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  • 1.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    Norwegian University of Science and Technology, Norway.
    Wernersson Brodin, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    The potential of TEMPO-oxidized cellulose nanofibrils as rheology modifiers in food systems2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 9, p. 5483-5496Article in journal (Refereed)
    Abstract [en]

    Abstract: Cellulose nanofibrils (CNFs) have been proposed for use in low-fat food products due to their availability and excellent viscosifying and gel forming abilities. As the CNFs are negatively charged, the presence of other components in foods, such as electrolytes and food additives such as xanthan gum is likely to affect their rheological properties. Hence, the study of these interactions can contribute valuable information of the suitability of CNFs as rheology modifiers and fat replacers. Rheological measurements on aqueous dispersions of TEMPO-oxidized CNFs were performed with variations in concentration of CNFs, concentration of electrolytes and with varying CNF/xanthan ratios. UV–Vis Spectroscopy was used to evaluate the onset of CNF flocculation/aggregation in the presence of electrolytes. The CNF dispersions followed a power-law dependency for viscosity and moduli on CNF concentration. Low electrolyte additions strengthened the CNF network by allowing for stronger interactions, while higher additions led to fibril aggregation, and loss of viscosity, especially under shear. The CNF/xanthan ratio, as well as the presence of electrolytes were shown to be key factors in determining whether the viscosity and storage modulus of CNF dispersions increased or decreased when xanthan was added. Graphical abstract: [Figure not available: see fulltext.].

  • 2.
    Alakalhunmaa, Suvi
    et al.
    University of Helsinki, Finland.
    Parikka, Kristi
    University of Helsinki, Finland.
    Penttilä, Paavo A.
    University of Helsinki, Finland.
    Cuberes, M. Teressa
    University of Castilla-La Mancha, Spain.
    Willför, Stefan
    Åbo Akademi University, Finland.
    Salmen, Lennart
    RISE, Innventia.
    Mikkonen, Kristi S.
    University of Helsinki, Finland.
    Softwood-based sponge gels2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 5, p. 3221-3238Article in journal (Refereed)
    Abstract [en]

    Crosslinking-aided gelation was utilized to prepare hydrogels from softwood polysaccharides, with spruce galactoglucomannans (GGM)—a group of largely unexploited hemicelluloses—as the main component, aiming at conversion into sponge-like aerogels. Cellulose nanofibrils were used for the formation of a reinforcing network, which was further crosslinked together with a GGM matrix by ammonium zirconium carbonate, an inorganic salt that is regarded as safe for use in food packaging. The hydrogels were freeze-dried into stiff, low-density aerogels with 98 % of their volume composed of air-filled pores. When immersed in water, the aerogels absorbed water up to 37 times their initial weight, demonstrating elasticity and repeatable and reversible sponge capacity. The developed concept reassembles the wood polysaccharides in a new way, creating interesting possibilities for utilizing the abundant “green gold,” GGM. The obtained biobased materials could find application potential, for example, in the field of food packaging and could contribute in the reduction of the usage of petroleum-based plastics in the future.

  • 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.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stridh, Kjell
    AkzoNobel, Stenungsund, Sverige.
    de Wit, Paul P.
    AkzoNobel, Arnhem, The Netherlands.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Is there a diffusion of alkali in the activation of dissolving cellulose pulp at low NAOH stoichiometric excess?2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 2, p. 1297-1308Article in journal (Refereed)
    Abstract [en]

    We conducted a quantitative study, following the degree of activation (i.e. the transformation to alkali cellulose, denoted as DoA) over time for dissolving cellulose pulp treated with different [NaOH] at low NaOH/anhydroglucose unit stoichiometric ratio (denoted as (r) ≤ 2.6). Our quantitative approach was based on Raman spectroscopy data, evaluated by partial least squares regression modelling. The results show strong influence of the (r) on DoA (increasing from DoA= 45% at (r) = 0.8, to DoA = 85% at (r) = 2.6), and its complex dependence on [NaOH]. At (r) = 0.8 the highest DoA (DoA ≳ 60%) was found at 30% [NaOH], while at (r) =1.3 it was found at 20% [NaOH] (DoA ≳ 80%). Although activation of cellulose happens in minutes at the studied temperature (30 °C), it was found that the reaction may be slow when a low (r) is used. A gradual increase of the DoA from ≈ 30% to ≈ 70% in time was seen when samples were activated with 30% [NaOH] at (r) = 0.8. At the same (r), a similar increase of DoA from ≈ 30 % to ≈ 60 % was also observed when 40% [NaOH] was used. Slow diffusion of NaOH through poorly swollen cellulose fibres is proposed as an explanation for this phenomenon. Lastly, solid-state CP/MAS NMR measurements suggest that at a fixed temperature, the Na-Cell allomorph mostly depends on [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, its influence might be affected by (r). 

  • 5.
    Aldaeus, Fredrik
    et al.
    RISE, Innventia.
    Larsson, Karolina
    RISE, Innventia.
    Stevanic Srndovic, Jasna
    RISE, Innventia.
    Kubat, Mikaela
    RISE, Innventia.
    Karlström, Katarina
    RISE, Innventia.
    Peciulyte, Ausra
    Chalmers University of Technology, Sweden.
    Olsson, Lilsbeth
    Chalmers University of Technology, Sweden.
    Larsson, Per Tomas
    RISE, Innventia.
    The supramolecular structure of cellulose-rich wood pulps can be a determinative factor for enzymatic hydrolysability2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 6, p. 3991-4002Article in journal (Refereed)
    Abstract [en]

    The enzymatic hydrolysability of three industrial pulps, five lab made pulps, and one microcrystalline cellulose powder was assessed using commercial cellulolytic enzymes. To gain insight into the factors that influence the hydrolysability, a thorough characterization of the samples was done, including their chemical properties (cellulose content, hemicellulose content, lignin content, and kappa number), their macromolecular properties (peak molar mass, number-average molar mass, weight-average molar mass, polydispersity, and limiting viscosity) and their supramolecular properties (fibre saturation point, specific surface area, average pore size, and crystallinity). The hydrolysability was assessed by determination of initial conversion rate and final conversion yield, with conversion yield defined as the amount of glucose in solution per unit of glucose in the substrate. Multivariate data analysis revealed that for the investigated samples the conversion of cellulose to glucose was mainly dependent on the supramolecular properties, such as specific surface area and average pore size. The molar mass distribution, the crystallinity, and the lignin content of the pulps had no significant effect on the hydrolysability of the investigated samples.

