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  • 51.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    Lindblad, Gunnar
    Iversen, Tommy
    A study of the photochromic behaviour of UV-irradiated mechanical pulps.1992Inngår i: Proc. 2nd European Workshop Lignocellulosic Pulp (EWLP), 1992, s. 183-186Konferansepaper (Fagfellevurdert)
  • 52.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    Lindblad, Gunnar
    Iversen, Tommy
    The light-induced colour reversion of groundwood pulps1991Inngår i: Proc 6th Int. Symp. Wood Pulp Chem., Melbourne, Australia, 1991, s. 439-442Konferansepaper (Fagfellevurdert)
  • 53.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Henschen, Jonatan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Esterification and hydrolysis of cellulose using oxalic acid dihydrate in a solvent-free reaction suitable for preparation of surface-functionalised cellulose nanocrystals with high yield2017Inngår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 19, s. 5564-5567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A one-pot esterification and hydrolysis of cellulose was carried outby treating cellulose fibres with molten oxalic acid dihydrate. Eachcellulose oxalate had a free carboxyl content above 1.2 mmol g−1and an average molecular weight of approximately 40 kDa.Aqueous suspensions of the oxalates were sonicated to preparecellulose nanocrystals with a gravimetric yield of 80.6%

  • 54.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Fibre & Polymer Technol, Stockholm, Sweden..
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Royal Inst Technol, Fiber & Polymer Technol, Stockholm, Sweden..
    Le Normand, Myriam
    Galderma, Uppsala, Sweden..
    WOBAMA wood based materials based on bark2016Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Artikkel i tidsskrift (Annet vitenskapelig)
  • 55.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Westman, Eva-Helena
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Josefin
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    CELL 28-Biointeractive fibers with antibacterial properties2008Inngår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY: Volume: 235, 2008, s. 28-CELL-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Growth of bacteria on various surfaces may cause major concern if encountered in the wrong environment.  The ability to impart antimicrobial properties onto surfaces is therefore desirable.  Modification of both glass surfaces and cellulose membranes using weak polyelectrolytes as antimicrobial agent is presented.  The aim was to incorporate a known carrier of antimicrobial activity into a multilayer structure of adsorbed polyelectolytes at different surfaces and evaluate the antibacterial activities.  The approach involved screening for antimicrobial activity in soln. of modified and unmodified polymers.  The polymers were evaluated against gram-neg. E. coli and gram-pos. B. subtilis. In order to elucidate the mode of action of the polymers, the charge was detd.  This is done since earlier studies have shown that both charge and degree of hydrophobicity are of importance in terms of exerted activity.  Results show that the chosen polymers exert activity in the immobilized state.  Different techniques have been used to evaluate the mechanisms.

  • 56.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Westman, Eva-Helena
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Cellulose films and fibres with antibacterial properties2007Konferansepaper (Fagfellevurdert)
  • 57. Elsander, A.
    et al.
    Ek, Monica
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Oxalic acid formation during ECF and TCF bleaching of kraft pulp2000Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 83, nr 2, s. 73-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of oxalic acid during bleaching of softwood kraft pulp was studied. The bleaching agents used were oxygen, hydrogen peroxide, chlorine dioxide, peracetic acid, and ozone. Formation of oxalic acid increased linearly with the reduction in kappa number. However, bleaching with peracetic acid produced less oxalic acid than the other bleaching agents. In ozone bleaching, about one-third of the oxalic acid formed is adsorbed on the pulp and not released until pulp pH is increased during a later stage, where it could combine with calcium ions to produce a calcium oxalate scale.

  • 58. Elsander, Anna
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Oxalic acid formation during ECF and TCF bleaching of kraft pulp1997Inngår i: Proceedings Minimum Effluent Mills Symposium, 1997, s. 63-66Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The formation of oxalic acid (I) during bleaching of softwood kraft pulp was studied.  Bleaching agents used were O, H2O2, ClO2, peracetic acid (II), and O3.  The formation of I acid increased linearly with the decrease in kappa no.  II bleaching gave less I than the other bleaching agents.  In O3 bleaching ∼1/3 of the formed I was adsorbed on the pulp and not released until a later stage.

