity and lamellar thickness (fold length) reduce the thermal resistance, which is reflected not only in the absolute value of kappa but also in more pronounced pressure and temperature dependencies approaching those of polycrystalline low-molecular weight materials. The results suggest that it is crucial to increase the lamellar thickness to significantly improve kappa of PE with randomly oriented lamellae.

1 - 26 of 26
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