  • 6. Alexandrescu, L.
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gatti, A.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cytotoxicity tests of cellulose nanofibril-based structures2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20Article in journal (Refereed)
  • 7.
    Alimadadi, Majid
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    3D-oriented fiber networks made by foam forming2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, ISSN 1572-882X, Vol. 23, no 1, p. 661-671Article in journal (Refereed)
    Abstract [en]

    In industrial applications, such as paper and nonwovens, cellulose fibers are used in the form of a network where the fibers are oriented more or less in the sheet-plane direction. However, in many biological systems, fibers are instead oriented in a three-dimensional (3D) space, creating a wide variety of functionalities. In this study we created a 3D-oriented fiber network on the laboratory scale and have identified some unique features of its structure and mechanical properties. The 3D fiber network sheets were prepared by using foam-forming as well as modifying consolidation and drying procedures. The fiber orientation and tensile/compression behavior were determined. The resulting sheets were extremely bulky (above 190 cm3/g) and had extremely low stiffness (or high softness) compared to the reference handsheets. Despite this high bulk, the sheets retained good structural integrity. We found that a 3D-oriented fiber network requires much less fiber-fiber contact to create a connected (“percolated”) network than a two-dimensionally oriented network. The compression behavior in the thickness direction was also unique, characterized by extreme compressibility because of its extreme bulk and a long initial increase in the compression load as well as high strain recovery after compression because of its fiber reorientation during compression.

  • 8.
    Alves, Luis
    et al.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol MEDITBIO, Campus Gambelas,Ed 8, P-8005139 Faro, Portugal..
    Antunes, Filipe E.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Topgaard, Daniel
    Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, S-22100 Lund, Sweden..
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Nanyang Technol Univ, Mat Sci & Engn, Singapore 639798, Singapore.
    Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 1, p. 247-258Article in journal (Refereed)
    Abstract [en]

    The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.

  • 9. Andreasson, B.
    et al.
    Forsstrom, J.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Determination of fibre pore structure: influence of salt, pH and conventional wet strength resins2005In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 12, no 3, p. 253-265Article in journal (Refereed)
    Abstract [en]

    It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.

  • 10. Andreasson, B.
    et al.
    Forsstrom, J.
    Wågberg, Lars
    KTH, Superseded Departments, Fibre and Polymer Technology.
    The porous structure of pulp fibres with different yields and its influence on paper strength2003In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 10, no 2, p. 111-123Article in journal (Refereed)
    Abstract [en]

    The porous structure of the interior of papermaking fibres is a well-known important property of the fibres. Changes of this structure will influence tensile and burst strength of paper formed from the fibres and a change in pore size of the pores within the fibre wall is also important for the ability of molecules to diffuse in and out of the fibre wall. Relevant examples of this latter effect are the removal of lignin during cooking and the addition of performance chemicals during papermaking. In this paper, pore sizes and the pore size distribution of unbleached softwood fibres have been studied. A well-characterised fibre material consisting of laboratory cooked spruce and pine pulp of various lignin contents was used. Pore size and pore size distribution were measured by studies of the relaxation behaviour of H-2 in fibres saturated with (H2O)-H-2. Beside this the total and surface charge of the fibres were also measured together with strength properties of papers from unbeaten fibres. For both pulps, there is a maximum in pore radius at a yield around 46%. Calculations of fibre wall volume from water retention values and yield levels show that there is a discontinuity in pore radius as a function of the fibre wall volume around a yield of 51%. It is suggested that this discontinuity is caused by the breakdown of the hemicellulose/ lignin matrix within the fibre wall at this yield level. The strength of the papers formed from the fibres shows a correlation with the surface charge of the fibres. Based on the change in surface charge with yield and the change in total charge with yield, this correlation is suggested to be due to an opening up of the external part of the fibre wall. This stresses the importance of the chemical composition and physical structure of the outer layer of the fibre wall.

  • 11. Andreasson, B
    et al.
    Forsström, Jennie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Determination of fibre pore structure: influence of salt, pH and conventional wet strength resins2005In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 12, no 3, p. 253-265Article in journal (Refereed)
    Abstract [en]

    It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.

  • 12.
    Apostolopoulou-Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lavoine, Nathalie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermal conductivity of hygroscopic foams based on cellulose nanofibrils and a nonionic polyoxamer2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 2, p. 1117-1126Article in journal (Refereed)
    Abstract [en]

    Nanocellulose-based lightweight foams are promising alternatives to fossil-based insulation materials for energy-efficient buildings. The properties of cellulose-based materials are strongly influenced by moisture and there is a need to assess and better understand how the thermal conductivity of nanocellulose-based foams depends on the relative humidity and temperature. Here, we report a customized setup for measuring the thermal conductivity of hydrophilic materials under controlled temperature and relative humidity conditions. The thermal conductivity of isotropic foams based on cellulose nanofibrils and a nonionic polyoxamer, and an expanded polystyrene foam was measured over a wide range of temperatures and relative humidity. We show that a previously developed model is unable to capture the strong relative humidity dependence of the thermal conductivity of the hygroscopic, low-density nanocellulose- and nonionic polyoxamer-based foam. Analysis of the moisture uptake and moisture transport was used to develop an empirical model that takes into consideration the moisture content and the wet density of the investigated foam. The new empirical model could predict the thermal conductivity of a foam with a similar composition but almost 3 times higher density. Accurate measurements of the thermal conductivity at controlled temperature and relative humidity and availability of simple models to better predict the thermal conductivity of hygroscopic, low-density foams are necessary for the development of nanocellulose-based insulation materials.

  • 13.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gallstedt, Mikael
    Lindström, Tom
    Oxygen and oil barrier properties of microfibrillated cellulose films and coatings2010In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 3, p. 559-574Article in journal (Refereed)
    Abstract [en]

    The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH's, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5-10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.

  • 14. Aulin, Christian
    et al.
    Gällstedt, Mikael
    RISE, Innventia.
    Lindström, Tom
    RISE, Innventia.
    Oxygen and oil barrier properties of microfibrillated cellulose films and coatings2010In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 3, p. 559-574Article in journal (Refereed)
    Abstract [en]

    The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH’s, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5-10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.

  • 15.
    Bardet, Raphael
    et al.
    Université Grenoble Alpes, France; CNRS, France.
    Reverdy, Charlène
    Université Grenoble Alpes, France; CNRS, France.
    Belgacem, Naceur
    Université Grenoble Alpes, France; CNRS, France.
    Leirset, Ingebjørg
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Bardet, Michel
    Université Grenoble Alpes, France; CEA, France.
    Bras, Julien
    Université Grenoble Alpes, France; CNRS, France.
    Substitution of nanoclay in high gas barrier films of cellulose nanofibrils with cellulose nanocrystals and thermal treatment2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1227-1241Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to design a nanocellulose based barrier film. For this purpose, cellulose nanofibrils (CNFs) are used as a matrix to create an entangled nanoporous network that is filled with two different nanofillers: nanoclay (reference), i.e. the mineral montmorillonite (MMT) and the bio-based TEMPO-oxidized cellulose nanocrystal (CNC-T), to produce different types of nanocelluloses and their main physical and chemical features were assessed. As expected, films based on neat CNFs exhibit good mechanical performance and excellent barrier properties at low moisture content. The introduction of 32.5 wt% of either nanofiller results in a significant improvement of barrier properties at high moisture content. Finally, thermal treatment of a dried CNF/CNC-T film results in a decrease of the oxygen permeability even at high moisture content (>70 %). This is mainly attributed to the hornification of nanocellulose. A key result of this study is that the oxygen permeability of an all-nanocellulose film in 85 % relative humidity (RH), is similar to CNF film with mineral nanoclay (MMT), i.e. 2.1 instead of 1.7 cm3 µm m−2 day−1 kPa−1, respectively.