  • 59. Engström, A. C.
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Improved accessibility and reactivity of dissolving pulp for the viscose process: Pretreatment with monocomponent endoglucanase2006Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, nr 6, s. 2027-2031Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A high accessibility is an essential prerequisite for a homogeneous substitution of cellulose material. In this study, chemical and enzymatic pretreatments to increase the accessibility of cellulose materials have been investigated. Dissolving pulp has been treated with a monocomponent endoglucanase. Fock's method, a microscale process similar to the viscose process, showed an increase in cellulose yield. Simultaneously, the viscosity decreased. To clarify whether the increase in reactivity was due solely to the decrease in the degree of polymerization, the dissolving pulp was also subjected to acid hydrolysis. At a given viscosity level, the enzymatic pretreated pulp had a higher reactivity than the pulp subjected to acid hydrolysis. To achieve 100% reactivity, according to Fock, the acid-treated pulp showed a lower molecular weight compared to the enzymatic-treated pulp. A monocomponent endoglucanase can thus be used to increase the reactivity and accessibility of dissolving pulp in the viscose process.

  • 60.
    Feng, Nianjie
    et al.
    Hubei Univ Technol, Wuhan 430068, Hubei, Peoples R China.;Nanjing Forestry Univ, Nanjing 210037, Jiangsu, Peoples R China..
    Guo, Lifang
    Nanjing Forestry Univ, Nanjing 210037, Jiangsu, Peoples R China..
    Ren, Hao
    Nanjing Forestry Univ, Nanjing 210037, Jiangsu, Peoples R China..
    Xie, Yimin
    Hubei Univ Technol, Wuhan 430068, Hubei, Peoples R China..
    Jiang, Zhihua
    Auburn Univ, Alabama Ctr Paper & Bioresource Engn, Auburn, AL 36849 USA..
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Zhai, Huamin
    Nanjing Forestry Univ, Nanjing 210037, Jiangsu, Peoples R China..
    Changes in chemical structures of wheat straw auto-hydrolysis lignin by 3-hydroxyanthranilic acid as a laccase mediator2019Inngår i: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 122, s. 210-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    3-Hydroxyanthranilic acid (3-HAA), as a potential natural laccase mediator, was shown to mediate the oxidation of non-phenolic lignin subunits. The problem of cost and toxicity of artificial mediators could be solved to some extent by a further study about the detailed changes of lignin chemistry structures in laccase 3-HAA system (LHS). In this work, wheat straw auto-hydrolysis lignin (AL) was prepared. Oxidations of AL by LHS and laccase 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) system were then investigated, respectively. Various structural changes of AL during the oxidation were characterized by different methods including phenolic hydroxyl group determination, nitrobenzene oxidation, ozonation, gel permeation chromatography, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy. The changes in AL chemical structures were found in LHS, including unit removal, bond cleavage and biopolymerization. Compared to laccase ABTS system, a selective removal of guaiacyl-type lignin in LHS was observed, based on the results of nitrobenzene oxidation and 2D NMR analysis. The selective removal of guaiacyl-type lignin was due to improved aromatic ring cleavage and weaken lignin biopolymerization. The selectivity of guaiacyl-type lignin removal in LHS plays an important role, especially for improving bioconversion efficiency of laccase for guaiacyl-rich lignocellulosic biomass.

  • 61. Feng, Nianjie
    et al.
    Ma, Qingzhi
    Yuan, Meiting
    Zhai, Huamin
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Improving Degradation Ability Toward Wheat Straw Chemical Composition by Co-Cultivation of Pycnoporus sanguineus with Candida tropicalis2015Inngår i: Journal of Biobased Materials and Bioenergy, ISSN 1556-6560, E-ISSN 1556-6579, Vol. 9, nr 6, s. 567-571Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is important for lignocellulosic bioconversion of wheat straw to be intensified by co-cultivation of Pycnoporus sanguineus with Candida tropicalis. The biodegradation properties, involving the enzymes composition and their activities, fibrous tissue morphologies, and chemical composition of co-cultivation, were studied. The co-cultivation obviously improved enzymes composition and enhanced carboxymethyl cellulase, xylanase and laccase activities. The co-cultivation increased the porosity of fibrous tissue in wheat straw. The co-cultivation is presented an advantageous performance in the aspects of lignin and carbohydrate degradation than the cultivation of P. sanguineus alone. The degradation process of the chemical composition in wheat straw by the co-cultivation can be divided into the first rapid phase and the following slow degradation one. The co-cultivation of P sanguineus with C. tropicalis increased the delignification by 15.2% in the rapid phase and the carbohydrate degradation ratio by 61.5% in the slow phase. The above intensifying degradation ability were resulted from the combination improvement of enzymes composition, their activities and fibrous tissue morphologies.

