Ändra sökning
Avgränsa sökresultatet
2345678 201 - 250 av 519
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 201.
    Henriksson, Gunnar
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Berglund, Jennie
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Wohlert, Jakob
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lawoko, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Aminzadeh, Selda
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Vilaplana, Francisco
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Non-cellulose wood polysaccharides - a need for a stricter structural and functional classification?2018Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Artikel i tidskrift (Övrigt vetenskapligt)
  • 202.
    Henschen, Jonatan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Bio-based preparation of nanocellulose and functionalization using polyelectrolytes2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Nanocellulosa, som kan utvinnas från skogsråvara, har de senaste åren fått mycket uppmärksamhet för sina intressanta egenskaper och breda användningsområde. Studierna i denna avhandling syftar till att vidga möjligheterna att använda nanocellulosa i olika applikationer. Detta har skett genom att utveckla en ny metod för att tillverka nanocellulosa och genom att studera möjligheten att adsorbera polyelektrolyter på material av nanocellulosa för att ändra hur bakterier interagerar med dessa.

    Nanocellulosan tillverkades genom att förbehandla pappersmassa med smält oxalsyra dihydrat. Reaktionsblandningen tvättades med etanol, aceton eller tetrahydrofuran innan den torkades och fibrillerades. Den resulterande nanocellulosan erhölls med högt utbyte, hade hög ytladdning (upp till 1,4 mmol g-1) och innehöll partiklar som både liknande nanofibriller och nanokristaller. Materialet visades kunna användas både för att tillverka Pickering emulsioner och tunna filmer med en styrka upp till 197 MPa, töjning upp till 5 %, E-modul upp till 10,6 GPa och syrepermeabilitet ner till 0.31 cm3 µm m‑2 dag‑kPa‑1.

    Genom att adsorbera polyvinylamin och polyakrylsyra på material av nanocellulosa visades det vara möjligt att påverka mängden bakterier som fäster till materialet. Substraten bestod både av kompakta filmer och porösa aerogeler. Genom att variera ytladdningen på materialen, ytans struktur och antalet adsorberade lager av polymererna var det möjligt att tillverka material med både hög och låg bakterieadhesion. Detta gör det möjligt att anpassa material för användning antingen som kontaktaktivt- eller icke-adhesivt antibakteriellt material. Båda dessa kan vara miljövänliga alternativ till dagens antibakteriella material.

    Nanocellulosa är ett material som inom snar framtid sannolikt kommer användas inom en mängd olika applikationer. För att öka mängden applikationer där nanocellulosa tillför ett stort värde är det nödvändigt att utveckla alternativa tillverkningsmetoder till dagens välkända, exempelvis, genom att använda den beskrivna oxaleringen som förbehandling. Förmågan att styra bakterieadhesionen på material av nanocellulosa ger därtill möjlighet att hitta nya användningsområden inom t.ex. hälso- och sjukvårdsbranschen.

  • 203.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Illergård, Josefin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Larsson, Per
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Antibacterial surface modification of nanocellulosic materials2015Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 249Artikel i tidskrift (Övrigt vetenskapligt)
  • 204.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Preparation of cellulose nanomaterials via cellulose oxalates2019Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 213, s. 208-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocellulose prepared from cellulose oxalate has been discussed as an alternative to other methods to prepare cellulose nanofibrils or crystals. The current work describes the use of a bulk reaction between pulp and oxalic acid dihydrate to prepare cellulose oxalate followed by homogenization to produce nanocellulose. The prepared nanocellulose is on average 350 nm long and 3–4 nm wide, with particles of size and shape similar to both cellulose nanofibrils and cellulose nanocrystals. Films prepared from this nanocellulose have a maximum tensile stress of 140–200 MPa, strain at break between 3% and 5%, and oxygen permeability in the range of 0.3–0.5 cm 3 μm m −2 day −1 kPa −1 at 50% relative humidity. The presented results illustrate that cellulose oxalates may be a low-cost method to prepare nanocellulose with properties reminiscent of those of both cellulose nanofibrils and cellulose nanocrystals, which may open up new application areas for cellulose nanomaterials.

  • 205.
    Herrera, A.
    et al.
    Charite Univ Med Berlin, Julius Wolff Inst, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Berlin Brandenburg Ctr, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Sch Regenerat Therapies, Augustenburger Pl 1, D-13353 Berlin, Germany.;Tech Univ Berlin, Str 17,Juni 135, D-10623 Berlin, Germany..
    Hellwig, Johannes
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. Tech Univ Berlin, Str 17,Juni 135, D-10623 Berlin, Germany..
    Leemhuis, H.
    Matricel GmbH, Kaiserstr 100, D-52134 Herzogenrath, Germany..
    von Klitzing, R.
    Tech Univ Berlin, Str 17,Juni 135, D-10623 Berlin, Germany.;Tech Univ Darmstadt, Alarich Weiss Str 10, D-64287 Darmstadt, Germany..
    Heschel, I
    Matricel GmbH, Kaiserstr 100, D-52134 Herzogenrath, Germany..
    Duda, G. N.
    Charite Univ Med Berlin, Julius Wolff Inst, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Berlin Brandenburg Ctr, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Sch Regenerat Therapies, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Univ Med Berlin, Ctr Musculoskeletal Surg, Augustenburger Pl 1, D-13353 Berlin, Germany..
    Petersen, A.
    Charite Univ Med Berlin, Julius Wolff Inst, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Berlin Brandenburg Ctr, Augustenburger Pl 1, D-13353 Berlin, Germany.;Charite Univ Med Berlin, Sch Regenerat Therapies, Augustenburger Pl 1, D-13353 Berlin, Germany..
    From macroscopic mechanics to cell-effective stiffness within highly aligned macroporous collagen scaffolds2019Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 103, artikel-id 109760Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the design of macroporous biomaterial scaffolds, attention is payed predominantly to the readily accessible macroscopic mechanical properties rather than to the mechanical properties experienced by the cells adhering to the material. However, the direct cell mechanical environment has been shown to be of special relevance for biological processes such as proliferation, differentiation and extracellular matrix formation both in vitro and in vivo. In this study we investigated how individual architectural features of highly aligned macroporous collagen scaffolds contribute to its mechanical properties on the macroscopic vs. the microscopic scale. Scaffolds were produced by controlled freezing and freeze-drying, a method frequently used for manufacturing of macroporous biomaterials. The individual architectural features of the biomaterial were carefully characterized to develop a finite element model (FE-model) that finally provided insights in the relation between the biomaterial's mechanical properties on the macro-scale and the properties on the micro-scale, as experienced by adhering cells. FE-models were validated by experimental characterization of the scaffolds, both on the macroscopic and the microscopic level, using mechanical compression testing and atomic force microscopy. As a result, a so-called cell-effective stiffness of these non-trivial scaffold architectures could be predicted for the first time. A linear dependency between the macroscopic scaffold stiffness and the cell-effective stiffness was found, with the latter being consistently higher by a factor of 6.4 +/- 0.6. The relevance of the cell-effective stiffness in controlling progenitor cell differentiation was confirmed in vitro. The obtained information about the cell-effective stiffness is of particular relevance for the early stages of tissue regeneration, when the cells first populate and interact with the biomaterial. Beyond the specific biomaterial investigated here, the introduced method is transferable to other complex biomaterial architectures. Design-optimization in 3D macroporous scaffolds that are based on a deeper understanding of the mechanical environment provided to the cells will help to enhance biomaterial-based tissue regeneration approaches.