  • 16.
    Bergenstrahle-Wohlert, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    d'Ortoli, Thibault Angles
    Sjoberg, Nils A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Widmalm, Goran
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    On the anomalous temperature dependence of cellulose aqueous solubility2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2375-2387Article in journal (Refereed)
  • 17. Bergenstråhle-Wohlert, M.
    et al.
    Berglund, L.A.
    Brady, J.W.
    Larsson, P.T.
    RISE, Innventia.
    Westlund, P.-O.
    Wohlert, J.
    Concentration enrichment of urea at cellulose surfaces: Results from molecular dynamics simulations and NMR spectroscopy2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, no 1, p. 1-12Article in journal (Refereed)
  • 18. Bergenstråhle-Wohlert, Malin
    et al.
    Angles d'Ortoli, Thibault
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sjöberg, Nils A.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wohlert, Jakob
    On the anomalous temperature dependence of cellulose aqueous solubility2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2375-2387Article in journal (Refereed)
    Abstract [en]

    The solubility of cellulose in water-based media is promoted by low temperature, which may appear counter-intuitive. An explanation to this phenomenon has been proposed that is based on a temperature-dependent orientation of the hydroxymethyl group. In this paper, this hypothesis is investigated using molecular dynamics computer simulations and NMR spectroscopy, and is discussed in conjunction with alternative explanations based on solvent–solute and solvent–solvent hydrogen bond formation respectively. It is shown that neither simulations nor experiments lend support to the proposed mechanism based on the hydroxymethyl orientation, whereas the two alternative explanations give rise to two distinct contributions to the hydration free energy of cellooligomers.

  • 19. Bergenstråhle-Wohlert, Malin
    et al.
    Berglund, Lars A
    Brady, John W
    Larsson, P Tomas
    Westlund, Per-Olof
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wohlert, Jakob
    Concentration enrichment of urea at cellulose surfaces: results from molecular dynamics simulations and NMR spectroscopy2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    A combined solid-state NMR and Molecular Dynamics simulation study of cellulose in urea aqueous solution and in pure water was conducted. It was found that the local concentration of urea is significantly enhanced at the cellulose/solution interface. There, urea molecules interact directly with the cellulose through both hydrogen bonds and favorable dispersion interactions, which seem to be the driving force behind the aggregation. The CP/MAS 13C spectra was affected by the presence of urea at high concentrations, most notably the signal at 83.4 ppm, which has previously been assigned to C4 atoms in cellulose chains located at surfaces parallel to the (110) crystallographic plane of the cellulose Iβ crystal. Also dynamic properties of the cellulose surfaces, probed by spin-lattice relaxation time 13CT 1 measurements of C4 atoms, are affected by the addition of urea. Molecular Dynamics simulations reproduce the trends of the T 1measurements and lends new support to the assignment of signals from individual surfaces. That urea in solution is interacting directly with cellulose may have implications on our understanding of the mechanisms behind cellulose dissolution in alkali/urea aqueous solutions.

  • 20.
    Bergenstråhle-Wohlert, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brady, John W.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Westlund, Per-Olof
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Concentration enrichment of urea at cellulose surfaces: results from molecular dynamics simulations and NMR spectroscopy2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    A combined solid-state NMR and Molecular Dynamics simulation study of cellulose in urea aqueous solution and in pure water was conducted. It was found that the local concentration of urea is significantly enhanced at the cellulose/solution interface. There, urea molecules interact directly with the cellulose through both hydrogen bonds and favorable dispersion interactions, which seem to be the driving force behind the aggregation. The CP/MAS (13)C spectra was affected by the presence of urea at high concentrations, most notably the signal at 83.4 ppm, which has previously been assigned to C4 atoms in cellulose chains located at surfaces parallel to the (110) crystallographic plane of the cellulose I beta crystal. Also dynamic properties of the cellulose surfaces, probed by spin-lattice relaxation time (13)CT (1) measurements of C4 atoms, are affected by the addition of urea. Molecular Dynamics simulations reproduce the trends of the T (1) measurements and lends new support to the assignment of signals from individual surfaces. That urea in solution is interacting directly with cellulose may have implications on our understanding of the mechanisms behind cellulose dissolution in alkali/urea aqueous solutions.

  • 21.
    Berglund, Jennie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Azhar, Shoaib
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    The structure of galactoglucomannan impacts the degradation under alkaline conditions2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Galactoglucomannan (GGM) from sprucewas studied with respect to the degradation behavior inalkaline solution. Three reference systems includinggalactomannan from locust bean gum, glucomannanfrom konjac and the linear water-soluble carboxymethylcellulose were studied with focus onmolecular weight, sugar composition, degradationproducts, as well as formed oligomers, to identifyrelative structural changes in GGM. Initially allmannan polysaccharides showed a fast decrease inthe molecular weight, which became stable in the laterstage. The degradation of the mannan polysaccharidescould be described by a function corresponding to thesum of two first order reactions; one slow that wasascribed to peeling, and one fast that was connectedwith hydrolysis. The galactose side group wasstable under conditions used in this study (150 min,90 C, 0.5 M NaOH). This could suggest that, apartfrom the covalent connection to C6 in mannose, thegalactose substitutions also interact non-covalentlywith the backbone to stabilize the structure againstdegradation. Additionally, the combination of differentbackbone sugars seems to affect the stability of thepolysaccharides. For carboxymethyl cellulose thedegradation was linear over time which furthersuggests that the structure and sugar composition playan important role for the alkaline degradation. Moleculardynamics simulations gave details about theconformational behavior of GGM oligomers in watersolution, as well as interaction between the oligomersand hydroxide ions.

  • 22. Berglund, Linn
    et al.
    Anugwom, Ikenna
    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, Turku, Finland.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aitomäki, Yvonne
    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, Turku, Finland.
    Oksman, Kristiina
    Switchable ionic liquids enable efficient nanofibrillation of wood pulp2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 8, p. 3265-3279Article in journal (Refereed)
    Abstract [en]

    Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

  • 23.
    Berglund, Linn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Anugwom, Ikenna
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University .
    Hedenström, Mattias
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University .
    Aitomäki, Yvonne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mikkola, Jyri-Pekka
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Fibre and Particle Engineering, University of Oulu.
    Switchable ionic liquids enable efficient nanofibrillation of wood pulp2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 8, p. 3265-3279Article in journal (Refereed)
    Abstract [en]

    Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

  • 24.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Stemme, S
    Dahlfors, T
    Arwin, H
    Ödberg, L
    Spectroscopic ellipsometry characterisation and estimation of the Hamaker constant of cellulose1999In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 6, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Calculations of Hamaker constants using Lifshitz theory require the availability of accurate dielectric data, especially in the visible-ultraviolet region. We present spectroscopic ellipsometry data on well defined cellulose films of a limited thickness range (100–140 layers) deposited on an oxidised and hydrophobised silicon substrate. The spectral data, representing measurements from a perpendicular orientation to the fibre deposition direction, was used for estimates of the necessary spectral parameters, i.e. the oscillator strengths and characteristic frequencies in the UV-range. Our calculations show that cellulose has a relatively low Hamaker constant in air (58 zJ) and water (8.0 zJ). The implications for the surface energy estimates of cellulose and colloidal interactions between cellulose and various types of fillers and coating colours were discussed.