  • 62. Flink, Johannes
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The effects of lignin structure from treatment of pulp with activated 1-hydroxybenzotrazole.1997Inngår i: Proceedings 9th Int. Symp. Wood Pulp Chem., 1997Konferansepaper (Fagfellevurdert)
  • 63.
    Garcia-Garcia, Daniel
    et al.
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Balart, Rafael
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Lopez-Martinez, Juan
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Moriana, Rosana
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time2018Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 5, s. 2925-2938Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNCs) were isolated for the first time from pine cones (PC) by alkali and bleaching treatments and subsequent sulfuric acid hydrolysis (64%) at 45 degrees C. The influence of the hydrolytic reaction time (30, 45, and 90 min) on the yield, chemical composition and structure, and thermal stability of CNCs was evaluated. The removal of non-cellulosic constituents during the alkaline and bleaching treatment resulted in high pure cellulosic fibres. The isolation of CNCs from these cellulosic fibres at different reaction times was verified by the nano-dimensions of the individual crystals (< 3 and < 335 nm of average diameter and length, respectively). The highest yield (15%) and the optimum CNCs properties in terms of aspect ratio, thermal stability and crystallinity were obtained for an extraction time of 45 min. PC appeared to be a new promising source of cellulose fibres and CNCs with potential to be applied as reinforcement in composites and for food-packaging.

  • 64.
    Gellerstedt, Göran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, MonicaKTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.Henriksson, GunnarKTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wood Chemistry and Wood Biotechnology2009Collection/Antologi (Fagfellevurdert)
    Abstract [en]

    The production of forestry products is based on a complex chain of knowledge in which the biological material wood with all its natural variability is converted into a variety of fiber-based products, each one with its detailed and specific quality requirements. This four volume set covers the entire spectrum of pulp and paper chemistry and technology from starting material to processes and products including market demands. Supported by a grant from the Ljungberg Foundation, the Editors at the Royal Institute of Technology, Stockholm, Sweden coordinated over 30 authors from university and industry to create this comprehensive overview. This work is essential for all students of wood science and a useful reference for those working in the pulp and paper industry or on the chemistry of renewable resources.

  • 65. Gil-Castell, O.
    et al.
    Badia, J. D.
    Kittikorn, Thorsak
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Prince of Songkla University, Thailand.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Skövde University, Sweden.
    Ribes-Greus, A.
    Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites2016Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 °C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 °C, since it represents the extreme degrading condition. The morphology and crystallinity of the biocomposites were evaluated by means of X-Ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The viscoelastic and thermal performance were assessed by means of dynamic mechanic thermal analysis (DMTA) and thermogravimetry (TGA). The presence of sisal generally diminished the thermal stability of the biocomposites, which was mitigated by the addition of the coupling agent. After composite preparation, the effectiveness of the sisal fibre was improved by the crystallisation of PLA around sisal, which increased the storage modulus and reduced the dampening factor. The presence of the coupling agent strengthened this effect. After hydrothermal ageing, crystallisation was promoted in all biocomposites therefore showing more fragile behaviour evidencing pores and cracks. However, the addition of coupling agent in the formulation of biocomposites contributed in all cases to minimise the effects of hydrothermal ageing.