  • 206.
    Herrera, Martha
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Thitiwutthisakul, Kasinee
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Rujitanaroj, Pim-on
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Rojas, Ramiro
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Preparation and evaluation of high-lignin content cellulose nanofibrils from eucalyptus pulp2018Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 5, s. 3121-3133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High Klason lignin content (23 wt%) cellulose nanofibrils (LCNF) were successfully isolated from eucalyptus pulp through catalyzed chemical oxidation, followed by high-pressure homogenization. LCNFs had a diameter of ca. 13 nm according to AFM evaluation. Dense films were obtained through vacuum filtration (nanopaper) and subjected to different drying methods. When drying under heat and mild vacuum (93 degrees C, 95 kPa) a higher water contact angle, lower roughness and oxygen transmission rate were observed, compared to those drying at room temperature under compression conditions. DSC experiments showed difference in signals associated to T-g of LCNF compared to CNF produced from spruce bleached pulp through enzymatic pre-treatment. The LCNF-based nanopaper showed mechanical properties slightly lower than for those made from cellulose nanofibrils, yet with increased hydrophobicity. In summary, the high-lignin content cellulose nanofibrils proved to be a suitable material for the production of low oxygen permeability nanopaper, with chemical composition close to native wood.

  • 207. Hohn, N.
    et al.
    Schlosser, S. J.
    Bießmann, L.
    Grott, S.
    Xia, S.
    Wang, K.
    Schwartzkopf, M.
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. Deutsches Elektronen-Synchrotron, Germany.
    Müller-Buschbaum, P.
    Readily available titania nanostructuring routines based on mobility and polarity controlled phase separation of an amphiphilic diblock copolymer2018Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, nr 11, s. 5325-5334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The amphiphilic diblock copolymer polystyrene-block-polyethylene oxide is combined with sol-gel chemistry to control the structure formation of blade-coated foam-like titania thin films. The influence of evaporation time before immersion into a poor solvent bath and polarity of the poor solvent bath are studied. Resulting morphological changes are quantified by scanning electron microscopy (SEM) and grazing incidence small angle X-ray scattering (GISAXS) measurements. SEM images surface structures while GISAXS accesses inner film structures. Due to the correlation of evaporation time and mobility of the polymer template during the phase separation process, a decrease in the distances of neighboring titania nanostructures from 50 nm to 22 nm is achieved. Furthermore, through an increase of polarity of an immersion bath the energetic incompatibility of the hydrophobic block and the solvent can be enhanced, leading to an increase of titania nanostructure distances from 35 nm to 55 nm. Thus, a simple approach is presented to control titania nanostructure in foam-like films prepared via blade coating, which enables an easy upscaling of film preparation.

  • 208.
    Hohn, Nuri
    et al.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Hetzenecker, Andreas E.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Giebel, Michael A.
    Tech Univ Munich, Dept Chem, Lehrstuhl Anorgan Chem Schwerpunkt Neue Mat, Lichtenbergstr 4, D-85747 Garching, Germany..
    Geier, Sebastian
    Tech Univ Munich, Dept Chem, Lehrstuhl Anorgan Chem Schwerpunkt Neue Mat, Lichtenbergstr 4, D-85747 Garching, Germany..
    Biessmann, Lorenz
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Koerstgens, Volker
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Saxena, Nitin
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Schlipf, Johannes
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany..
    Ohm, Wiebke
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Deimel, Peter S.
    Tech Univ Munich, Phys Dept, Lehrstuhl Mol Nanowissensch & Chem Phys Grenzflac, James Franck Str 1, D-85748 Garching, Germany..
    Allegretti, Francesco
    Tech Univ Munich, Phys Dept, Lehrstuhl Mol Nanowissensch & Chem Phys Grenzflac, James Franck Str 1, D-85748 Garching, Germany..
    Barth, Johannes V.
    Tech Univ Munich, Phys Dept, Lehrstuhl Mol Nanowissensch & Chem Phys Grenzflac, James Franck Str 1, D-85748 Garching, Germany..
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Faessler, Thomas F.
    Tech Univ Munich, Dept Chem, Lehrstuhl Anorgan Chem Schwerpunkt Neue Mat, Lichtenbergstr 4, D-85747 Garching, Germany..
    Mueller-Buschbaum, Peter
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, James Franck Str 1, D-85748 Garching, Germany.;Tech Univ Munich, Heinz Maier Leibnitz Zentrum MLZ, Lichtenbergstr 1, D-85748 Garching, Germany..
    Amphiphilic diblock copolymer-mediated structure control in nanoporous germanium-based thin films2019Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, nr 4, s. 2048-2055Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fabrication of porous, foam-like germanium-based (Ge-based) nanostructures is achieved with the use of the amphiphilic diblock copolymer polystyrene-b-polyethylene oxide as structure directing agent. Basic concepts of block copolymer assisted sol-gel synthesis are successfully realized based on the [Ge-9](4-) Zintl clusters as a precursor for Ge-based thin films. Material/elemental composition and crystalline Ge-based phases are investigated via X-ray photoelectron spectroscopy and X-ray diffraction measurements, respectively. Poor-good solvent pair induced phase separation leads to pore sizes in the Ge-based films up to 40 nm, which can be tuned through a change of the molar mixing ratio between polymer template and precursor as proven by grazing incidence small angle X-ray scattering and scanning electron microscopy.