  • 25.
    Bondeson, Daniel
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Mathew, Aji P.
    Oksman, Kristiina
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Optimization of the Isolation of Nanocrystals from Microcrystalline Cellulose by Acid Hydrolysis2006In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 13, no 2, p. 171-180Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).

  • 26.
    Bozic, Mojca
    et al.
    Faculty of Mechanical Engineering, Institute for Engineering Materials and Design, University of Maribor.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kokol, Vanja
    Faculty of Mechanical Engineering, Institute for Engineering Materials and Design, University of Maribor.
    Enzymatic phosphorylation of cellulose nanofibers to new highly-ions adsorbing, flame-retardant and hydroxyapatite-growth induced natural nanoparticles2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2713-2726Article in journal (Refereed)
    Abstract [en]

    This study confirms the enzyme-mediated phosphorylation of cellulose nanofibers (CNF) by using hexokinase and adenosine-5’-triphosphate (ATP) in the presence of Mg-ions, resulting in a phosphate group’s creation predominantly at C-6-O positioned hydroxyl groups of cellulose monomer rings. A proof-of-concept is provided using 12C CPMAS, 31P MAS NMR, ATR-FTIR and XPS analyzing methods. The degree of substitution is determined for the first time by ATR-FTIR spectroscopy being in a correlation with XPS and potentiometric titration results. From the thermal degradation measurements using TGA, the C-6-O phosphorylation was found to noticeably prevent the CNF derivatives from weight loss in the pyrolysis process, thus, providing them flame-resistance functionality. Furthermore, phosphorylation significantly enhanced adsorption capacity of Fe3+ ions making them interesting for fabrication of biobased filters and membranes. Finally, the biomimetic growth of Ca-P crystals (hydroxyapatite) in simulated body fluid was characterized by SEM and showing further practicability for biomedical materials.

  • 27.
    Butchosa, Nuria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Leijon, Felicia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Bulone, Vincent
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Zhou, Qi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Stronger cellulose microfibril network structure through the expression of cellulose-binding modules in plant primary cell walls2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 5, p. 3083-3094Article in journal (Refereed)
    Abstract [en]

    Cellulose-binding modules (CBMs) are non-catalytic domains typically occurring in glycoside hydrolases. Their specific interaction with diverse polysaccharides assists hydrolysis by the catalytic subunits. In this work, we have exploited the interactions between a CBM from family 3 (CBM3) and cell wall polysaccharides to alter the structure and mechanical properties of cellulose microfibrils from BY-2 tobacco cell suspension cultures. A CBM3 from Clostridium thermocellum was overexpressed in the cells using Agrobacterium-mediated transformation. Water suspensions of cellulose microfibrils were prepared by the removal of the non-cellulosic components of the primary cell walls, followed by mild disintegration using sonication. The morphology of the microfibrils was characterized by transmission electron microscopy and atomic force microscopy. These cellulose microfibrils were further hydrolyzed with 64wt% sulfuric acid to produce cellulose nanocrystals (CNCs). The average length of CNCs prepared from the CBM3-transformed cells was 201nm, higher than that from the wild-type cells (122nm). In addition, the mechanical properties and deformation mechanism of nanopapers prepared from suspensions of cellulose microfibrils were investigated. The nanopapers obtained from the CBM3-transformed cells exhibited enhanced tensile strength and work of fracture, 40% and 128% higher than those prepared from wild-type tobacco cells, respectively. [GRAPHICS] .

  • 28.
    Butchosa, Núria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 6, p. 4349-4358Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) are difficult to redisperse in water after they have been completely dried due to the irreversible agglomeration of cellulose during drying. Here, we have developed a simple process to prepare water-redispersible dried CNFs by the adsorption of small amounts of carboxymethyl cellulose (CMC) and oven drying. The adsorption of CMC onto CNFs in water suspensions at 22 and 121 °C was studied, and the adsorbed amount of CMC was measured via conductimetric titration. The water-redispersibility of dried CNFs adsorbed with different amounts of CMC was characterized by sedimentation test. Above a critical threshold of CMC adsorption, i.e. 2.3 wt%, the oven dried CNF–CMC sample was fully redispersible in water. The morphology, rheological, and mechanical properties of water-redispersed CNF–CMC samples were investigated by field emission scanning electron microscopy, viscosity measurement, and tensile test, respectively. The water-redispersed CNFs preserved the original properties of never dried CNFs. This new method will facilitate the production, transportation and storage, and large-scale industrial applications of CNFs.

  • 29.
    Carlsson, Linn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ingverud, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Blomberg, Hanna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Surface characteristics of cellulose nanoparticles grafted by surface-initiated ring-opening polymerization of epsilon-caprolactone2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1063-1074Article in journal (Refereed)
    Abstract [en]

    In this study, surface-initiated ring-opening polymerization has been employed for the grafting of epsilon-caprolactone from cellulose nanoparticles, made by partial hydrolysis of cellulose cotton linters. A sacrificial initiator was employed during the grafting reactions, to form free polymer in parallel to the grafting reaction. The degree of polymerization of the polymer grafts, and of the free polymer, was varied by varying the reaction time. The aim of this study was to estimate the cellulose nanoparticle degree of surface substitution at different reaction times. This was accomplished by combining measurement results from spectroscopy and chromatography. The prepared cellulose nanoparticles were shown to have 3.1 (+/- 0.3) % of the total anhydroglucose unit content present at the cellulose nanoparticle surfaces. This effectively limits the amount of cellulose that can be targeted by the SI-ROP reactions. For a certain SI-ROP reaction time, it was assumed that the resulting degree of polymerization (DP) of the grafts and the DP of the free polymer were equal. Based on this assumption it was shown that the cellulose nanoparticle surface degree of substitution remained approximately constant (3-7 %) and seemingly independent of SI-ROP reaction time. We believe this work to be an important step towards a deeper understanding of the processes and properties controlling SI-ROP reactions occurring at cellulose surfaces.