  • 66. Gil-Castell, O.
    et al.
    Badia, J. D.
    Kittikorn, Thorsak
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. Prince of Songkla University Songkhla, Thailand.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Martinez-Felipe, A.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. University of Skövde, Sweden.
    Ribes-Greus, A.
    Hydrothermal ageing of polylactide/sisal biocomposites. Studies of water absorption behaviour and Physico-Chemical performance2014Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, s. 212-222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a faster formation of crystalline domains in the PIA matrix occurred the higher the amount of fibre was, which acted as a nucleating agent. Higher crystallinity was considered as a barrier against the advance of penetrant and a reduction in the diffusion coefficient was shown. The addition of coupling agent presented a different influence depending on the composition, showing an inflection point around 20% of sisal fibre.

  • 67.
    Guo, Lifang
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lennholm, Helena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Zhai, H.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Structural and functional modification of cellulose nanofibrils using graft copolymerization with glycidyl methacrylate by Fe 2+ –thiourea dioxide–H 2 O 2 redox system2019Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, nr 8, s. 4853-4864Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: To graft epoxy and ester functional groups onto cellulose nanofibrils (CNFs) and to overcome their poor hydrophobicity, we studied the modification of CNFs using graft copolymerization with glycidyl methacrylate (GMA) by a Fe 2+ –thiourea dioxide–H 2 O 2 initiator system (Fe 2+ –TD–H 2 O 2 ) in aqueous solution. The synthesized poly (GMA)-grafted CNF (CNF-g-PGMA) was characterized by FTIR, AFM, XRD, water contact angle, and TGA. GMA was successfully grafted onto the CNFs by Fe 2+ –TD–H 2 O 2 , the epoxy groups and ester groups of GMA were clearly present and intact in the CNF-g-PGMA, and TD is an important component of the initiator system under relatively mild graft conditions. CNF-g-PGMA may be an important intermediate because of its epoxy and ester functional groups. The main nanostructure of the CNFs was retained after graft copolymerization, and there were no obvious effects of graft copolymerization on the crystalline structure of the CNF backbone, although the crystalline index slightly decreased with the increased percentage of grafting. Graft copolymerization significantly modifies the CNF hydrophobicity. This strategy could extend the applications of CNFs into many areas. Graphical abstract: [Figure not available: see fulltext.]

  • 68.
    Gustafsson, Roland
    et al.
    KTH, Tidigare Institutioner, Pappers- och massateknik.
    Ek, Monica
    KTH, Tidigare Institutioner, Pappers- och massateknik.
    Teder, Ants
    KTH, Tidigare Institutioner, Pappers- och massateknik.
    Polysulphide pretreatment of softwood for increased delignification and higher pulp viscosity2004Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 30, nr 5, s. 129-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of polysulphide pretreatment under various conditions prior to a kraft cook was investigated for spruce (Picea abies) chips using a technique with a liquor:wood ratio of 67:1 to keep the liquor composition as constant as possible during the pretreatment and cooking phases. If the polysulphidepretreatment is carried out at a very high hydroxide concentration, 1.5 mol OH-/L, three independent positive effects (compared with a corresponding sulphide pretreatment without polysulphide) can be observed: more extensive delignification; higher pulp, viscosity; and higher carbohydrate yield. When the alkali change was changed in the subsequent kraft cook (in the range 0.15-0.60 mol/L), the increase in delignification extent as a result of polysulphide pretreatment was not affected but the relative carbohydrate yield increase was favoured by a higher alkali charge during cooking. On the other hand, the absolute carbohydrate yield is favoured by a intermediate alkali charge.

  • 69.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Larsson, Per A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Contact-active antibacterial aerogels from cellulose nanofibrils2016Inngår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 146, s. 415-422Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of cellulose aerogels as antibacterial materials has been investigated by applying a contact-active layer-by-layer modification to the aerogel surface. Studying the adsorption of multilayers of polyvinylamine (PVAm) and polyacrylic acid to aerogels comprising crosslinked cellulose nanofibrils and monitoring the subsequent bacterial adhesion revealed that up to 26 mg PVAm g aerogel−1 was adsorbed without noticeably affecting the aerogel structure. The antibacterial effect was tested by measuring the reduction of viable bacteria in solution when the aerogels were present. The results show that >99.9% of the bacteria adhered to the surface of the aerogels. Microscopy further showed adherence of bacteria to the surfaces of the modified aerogels. These results indicate that it is possible to create materials with three-dimensional cellulose structures that adsorb bacteria with very high efficiency utilizing the high specific surface area of the aerogels in combination with their open structure.