  • 209.
    Hohn, Nuri
    et al.
    Tech Univ Munich, Lehrstuhl Funkt Mat, Dept Phys, James Franck Str 1, D-85748 Garching, Germany. chwartzkopf, Matthias; Roth, Stephan V..
    Shlosser, Steffen J.
    Biessmann, Lorenz
    Song, Lin
    Grott, Sebastian
    Xia, Senlin
    Wang, Kun
    Schwartzkopf, Matthias
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Mueller-Buschbaum, Peter
    Impact of Catalytic Additive on Spray Deposited and Nanoporous Titania in Films Observed via in Situ X-ray Scattering: Implications for hanced Photovoltaics2018Ingår i: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 1, nr 8, s. 4227-4235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the aim of obtaining nanostructured titania thin films for the tential use in hybrid or dye sensitized solar cells, the amphiphilic block copolymer polystyrene-b-poly(ethylene oxide) is employed as a ructure directing template in combination with solgel chemistry. For sy upscaling, spraying is used as a deposition technique. In situ azing incidence small-angle X-ray scattering (GISAXS) measurements are rformed during spraying and show that most titania structures are ready formed within the solution prior to deposition. However, ructural rearrangement is enabled during the deposition period when all amounts of hydrochloric acid (HCl) are used as a catalytic ditive to the spray solution. This behavior is ascribed to an altering the reaction dynamics and phase separation in the presence of HCl, ich significantly improves the templating effect of the employed block copolymer. With HCl as an additive the final nanoscale rphologies exhibit smaller pore sizes and strongly enhanced order as mpared to thin films sprayed from solutions that do not contain HCl as antified with atomic force microscopy, scanning electron microscopy, d GISAXS.

  • 210.
    Holder, Shima
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Nilsson, Fritjof
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Understanding and modelling the diffusion process of low molecular weight substances in polyethylene pipes2019Ingår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, s. 301-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Peroxides are widely used as crosslinkers in polyethylene (PE) drinking water pipes. Cross-linked polyethylene (PEX) has better mechanical properties than PE, but peroxide decomposition by-products can migrate from PEX water pipes into the drinking water unless sufficient preventive actions are undertaken. This work systematically examines the migration of tert-Butyl methyl ether (MTBE), a dominating crosslinking by-product from PEX water pipes, into tap water by utilizing both experimental techniques and finite element (FEM) diffusion modeling. The effects of pipe geometry, tap water temperature (23–80 °C), boundary conditions (air or water interface) and degasing (at 180 °C) were considered. The MTBE diffusivity increased strongly with increasing temperature and it was concluded that a desired water quality can be achieved with proper degasing of the PEX pipes. As the FEM simulations were in excellent agreement with the experimental results, the model can accurately predict the MTBE concentration as a function of time, water temperature and PEX pipe geometry, and enable the pipe manufacturers to aid in ensuring desirable drinking water quality.

  • 211.
    Hollertz, Rebecca
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    López Durán, Vernica
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Larsson, Per A.
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Chemically modified cellulose micro- and nanofibrils as paper-strength additives2017Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, nr 9, s. 3883-3899Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chemically modified cellulose micro- and nanofibrils were successfully used as paper strength additives. Three different kinds of cellulose nanofibrils (CNFs) were studied: carboxymethylated CNFs, periodate-oxidised carboxymethylated CNFs and dopamine-grafted carboxymethylated CNFs, all prepared from bleached chemical fibres of dissolving grade, and one microfibrillated cellulose from unbleached kraft fibres. In addition to mechanical characterization of the final paper sheets the fibril retention, sheet density and sheet morphology were also studied as a function of addition of the four different cellulose fibrils. In general, the cellulose fibrils, when used as additives, significantly increased the tensile strength, Young’s modulus and strain-at-break of the paper sheets. The effects of the different fibrils on these properties were compared and evaluated and used to analyse the underlying mechanisms behind the strengthening effect. The strength-enhancing effect was most pronounced for the periodate-oxidised CNFs when they were added together with polyvinyl amine (PVAm) or poly(dimethyldiallylammonium chloride) (pDADMAC). The addition of periodate-oxidised CNFs, with pDADMAC as retention aid, resulted in a 37% increase in tensile strength at a 2 wt% addition and an 89% increase at a 15 wt% addition (from 67 to 92 and 125 kNm/kg, respectively) compared to a reference with only pDADMAC. Wet-strong sheets with a wet tensile index of 30 kNm/kg were also obtained when periodate-oxidised CNFs and PVAm were combined. This significant increase in wet strength is suggested to be the result of a formation of cross-links between the aldehyde groups, introduced by the periodate oxidation, and hydroxyl groups on the lignocellulosic fibres and the primary amines of PVAm. Even though less significant, there was also an increase in wet tensile strength when pDADMAC was used together with periodate-oxidised fibrils which shows that the aldehyde groups are able to increase the wet strength without the presence of the primary amines of the PVAm. As an alternative method to strengthen the fibre network, carboxymethylated CNFs grafted with dopamine, by an ethyl dimethylaminopropyl carbodiimide coupling, were used as a strength additive. When used as an additive, these CNFs showed a strong propensity to form films on and around the fibres and significantly increased the mechanical properties of the sheets. Their addition resulted in an increase in the Young´s modulus by 41%, from 5.1 to 7.2 GPa, and an increase in the tensile strength index of 98% (from 53 to 105 kNm/kg) with 5 wt% retained dopamine-grafted CNFs.

  • 212.
    Hua, Geng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Franzén, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Odelius, Karin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Phosphazene-Catalyzed Regioselective Ring-Opening Polymerization of rac-1-Methyl Trimethylene Carbonate: Colder and Less is Better2019Ingår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 52, nr 7, s. 2681-2690Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The regioselective organocatalytic ring-opening polymerization (ROP) of a 6-membered cyclic carbonate, rac-1-methyl trimethylene carbonate, was studied using phosphazene base (t-BuP2) as the principle catalyst. The influence on the reaction kinetics caused by the reaction temperature (-74-60 degrees C), catalyst loading (0.5-2.5%), and reaction solvent (toluene and tetrahydrofuran) was systematically tuned and followed by H-1 NMR. All studied reactions reached close to or above 90% monomer conversion in 3 h, and all exhibited typical equilibrium polymerization behavior that is inherent to 6-membered cyclic carbonates. Good control over the molecular weight and distribution of the polycarbonate product was obtained in most studied conditions, with M-n ranging from similar to 4k to similar to 20k and D < 1.2. The regioregularity (X-reg) of the resulting polycarbonate was thoroughly studied using various NMR techniques, with the highest X-reg obtained being.0.90. The major influence from the reaction conditions on both the ROP kinetics and X-reg are as follows: higher reaction temperature resulted in a decrease of both; higher catalyst loading resulted in a faster ROP reaction but a slight decrease in X-reg; and toluene being a better solvent resulted in both faster reaction and higher X-reg. Throughout this study, we have demonstrated the possibility to synthesize regioregular aliphatic polycarbonate using an organic base as the ROP catalyst, contrary to the existing studies on similar systems where only metal-base catalysts were in focus and our systems showed similar high X-reg of the product.

