Björn Olander

KTH Royal Institute of Technology, Tukholma, Stockholm, Sweden

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Publications (6)16.26 Total impact

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    ABSTRACT: Silicone elastomers were surface modified by oxygen microwave plasma under different conditions and the elemental composition was followed by X-ray photoelectron spectroscopy (XPS). The changes in elemental composition were mapped by a method based on ternary XPS diagrams that we have recently developed. Already at the shortest treatment times, 5 s, the change in surface composition is more than one-half the maximum change obtained on prolonged exposure. After this initial change, the surface gradually oxidizes toward the final composition. Curve resolutions of C1s and Si2p XPS data showed that the initial jump in surface composition is caused by an oxidation of silicon where one of the two methyl groups are replaced by an oxygen. The second methyl group appears to be more difficult to remove, but as the treatment progresses, the number of oxygen bonded to silicon gradually increases. The dominating form of carbon acts as unoxidized methyl groups throughout the process, but the total carbon percentage decreases as the treatment progresses. This indicates either that the methyl groups are removed without prior oxidation or that the methyl groups are removed shortly after oxidation. A silica-like surface layer was formed on prolonged plasma treatment under all the investigated conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4098–4104, 2004
    Journal of Applied Polymer Science 01/2004; 91(6):4098 - 4104. · 1.40 Impact Factor
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    ABSTRACT: Plasma treatment of poly(dimethyl siloxane) (PDMS) leads to changes in the surface composition that can be followed by X-ray photoelectron spectroscopy (XPS). Prolonged plasma treatment in argon or hydrogen leads to an increase in oxygen, a decrease in carbon, and only minor changes in the silicon content. The extent of the change in elemental composition is dependent on the plasma conditions (e.g., the power and pressure during the treatment). We have determined how these parameters influence the surface composition of PDMS exposed to argon and hydrogen microwave plasma as a function of treatment time. A model has been developed describing the extent of change in surface composition under different plasma conditions. The power had a large impact on the rate of change in elemental surface composition, whereas the pressure had only a minor influence. We show that the rate of change in elemental composition can be described by one factor common for all treatments and one factor specific for each plasma condition of power, pressure, and gas. Using this model we can determine the plasma parameters and treatment time to obtain any desired extent of surface modification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1378–1383, 2003
    Journal of Applied Polymer Science 08/2003; 90(5):1378 - 1383. · 1.40 Impact Factor
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    ABSTRACT: Primary amines covalently bonded to the surface of poly(dimethylsiloxane) were obtained by hydrosilylation grafting of aminopropyl vinyl ether to Si-H groups formed during argon plasma treatment. The amine groups were derivatized using pentafluorobenzaldehyde and characterized by X-ray photoelectron spectroscopy. The graft yield was about 3% grafted molecules within the depth of the analysis. The terminal aldehyde groups of diazotized heparin was also coupled to the primary amines. This led to a silicone elastomer with covalently bonded heparin which was expected to be hydrolytically stable. This method of bonding primary amines to the surface of silicone elastomers and the subsequent coupling of aldehyde-containing molecules is a promising way of obtaining novel biomaterials.
    Biomacromolecules 01/2003; 4(1):145-8. · 5.37 Impact Factor
  • Björn Olander, Ann‐Christine Albertsson
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    ABSTRACT: The use of a ternary XPS diagram to follow surface modification processes involving three elements is described. The elemental composition is represented by a single data point on a plane instead of by two or three elemental ratios or percentages. Vectors are defined between the data points, and simple vector algebra is used to interpret the results. The extent of the surface change is determined by calculating the length of the vector from untreated to a treated composition point, and this leads to a value for the overall change in elemental composition. The direction of the vector indicates how the changes in the individual elemental percentages are related to each other, i.e. what elemental composition the surface is approaching. The ternary XPS diagram is demonstrated and compared with elemental percentages and ratios using XPS data from hydrogen microwave plasma-treated polydimethylsiloxane. Copyright © 2002 John Wiley & Sons, Ltd.
    Surface and Interface Analysis 07/2002; 33(7). · 1.39 Impact Factor
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    ABSTRACT: A method of grafting well-defined and hydrolytically stable surface structures onto cross-linked poly(dimethylsiloxane) (PDMS) has been developed. In the first step, argon microwave plasma was used to introduce Si-H groups onto the surface. In the second step, allyltetrafluoroethyl ether was grafted to these Si-H groups using a platinum-catalyzed hydrosilylation reaction. The influences of the plasma parameters of power, pressure, and treatment time on the surface composition, both before and after the hydrosilylation step, were investigated by X-ray photoelectron spectroscopy and contact angle measurements. It was found that the pressure had little influence on the results, whereas the power and treatment time determined the rate of change in surface composition during the plasma treatment. The graft yield reached a plateau value corresponding to about 5% grafted molecules in the analyzed surface region. Hydrosilylation grafting of PDMS is a promising method to obtain biomaterials with hydrolytically stable structures covalently bound to the surface.
    Biomacromolecules 01/2002; 3(3):505-10. · 5.37 Impact Factor
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    ABSTRACT: Chitosan and chitosan hydrogel were immobilized on both the inside and outside surfaces of high density polyethylene (HDPE) tubes with 2.5×4 mm diameters. First, acrylic acid was grafted on the surfaces of HDPE by electron beam (2.5 Mrad) preirradiation method. Then chitosan/HCl and chitosan/lactic acid solutions were coated on the modified hydrophilic HDPE surfaces, the latter could form a pH-sensitive hydrogel layer on the surfaces. The tube surfaces were further modified with heparin by surface interpenetrating method to improve blood compatibility. ATR-FTIR and ESCA methods were used to characterize the coated surfaces. The morphology changes were monitored by Scanning Electron Microscope (SEM).
    Polymer Bulletin 01/2001; 46(2):223-229. · 1.33 Impact Factor