  • 70.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Larsson, Per
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Antibacterial aerogels from cellulose nanofibrils2016Inngår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Artikkel i tidsskrift (Annet vitenskapelig)
  • 71.
    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 materials2015Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 249Artikkel i tidsskrift (Annet vitenskapelig)
  • 72.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Larsson, Per A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Bacterial adhesion to polyvinyl-amine-modified nanocellulose filmsManuskript (preprint) (Annet vitenskapelig)
  • 73.
    Henschen, Jonatan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Larsson, Per A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Bacterial adhesion to polyvinylamine-modified nanocellulose films2017Inngår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 151, s. 224-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibril (CNF) materials have been widely studied in recent years and are suggested for a wide range of applications, e.g., medical and hygiene products. One property not very well studied is the interaction between bacteria and these materials and how this can be controlled. The current work studies how bacteria adhere to different CNF materials modified with polyelectrolyte multilayers. The tested materials were TEMPO-oxidized to have different surface charges, periodate-oxidized to vary the water interaction and hot-pressed to alter the surface structure. Then, multilayers were constructed using polyvinylamine (PVAm) and polyacrylic acid. Both the material surface charge and water interaction affect the amount of polymer adsorbed to the surfaces. Increasing the surface charge decreases the adsorption after the first PVAm layer, possibly due to conformational changes. Periodate-oxidized and crosslinked films have low initial polymer adsorptions; the decreased swelling prevents polymer diffusion into the CNF micropore structure. Microscopic analysis after incubating the samples with bacterial suspensions show that only the materials with the lowest surface charge enable bacteria to adhere to the surface because, when adsorbing up to 5 layers PVAm/PAA, the increased anionic surface charge appears to decrease the net surface charge. Both the amounts of PVAm and PAA influence the net surface charge and thus the bacterial adhesion. The structure generated by the hot-pressing of the films also strongly increases the number of bacteria adhering to the surfaces. These results indicate that the bacterial adhesion to CNF materials can be tailored using polyelectrolyte multilayers on different CNF substrates.

  • 74.
    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 oxalates2019Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 213, s. 208-216Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 75. Hermosilla, Viviana
    et al.
    Ibarra, David
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    On the accessibility and reactivity of different kraft pulps used for cellulose derivatives2007Konferansepaper (Fagfellevurdert)
  • 76. Hermosilla, Viviana
    et al.
    Nanko, Hiroushi
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Influence of Mechanical and Enzymatic Treatment on Cellulose Accessibility2007Konferansepaper (Fagfellevurdert)
  • 77.
    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 cellulose2019Inngår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikkel i tidsskrift (Annet vitenskapelig)
  • 78.
    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 cellulose2019Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, nr 1, s. 665-677Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 79.
    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 copolymer2018Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 3, s. 2115-2128Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 80.
    Ibarra, David
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Kopcke, Viviana
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Influence of a novel laboratory endoglucanase on the reactivity and accessibility of dissolving pulp2008Inngår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 2008Konferansepaper (Fagfellevurdert)
    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. cellulose derivs. which have many important applications in the fiber, paper, membrane, polymer, and paints industries.  A raw material with high cellulose content is required for the prodn. of cellulose derivs., e.g. cotton and dissolving pulp are used.  Cellulose forms a network structure of fibrils and fibrilar aggregations.  Intermol. hydrogen bonds, dipole interactions, and van der Waals interactions bind the cellulose mols. intensively together.  The accessibility and reactivity of the cellulose in wood pulps to solvents and reactive agents is usually limited.  In this respect, different types of pre-treatments have been assayed to increase the reactivity of cellulose, among them the use of enzymes such as monocomponent cellulases and cellulase mixt.  In this work, was investigated the influence of a novel lab. enzyme, from Paenibacillus sp. Strain BP-23, on a com. dissolving pulp from Eucalyptus globulus, in terms of enzyme dosage and incubation time.  Evaluation of these parameters in terms of accessibility and reactivity, according to Fockxs method, were investigated.  Structural characterization and mol. wt. distribution were carried out using 13C-CP/MAS NMR (Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonanse) and SEC (Size Exclusion Chromatog.), resp.