  • 213.
    Hua, Geng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsen, Peter
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Franzen, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Odelius, Karin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Anionic polycondensation and equilibrium driven monomer formation of cyclic aliphatic carbonates2018Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, nr 68, s. 39022-39028Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current work explores the sodium hydride mediated polycondensation of aliphatic diols with diethyl carbonate to produce both aliphatic polycarbonates and cyclic carbonate monomers. The lengths of the diol dictate the outcome of the reaction; for ethylene glycol and seven other 1,3-diols with a wide array of substitution patterns, the corresponding 5-membered and 6-membered cyclic carbonates were synthesized in excellent yield (70-90%) on a 100 gram scale. Diols with longer alkyl chains, under the same conditions, yielded polycarbonates with an M-w ranging from 5000 to 16000. In all cases, the macromolecular architecture revealed that the formed polymer consisted purely of carbonate linkages, without decarboxylation as a side reaction. The synthetic design is completely solvent-free without any additional post purification steps and without the necessity of reactive ring-closing reagents. The results presented within provide a green and scalable approach to synthesize both cyclic carbonate monomers and polycarbonates with possible applications within the entire field of polymer technology.

  • 214.
    Hua, Geng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Ring-opening Approaches to Functional Renewable Polymers2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 215.
    Huang, Tianxiao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Betulin-modified cellulosic textile fibers with improved water repellency, hydrophobicity and antibacterial properties2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Textiles made from natural sources, such as cotton and flax, have advantages over those made of synthetic fibers in terms of sustainability. Unlike major synthetic fibers that have a negative impact on the environment due to poor biodegradability, cotton cellulose is a renewable material.Cotton cellulose fibers exhibit various attractive characteristics such as softness and inexpensiveness. Cellulosic textiles can be easily wetted, since the structure contains a large amount of hydrophilic hydroxyl groups, and when water repellency is needed, this is a disadvantage. Currently, paraffin waxes or fluorinated silanes are used to achieve hydrophobicity, but this contradicts the concept of green chemistry since these chemicals are not biodegradable. The use of bio-based materials like forest residues or side-streams from forest product industries might be a good alternative, since this not only decreases the pressure on the environment but can also increase the value of these renewable resources.Betulin is a hydrophobic extractive present in the outer bark of birch trees (Betula verrucosa). Nowadays, the birch bark containing betulin generated in the paper industry is disposed of by incineration as a solid fuel to provide energy, but this application is not highly valuable and this motivates us to see whether betulin can be used as a hydrophobe to prepare waterproof cellulosic textiles. Methods of dip-coating, film compression molding and grafting were performed to build “betulin-cellulosic textile system” to render the textile with hydrophobicity and other functions. The textile impregnated in a solution of betulin-based copolymer exhibited a contact angle of 151°, which indicated that superhydrophobicity can be reached. AATCC water spray test results showed that cellulosic textile coated with betulin-based film had a water repellency of 80, which is the third highest class according to the rating standards. Betulin-grafted textiles were also prepared and showed a static water contact angle of 136°, and an antibacterial property with a bacterial removal of 99%.This thesis proposes that betulin can be used as a green alternative in functional material preparation. By developing betulin, a more value-added application rather than incineration can be achieved.

  • 216.
    Huang, Tianxiao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Chen, Chao
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal Inst Technol, Stockholm, Sweden..
    Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose2019Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikel i tidskrift (Övrigt vetenskapligt)
  • 217.
    Huang, Tianxiao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Chen, Chao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose2019Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, nr 1, s. 665-677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Betulin, a natural compound extractable from the outer bark of birch, can be used to improve the properties of cellulosic textile fibres. Herein, oxidation was performed to prepare carboxyl-functionalized cellulose, which was subsequently covalently attached by betulin through esterification. The surface-modified cellulosic textile fibres showed a substantially improved hydrophobicity, as indicated by a water contact angle of 136°. Moreover, the material showed excellent antibacterial properties, as indicated by over 99% bacterial removal and growth inhibition, in both Gram-positive and Gram-negative bacterial assays. The method of surface-modification of the cellulosic materials adapted in this study is simple and, to the best of our knowledge, has not been carried out before. The results of this study prove that betulin, a side-stream product produced by forest industry, could be used in value-added applications, such as for preparing functional materials. Additionally, this modification route can be envisaged to be applied to other cellulose sources (e.g., microfibrillated cellulose) to achieve the goal of functionalization.

  • 218.
    Huang, Tianxiao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Water repellency improvement of cellulosic textile fibers by betulin and a betulin-based copolymer2018Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 3, s. 2115-2128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Betulin is a naturally abundant and hydrophobic compound in the outer bark of birch and can readily be obtained by solvent extraction. Here, solutions of betulin were used to treat cotton fabrics and improve their water repellency. Cotton fabric impregnated in a solution of betulin in ethanol showed a contact angle for water of approximately 153A degrees and reached a water repellency score of 70 according to a standard water repellency test method. A betulin-terephthaloyl chloride (TPC) copolymer was synthesized. Both betulin and betulin-TPC copolymer were characterized by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The copolymer was characterized by size exclusion chromatography and differential scanning calorimetry. When impregnated with a solution of betulin-TPC copolymer in tetrahydrofuran, a cotton fabric showed a water contact angle of 151A degrees and also reached a water repellency score of 70. Films based on betulin and betulin-TPC copolymer were prepared and coated onto the surface of the fabrics by compression molding. These coated fabrics showed water contact angles of 123A degrees and 104A degrees respectively and each reached a water repellency score of 80.

