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  • 1. Andersson, L.
    et al.
    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.
    Bergström, Lennart
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Stockholm University.
    Evaluating pore space in macroporous ceramics with water-based porosimetry2013In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 96, no 6, p. 1916-1922Article in journal (Refereed)
    Abstract [en]

    We show that water-based porosimetry (WBP), a facile, simple, and nondestructive porosimetry technique, accurately evaluates both the pore size distribution and throat size distribution of sacrificially templated macroporous alumina. The pore size distribution and throat size distribution derived from the WBP evaluation in uptake (imbibition) and release (drainage) mode, respectively, were corroborated by mercury porosimetry and X-ray micro-computed tomography (μ-CT). In contrast with mercury porosimetry, the WBP also provided information on the presence of "dead-end pores" in the macroporous alumina.

  • 2.
    Bergenstråhle, Malin
    et al.
    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.
    Larsson, Per Tomas
    STFI-PACKFORSK AB.
    Mazeau, Karim
    CERMAV-CNRS.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dynamics of Cellulose-Water Interfaces: NMR Spin-Lattice Relaxation Times Calculated from Atomistic Computer Simulations2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 9, p. 2590-2595Article in journal (Refereed)
    Abstract [en]

    Solid-state nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy has often been used to study cellulose structure, but some features of the cellulose NMR spectrum are not yet fully understood. One such feature is a doublet around 84 ppm, a signal that has been proposed to originate from C4 atoms at cellulose fibril surfaces. The two peaks yield different T1, differing by approximately a factor of 2 at 75 MHz. In this study, we calculate T1 from C4-H4 vector dynamics obtained from molecular dynamics computer simulations of cellulose Iβ-water interfacial systems. Calculated and experimentally obtained T1 values for C4 atoms in surface chains fell within the same order of magnitude, 3-20 s. This means that the applied force field reproduces relevant surface dynamics for the cellulose-water interface sufficiently well. Furthermore, a difference in T1 of about a factor of 2 in the range of Larmor frequencies 25-150 MHz was found for C4 atoms in chains located on top of two different crystallographic planes, namely, (110) and (10). A previously proposed explanation that the C4 peak doublet could derive from surfaces parallel to different crystallographic planes is herewith strengthened by computationally obtained evidence. Another suggested basis for this difference is that the doublet originates from C4 atoms located in surface anhydro-glucose units with hydroxymethyl groups pointing either inward or outward. This was also tested within this study but was found to yield no difference in calculated T1.

  • 3.
    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.

  • 4.
    Butchosa, Nuria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Brown, Christian
    KTH, School of Biotechnology (BIO), Glycoscience.
    Larsson, Per Tomas
    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.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Nanocomposites of bacterial cellulose nanofibers and chitin nanocrystals: fabrication, characterization and bactericidal activity2013In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 15, no 12, p. 3404-3413Article in journal (Refereed)
    Abstract [en]

    An environmentally friendly approach was implemented for the production of nanocomposites with bactericidal activity, using bacterial cellulose (BC) nanofibers and chitin nanocrystals (ChNCs). The antibacterial activity of ChNCs prepared by acid hydrolysis, TEMPO-mediated oxidation or partial deacetylation of a-chitin powder was assessed and the structure of the ChNC nanoparticles was characterized by X-ray diffraction, atomic force microscopy, and solid-state C-13-NMR. The partially deacetylated ChNCs (D-ChNC) showed the strongest antibacterial activity, with 99 +/- 1% inhibition of bacterial growth compared to control samples. Nanocomposites were prepared from BC nanofibers and D-ChNC by (i) in situ biosynthesis with the addition of D-ChNC nanoparticles in the culture medium of Acetobacter aceti, and (ii) post-modification by mixing D-ChNC with disintegrated BC in an aqueous suspension. The structure and mechanical properties of the BC/D-ChNC nanocomposites were characterized by Fourier transform infrared spectroscopy, elemental analysis, field-emission scanning electron microscopy, and an Instron universal testing machine. The bactericidal activity of the nanocomposites increased with the D-ChNC content, with a reduction in bacterial growth by 3.0 log units when the D-ChNC content was 50%. D-ChNC nanoparticles have great potential as substitutes for unfriendly antimicrobial compounds such as heavy metal nanoparticles and synthetic polymers to introduce antibacterial properties to cellulosic materials.

  • 5.
    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.

  • 6.
    Carlsson, Linn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating 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), Centres, Wallenberg Wood Science Center.
    Ingverud, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Blomberg, Hanna
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Solid State CP/MAS 13C-NMR investigation of hydrolyzed cotton linters grafted by surface‐initiated ring‐opening polymerization of ε‐caprolactoneManuscript (preprint) (Other academic)
  • 7.
    Carrick, Christopher
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Stefan B.
    Larsson, Per Tomas
    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.
    Lightweight, Highly Compressible, Noncrystalline Cellulose Capsules2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 26, p. 7635-7644Article in journal (Refereed)
    Abstract [en]

    We demonstrate how to prepare extraordinarily deformable, gas-filled, spherical capsules from nonmodified cellulose. These capsules have a low nominal density, ranging from 7.6 to 14.2 kg/m(3), and can be deformed elastically to 70% deformation at 50% relative humidity. No compressive strain-at-break could be detected for these dry cellulose capsules, since they did not rupture even when compressed into a disk with pockets of highly compressed air. A quantitative constitutive model for the large deformation compression of these capsules is derived, including their high-frequency mechanical response and their low-frequency force relaxation, where the latter is governed by the gas barrier properties of the dry capsule. Mechanical testing corroborated these models with good accuracy. Force relaxation measurements at a constant compression rendered an estimate for the gas permeability of air through the capsule wall, calculated to 0.4 mL mu m/m(2) days kPa at 50% relative humidity. These properties taken together open up a large application area for the capsules, and they could most likely be used for applications in compressible, lightweight materials and also constitute excellent model materials for adsorption and adhesion studies.