  • 81.
    Ibarra, David
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Köpcke, Viviana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Behavior of different monocomponent endoglucanases on the accessibility and reactivity of dissolving-grade pulps for viscose process2010Inngår i: Enzyme and microbial technology, ISSN 0141-0229, E-ISSN 1879-0909, Vol. 47, s. 355-362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three different commercial monocomponent endoglucanases, with and without a cellulose-binding domain (CBD) and differences in their glycosidic hydrolysis mechanisms, were compared with respect to their ability to enhance the accessibility and reactivity of dissolving-grade pulps for viscose production. Hardwood (eucalyptus) and softwood (mixture of Norway spruce and Scots pine) commercial dried and never-dried bleached sulfite dissolving pulps were used for this purpose. The effects of the enzymatic treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, and recording of molecular weight distributions. Among the different assayed enzymes, endoglucanase with a CBD and an inverting hydrolysis mechanism was found to be the most effective in increasing the reactivity of both pulps. Simultaneously, the viscosity decreased, being more marked for softwood dissolving pulp. A narrower molecular weight distribution, with a great reduction in the amount of long-chain cellulose molecules was observed in both pulps, being more pronounced for softwood dissolving pulp. By contrast, endoglucanase without a CBD and a retaining hydrolysis mechanism showed a barley enhancement of the studied properties. The effects of the different endoglucanase treatments were more pronounced when never-dried dissolving pulps were used.

  • 82.
    Ibarra, David
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Köpcke, Viviana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps2009Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, nr 6, s. 721-730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The feasibility of producing dissolving grade pulps for viscose production from different fiber raw materials, such as paper grade pulps from wood and non-woody plants, was investigated. Commercial dried bleached hardwood kraft pulps from eucalypt, and bleached non-wood soda/AQ pulps from flax, hemp, sisal, abaca, and jute, were subjected to enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of cellulose and to reduce their hemicellulose content. A commercial monocomponent endoglucanase and a commercial xylanase were employed for biochemical treatment. The chemical treatment consisted of cold alkaline extraction. The effects of these pre-treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, determination of hemicellulose content, and recording of molecular weight distributions. The results were compared to those of commercial bleached eucalypt dissolving pulp. Eucalypt and sisal pulps showed high improvement in reactivity, reaching levels near or even higher than that of the eucalypt dissolving pulp (65%-70%), and a low hemicellulose content (2%-4%), when both were submitted to a sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction, and a final endoglucanase treatment. However, the viscosity decreased considerably. A uniform and narrow molecular weight distribution was observed in both eucalypt and sisal pulps after this sequential pre-treatment.

  • 83. Ibarra, David
    et al.
    Köpcke, Viviana
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Influence of a monocomponent endoglucanase on different fibre raw materials: Study of accessability and reactivity.2008Inngår i: 10th EWLP: European Workshop on Lignocellulosics and Pulp, 2008, s. 48-51Konferansepaper (Fagfellevurdert)
  • 84. 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 reactivity2008Konferansepaper (Fagfellevurdert)
  • 85.
    Ibarra, David
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Köpcke, Viviana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp2010Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, nr 19, s. 7416-7423Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 86.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Biointeractive fibres with antibacterial properties: a multilayer build-up study2008Konferansepaper (Fagfellevurdert)
  • 87.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Enarsson, Lars-Erik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Interactions of Hydrophobically Modified Polyvinylamines: Adsorption Behavior at Charged Surfaces and the Formation of Polyelectrolyte Multilayers with Polyacrylic Acid2010Inngår i: ACS Applied Materials & Interfaces, ISSN 1944-8244, Vol. 2, nr 2, s. 425-433Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure and adsorption behaviors of two types of hydrophobically modified polyvinylamines (PVAm) containing substituents of hexyl and octyl chains were compared to a native polyvinylamine sample. The conformation of dissolved polyvinylamines was studied in aqueous salt solutions using dynamic light scattering. Modified PVAm showed hydrodynamic diameters similar to native PVAm, which indicated that all PVAm polymers were present as single molecules in solution. The adsorption of the polyvinylamines, both native and hydrophobically modified, from aqueous solution onto negatively charged silica surfaces was studied in situ by reflectometry and quartz crystal microgravimetry with dissipation. Polyelectrolyte multilayers; (PEM) with up to nine individual layers were formed together with poly(acrylic acid). Obtained PEM structures were rigid and showed high adsorbed amounts combined with low dissipation, with similar results for both the modified and unmodified PVAm. This suggests that electrostatics dominated the PEM formation. At lower salt concentrations, the hydrophobically modified PVAm produced multilayers with low water contents, indicating that secondary interactions induced by the hydrophobic constituents can also have a significant influence on the properties of the formed layers. The surface structure of PEMs with nine individual layers was imaged in dry state using atomic force microscopy in a dynamic mode. Modified PVAm was found to induce a different structure of the PEM at 100 mM, with larger aggregates compared to those of native PVAm. From these results, it is proposed that modified PVAm can induce aggregation within the PEM, whereas PVAm remains as single molecules in solution.