  • 219.
    Hult, Daniel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Versatile Synthetic Strategies to Highly Functional Polyesters and Polycarbonates2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Polymers have become ubiquitous in today’s society and are found in everything from household items to airplanes and automobiles. Synthetic polymeric materials are as diverse as their applications and their final properties are highly reliant on the building blocks and methods used to assemble them. In the field of biomedical materials, polyesters and polycarbonates have been hailed as excellent materials in large part due to their inherent hydrolytic degradability. With this in mind, careful choice of monomers can ensure that materials not only conform to the desired physical properties, but also elicit a favorable biological response. The utilization of post-polymerization modification of these promising materials has the capability of opening up further avenues to target even more advanced applications. Unfortunately, rigorous and difficult reaction conditions, including multi-step synthesis have to a certain extent held back the adoption of these complex functional materials in applied research. In a pragmatic approach, a sustainable framework was developed in this thesis to seek out more practical methods, limiting the amount of reaction steps and overtly hazardous chemicals.

    In a first study, we set out to simplify and scale-up the synthesis of cyclic carbonates with pendant functional groups, capable of undergoing controlled ring-opening polymerization. By avoiding the use of protective-group chemistry we were able two devise a two-step method to create a library of functional monomers. Results in this study show that reactive intermediates could be isolated on 100 g scales, which in a second step was functionalized with a desired alcohol.

    With this framework in mind, key practical decisions were made to drastically re-think the work up procedures for greater scalability of bis-MPA dendrimers. In this work, a more efficient, scalable and sustainable approach was devised. Elimination of traditional arduous purification steps led to the synthesis of monodisperse dendrimers up to the sixth generation, with 192 functional groups on 50 g scales. Further work included the omission of protective group-chemistry, using orthogonal functional groups to cut the number of synthetic steps by half.

    The know-how developed in the first two projects led us to pursue greater scalability of functional polycarbonates through a simpler polymerization technique. The method allowed the step-growth polymerization of functional materials from more easily accessible monomers isolated on 100 g scales. Subsequent polymerization afforded materials with glass transition temperatures in the range of -45 °C to 169 °C. The method served as a complement to cyclic carbonates, offering a wider range of functional monomers. Furthermore, by careful choice of assembly method, both alternating and scrambled compositions could be achieved.

    In a final study, we set out to take advantage of the scrambling mechanism. Control of the final composition of highly rigid degradable polycarbonates was pursued, using renewable building-blocks derived from sugar. In a proof of concept study, thermal and hydrolytic stability of these materials is shown to be dependent on both amount and configuration of each monomer in the final material.

  • 220.
    Hult, Daniel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Garcia-Gallego, Sandra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Ingverud, Tobias
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Andrén, Oliver
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Malkoch, Michael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Degradable High Tg Sugar Derived Polycarbonates from Isosorbide and Dihydroxyacetone2018Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 9, nr 17, s. 2238-2246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polycarbonates from isosorbide and dihydroxyacetone (DHA) have been synthesised using organocatalytic step-growth polymerization of their corresponding diols and bis-carbonylimidazolides monomers. By choice of feed ratio and monomer activation, either isosorbide or ketal protected DHA, random and alternating poly(Iso-co-DHA) carbonates have been formed. Thermal properties by DSC and TGA were herein strongly correlated to monomer composition. Dilution studies using 1H-NMR of a model compound DHA-diethyl carbonate in acetonitrile and deuterated water highlighted the influence of α-substituents on the keto/hydrate equilibrium of DHA. Further kinetics studies of in the pH* range of 4.7 to 9.6 serve to show the hydrolytic pH-profile of DHA-carbonates. The Hydrolytic degradation of deprotected polymer pellets show an increased degradation with increasing DHA content. Pellets with a random or alternating configuration show different characteristics in terms of mass loss and molecular weight loss profile over time.

  • 221.
    Hult, Daniel
    et al.
    KTH.
    Olsson, Vilhelm
    KTH.
    Garcia-Gallego, Sandra
    KTH.
    Malkoch, Michael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Versatile chemistries to highly functional polyesters and polycarbonates2018Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Artikel i tidskrift (Övrigt vetenskapligt)
  • 222. Ibarra, David
    et al.
    Köpcke, Viviana
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Influence of a monocomponent endoglucanase on different fibre raw materials: Study of accessability and reactivity2008Konferensbidrag (Refereegranskat)
  • 223.
    Ihrner, Niklas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Structural Lithium Ion Battery Electrolytes2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A major challenge in the electrification of vehicles in the transport industry is that batteries are heavy, which reduces their effectiveness in mobile applications. A solution to this is structural batteries, which are batteries that can carry mechanical load while simultaneously storing energy. This can potentially lead to large weight savings on a systems level, since they may allow replacement of load bearing structures with structural batteries. Carbon fibers are suitable for structural batteries because they have superb mechanical properties and readily intercalate lithium ions, i.e. they can be used as electrodes in a lithium ion battery. However, to utilize carbon fibers in structural batteries, a polymer (matrix) is needed to form a composite battery. The polymer is required to have high modulus and high ion transport properties, which are inversely related, to function as an electrolyte. This thesis focuses on the development and characterization of such polymer electrolytes.

    The first study was performed on a homogenous polymer electrolyte based on plasticized polyethylene glycol-methacrylate. The influence of crosslink density, salt concentration and plasticizer concentration on the mechanical and electrochemical properties were investigated. Increases in both ionic conductivity and storage modulus were obtained when, compared to non-plasticized systems. However, at high storage modulus (E’>500 MPa) the ionic conductivity (𝜎<10-7 S cm-1) is far from good enough for the realization of structural batteries.

    In a second study, phase separated systems were therefore investigated. Polymerization induced phase separation (PIPS) via UV-curing was utilized to the produce structural battery electrolytes (SBE), consisting of liquid electrolyte and a stiff vinyl ester thermoset. The effect of monomer structure and volume fraction of liquid electrolyte on the morphology, electrochemical and mechanical properties were investigated. High storage modulus (750 MPa) in combination with high ionic conductivity (1.5 x 10-4 S cm-1) were obtained at ambient temperature. A SBE carbon fiber lamina half-cell was prepared via vacuum infusion and electrochemically cycled vs lithium metal. The results showed that both ion transport and load transfer was enabled through the SBE matrix.

    In the third study the mechanical and electrochemical properties of the SBE-carbon fiber lamina were investigated and the multifunctional performance was evaluated. A new formulation of SBE, with a small addition of thiol monomer, were prepared with improved electrochemical and mechanical properties. The mechanical properties of the SBE carbon fiber lamina did not deteriorate after electrochemical cycling. The capacity of the SBE carbon fiber lamina half-cell was 232 ± 26 mAh g-1, at a C/20 charge rate. Furthermore, the lamina displayed multifunctional performance, compared to the monofunctional properties of its constituents.