  • 8.
    Carrick, Christopher
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ruda, Marcus
    Pettersson, Bert
    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, 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.
    Hollow cellulose capsules from CO2 saturated cellulose solutions - Their preparation and characterization2013In: RSC Advances, ISSN 2046-2069, Vol. 3, no 7, p. 2462-2469Article in journal (Refereed)
    Abstract [en]

    A new material consisting of mm-sized hollow cellulose spheres, for biomedical applications or for the preparation of low weight porous materials has been prepared by a unique solution precipitation (SP) method. The technique is based on three separate steps. In the first step, high molecular mass, non-modified cellulose is dissolved in a suitable solvent. This cellulose solution is then saturated with a suitable gas (CO2 or N2 in the present work) and finally this gas-saturated solution is drop-wise added to a water reservoir. In this step, the cellulose is precipitated and a gas bubble is nucleated in the center of the cellulose sphere. When stored in water, the hollow center is filled with water, indicating that the capsule wall is porous in nature. This was also supported by BET-area measurements as well as by high resolution SEM-images of broken capsule walls. The internal void volume of a capsule was about 5 μl and the wall volume was about 8 μl. It was also established that the properties of the cellulose capsules, i.e. wall and void volume, the specific surface area, the average pore size of the capsule wall, the wall density, and the compressive load capacity could be tuned by the choice of cellulose concentration in the solution before precipitation. The capsule wall volume and void volume were also affected by the choice of gas, the gas pressure and the gas dissolution time during the gas saturation step. The response of the cellulose wall of the prepared capsules to changes in pH and ion concentration in the surrounding solution was also investigated. The swelling-shrinking behavior was further investigated by introducing more charges to the capsule wall, via carboxymethylation of the cellulose. This was achieved by using carboxymethylated cellulose which increased the swelling-shrinking effect. The results show a typical polyelectrolyte gel behavior of the capsule wall and the wet modulus of the cellulose wall was determined to be between 0.09-0.2 MPa depending on the charge of the cellulose in the capsule wall. Furthermore, the freeze dried cellulose spheres had a modulus of 1.9-7.4 MPa, depending on the cellulose concentration during the preparation of the spheres. These cellulose capsules are suitable both for the preparation of porous materials, where these larger spheres are joined together in 3D-shaped materials, and for controlled release where the interior of the capsules is filled with active substances and these substances are released by controlling the pores in the capsule walls.

  • 9.
    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.

  • 10.
    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.

  • 11.
    Ek, Monica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    Production of dissolving grade pulps from non-wood paper grade pulps using enzymatic and chemical pre-treatments for the viscose process2010Conference paper (Refereed)
    Abstract [en]

    Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, e.g.  Paper and board but also cellulose-based products which have many important applications in the pharmaceutical, textile, food and paint industries.  A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for the prodn. of these products, e.g.  Cotton and dissolving grade pulp are used.  However, the high cost prodn. of dissolving grade pulps has aroused the possibility of upgrading paper grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps.  This study reports the feasibility to produce dissolving grade pulps from different pulps, i.e.  Non-wood paper grade pulps and conventional hardwood kraft pulps, employing enzymic and chem. pretreatments.  A monocomponent endoglucanase and a xylanase followed by alk. extn. were tested in order to increase the accessibility and reactivity of the cellulose pulp and decrease the hemicellulose content, resp.  An optimization of these treatments in terms of enzyme dosage, incubation time and a possible combination of them was investigated.  The treatment effects on reactivity according to Fock's method, viscosity, hemicellulose content and mol. wt. distribution, using size exclusion chromatog. (SEC), were analyzed.  The characterization of cellulose structure after the enzymic and chem. treatments was investigated by different techniques.

  • 12.
    Ek, Monica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Characterization of dissolving pulps produced from Kraft pulps2009Conference paper (Refereed)
  • 13. Falt, S.
    et al.
    Wågberg, Lars
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Vesterlind, E. L.
    Larsson, Per Tomas
    Model films of cellulose II - improved preparation method and characterization of the cellulose film2004In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 2, p. 151-162Article in journal (Refereed)
    Abstract [en]

    An optimization study of the preparation of spin-coated cellulose model films from the NMMO/DMSO system on silicon wafers has been made. The study shows that the cellulose concentration in the solution determines the cellulose film thickness and that the temperature of the solution affects the surface roughness. A lower solution temperature results in a lower surface roughness at cellulose concentrations below 0.8%. Using the described method, it is possible to prepare films with thicknesses of 30-90 nm with a constant surface roughness by changing the cellulose concentration, i.e. by dilution with DMSO. On these films, water has a contact angle less than 20degrees and about 50% of the material can, according to CP/MAS C-13-NMR spectroscopy on corresponding fibrous material, be considered to consist of crystalline cellulose II type material. It has further been shown that AFM can be used to determine the thickness of cellulose films, in both dry and wet states. In this method, the difference in height between the top surface and the underlying wafer has been measured at an incision made into the cellulose film. The cellulose films have also been spin-coated with the same technique as on the silicon oxide wafer onto the crystal in a quartz crystal microbalance (QCM). These model films were found to be suitable for swelling measurements with the QCM. The films were very stable during this type of measurement and films with different amounts of charges gave different swelling responses depending on their charges. As expected, films with a higher charge showed a higher swelling.

  • 14.
    Halonen, Helena
    et al.
    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, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mercerized cellulose biocomposites: A study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 1, p. 57-65Article in journal (Refereed)
    Abstract [en]

    In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.

  • 15.
    Horvath, Andrew T.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pelton, Robert
    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.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Effect of Cross-Linking Fiber Joints on the Tensile and Fracture Behavior of Paper2010In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, Vol. 49, no 14, p. 6422-6431Article in journal (Refereed)
    Abstract [en]

    The tensile and fracture properties of cross-linked paper were investigated at low and high relative humidity by cross-linking the joints formed between fibers. Cationic acetal dextran served as a model cross-linking agent, as it can be prepared to adsorb specifically to the fiber surface. Thus, cross-linking occurs only in the joints between fibers. The kinetics of hydrolysis was investigated to optimize the stock preparation, such that the resulting aldehyde groups react as the paper is dried. The effect of the cross-link density on the tensile and fracture properties was studied by varying the amount of acetal groups adsorbed to the pulp fibers. At low humidity, cross-linking improved the tensile and fracture properties of paper, although lower cross-link densities yielded better properties. Cross-linking was not effective at high relative humidty, as the tensile strength and stiffness were not improved. However, the fracture properties were significantly improved.

  • 16.
    Ibarra, David
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 19, p. 7416-7423Article in journal (Refereed)
    Abstract [en]

    A sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction and a final endoglucanase treatment was investigated as a process for upgrading non-wood paper-grade pulps to dissolving-grade pulps for viscose production. Five commercial dried bleached non-wood soda/ AQ paper pulps, from flax, hemp, sisal, abaca, and jute, were studied for this purpose. Commercial dried bleached eucalyptus dissolving pulp was used as reference sample. Sisal pulp showed the highest improvement in Fock's reactivity, reaching levels nearly as high or even higher than that of eucalyptus dissolving pulp (65%), and a low hemicellulose content (3-4%) when was subjected to this sequence of treatments. The viscosity, however, decreased considerably. A uniform and narrow molecular weight distribution was observed by size exclusion chromatography. C-13 nuclear magnetic resonance spectroscopy and Raman microspectroscopy revealed that the cellulose structure consisted of cellulose I.

  • 17.
    Kaldéus, Tahani
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioecon, Drottning Kristinas Väg 61, S-11486 Stockholm, Sweden..
    Boujemaoui, Assya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Malmström, Eva
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    One-pot preparation of bi-functional cellulose nanofibrils2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 12, p. 7031-7042Article in journal (Refereed)
    Abstract [en]

    Herein, we present a route to obtain bi-functional cellulose nanofibrils (CNF) by a one-pot approach using an already established functionalisation route, carboxymethylation, to which a subsequent functionalisation step, allylation or alkynation, has been added in the same reaction pot, eliminating the need of solvent exchange procedures. The total charge of the fibres and the total surface charge of the nanofibrils were determined by conductometric and polyelectrolyte titration, respectively. Furthermore, the allyl and alkyne functionalised cellulose were reacted with methyl 3-mercaptopropionate and azide-functionalised disperse red, respectively, to estimate the degree of functionalisation. The samples were further assessed by XPS and FT-IR. Physical characteristics were evaluated by CP/MAS C-13-NMR, XRD, AFM and DLS. This new approach of obtaining bi-functionalised CNF allows for a facile and rapid functionalisation of CNF where chemical handles can easily be attached and used for further modification of the fibrils.

  • 18.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Fall, Andreas
    RISE Bioeconomy.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. RISE Bioeconomy.
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    De-watering of Cellulose-based Gel Networks Targeting Different Factors Contributing to the Swelling PressureManuscript (preprint) (Other academic)
  • 19.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. RISE Bioeconomy.
    Hansson, Per
    Uppsala University, Dep. of Pharmacy, Uppsala Biomedical Center.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks2019In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, no 4, p. 1603-1612Article in journal (Refereed)
    Abstract [en]

    Noncrystalline cellulose-based gel beads were used as a model material to investigate the effect of osmotic stress on a cellulosic network. The gel beads were exposed to osmotic stress by immersion in solutions with different concentrations of high molecular mass dextran and the equilibrium dimensional change of the gel beads was studied using optical microscopy. The volume fraction of cellulose was calculated from the volume of the gel beads in dextran solutions and their dry content and the relation between the cellulose volume fraction and the total osmotic pressure was thus obtained. The results show that the contribution to the osmotic pressure from counterions increases the water-retaining capacity of the beads at high osmotic pressures but also that the main factor controlling the gel bead collapse at high osmotic strains is the resistance to the deformation of the polymer chain network within the beads. Furthermore, the osmotic pressure associated with the deformation of the polymer network, which counteracts the deswelling of the beads, could be fitted to the Wall model indicating that the response of the cellulose polymer networks was independent of the charge of the cellulose. The best fit to the Wall model was obtained when the Flory-Huggins interaction parameter () of the cellulose-water system was set to 0.55-0.60, in agreement with the well-established insolubility of high molecular mass β-(1,4)-d-glucan polymers in water.

  • 20.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. RISE Bioeconomy.
    Pettersson, Torbjörn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Elasticity and Ion-Induced Swelling of Cellulose Fibrillar Networks and GelsManuscript (preprint) (Other academic)
  • 21.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden.
    Yu, Shun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Pendergraph, Samuel Allen
    RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden..
    Pettersson, Torbjörn
    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.
    Hellwig, Johannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    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.
    Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed)
    Abstract [en]

    Macroscopic beads of water-based gels consisting of uncharged and partially charged beta-(1,4)-D-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling.

  • 22. Kopcke, Viviana
    et al.
    Ibarra, David
    Larsson, Per Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Optimization of enzymatic and chemical treatments to use Eucalyptus kraft pulp as dissolving pulp2010In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 1, no 17, p. 34-Article in journal (Refereed)
  • 23. Köpcke, Viviana
    et al.
    Ibarra, David
    Larsson, Per Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Feasibility study on converting paper-grade pulps to dissolving-grade pulps2010Conference paper (Refereed)
  • 24.
    Köpcke, Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Optimization of treatment sequences for the production of dissolving pulp from birch kraft pulp2010In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 1, p. 31-38Article in journal (Refereed)
    Abstract [en]

    As a continuation of our work, the viability of converting paper-grade kraft pulps into dissolving-grade pulps, for several raw materials, has been presented. It has been demonstrated that a combination of an enzymatic treatment using a commercial xylanase followed by alkali extraction resulted in an efficient hemicellulose removal. Furthermore, the cellulose reactivity could be enhanced by an additional enzymatic treatment using a commercial monocomponent endoglucanase. As a result, pulps with the characteristics of those of a commercial dissolving pulp, in terms of hemicellulose content and cellulose reactivity, were obtained. The viscosity of the treated pulps, however, was significantly affected by the treatments; they present lower values than those suitable for the production of cellulose derivatives and regenerated cellulose. The pulps, on the other hand, contained mostly cellulose II, which may also affect the process. Therefore, as a continuation of this work, an optimization of the sequences of treatments as well as a study of the parameters involved was performed in order to overcome the low viscosity values and the presence of cellulose II. After the optimization, it was observed that the xylanase treatment could be replaced by an alkali extraction step, the reaction time for the alkali treatment could be shortened, the viscosity could be increased and pulps containing cellulose I could be obtained. ;  In addition, the hemicellulose content and cellulose reactivity values remained in the range of those of a commercial dissolving-grade pulp.