  • 88.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Römling, Ute
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Antibacterial Polyelectrolyte Multilayers on Cellulosic Pulp FibresManuskript (preprint) (Annet vitenskapelig)
  • 89.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Römling, Ute
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Biointeractive antibacterial fibres using polyelectrolyte multilayer modification2012Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, nr 5, s. 1731-1741Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contact-active antibacterial surfaces are a novel tool in the antibacterial battle. The preparation of such surfaces usually involves harsh reaction conditions and organic solvents. A more sustainable alternative would involve physical adsorption of water-soluble polyelectrolytes using a renewable substrate. Here, highly charged cationic polyvinylamines (PVAm), with or without hydrophobic modifications, have been adsorbed onto the naturally anionic cellulosic wood-fibres. To increase the amount of PVAm, polyelectrolyte multilayers were prepared using polyacrylic acid as the anionic polyelectrolyte. The modified fibres were characterised for PVAm content, water retention and antibacterial properties. The use of multilayers increased the total polymer content without notably reducing the water swelling. The fibres were shown to have excellent bioactive properties and reduced waterborne Escherichia coli and Bacillus subtilis by more than 99.9 %, which is a generally accepted definition of an antibacterial material. A large reduction in bacterial growth was observed upon addition of nutrients, although minor growth was detected after 24 h. The results further show that one adsorbed polymer layer was sufficient to obtain a contact-active surface, which makes the PVAm multilayer system seemingly unique. No polymer leaching from any of the samples was detected, indicating that the fibres work via a contact-active antibacterial mechanism. The results show the feasibility of constructing a sustainable antibacterial material using a renewable substrate and water-based solutions in the material construction process.

  • 90.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Römling, Ute
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Tailoring the effect of antibacterial polyelectrolyte multilayers by choice of cellulosic fiber substrate2013Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, nr 5, s. 573-578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a need for new, antibacterial cellulose-based materials. Antibacterial cellulosic fibers with irreversibly attached polyvinylamine (PVAm) and polyacrylic acid (PAA) in multilayers were developed based on a water-based physical adsorption process. The antibacterial substance is thus prevented from leaching, in contrast to materials containing, for example, silver. It was shown on fibers from different sources that the antibacterial effect against both Escherichia coli and Bacillus subtilis can be tailored. The efficiency correlated with the initial fiber charge, which in turn correlated with the amount of adsorbed PVAm. In the case of highly charged fibers, the antibacterial efficacy was more than 99.9%. A sustainable antibacterial material can be obtained in a simple way based on a water-based process.