    In the final study, a new curing method was investigated, since UV-curing cannot be used to prepare full-cell carbon fiber composite structural batteries. Thermal curing was investigated to prepare the SBE. The PIPS was not adversely affected by the change in curing method, and the length scale of the phase separation in the SBE was slightly larger compared to UV-cured SBEs. The thermally cured SBEs exhibited improved thermomechanical properties without a reduction in the electrochemical properties. Thermal curing did not affect the electrochemical properties of the SBE carbon fiber lamina, however the type of carbon fiber utilized was found to negatively affect the cycling performance.

    Publikationen är tillgänglig i fulltext från 2020-03-25 10:42
  • 224.
    Ingverud, Tobias
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Exploring crosslinked networks of polymers and hybrid cellulose materials2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Polymerkemin har under de senaste decennierna haft en enorm utveckling, vilket har resulterat i nya funktionella material med banbrytande applikationer. Denna utveckling har drivits på av starka tvärvetenskapliga allianser mellan medicin, biologi, kemi och materialvetenskap. Termoresponsiva block-sampolymerer har bland annat tagits fram för sin förmåga att själv-organiseras, vilken möjliggör inkapsling och frisättning av medicin. Den dendritiska polymerfamiljen har visat sig vara ett utmärkt exempel på högreaktiva och interaktiva funktionella material, speciellt lämpliga för biomedicinska tillämpningar. Betydelsen av aminer är stor i allmänhet och speciellt inom polymerkemin, tack vare deras nukleofila egenskaper i reaktioner, men också för deras förmåga att interagera med andra fysikaliska konstellationer. Det finns också en ökad medvetenhet om vår ökande levnadsstandard, effekterna av klimatförändringar och jordens befolkningstillväxt. Dessa utmaningar, behöver vårt yttersta fokus och ökad kunskap, för att styra våra steg mot en mer biobaserad cirkulär ekonomi. I Sverige skulle vi kunna ta bättre hand om vår skog och utnyttja dess fina råmaterial och förädla den till nya material. Denna avhandling strävar efter spontan tvärbindning av olika funktionella polymerer, med fokus på hybridisering med nanocellulosa-material.

    Initialt framställdes interaktiva, permanent laddade, amin-funktionella termoresponsiva tri- och stjärnblocksampolymerer. Dessa utvärderades och användes som elektrostatisk makro-tvärbindare för cellulosa nanofibriller (CNF), vilket resulterade i hydrogeler med låg torrhalt och anmärkningsvärd termoresponsivitet och skjuvningsmodul.

    För det andra utvecklades och utvärderades reaktiva och interaktiva aminfunktionella dendritiska linjär-dendritiska (DLD)-polymerer in vitro och in vivo. DLD-polymererna användes som antibakteriella hydrogeler som var snabbnedbrytande och verkade hämmande för kirurgiskt påverkad sårinfekiton (SSI). Tvärbindning av poly(etylen glykol) (PEG) systemet optimerades för snabb applicering under fysiologiska förhållanden i from av tvåkomponentssystem samt för att kunna matcha olika vävnaders skjuvningsmodul.

    För det tredje introducerades och karakteriserades Helux, den hyperförgrenade kommersiella heterofunktionella poly(amidoamin) karboxylat polymeren. Aminreaktioner utfördes för att demonstrera lättillgängliga modifieringar av Helux. Hetero-funktionaliteten utvärderades genom att öka molekylvikten och sedan bilda självtvärbundna Heluxfilmer. Dessutom framställdes även tvåkomponents-hydrogeler baserat på Helux och PEG som visade temperaturhärdningsberoende skjuvningsmodul.

    Slutligen användes Helux i kombination med CNF för att visa potentialen i att blanda på nanonivå utan aggregering. CNF-Helux visade sig kunna bilda hydrogeler och våtstabila termo-tvärbundna CNF-Helux-kompositsammansättningar, såsom filmer och aerogeler, redo för ytmodifiering av kvarvarande amin-grupper i de bildade 3D-nätverken.

    Publikationen är tillgänglig i fulltext från 2020-04-16 12:13
  • 225.
    Ingverud, Tobias
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Erlandsson, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Malkoch, Michael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    The combination of a dendritic polyampholyte and cellulose nanofibrils – a new type of functional materialManuskript (preprint) (Övrigt vetenskapligt)
  • 226.
    Ingverud, Tobias
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Malkoch, Michael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Helux: A heterofunctional hyperbranched poly(amido amine) carboxylateManuskript (preprint) (Övrigt vetenskapligt)
  • 227.
    Jara, Rory
    et al.
    SI Grp, Proc Technol Grp, Morgantown, WV USA.;West Virginia Univ, Wood Sci & Technol Dept, Morgantown, WV 26506 USA..
    Lawoko, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    van Heiningen, Adriaan
    Univ Maine, 537 Jenness Hall, Orono, ME 04469 USA..
    Intrinsic dissolution kinetics and topochemistry of xylan, mannan, and lignin during auto-hydrolysis of red maple wood meal2019Ingår i: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 97, nr 3, s. 649-661Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High temperature aqueous treatment of wood is the preferred technology for deconstructing lignocellulosics. Many studies have been carried out on the kinetics and mechanism of hot-water extraction. However, most were performed in batch or integral plug flow reactors, which are not optimal for measuring intrinsic dissolution kinetics of the lignocellulosic components. Therefore, we used a continuous mixed batch reactor (or Berty reactor) to determine the intrinsic dissolution kinetics of xylan, mannan, and lignin from milled hardwood (Acer rubrum) at three different temperatures (150, 160, and 170 degrees C) and four constant pH values: 2, 3, 4, and 5. During the initial phase of autohydrolysis (carbohydrate-free), lignin and (lignin-free) xylan dissolve starting at a high rate and then a slowly decreasing rate, respectively. This is followed by the dissolution of xylan-lignin complexes and finally cellulose xylan complexes when cellulose has been significantly hydrolysed. The kinetics and molecular weight distribution of the removed wood polymers are used to describe the topochemistry of autohydrolysis based on recent knowledge of the ultrastructure of hardwood fibres.