  • 25.
    Köpcke, Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp2010In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 1, no 1Article in journal (Refereed)
  • 26.
    Larsson, Per Tomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Karlsson, Rose-Marie Pernilla
    Westlund, Per-Olof
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Internal Structure of Isolated Cellulose I Fibril Aggregates in the Water Swollen State2017In: Nanocelluloses: Their Preparation, Properties, and Applications / [ed] Agarwal, UP Atalla, RH Isogai, A, American Chemical Society (ACS), 2017, Vol. 1251, p. 91-112Conference paper (Refereed)
    Abstract [en]

    By combining H-2-NMRD and CP/MAS C-13-NMR measurements of water-based cellulose gels and of water swollen pulps it was possible to estimate the nature of the interior structure of cellulose fibril aggregates. A set of samples with high cellulose purity and low charge was used. The interpretation of data was based on a relaxation model describing the exchange dynamics for deuterium exchange between water molecules and cellulose hydroxyl groups. The theoretical model used made it possible to calculate cellulose surface-to-volume ratios (q-values) from both H-2-NMRD and CP/MAS C-13-NMR data. Good consistency between H-2-NMRD and CP/MAS C-13-NMR data was found. In all investigated samples the cellulose fibril aggregates showed a different degree of "openness" interpreted as the presence of interstitial water inside fibril aggregates. One result also showed that an increased degree of fibril aggregate openness results from the TEMPO-oxidation. Common to all samples was that in the water swollen state water molecules could access part of the fibril aggregate interior.

  • 27.
    Larsson, Per Tomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Innventia AB.
    Karlsson, Rose-Marie Pernilla
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Westlund, Per-Olof
    Umeå university, Dep. of Chemistry, Umeå.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Internal Structure of Isolated Cellulose I Fibril Aggregates in the Water Swollen State2017In: Nanocelluloses: Their Preparation, Properties and Applications, Washington, DC: American Chemical Society (ACS), 2017Chapter in book (Refereed)
    Abstract [en]

    By combining H-2-NMRD and CP/MAS C-13-NMR measurements of water-based cellulose gels and of water swollen pulps it was possible to estimate the nature of the interior structure of cellulose fibril aggregates. A set of samples with high cellulose purity and low charge was used. The interpretation of data was based on a relaxation model describing the exchange dynamics for deuterium exchange between water molecules and cellulose hydroxyl groups. The theoretical model used made it possible to calculate cellulose surface-to-volume ratios (q-values) from both H-2-NMRD and CP/MAS C-13-NMR data. Good consistency between H-2-NMRD and CP/MAS C-13-NMR data was found. In all investigated samples the cellulose fibril aggregates showed a different degree of "openness" interpreted as the presence of interstitial water inside fibril aggregates. One result also showed that an increased degree of fibril aggregate openness results from the TEMPO-oxidation. Common to all samples was that in the water swollen state water molecules could access part of the fibril aggregate interior.

  • 28.
    Larsson, Per Tomas
    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.
    Svensson, Anna
    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.
    A new, robust method for measuring average fibre wall pore sizes in cellulose I rich plant fibre walls2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 2, p. 623-631Article in journal (Refereed)
    Abstract [en]

    A new, robust method for measuring the average pore size of water-swollen, cellulose I rich fibres is presented. This method is based on the results of solid-state NMR, which measures the specific surface area (area/solids mass) of water-swollen samples, and of the fibre saturation point (FSP) method, which measures the pore volume (water mass/solids mass) of water-swollen samples. These results are suitable to combine since they are both recorded on water-swollen fibres in excess water, and neither requires the assumption of any particular pore geometry. The new method was used for three model samples and reasonable average pore size measurements were obtained for all of them. The structural characterization of water-swollen samples was compared with the dry structure of fibres as revealed using BET nitrogen gas adsorption after a liquid exchange procedure and careful drying. It was concluded that the structure of the water-swollen fibres sets an upper limit on what is obtainable in the dry state.

  • 29.
    Larsson, Per Tomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Stockholm, Sweden.;KTH, WWSC, Stockholm, Sweden..
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH Fibre Polymer Tech, Stockholm, Sweden..
    Westlund, Per-Olof
    Umea Univ, Chem, Umea, Sweden..
    Karlsson, Pernilla
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, WWSC, Stockholm, Sweden..
    Internal structure of cellulose I fibril aggregates studied by a combination of structure and dynamics measurements2016In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Article in journal (Other academic)
  • 30.
    Lingström, Rikard
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per Tomas
    STFI-Packforsk AB.
    Formation of polyelectrolyte multilayers on fibres: Influence on wettability and fibre/fibre interaction2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 296, no 2, p. 396-408Article in journal (Refereed)
    Abstract [en]

    Polydimethyldiallylammonium chloride (PDADMAC) and polystyrene sulfonate (PSS) have been used to build-up polyelectrolyte multilayers (PEMs) on chemical soft wood fibres and on SiO2 at various electrolyte concentrations. Adsorption Onto SiO2 was studied using a stagnation point adsorption reflectometer (SPAR), and the adsorbed amount of PDADMAC and PSS on the fibres was determined using nitrogen analysis and Schoniger burning, respectively. The adsorption onto the two substrates was then compared. Paper testing showed that the tensile index (TI) increased by about 90% when 11 layers had been adsorbed, and that there was a correlation between the adsorbed amount and the increase in TI. It was also shown that the particular polymer present in the outermost layer significantly influenced the TI, and that PDADMAC produced a higher TI. A correlation between the adsorbed amount and the TI was also found. Individual fibres were partly treated with a PEM and analysed using a dynamic contact angle analyser (DCA) and environmental scanning electron microscopy (ESEM).

  • 31.
    Lo Re, Giada
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Spinella, Stephen
    NYU Tandon School of Engineering, Six Metrotech Center, Brooklyn, New York 11201, United States.
    Boujemaoui, Assya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Vilaseca, Fabiola
    BIMATEC Group, Department of Chemical Engineering, Agricultural and Food Technology, University of Girona, C/Maria Aurèlia Capmany 61, 17003 Girona, Spain.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioeconomy, Teknikringen 56, Stockholm, SE-100 44, Sweden.
    Adås, Fredrik
    RISE Bioeconomy, Teknikringen 56, Stockholm, SE-100 44, Sweden.
    Berglund, Lars
    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, Biocomposites.
    Poly(ε-caprolactone) Biocomposites Based on Acetylated Cellulose Fibers and Wet Compounding for Improved Mechanical Performance2018In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 6, p. 6753-6760Article in journal (Refereed)
    Abstract [en]

    Poly(epsilon-caprolactone) (PCL) is a ductile thermoplastic, which is biodegradable in the marine environment. Limitations include low strength, petroleum-based origin, and comparably high cost. Cellulose fiber reinforcement is therefore of interest although uniform fiber dispersion is a challenge. In this study, a one-step wet compounding is proposed to validate a sustainable and feasible method to improve the dispersion of the cellulose fibers in hydrophobic polymer matrix as PCL, which showed to be insensitive to the presence of the water during the processing. A comparison between unmodified and acetylated cellulosic wood fibers is made to further assess the net effect of the wet feeding and chemical modification on the biocomposites properties, and the influence of acetylation on fiber structure is reported (ATR-FTIR, XRD). Effects of processing on nano fibrillation, shortening, and dispersion of the cellulose fibers are assessed as well as on PCL molar mass. Mechanical testing, dynamic mechanical thermal analysis, FE-SEM, and X-ray tomography is used to characterize composites. With the addition of 20 wt % cellulosic fibers, the Young's modulus increased from 240 MPa (neat PCL) to 1850 MPa for the biocomposites produced by using the wet feeding strategy, compared to 690 MPa showed for the biocomposites produced using dry feeling. A wet feeding of acetylated cellulosic fibers allowed even a greater increase, with an additional 46% and 248% increase of the ultimate strength and Young's modulus, when compared to wet feeding of the unmodified pulp, respectively.

  • 32.
    Malm, Erik
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Wickholm, Kristina
    Larsson, Per Tomas
    Iversen, Tommy
    The surface structure of well-ordered native cellulose fibrils in contact with water2010In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 345, no 1, p. 97-100Article in journal (Refereed)
    Abstract [en]

    CP/MAS C-13 NMR spectroscopy was used in combination with spectral fitting to examine the surface structure of hydrated cellulose I fibrils from Halocynthia and Gluconoacetobacter xylinus. To increase the spectral intensities and minimize signal overlap, G. xylinus celluloses site-specifically enriched in C-13 either on C4 or on both C1 and C6 were examined. The experimental data showed multiple C4 and C6 signals for the water accessible fibril surfaces in the highly crystalline celluloses. These signal multiplicities were attributed to structural features in the surface layers induced by the fibril interior, and could not be extracted by spectral fitting in celluloses with a lower degree of crystallinity such as cellulose from cotton.

  • 33.
    Mattozzi, Alessandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per Tomas
    Hedenqvist, Mikael. S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    n-Hexane sorption in poly(ethylene-co-octene)s: effect on phase composition and character2010In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 46, no 3, p. 381-388Article in journal (Refereed)
    Abstract [en]

    Diffusion of small-molecule penetrants in semi-crystalline polymers is retarded by two factors: penetrant detour bypassing impenetrable crystals and the constraining effect of the crystals on the amorphous component. Previous experiments have shown that the latter factor becomes much less important at higher penetrant concentration in the polymer. Structural changes in a series of poly(ethylene-co-1-octene)s occurring on saturation in n-hexane at 296 K, covering a wide range of crystallinity (17–75 wt.%), were studied by wide-angle X-ray scattering, Raman spectroscopy and NMR spectroscopy. Densification of the crystal unit cell and partial dissolution of the interfacial component on n-hexane sorption are the main experimental findings. The conclusion is that the penetrant molecules increase the mobility of the polymer chain segments adjacent to the crystal interface, enabling better packing of the crystal stems and importantly also causes a reduction in the constraining factor (β) for diffusion.

  • 34.
    Mittal, Nitesh
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Ansari, Farhan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Materials Science and Engineering, Stanford University, Stanford, CA, United States.
    Gowda, Krishne, V
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Brouzet, Christophe
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Chen, Pan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioeconomy, P.O. Box 5604, Stockholm, SwedenRISE Bioeconomy, P.O. Box 5604, Stockholm, Sweden.
    Roth, Stephan Volkher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    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.
    Kotov, Nicholas Alexander
    Söderberg, Daniel
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 7, p. 6378-6388Article in journal (Refereed)
    Abstract [en]

    Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.

  • 35.
    Nilsson, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Galland, Sylvain
    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.
    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.
    Gamstedt, E. Kristofer
    Uppsala University.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Compression molded wood pulp biocomposites: A study of hemicellulose influence on cellulose supramolecular structure and material properties2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 3, p. 751-760Article in journal (Refereed)
    Abstract [en]

    In this study, the importance of hemicellulose content and structure in chemical pulps on the property relationships in compression molded wood pulp biocomposites is examined. Three different softwood pulps are compared; an acid sulfite dissolving grade pulp with high cellulose purity, an acid sulfite paper grade pulp and a paper grade kraft pulp, the latter two both containing higher amounts of hemicelluloses. Biocomposites based the acid sulfite pulps exhibit twice as high Young's modulus as the composite based on paper grade kraft pulp, 11-12 and 6 GPa, respectively, and the explanation is most likely the difference in beating response of the pulps. Also the water retention value (WRV) is similarly low for the two molded sulfite pulps (0.5 g/g) as compared to the molded kraft pulp (0.9 g/g). The carbohydrate composition is determined by neutral sugar analysis and average molar masses by SEC. The cellulose supramolecular structure (cellulose fibril aggregation) is studied by solid state CP/MAS 13C-NMR and two forms of hemicellulose are assigned. During compression molding, cellulose fibril aggregation occurs to higher extent in the acid sulfite pulps as compared to the kraft pulp. In conclusion, the most important observation from this study is that the difference in hemicellulose content and structure seems to affect the aggregation behaviour and WRV of the investigated biocomposites.

  • 36.
    Nilsson, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Galland, Sylvain
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Nishino, Takashi
    Dept. of Chem. Sci. and Engng., Kobe Univ. Rokko, Nada, Kobe, Japan.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A non-solvent approach for high-stiffness all-cellulose biocomposites based on pure wood cellulose2010In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, no 12, p. 1704-1712Article in journal (Refereed)
    Abstract [en]

    All-cellulose composites are commonly prepared using cellulose solvents. In this study, moldable all-cellulose I wood fiber materials of high cellulose purity (97%) were successfully compression molded. Water is the only processing aid. The material is interesting as a "green" biocomposite for industrial applications. Dissolving wood fiber pulps (Eucalyptus hardwood and conifer softwood) are used and the influence of pulp origin, beating and pressing temperature (20-180 degrees C) on supramolecular cellulose nanostructure is studied by solid state CP/MAS C-13 NMR. Average molar mass is determined by SEC to assess process degradation effects. Mechanical properties are determined in tensile tests. High-density composites were obtained with a Young's modulus of up to 13 GPa. In addition, nanoscale cellulose fibril aggregation was confirmed due to processing, and resulted in a less moisture sensitive material.

  • 37. Nocanda, Xolani
    et al.
    Larsson, Per Tomas
    Spark, Andrew
    Lush, Tamara
    Olsson, Ann
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Madikane, Mzekelo
    Bissessur, Ajay
    Iversen, Tommy
    Cross polarisation/magic angle spinning C-13-NMR spectroscopic studies of cellulose structural changes in hardwood dissolving pulp process2007In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, no 6, p. 675-679Article in journal (Refereed)
    Abstract [en]

    Cross polarisation/magic angle spinning C-13 NMR spectroscopy has been used to study structural changes in cellulose induced by the dissolving pulp process. The cellulose structure in several dissolving pulps was investigated for commercial and laboratory cooked Eucalyptus 92 alpha and 96 alpha. The average lateral dimension, or average thickness, of the cellulose fibril aggregates is related to the amount of surface area exposed and could be one controlling factor for the chemical reactivity of commercial dissolving pulps during modification reactions. The thickness of the cellulose fibril aggregates governs the amount of surface area present in the fibre wall, and cellulose surface material constitutes the part of the cellulose that is directly accessible to reagents. In all sample series investigated, the raw pulp was found to be less aggregated than the corresponding bleached final pulp. Furthermore, an irreversible increase in fibril aggregate width was observed on free drying for both laboratory cooked and commercial pulps. Upon rewetting with water, the freely dried 96 alpha pulp was found to be more aggregated than the freely dried 92 alpha pulp, although sugar analysis showed very similar carbohydrate compositions. As indicated by the molecular mass distribution, the commercial 92 alpha pulp contained larger amounts of degraded cellulose; this may be a plausible explanation for the different behaviour of the 92 alpha and 96 alpha pulps during free drying.

  • 38.
    Ottesen, Vegar
    et al.
    NTNU, Dept Chem Engn, Trondheim, Norway..
    Larsson, Per Tomas
    KTH.
    Chinga-Carrasco, Gary
    Rise PFI, Trondheim, Norway..
    Syverud, Kristin
    NTNU, Dept Chem Engn, Trondheim, Norway.;Rise PFI, Trondheim, Norway..
    Gregersen, Oyvind Weiby
    NTNU, Fac Nat Sci, Trondheim, Norway..
    Mechanical properties of cellulose nanofibril films: effects of crystallinity and its modification by treatment with liquid anhydrous ammonia2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 11, p. 6615-6627Article in journal (Refereed)
    Abstract [en]

    The influence of cellulose crystallinity on mechanical properties of cellulose nano-fibrils (CNF) was investigated. Degree of crystallinity (DoC) was modified using liquid anhydrous ammonia. Such treatment changes crystal allomorph from cellulose I to cellulose III, a change which was reversed by subsequent boiling in water. DoC was measured using solid state nuclear magnetic resonance (NMR). Crystalline index (CI) was also measured using wide angle X-ray scattering (WAXS). Cotton linters were used as the raw material. The cotton linter was ammonia treated prior to fibrillation. Reduced DoC is seen to associate with an increased yield point and decreased Young modulus. Young modulus is here defined as the maximal slope of the stress-strain curves. The association between DoC and Young modulus or DoC and yield point are both statistically significant. We cannot conclude there has been an effect on strainability. While mechanical properties were affected, we found no indication that ammonia treatment affected degree of fibrillation. CNF was also studied in air and liquid using atomic force microscopy (AFM). Swelling of the nanofibers was observed, with a mean diameter increase of 48.9%.

  • 39. Peciulyte, Ausra
    et al.
    Anasontzis, George E.
    Karlström, Katarina
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Olsson, Lisbeth
    Morphology and enzyme production of Trichoderma reesei Rut C-30 are affected by the physical and structural characteristics of cellulosic substrates2014In: Fungal Genetics and Biology, ISSN 1087-1845, E-ISSN 1096-0937, Vol. 72, p. 64-72Article in journal (Refereed)
    Abstract [en]

    The industrial production of cellulolytic enzymes is dominated by the filamentous fungus Trichoderma reesei (anamorph of Hypocrea jecorina). In order to develop optimal enzymatic cocktail, it is of importance to understand the natural regulation of the enzyme profile as response to the growth substrate. The influence of the complexity of cellulose on enzyme production by the microorganisms is not understood. In the present study we attempted to understand how different physical and structural properties of cellulose-rich substrates affected the levels and profiles of extracellular enzymes produced by T. reesei. Enzyme production by T. reesei Rut C-30 was studied in submerged cultures on five different cellulose-rich substrates, namely, commercial cellulose Avicel (R) and industrial-like cellulosic pulp substrates which consist mainly of cellulose, but also contain residual hemicellulose and lignin. In order to evaluate the hydrolysis of the substrates by the fungal enzymes, the spatial polymer distributions were characterised by cross-polarisation magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS C-13-NMR) in combination with spectral fitting. Proteins in culture supernatants at early and late stages of enzyme production were labeled by Tandem Mass Tags (TMT) and protein profiles were analysed by liquid chromatography-tandem mass spectrometry. The data have been deposited to the ProteomeXchange with identifier PXD001304. In total 124 proteins were identified and quantified in the culture supernatants, including cellulases, hemicellulases, other glycoside hydrolases, lignin-degrading enzymes, auxiliary activity 9 (AA9) family (formerly GH61), supporting activities of proteins and enzymes acting on cellulose, proteases, intracellular proteins and several hypothetical proteins. Surprisingly, substantial differences in the enzyme profiles were found even though there were minor differences in the chemical composition between the cellulose-rich substrates.

  • 40. Peciulyte, Ausra
    et al.
    Karlström, Katarina
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Olsson, Lisbeth
    Impact of the supramolecular structure of cellulose on the efficiency of enzymatic hydrolysis2015In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 8, article id 56Article in journal (Refereed)
    Abstract [en]

    Background: The efficiency of enzymatic hydrolysis is reduced by the structural properties of cellulose. Although efforts have been made to explain the mechanism of enzymatic hydrolysis of cellulose by considering the interaction of cellulolytic enzymes with cellulose or the changes in the structure of cellulose during enzymatic hydrolysis, the process of cellulose hydrolysis is not yet fully understood. We have analysed the characteristics of the complex supramolecular structure of cellulose on the nanometre scale in terms of the spatial distribution of fibrils and fibril aggregates, the accessible surface area and the crystallinity during enzymatic hydrolysis. Influence of the porosity of the substrates and the hydrolysability was also investigated. All cellulosic substrates used in this study contained more than 96% cellulose. Results: Conversion yields of six cellulosic substrates were as follows, in descending order: nano-crystalline cellulose produced from never-dried soda pulp (NCC-OPHS-ND) > never-dried soda pulp (OPHS-ND) > dried soda pulp (OPHS-D) > Avicel > cotton treated with sodium hydroxide (cotton + NaOH) > cotton. Conclusions: No significant correlations were observed between the yield of conversion and supramolecular characteristics, such as specific surface area (SSA) and lateral fibril dimensions (LFD). A strong correlation was found between the average pore size of the starting material and the enzymatic conversion yield. The degree of crystallinity was maintained during enzymatic hydrolysis of the cellulosic substrates, contradicting previous explanations of the increasing crystallinity of cellulose during enzymatic hydrolysis. Both acid and enzymatic hydrolysis can increase the LFD, but no plausible mechanisms could be identified. The sample with the highest initial degree of crystallinity, NCC-OPHS-ND, exhibited the highest conversion yield, but this was not accompanied by any change in LFD, indicating that the hydrolysis mechanism is not based on lateral erosion.

  • 41. Pääkkö, M.
    et al.
    Ankerfors, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kosonen, H.
    Nykänen, A.
    Ahola, S.
    Österberg, M.
    Ruokolainen, J.
    Laine, J.
    Larsson, Per Tomas
    Ikkala, O.
    Lindström, Tom
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 6, p. 1934-1941Article in journal (Refereed)
    Abstract [en]

    Toward exploiting the attractive mechanical properties of cellulose I nanoelements, a novel route is demonstrated, which combines enzymatic hydrolysis and mechanical shearing. Previously, an aggressive acid hydrolysis and sonication of cellulose I containing fibers was shown to lead to a network of weakly hydrogen-bonded rodlike cellulose elements typically with a low aspect ratio. On the other hand, high mechanical shearing resulted in longer and entangled nanoscale cellulose elements leading to stronger networks and gels. Nevertheless, a widespread use of the latter concept has been hindered because of lack of feasible methods of preparation, suggesting a combination of mild hydrolysis and shearing to disintegrate cellulose I containing fibers into high aspect ratio cellulose I nanoscale elements. In this work, mild enzymatic hydrolysis has been introduced and combined with mechanical shearing and a high-pressure homogenization, leading to a controlled fibrillation down to nanoscale and a network of long and highly entangled cellulose I elements. The resulting strong aqueous gels exhibit more than 5 orders of magnitude tunable storage modulus G' upon changing the concentration. Cryotransmission electron microscopy, atomic force microscopy, and cross-polarization/magic-angle spinning (CP/MAS) C-13 NMR suggest that the cellulose I structural elements obtained are dominated by two fractions, one with lateral dimension of 5-6 nm and one with lateral dimensions of about 10-20 nm. The thicker diameter regions may act as the junction zones for the networks. The resulting material will herein be referred to as MFC (microfibrillated cellulose). Dynamical rheology showed that the aqueous suspensions behaved as gels in the whole investigated concentration range 0.125-5.9% w/w, G' ranging from 1.5 Pa to 10(5) Pa. The maximum G' was high, about 2 orders of magnitude larger than typically observed for the corresponding nonentangled low aspect ratio cellulose I gels, and G' scales with concentration with the power of approximately three. The described preparation method of MFC allows control over the final properties that opens novel applications in materials science, for example, as reinforcement in composites and as templates for surface modification.