  • 91.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Römling, Ute
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The Antibacterial Effect of Contact-Active Multilayers: A Mechanistic ApproachManuskript (preprint) (Annet vitenskapelig)
  • 92.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Westman, Eva-Helena
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Making biointeractive fibres: Build-up of antibacterial multilayers studied by SPAR2008Konferansepaper (Fagfellevurdert)
  • 93.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Antibacterial Fibres2013Inngår i: Pulp Production and Processing: From Papermaking to High-Tech Products / [ed] Valentin Popa, smithers rapra , 2013, 1st, s. 413-438Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 94.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Bacterial-growth inhibiting properties of multilayers formed with modified polyvinylamine2011Inngår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 88, nr 1, s. 115-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New methods are needed to fight antibiotic-resistant bacteria. One alternative that has been proposed is non-leaching, permanently antibacterial surfaces. In this study, we test multilayers formed with antibacterial cationic polyvinylamine (PVAm) and polyacrylic acid (PAA) in a growth-inhibition assay. Both hydrophobically modified and native PVAm were investigated. Multilayers did reduce the bacterial growth, as compared to single layers. However, the sampling time in the assay was critical, as the treated surface area is a capacity-limiting factor. After 2 h incubation, a maximal growth inhibition of more than 99% was achieved with multilayers. In contrast, after 8 h we observed a maximal growth-inhibition of 40%. At longer incubation times, the surface becomes saturated, which explains the observed time-dependent effectiveness. The polymers giving multilayers with the strongest growth-inhibiting properties were native PVAm and PVAm modified with C(8), which also were the polymers with highest charge density. We therefore conclude that this effect is mainly an electrostatically driven process. Viability staining using a fluorescent stain showed a high viability rate of the adhered bacteria. The multilayers are therefore more bacteriostatic than antibacterial.

  • 95.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Biointeractive fibers: Antibacterial cellulose via polymer adsorption2011Konferansepaper (Fagfellevurdert)
  • 96.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Biointeractive fibres with antibacterial properties2010Konferansepaper (Fagfellevurdert)
  • 97.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Biointeractive fibres-antibacterial cellulose via polymer adsorption2011Inngår i: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC, 2011, s. 1378-1379Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The world is in desperate need of new methods for controlling microbial growth. Antibacterial surfaces, with antibacterial polymers irreversible attached, is a promising alternative. By targeting the bacterial membrane, the risk of evolving resistant bacteria is reduced. The attachment of the polymers prevents unwanted leaching and keeps a high, active surface concentration. The making of such surfaces does however involve harsh reaction conditions and is thus unsuitable for use in large scale. Using the polyelectrolyte multilayer (PEM) technique we here electrostatically adsorb cationic antibacterial polymers. This takes place in aqueous solutions and in room temperature, making it an appealing alternative. Previous studies performed in our group have focused on model surfaces to get fundamental knowledge about the multilayer properties. Here the PEMs are applied on cellulosic pulp and tested for antibacterial properties against E. coli and B. subtilis. The obtained material was found to be antibacterial against both bacterial strains. These antibacterial fibers, produced in a safe, sustainable process, will give opportunities for new products and new applications.

  • 98.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Contact-active antibacterial multilayers on fibres: a step towards understanding the antibacterial mechanism by increasing the fibre charge2015Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 3, s. 2023-2034Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contact-active antibacterial materials with irreversibly attached antibacterial agents have been developed as an environmentally friendly alternative to traditional biocide treatments. Of particular interest are materials fabricated through the physical adsorption of charged polymers. This simple method allows for the use of water-based processes and materials originating from renewable sources, e.g., cellulosic fibres. Furthermore, by varying the process parameters, such as ionic strength, it is possible to tune the properties of the adsorbed polymer layer. However, the underlying antibacterial mechanism remains obscure, and this hinders the rational design of antibacterial multilayers. To gain further insight into the antibacterial mechanisms of physically adsorbed multilayers of polyvinylamine and polyacrylic acid, the surface charge of cellulose fibres was increased via radical oxidation. This oxidation increased the amount of polymer that was adsorbed and resulted in increased antibacterial efficacy against both Escherichia coli and Bacillus subtilis compared with polymer-modified unoxidised fibres. Electron microscopy analysis of the E. coli adhered to the fibres revealed that the multilayer treatment resulted in elongated bacteria with deformed cell walls. This work demonstrates the importance of electrostatic interaction to the antibacterial effect of polymer-modified fibres.

  • 99.
    Illergård, Josefin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Contact-active antibacterial polyelectrolyte multilayers: The influence of substrate2013Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245, s. 515-PMSE-Artikkel i tidsskrift (Annet vitenskapelig)
  • 100. Iversen, Tommy
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Inorganic and organometallic polymers II: advanced materials and intermediates1993Konferansepaper (Fagfellevurdert)
1234 51 - 100 of 182
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