  • 228.
    Jawerth, Marcus
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lawoko, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Renewable thermosetting resins based on refined technical lignin: fractionation, modification and valorization2019Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikel i tidskrift (Övrigt vetenskapligt)
  • 229.
    Jawerth, Marcus
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lundmark, Stefan
    Perstorp AB, Perstorp, Sweden..
    Gioia, Claudio
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lawoko, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    A retrosynthesis perspective on new thermoset resin applications based on industrial Kraft lignin2018Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Artikel i tidskrift (Övrigt vetenskapligt)
  • 230.
    Jawerth, Marcus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Royal Inst Technol, Wallenberg Wood Sci Ctr, Stockholm, Sweden..
    Lawoko, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Royal Inst Technol, Wallenberg Wood Sci Ctr, Stockholm, Sweden..
    Lundmark, Stefan
    Perstorp AB, Perstorp, Sweden..
    Berumen, Catalina Perez
    Univ Autonoma Coahuila, Saltillo, Coahuila, Mexico..
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. Royal Inst Technol, Stockholm, Sweden..
    Modification of low molecular weight lignin model compounds for thermoset resin applications2016Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Artikel i tidskrift (Övrigt vetenskapligt)
  • 231.
    Johannisson, Wilhelm
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Ihrner, Niklas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Carlstedt, D.
    Asp, L. E.
    Sieland, F.
    Multifunctional performance of a carbon fiber UD lamina electrode for structural batteries2018Ingår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 168, s. 81-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In electric transportation there is an inherent need to store electrical energy while maintaining a low vehicle weight. One way to decrease the weight of the structure is to use composite materials. However, the electrical energy storage in today's systems contributes to a large portion of the total weight of a vehicle. Structural batteries have been suggested as a possible route to reduce this weight. A structural battery is a material that carries mechanical loads and simultaneously stores electrical energy and can be realized using carbon fibers both as a primary load carrying material and as an active battery electrode. However, as yet, no proof of a system-wide improvement by using such structural batteries has been demonstrated. In this study we make a structural battery composite lamina from carbon fibers with a structural battery electrolyte matrix, and we show that this material provides system weight benefits. The results show that it is possible to make weight reductions in electric vehicles by using structural batteries. 

  • 232.
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    New vinyl ether monomers via lipase catalysis towards cationically crosslinkable thermosets2019Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikel i tidskrift (Övrigt vetenskapligt)
  • 233.
    Josefsson, Peter
    et al.
    KTH.
    Wågberg, Lars
    KTH.
    Henriksson, Gunnar
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    CELL 114-Mode of action of fungal cellulases studied using model cellulose films and a quartz crystal microbalance2007Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 233, s. 773-773Artikel i tidskrift (Övrigt vetenskapligt)
  • 234.
    Kaldéus, Tahani
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Surface modification approaches of cellulose nanofibrils and their effect on dispersibility2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the strive to find and develop sustainable bio-based materials an increased interest for nanocellulosic materials as attractive alternatives has arisen during the past decades. This can be attributed to their abundant renewability, remarkable inherent mechanical properties and their capability to be chemically modified. Cellulose nanofibrils (CNFs) are commonly obtained from wood pulp fibres and prepared through mechanical, chemical and/or enzymatic treatments. However, due to their hydrophilic nature and tendency to self-aggregate, their surface chemistry need to be altered to fully utilise their inherent properties and enable their usage in conventional large-scale industrial processes.

    This thesis work focuses on elucidating the fundamental aspects of the colloidal stability of highly concentrated CNF dispersions and the redispersibility of dried CNFs. Small amounts of amine-terminated poly(ethylene glycol) (PEG) were used to sterically stabilise the CNFs at higher fibril concentrations and delay the dispersion-arrested state transition (Paper I). The redispersibility of dried CNFs was studied for differently charged CNFs as a function of redispersing agents such as carboxymethyl cellulose (CMC), PEG and lignin (Paper II).

    This thesis presents green, facile modification approaches as well as strategies for improved dispersibility and compatibility with polymer matrices. The commercially established carboxymethylation process was expanded with a subsequent functionality step, yielding a mild, versatile one-pot protocol for the preparation of bi-functional CNFs (Paper III). Further, reactive amphiphilic macromolecules with targeted side-chain functionalities were used to compatibilise the CNF surface by water-based approaches. In the first study, a macroinitiator was used for the development of a versatile, yet facile, protocol for the controlled polymerisation of both hydrophilic and hydrophobic monomers in water from the CNF surface (Paper IV). In the second study, a reactive macro-compatibiliser was used to molecularly engineer the interface between CNFs and a polymer matrix by reactive-melt processing, yielding nanocomposites with improved stiffness while maintaining the deformability (Paper V).

    Publikationen är tillgänglig i fulltext från 2020-02-22 11:00
  • 235.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. RISE Bioecon, Drottning Kristinas Väg 61, S-11486 Stockholm, Sweden..
    Boujemaoui, Assya
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    One-pot preparation of bi-functional cellulose nanofibrils2018Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 12, s. 7031-7042Artikel i tidskrift (Refereegranskat)
    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.

  • 236.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Leggieri, Maria Rosella Telaretti
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Sanchez, Carmen
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    All-Aqueous SI-ARGET ATRP from Cellulose Nanofibrils Using Hydrophilic and Hydrophobic Monomers2019Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, nr 5, s. 1937-1943Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An all-water-based procedure for "controlled" polymer grafting from cellulose nanofibrils is reported. Polymers and copolymers of poly(ethylene glycol) methyl ether methacrylate (POEGMA) and poly(methyl methacrylate) (PMMA) were synthesized by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) from the cellulose nanofibril (CNF) surface in water. A macroinitiator was electrostatically immobilized to the CNF surface, and its amphiphilic nature enabled polymerizations of both hydrophobic and hydrophilic monomers in water. The electrostatic interactions between the macroinitiator and the CNF surface were studied by quartz crystal microbalance with dissipation energy (QCM-D) and showed the formation of a rigid adsorbed layer, which did not desorb upon washing, corroborating the anticipated electrostatic interactions. Polymerizations were conducted from dispersed modified CNFs as well as from preformed modified CNF aerogels soaked in water. The polymerizations yielded matrix-free composite materials with a CNF content of approximately 1-2 and 3-6 wt % for dispersion-initiated and aerogel-initiated CNFs, respectively.