  • 42.
    Sjöstedt, Anna
    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.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Wågberg, Lars
    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.
    Structural changes during swelling of highly charged cellulose fibres2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 45-CELL-Article in journal (Other academic)
  • 43.
    Sjöstedt, Anna
    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.
    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.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    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.
    Structural changes during swelling of highly charged cellulose fibres2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 5, p. 2943-2953Article in journal (Refereed)
    Abstract [en]

    Structural changes of fibrils and fibril aggregates in the fibre wall were studied after oxidation of the cellulose by 2,2,6,6-tetramethyl-1-piperidinyloxy to high charge densities (highest charge density: 1300 mu eq/g). The increase in pore volume was measured by mini-WRV at two different pH levels, and the supramolecular structure in the fibre wall in terms of aggregate size, specific surface area and average pore size was measured by solid state NMR, DVS desorption and BET N-2 gas adsorption. A structural change in the arrangement of the fibrils inside the fibril aggregates was observed although the oxidation did not lead to a complete liberation of individual fibrils, i.e. they still exist as an aggregated structure after oxidation. Theoretical estimates suggest that the electrostatic repulsion energy connected with the increase in surface charge of the fibrils can be sufficient to gradually separate the fibrils enough to expose all fibril surfaces to oxidation chemicals.

  • 44.
    Svensson, Anna
    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.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salazar-Alvarez, German
    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.
    Preparation of dry ultra-porous cellulosic fibres: Characterization and possible initial uses2013In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 92, no 1, p. 775-783Article in journal (Refereed)
    Abstract [en]

    Dry ultra-porous cellulose fibres were obtained using a liquid exchange procedure in which water was replaced in the following order: water, methanol, acetone, and finally pentane: thereafter, the fibres were dried with Ar(g). The dry samples (of TEMPO-oxidized dissolving pulp) had a specific surface area of 130 m(2) g(-1) as measured using BET nitrogen gas adsorption. The open structure in the dry state was also revealed using field emission scanning electron microscopy. This dry open structure was used as a scaffold for in situ polymerization. Both poly(methyl methacrylate) and poly(butylacrylate) were successfully used as matrix polymers for the composite material (fibre/polymer), comprising approximately 20 wt% fibres. Atomic force microscopy phase imaging indicated a nanoscale mixing of the matrix polymer and the cellulose fibril aggregates and this was also supported by mechanical testing of the prepared composite where the open fibre structure produced superior composites. The fibre/polymer composite had a significantly reduced water absorption capacity also indicating an efficient filling of the fibre structure with the matrix polymer.

  • 45.
    Zhou, Qi
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Malm, Erik
    KTH, School of Biotechnology (BIO), Glycoscience.
    Nilsson, Helena
    Larsson, Per Tomas
    Iversen, Tommy
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Biomimetic design of cellulose-based nanostructured composites using bacterial cultures2009In: Polymer Preprints, ISSN 0032-3934, Vol. 50, no 2, p. 7-8Article in journal (Refereed)
  • 46.
    Zhou, Qi
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Biotechnology (BIO), Glycoscience.
    Malm, Erik
    KTH, School of Biotechnology (BIO), Glycoscience.
    Nilsson, Helena
    Larsson, Per Tomas
    Iversen, Tommy
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Nanostructured biocomposites based on bacterial cellulosic nanofibers compartmentalized by a soft hydroxyethylcellulose matrix coating2009In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 5, no 21, p. 4124-4130Article in journal (Refereed)
    Abstract [en]

    Biomimetic approaches involving environmentally-friendly synthetic pathways provide an opportunity to elaborate novel high-performance biocomposites. Here we have developed a low-energy biosynthetic system for the production of a high-strength composite material consisting of self-assembled and nanostructured cellulosic nanofibers. This biocomposite is analogous to natural composite materials with high strength and hierarchical organization such as wood or tendon. It was generated by growing the bacterium Acetobacter, which naturally produces cellulosic nanofibers, in the presence of hydroxyethylcellulose (HEC). Individual cellulose fibrils were coated by HEC and exhibited a smaller lateral dimension than pure bacterial cellulose (BC) fibrils. They self-assembled to form compartmentalized nanofibers and larger cellulose fibril aggregates compared to pure BC. The tensile strength of nanocomposite films prepared from the compartmentalized cellulosic nanofibers was 20% higher than that of pure BC sheets and wood cellulose nanopapers, and 60% higher than that of conventional BC/HEC blends, while no strain-to-failure decrease was observed. The thin nanoscale coating consisting of hydrated HEC significantly increased the mechanical performance of the nanocomposite films by provoking compartmentalization of individual fibrils.

  • 47. Östlund, Åsa
    et al.
    Idström, Alexander
    Olsson, Carina
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Nordstierna, Lars
    Modification of crystallinity and pore size distribution in coagulated cellulose films2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 4, p. 1657-1667Article in journal (Refereed)
    Abstract [en]

    In this study the effects of altering the coagulation medium during regeneration of cellulose dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate, were investigated using solid-state NMR spectroscopy and NMR cryoporometry. In addition, the influence of drying procedure on the structure of regenerated cellulose was studied. Complete conversion of the starting material into regenerated cellulose was seen regardless of the choice of coagulation medium. Coagulation in water predominantly formed cellulose II, whereas coagulation in alcohols mainly generated non-crystalline structures. Subsequent drying of the regenerated cellulose films, induced hornification effects in the form of irreversible aggregation. This was indicated by solid-state NMR as an increase in signal intensity originating from crystalline structures accompanied by a decrease of signal intensity originating from cellulose surfaces. This phenomenon was observed for all used coagulants in this study, but to various degrees with regard to the polarity of the coagulant. From NMR cryoporometry, it was concluded that drying induced hornification generates an increase of nano-sized pores. A bimodal pore size distribution with pore radius maxima of a few nanometers was observed, and this pattern increased as a function of drying. Additionally, cyclic drying and rewetting generated a narrow monomodal pore size pattern. This study implies that the porosity and crystallinity of regenerated cellulose can be manipulated by the choice of drying condition.

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