  • 30.
    Carlsson, Linn
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ingverud, Tobias
    KTH Royal Institute of Technology, Sweden.
    Blomberg, Hanna
    KTH Royal Institute of Technology, Sweden.
    Carlmark, Anna
    KTH Royal Institute of Technology, Sweden.
    Larsson, Per Tomas
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Malmström, Eva
    KTH Royal Institute of Technology, Sweden.
    Surface characteristics of cellulose nanoparticles grafted by surface-initiated ring-opening polymerization of ε-caprolactone2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1063-1074Article in journal (Refereed)
    Abstract [en]

    In this study, surface-initiated ring-opening polymerization has been employed for the grafting of e-caprolactone from cellulose nanoparticles, made by partial hydrolysis of cellulose cotton linters. A sacrificial initiator was employed during the grafting reactions, to form free polymer in parallel to the grafting reaction. The degree of polymerization of the polymer grafts, and of the free polymer, was varied by varying the reaction time. The aim of this study was to estimate the cellulose nanoparticle degree of surface substitution at different reaction times. This was accomplished by combining measurement results from spectroscopy and chromatography. The prepared cellulose nanoparticles were shown to have 3.1 (±0.3) % of the total anhydroglucose unit content present at the cellulose nanoparticle surfaces. This effectively limits the amount of cellulose that can be targeted by the SI-ROP reactions. For a certain SIROP reaction time, it was assumed that the resulting degree of polymerization (DP) of the grafts and the DP of the free polymer were equal. Based on this assumption it was shown that the cellulose nanoparticle surface degree of substitution remained approximately constant (3–7 %) and seemingly independent of SI-ROP reaction time. We believe this work to be an important step towards a deeper understanding of the processes and properties controlling SI-ROP reactions occurring at cellulose surfaces.

  • 31.
    Cervin, Nicholas Tchang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Aulin, Christian
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 2, p. 401-410Article in journal (Refereed)
    Abstract [en]

    A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the aerogel and the aerogel can then be reused for a second absorption cycle.

  • 32. Cervin, N.T.
    et al.
    Aulin, C.
    RISE, Innventia.
    Larsson, P.T.
    RISE, Innventia.
    Wågberg, L.
    Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, no 2, p. 401-410Article in journal (Refereed)
  • 33.
    Changqing, Ruan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Lindh, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    A green and simple method for preparation of an efficient palladium adsorbent based on cysteine functionalized2,3-dialdehyde cellulose2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2627-2638Article in journal (Refereed)
    Abstract [en]

    A green and efficient adsorbent for adsorption of palladium ions was prepared from 2,3-dialdehyde cellulose (DAC) originating from nanocellulose from the green algae Cladophora. The DAC was functionalized with cysteine via reductive amination in a convenient one-pot procedure to provide the adsorbent. The adsorption properties for adsorbing palladium(II) ions, including capacity, adsorption isotherm and kinetics, were studied. The successful reductive amination of cysteine with 2,3-dialdehyde cellulose was confirmed by FT-IR, elemental analysis and XPS. The adsorbent was characterized by SEM, XRD, gas adsorption and TGA. The adsorbent had a high adsorption capacity (130 mg palladium per gram adsorbent) and enabled fast adsorption of palladium(II) ions from solution (80 % of maximum capacity reached in 2 h). Adsorbent materials suitable for both filters (fibrous) and column matrixes (spherical particles) could be obtained in an efficient manner by controlling the degree of oxidation while producing the DAC material.

  • 34. Charani, P. Rezayati
    et al.
    Dehghani-Firouzabadi, M.
    Afra, E.
    Blademo, A.
    Naderi, A.
    Lindström, Tom
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Production of microfibrillated cellulose from unbleached kraft pulp of Kenaf and Scotch Pine and its effect on the properties of hardwood kraft: microfibrillated cellulose paper2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 5, p. 2559-2567Article in journal (Refereed)
    Abstract [en]

    This work investigated the effect of using Kenaf bast fibre kraft pulps compared to Scotch Pine kraft pulps for producing microfibrillated cellulose (MFC) and its employment for improving mechanical and physical properties of handsheets made from unbleached kraft hardwood pulp. It was shown that MFC based on Kenaf fibres can be produced at higher consistencies [> 5 % (w/w)] compared to when Scotch Pine is employed [a parts per thousand 2 % (w/w)] as raw material. The possibility of using a higher consistency when processing Kenaf is beneficial for the processing in microfluidizers. The rheological properties of the products were shown to be consistent with what is known for MFC-based systems. The studies indicate that the mechanical properties of handsheets from unbleached kraft hardwood pulp can be improved by replacing part of the unbleached kraft hardwood pulp fibres with either unbleached kraft Kenaf pulp or unbleached Scotch Pine kraft pulp. However, the same levels of improvements were obtained when using only a small amount [a parts per thousand 6 % (w/w)] of MFC based on Kenaf or Scotch Pine, when introduced into the system either as a dry strength additive or by coating pre-made handsheets. Finally, it was shown that the incorporation of MFC in handsheets decreases the air-permeability; this effect became amplified when the MFC was applied as a coating onto the handsheets.

  • 35. Chen, Pan
    et al.
    Ogawa, Yu
    Nishiyama, Yoshiharu
    Bergenstråhle-Wohlert, Malin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mazeau, Karim
    Alternative hydrogen bond models of cellulose II and IIII based on molecular force-fields and density functional theory2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 3, p. 1485-1493Article in journal (Refereed)
    Abstract [en]

    Alternative hydrogen-bond structures were found for cellulose II and IIII based on molecular dynamics simulations using four force fields and energy optimization based on density functional theory. All the modeling results were in support to the new hydrogen-bonding network. The revised structures of cellulose II and IIII differ with the fiber diffraction models mainly in the orientation of two hydroxyl groups, namely, OH2 and OH6 forming hydrogen-bond chains perpendicular to the cellulose molecule. In the alternative structures, the sense of hydrogen bond is inversed but little difference can be seen in hydrogen bond geometries. The preference of these alternative hydrogen bond structures comes from the local stabilization of hydroxyl groups with respect to the beta carbon. On the other hand when simulated fiber diffraction patterns were compared with experimental ones, the current structure of cellulose II with higher energy and the alternative structure of cellulose IIII with lower energy were in better agreement.

  • 36.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. South China Univ Technol, State Key Lab Pulp & Paper Engn, Guangzhou 510640, Guangdong, Peoples R China.
    Ogawa, Yu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Nishiyama, Yoshiharu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Ismail, Ahmed E.
    West Virginia Univ, Dept Chem & Biomed Engn, Morgantown, WV 26505 USA..
    Mazeau, Karim
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    I alpha to I beta mechano-conversion and amorphization in native cellulose simulated by crystal bending2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 8, p. 4345-4355Article in journal (Refereed)
    Abstract [en]

    The bending of rod-like native cellulose crystals with degree of polymerization 40 and 160 using molecular dynamics simulations resulted in a deformation-induced local amorphization at the kinking point and allomorphic interconversion between cellulose I alpha and I beta in the unbent segments. The transformation mechanism involves a longitudinal chain slippage of the hydrogen-bonded sheets by the length of one anhydroglucose residue ( 0.5 nm), which alters the chain stacking from the monotonic (I alpha) form to the alternating I beta one or vice versa. This mechanical deformation converts the I alpha form progressively to the I beta form, as has been experimentally observed for ultrasonication of microfibrils. I beta is also able to partially convert to I alpha-like organization but this conversion is only transitory. The qualitative agreement between the behavior of ultrasonicated microfibrils and in silico observed I alpha -> I beta conversion suggests that shear deformation and chain slippage under bending deformation is a general process when cellulose fibrils experience lateral mechanical stress.

  • 37.
    Choong, Ferdinand X.
    et al.
    Swedish Medical Nanoscience Center, Department of Neuroscience Karolinska Institutet, Stockholm, Sweden.
    Lantz, Linda
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Shirani, Hamid
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Schulz, Anette
    Swedish Medical Nanoscience Center, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Nilsson, K. Peter R.
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Edlund, Ulrica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Richter-Dahlfors, Agneta
    Swedish Medical Nanoscience Center, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Stereochemical Identification of Glucans by a Donor-Acceptor-Donor Conjugated Pentamer Enables Multi-Carbohydrate Anatomical Mapping in Plant Tissues2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 7, p. 4253-4264Article in journal (Refereed)
    Abstract [en]

    Optotracing is a novel method for analytical imaging of carbohydrates in plant and microbial tissues. This optical method applies structure-responsive oligothiophenes as molecular fluorophores emitting unique optical signatures when bound to polysaccharides. Herein, we apply Carbotrace680, a short length anionic oligothiophene with a central heterocyclic benzodithiazole (BTD) motif, to probe for different glucans. The donor-acceptor-donor type electronic structure of Carbotrace680 provides improved spectral properties compared to oligothiophenes due to the possibility of intramolecular charge-transfer transition to the BTD motif. This enables differentiation of glucans based on the glycosidic linkage stereochemistry. Thus -configured starch is readily differentiated from -configured cellulose. The versatility of optotracing is demonstrated by dynamic monitoring of thermo-induced starch remodelling, shown in parallel by spectrophotometry and microscopy of starch granules. Imaging of Carbotrace680 bound to multiple glucans in plant tissues provided direct identification of their physical locations, revealing the spatial relationship between structural (cellulose) and storage (starch) glucans at sub-cellular scale. Our work forms the basis for the development of superior optotracers for sensitive detection of polysaccharides. Our non-destructive method for anatomical mapping of glucans in biomass will serve as an enabling technology for developments towards efficient use of plant-derived materials and biomass.

  • 38.
    Choong, Ferdinand X.
    et al.
    Karolinska Inst, Sweden.
    Lantz, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Shirani, Hamid
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Schulz, Anette
    Karolinska Inst, Sweden.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Edlund, Ulrica
    KTH Royal Inst Technol, Sweden.
    Richter-Dahlfors, Agneta
    Karolinska Inst, Sweden.
    Stereochemical identification of glucans by a donor-acceptor-donor conjugated pentamer enables multi-carbohydrate anatomical mapping in plant tissues2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 7, p. 4253-4264Article in journal (Refereed)
    Abstract [en]

    Optotracing is a novel method for analytical imaging of carbohydrates in plant and microbial tissues. This optical method applies structure-responsive oligothiophenes as molecular fluorophores emitting unique optical signatures when bound to polysaccharides. Herein, we apply Carbotrace680, a short length anionic oligothiophene with a central heterocyclic benzodithiazole (BTD) motif, to probe for different glucans. The donor-acceptor-donor type electronic structure of Carbotrace680 provides improved spectral properties compared to oligothiophenes due to the possibility of intramolecular charge-transfer transition to the BTD motif. This enables differentiation of glucans based on the glycosidic linkage stereochemistry. Thus -configured starch is readily differentiated from -configured cellulose. The versatility of optotracing is demonstrated by dynamic monitoring of thermo-induced starch remodelling, shown in parallel by spectrophotometry and microscopy of starch granules. Imaging of Carbotrace680 bound to multiple glucans in plant tissues provided direct identification of their physical locations, revealing the spatial relationship between structural (cellulose) and storage (starch) glucans at sub-cellular scale. Our work forms the basis for the development of superior optotracers for sensitive detection of polysaccharides. Our non-destructive method for anatomical mapping of glucans in biomass will serve as an enabling technology for developments towards efficient use of plant-derived materials and biomass. [GRAPHICS] .

  • 39.
    Colic, Miodrag
    et al.
    Medical Faculty of the Military Medical Academy, University of Defense in Belgrade, Serbia.
    Mihajlovic, Dusan
    Medical Faculty of the Military Medical Academy, University of Defense in Belgrade, Serbia.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Naseri, Narges
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kokol, Vanja
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Cytocompatibility and immunomodulatory properties of wood based nanofibrillated cellulose2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 1, p. 763-778Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs), unique and promising natural materials have gained significant attention recently for biomedical applications, due to their special biomechanical characteristics, surface chemistry, good biocompatibility and low toxicity. However, their long bio-persistence within organisms may provoke chronic immune reactions and this aspect of CNFs has not been studied to date. Therefore, the aim of this work was to examine and compare the biocompatibility and immunomodulatory properties of CNFs in vitro. CNFs (diameters of 10-70nm; lengths of a few microns) were prepared from Norway spruce (Picea abies) by mechanical fibrillation and high pressure homogenisation. L929 cells, rat thymocytes or human peripheral blood mononuclear cells (PBMNCs) were cultivated with CNFs. None of the six concentrations of CNFs (31.25µg/ml – 1mg/ml) induced cytotoxicity and oxidative stress in the L929 cells, nor induced necrosis and apoptosis of the thymocytes and PBMNCs. Higher concentrations (250µg/ml – 1mg/ml) slightly inhibited the metabolic activities of the L929 cells as a consequence of inhibited proliferation. The same concentrations of CNFs suppressed the proliferation of PBMNCs to phytohemaglutinine, a T-cell mitogen, and the process was followed by down-regulation of interleukin-2 (IL-2) and interferon-γ (IFN-γ) production. The highest concentration of CNFs inhibited IL-17A but increased IL-10 and IL-6 production. The secretions of the inflammatory cytokines, IL-1β and the tumor necrosis factor-α (TNF-α) as well as Th2 cytokine (IL-4), remained unaltered. In conclusion, the results suggest that these CNFs are biocompatible, non-inflammatory and non-immunogenic nanomaterial. Higher concentrations seem to be tollerogenic to the immune system, a characteristic very desirable for implantable biomaterials.

  • 40. Colombani, A.
    et al.
    Djerbi, Soraya
    KTH, Superseded Departments, Biotechnology.
    Bessueille, L.
    Blomqvist, Kristina
    KTH, Superseded Departments, Biotechnology.
    Ohlsson, Anna
    KTH, Superseded Departments, Biotechnology.
    Berglund, Torkel
    KTH, Superseded Departments, Biotechnology.
    Teeri, Tuula
    KTH, Superseded Departments, Biotechnology.
    Bulone, V.
    In vitro synthesis of (1→3)-β-D-glucan (callose) and cellulose by detergent extracts of membranes from cell suspension cultures of hybrid aspen2004In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 3-4, p. 313-327Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to optimize the conditions for in vitro synthesis of (1 --> 3)-beta-D-glucan (callose) and cellulose, using detergent extracts of membranes from hybrid aspen (Populus tremula x tremuloides) cells grown as suspension cultures. Callose was the only product synthesized when CHAPS extracts were used as a source of enzyme. The optimal reaction mixture for callose synthesis contained 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 8 mM Ca2+, and 20 mM cellobiose. The use of digitonin to extract the membrane-bound proteins was required for cellulose synthesis. Yields as high as 50% of the total in vitro products were obtained when cells were harvested in the stationary phase of the growth curve, callose being the other product. The optimal mixture for cellulose synthesis consisted of 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 1 mM Ca2+, 8 mM Mg2+, and 20 mM cellobiose. The in vitro beta-glucans were identified by hydrolysis of radioactive products, using specific enzymes. C-13-Nuclear magnetic resonance spectroscopy and transmission electron microscopy were also used for callose characterization. The (1-->3)-beta-D-glucan systematically had a microfibrillar morphology, but the size and organization of the microfibrils were affected by the nature of the detergent used for enzyme extraction. The discussion of the results is included in a short review of the field that also compares the data obtained with those available in the literature. The results presented show that the hybrid aspen is a promising model for in vitro studies on callose and cellulose synthesis.

  • 41.
    Correia, Viviane da Costa
    et al.
    Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering, University of São Paulo.
    Santos, Vlademir dos
    Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering, University of São Paulo.
    Sain, Mohini
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Santos, Sergio Francisco
    Department of Materials and Technology, Faculty of Engineering, São Paulo State University.
    Leão, Alcides Lopes
    Department of Rural Engineering, Sao Paulo State University.
    Junior, Holmer Savastano
    Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering, University of São Paulo.
    Grinding process for the production of nanofibrillated cellulose based on unbleached and bleached bamboo organosolv pulp2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 5, p. 2971-2987Article in journal (Refereed)
    Abstract [en]

    Nanofibrillated cellulose (NFC) is a type of nanomaterial based on renewable resources and produced by mechanical disintegration without chemicals. NFC is a potential reinforcing material with a high surface area and high aspect ratio, both of which increase reinforcement on the nanoscale. The raw materials used were unbleached and bleached bamboo organosolv pulp. Organosolv pulping is a cleaner process than other industrial methods (i.e. Kraft process), as it uses organic solvents during cooking and provides easy solvent recovery at the end of the process. The NFC was produced by treating unbleached and bleached bamboo organosolv pulps for 5, 10, 15 and 20 nanofibrillation cycles using the grinding method. Chemical, physical and mechanical tests were performed to determine the optimal condition for nanofibrillation. The delamination of the S2 layer of the fibers during nanofibrillation contributed to the partial removal of amorphous components (mainly lignin), which have low polarity and improved the adhesion of the fibers, particularly the unbleached cellulose. The transverse modulus of elasticity of the unbleached NFC was highest after 10 nanofibrillation cycles. Further treatment cycles decreased the modulus due to the mechanical degradation of the fibers. The unbleached NFC produced by 10 cycles have a greater transverse modulus of elasticity, the crystallite size showed increase with the nanofibrillation, and after 5 nanofibrillation cycles, no differences are observed in the morphology of the fibers.

  • 42.
    Cui, Sheng
    et al.
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China.;Jiangsu Collaborat Innovat Ctr Adv Inorgan Funct, Nanjing 210009, Jiangsu, Peoples R China..
    Wang, Xue
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China.;Jiangsu Collaborat Innovat Ctr Adv Inorgan Funct, Nanjing 210009, Jiangsu, Peoples R China..
    Zhang, Xin
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China.;Nanjing Gen Hosp, Dept Neurosurg, Nanjing 210002, Jiangsu, Peoples R China.;Jiangsu Collaborat Innovat Ctr Adv Inorgan Funct, Nanjing 210009, Jiangsu, Peoples R China..
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tang, Xianglong
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China..
    Lin, Benlan
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China..
    Wu, Qi
    Nanjing Gen Hosp, Dept Neurosurg, Nanjing 210002, Jiangsu, Peoples R China..
    Shen, Xiaodong
    Nanjing Tech Univ, Coll Mat Sci & Engn, State Key Lab Mat Oriented Chem Engn, Nanjing 210009, Jiangsu, Peoples R China.;Jiangsu Collaborat Innovat Ctr Adv Inorgan Funct, Nanjing 210009, Jiangsu, Peoples R China..
    Preparation of magnetic MnFe2O4-Cellulose aerogel composite and its kinetics and thermodynamics of Cu(II) adsorption2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 1, p. 735-751Article in journal (Refereed)
    Abstract [en]

    In this paper, a MnFe2O4-Cellulose magnetic composite aerogel (MnCA) with high adsorption capacity was fabricated by in situ incorporating MnFe2O4 to regenerated cellulose hydrogel matrix, followed by CO2 supercritical drying. A green synthetic strategy was performed by using renewable cellulose materials, environmentally benign cellulose solvents and facile synthetic conditions. The results showed that the obtained magnetic cellulose aerogel had a continuous and tiered three dimensional network with interconnected fibrils of about 30 nm in width, which was similar to those of cellulose aerogel prepared from NaOH/urea solution via CO2 supercritical drying. Meanwhile, they had high specific surface areas of 236-288 m(2)/g and total pore volume of 0.55-0.88 cm(3)/g. In addition, the hybrid aerogel showed superparamagnetism with maximum saturation magnetization reaching up to 18.53 emu/g. The magnetic nanocomposite aerogel could be used for biological and environmental applications. The adsorption test showed that MnCA had rapid adsorption rate and excellent adsorption ability of removing heavy metal ions in aqueous solution which could attain to 63.3 mg/g within 100 min. Moreover, all the composite aerogels exhibited good reusability and could be easily reused from the water after adsorption.

  • 43. Cunha, A.G.
    et al.
    Zhou, Q.
    Larsson, P.T.
    RISE, Innventia.
    Berglund, L.A.
    Topochemical acetylation of cellulose nanopaper structures for biocomposites: Mechanisms for reduced water vapour sorption2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2773-2787Article in journal (Refereed)
  • 44.
    Cunha, Ana Gisela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. INNVENTIA AB, Sweden.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Topochemical acetylation of cellulose nanopaper structures for biocomposites: mechanisms for reduced water vapour sorption2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2773-2787Article in journal (Refereed)
    Abstract [en]

    Moisture sorption decreases dimensional stability and mechanical properties of polymer matrix biocomposites based on plant fibers. Cellulose nanofiber reinforcement may offer advantages in this respect. Here, wood-based nanofibrillated cellulose (NFC) and bacterial cellulose (BC) nanopaper structures, with different specific surface area (SSA), ranging from 0.03 to 173.3 m(2)/g, were topochemically acetylated and characterized by ATR-FTIR, XRD, solid-state CP/MAS C-13-NMR and moisture sorption studies. Polymer matrix nanocomposites based on NFC were also prepared as demonstrators. The surface degree of substitution (surface-DS) of the acetylated cellulose nanofibers is a key parameter, which increased with increasing SSA. Successful topochemical acetylation was confirmed and significantly reduced the moisture sorption in nanopaper structures, especially at RH = 53 %. BC nanopaper sorbed less moisture than the NFC counterpart, and mechanisms are discussed. Topochemical NFC nanopaper acetylation can be used to prepare moisture-stable nanocellulose biocomposites.

  • 45.
    Dahlman, Olof
    et al.
    STFI.
    Jacobs, Anna
    STFI.
    Sjöberg, John
    STFI.
    Molecular properties of hemicelluloses located in the surface and inner layers of hardwood and softwood pulps2003In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 10, no 4, p. 325-334Article in journal (Refereed)
  • 46.
    Deepa, B.
    et al.
    Department of Chemistry, Bishop Moore College, Mavelikara, 690101, Kerala.
    Abraham, Eldho
    Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University, Jerusalem.
    Cordeiro, Nerida
    Competence Centre in Exact Science and Engineering, University of Madeira.
    Mozetic, Milan
    Department of Surface Engineering, Jozef Stefan Institute.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Faria, Marisa
    Competence Centre in Exact Science and Engineering, University of Madeira.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, Department of Chemistry, C.M.S. College, Kottayam, 686001, Kerala.
    Pothan, Laly A.
    Department of Chemistry, Bishop Moore College, Mavelikara, 690101, Kerala.
    Utilization of various lignocellulosic biomass for the production of nanocellulose: a comparative study2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1075-1090Article in journal (Refereed)
    Abstract [en]

    Nanocellulose was successfully extracted from five different lignocellulosic biomass sources viz. banana rachis, sisal, kapok, pineapple leaf and coir using a combination of chemical treatments such as alkaline treatment, bleaching and acid hydrolysis. The shape, size and surface properties of the nanocellulose generally depend on the source and hydrolysis conditions. A comparative study of the fundamental properties of raw material, bleached and nanocellulose was carried out by means of Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, birefringence, X-ray diffraction, inverse gas chromatography and thermogravimetric analysis. Through the characterization of the nanocellulose obtained from different sources, the isolated nanocellulose showed an average diameter in the range of 10–25 nm, high crystallinity, high thermal stability and a great potential to be used with acid coupling agents due to a predominantly basic surface. This work provides an insight into the effective utilization of a variety of plant biomass as a potential source for nanocellulose extraction.

  • 47.
    Djafari Petroudy, Seyed Rahman
    et al.
    Shahid Beheshti University, Iran.
    Ghasemian, Ali
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Resalati, Hossein
    Sari University of Agricultural Sciences and Natural Resources, Iran.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    The effect of xylan on the fibrillation efficiency of DED bleached soda bagasse pulp and on nanopaper characteristics2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 1, p. 385-395Article in journal (Refereed)
    Abstract [en]

    Xylan is the second most abundant polysaccharide and the most abundant hemicellulose component of soda bagasse pulp. In this study, bleached soda bagasse pulp (SB) and bleached bagasse dissolving pulp (DB) with varying amounts of xylan were fibrillated with a homogenization process. The produced fibrillated materials were used for making nanopaper structures. The surface, physical, mechanical and optical properties of the nanopaper were measured, and the effect of xylan was assessed. Laser profilometry (LP) and field emission scanning electron microscopy were applied to study the degree of the fibrillation. The pulp having the highest xylan content, SB, showed the highest yield of cellulose nanofibrils. Nanopaper produced from SB had a more consolidated structure than that produced from DB. Additionally, SB nanopaper yielded higher tensile strength, lower LP roughness, a higher barrier against oxygen and lower opacity. These results indicate a higher degree of fibrillation of the SB pulp compared to the DB pulp. Hence, the positive effect of xylan for facilitating the fibrillation of the starting pulp fibers was demonstrated.

  • 48. Djahedi, Cyrus
    et al.
    Bergenstrahle-Wohlert, Malin
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Role of hydrogen bonding in cellulose deformation: the leverage effect analyzed by molecular modeling2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2315-2323Article in journal (Refereed)
  • 49.
    Djerbi, Soraya
    et al.
    KTH, Superseded Departments, Biotechnology.
    Aspeborg, Henrik
    KTH, Superseded Departments, Biotechnology.
    Nilsson, Peter
    KTH, Superseded Departments, Biotechnology.
    Blomqvist, Kristina
    KTH, Superseded Departments, Biotechnology.
    Teeri, Tuula
    KTH, Superseded Departments, Biotechnology.
    Identification and expression analysis of genes encoding putative cellulose synthases (CesA) in the hybrid aspen, Populus tremula (L.) × P. tremuloides (Michx.)2004In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 3-4, p. 301-312Article in journal (Refereed)
    Abstract [en]

    Cellulose is synthesized in plant cell walls by large membrane-bound protein complexes proposed to contain several copies of the catalytic subunit of the cellulose synthase, CesA. Here we report identification of 10 distinct CesA genes within a database of 100,000 ESTs of the hybrid aspen, Populus tremula (L.) x P. tremuloides (Michx.). Expression analyses in normal wood undergoing xylogenesis and in tension wood indicate xylem specific expression of four putative CesA isoenzymes, PttCesA1, PttCesA3-1, PttCesA3-2 and PttCesA9. Both the protein sequences and the expression profiles of PttCesA3-1 and PttCesA3-2 are very similar, and they may thus represent redundant copies of an enzyme with essentially the same function. Further, one of the generally more constitutively expressed CesA genes, PttCesA2, seems to be activated on the opposite side of a tension wood induced stem, while PttCesA6 appears to be more specific for leaf tissues. The rest of the hybrid aspen CesA genes were found to be relatively evenly expressed over the poplar tissues hereby studied.

  • 50.
    Enebro, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Siika-Aho, Matti
    VTT Technical Research Center of Finland, Espoo.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Investigation of endoglucanase selectivity on carboxymethyl cellulose by mass spectrometric techniques2009In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, no 2, p. 271-280Article in journal (Refereed)
    Abstract [en]

    The benefits of applying cellulose selective enzymes as analytical tools for chemical structure characterization of cellulose derivatives have been frequently addressed over the years. In a recent study the high selectivity of cellulase Cel45A from Trichoderma reesei (Tr Cel45A) was utilized for relating the chemical structure to the flow properties of carboxymethyl cellulose (CMC). However, in order to take full advantage of the enzymatic hydrolysis the enzyme selectivity on the cellulose substrate must be further investigated. Therefore, the selectivity of Tr Cel45A on CMC was studied by chemical sample preparation of the enzyme products followed by mass spectrometric chemical structure characterization. The results strongly suggest that, in accordance with recent studies, also this highly selective endoglucanase is able to catalyze hydrolysis of glucosidic bonds adjacent to mono-substituted anhydroglucose units (AGUs). Furthermore, the results also indicate that substituents on the nearby AGUs will affect the hydrolysis.

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