  • 237.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Malmström, Eva
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Controlling the dispersion properties of nanocellulose systems by surface modification2019Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikel i tidskrift (Övrigt vetenskapligt)
  • 238.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Nordenström, Malin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Erlandsson, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Redispersibility properties of dried cellulose nanofibrils - influence on structure and mechanical propertiesManuskript (preprint) (Övrigt vetenskapligt)
  • 239.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Nordenström, Malin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Erlandsson, Johan
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Redispersibility properties of dried cellulose nanofibrils - influence on structure and mechanical properties2019Ingår i: Artikel i tidskrift (Övrigt vetenskapligt)
  • 240.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Telaretti Leggieri, Maria Rosella
    Cobo Sanchez, Carmen
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    All-aqueous SI-ARGET ATRP from cellulose nanofibrils using hydrophilic and hydrophobic monomers2019Ingår i: Artikel i tidskrift (Övrigt vetenskapligt)
  • 241.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Träger, Andrea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Berglund, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lo Re, Giada
    Chalmers University of Technology.
    Molecular engineering of cellulose-PCL bio-nanocomposite interface by reactive amphiphilic copolymer nanoparticles2019Ingår i: Artikel i tidskrift (Refereegranskat)
  • 242.
    Kaldéus, Tahani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Träger, Andrea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lo Re, Giada
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Molecular Engineering of the Cellulose-Poly(Caprolactone) Bio-Nanocomposite Interface by Reactive Amphiphilic Copolymer Nanoparticles2019Ingår i: ACS NANO, Vol. 13, nr 6, s. 6409-6420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.

  • 243.
    Karim, Zoheb
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    De-Castro, Daniele Oliveira
    KTH.
    Svedberg, A.
    Söderberg, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Wågberg, Lars
    KTH.
    Berglund, Lars
    KTH.
    Forming a cellulose based nanopaper using XPM2017Ingår i: International Conference on Nanotechnology for Renewable Materials 2017, TAPPI Press , 2017, s. 399-407Konferensbidrag (Refereegranskat)
  • 244.
    Karlsson, Josefin
    et al.
    KTH. Royal Inst Technol, S-10044 Stockholm, Sweden..
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Enarsson, Lars-Erik
    KTH.
    Wågberg, Lars
    KTH.
    CELL 283-Making biointeractive fibers: Buildup of antibacterial multilayers studied by QCM-D and SPAR2008Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235Artikel i tidskrift (Övrigt vetenskapligt)
  • 245.
    Karlsson, Mattias E.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mamie, Yann C.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Calamida, Andrea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Gardner, James M.
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 17, s. 5079-5087Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.

  • 246.
    Karlsson, Pernilla
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Swelling of Cellulose Fibrillar Matrices and Gels2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    One of the major challenges of today´s society is to find a sustainable way to create a living based on the resources on earth. It is a challenge that includes a transition from fossil-based materials to renewable/biodegradable raw materials and also the creation of an environmentally friendly circular material flow. In the search for renewable and biodegradable raw materials, the forest has gained renewed interest. In Sweden, 70 % of the area is covered with forest and, together with a long history of a sustainable forestry, this means that there are environmental and economic gains if this resource is utilized in a correct way and research and development into new wood-based materials has advanced significantly during the last decades. The wood component that has gained the most attention is cellulose and due to the ability of cellulose to act as a light-weight reinforcing component in composites and also due to the variability by which cellulose can be modified in order to obtain a wide range of useful properties. One advantage of cellulose-based materials is that they can be processed in water since the cellulose is hydrophilic and is softened by exposure to water. At the same time, this is one of the major drawbacks of cellulose-based materials since their properties deteriorate when exposed to water, whether as moist air or as condensed liquid. To optimize the use of cellulose fibers/fibrils/gels, knowledge of the effect on the inherent properties of cellulose in contact with water needs to be extended. This project has therefore focused on a fundamental understanding of the reasons behind the water uptake/swelling in a cellulose-rich fiber assembly immersed in water.

    The project has included the development and characterization of cellulose model materials in the form of gel (beads) and fibrillar (filaments) networks, for which the swelling was measured as a dimensional change in different aqueous environments. In one of the subprojects, the ion-induced swelling in different cellulose networks was measured on model materials and it was shown that the ion-induced contribution to the swelling was not only dependent on pH and salt concentration in the aqueous solution but also on the stiffness and structure of the network. Thermodynamic models describing gel swelling were used to separate and quantify the osmotic pressure associated with different factors contributing to the total osmotic pressure (ions, mixing and network) of never-dried gel beads. It was thus possible to identify the factor which had a dominant influence in the osmotic pressure and hence most important on the swelling of the systems. Never-dried gel beads showed that the network entropy was the most important factor controlling the swelling of the beads up to a volume fraction of cellulose of 35 %. Above this volume fraction the mixing entropy was found to dominate the swelling. It was also found that the distribution of the total osmotic pressure on these three factors was dependent on the network structure, as the distribution changed when the beads were dried and rewetted compared to the never-dried beads. Finally the de-watering ability of the gel beads in different environments was studied, and also after different modifications targeting the properties shown to have the most dominant effect on the osmotic swelling pressure (ion, mix and network). It was possible to quantify how the gel beads were dewatered to different degrees if e.g. hydrogen was chosen as the counter-ion to the carboxyl groups, if the polarity of the solution was lowered and if the structure of cellulose was changed. This information can, for example, be used to predict how nanocellulose based networks are dewatered under different conditions and this is essential for the preparation of materials based on cellulose nanofibrils.

    Publikationen är tillgänglig i fulltext från 2021-12-31 14:00
  • 247.
    Karlsson, Pernilla
    et al.
    KTH.
    Larsson, Tomas
    Innventia AB, Stockholm, Sweden..
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Cellulose-based gel beads for quantifying the swelling behavior of plant fibers2018Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Artikel i tidskrift (Övrigt vetenskapligt)
  • 248.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Fall, Andreas
    RISE Bioeconomy.
    Larsson, Per Tomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. RISE Bioeconomy.
    Wågberg, Lars
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    De-watering of Cellulose-based Gel Networks Targeting Different Factors Contributing to the Swelling PressureManuskript (preprint) (Övrigt vetenskapligt)
  • 249.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Larsson, Per Tomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. RISE Bioeconomy.
    Hansson, Per
    Uppsala University, Dep. of Pharmacy, Uppsala Biomedical Center.
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks2019Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, nr 4, s. 1603-1612Artikel i tidskrift (Refereegranskat)
    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.

  • 250.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Larsson, Per Tomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. RISE Bioeconomy.
    Pettersson, Torbjörn
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Elasticity and Ion-Induced Swelling of Cellulose Fibrillar Networks and GelsManuskript (preprint) (Övrigt vetenskapligt)
2345678 201 - 250 av 519
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf