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  • 1.
    Adolfsson, Karin H.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Xie, L.
    Hassanzadeh, Salman
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Zero-Dimensional and Highly Oxygenated Graphene Oxide for Multifunctional Poly(lactic acid) Bionanocomposites2016In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 4, no 10, p. 5618-5631Article in journal (Refereed)
    Abstract [en]

    The unique strengths of 2D graphene oxide nanosheets (GONSs) in polymer composites are thwarted by nanosheet agglomeration due to strong intersheet attractions. Here, we reveal that shrinking the planar size to 0D graphene oxide quantum dots (GOQDs), together with the intercalation of rich oxygen functional groups, reduces filler aggregation and enhances interfacial interactions with the host polymer. With poly(lactic acid) (PLA) as a model matrix, atomic force microscopy colloidal probe measurements illustrated that a triple increase in adhesion force to PLA was achieved for GOQDs (234.8 nN) compared to GONSs (80.4 nN), accounting for the excellent exfoliation and dispersion of GOQDs in PLA, in contrast to the notable agglomeration of GONSs. Although present at trace amount (0.05 wt %), GOQDs made a significant contribution to nucleation activity, mechanical strength and ductility, and gas barrier properties of PLA, which contrasted the inferior efficacy of GONSs, accompanied by clear distinction in film transparency (91% and 50%, respectively). Moreover, the GOQDs with higher hydrophilicity accelerated the degradation of PLA by enhancing water erosion, while the GONSs with large sheet surfaces gave a higher hydrolytic resistance. Our findings provide conceptual insights into the importance of the dimensionality and surface chemistry of GO nanostructures in the promising field of bionanocomposites integrating high strength and multifunction (e.g., enhanced transparency, degradation and gas barrier).

  • 2.
    Ankerfors, Caroline
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lars, Wågberg
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Use of PECs and PEMs from polymers and nanoparticles to create sacrificial bonds between surfacesManuscript (preprint) (Other academic)
  • 3.
    Ankerfors, Caroline
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Use of polyelectrolyte complexes and multilayers from polymers and nanoparticles to create sacrificial bonds between surfaces2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 391, p. 28-35Article in journal (Refereed)
    Abstract [en]

    In this study, particle polyelectrolyte complexes (PPECs) were formed by mixing cationic polyacrylamide (CPAM) and silica nanoparticles using the jet mixing technique. Within certain limits, the size of the formed PPECs could be controlled. The aim was to prepare PPECs with embedded sacrificial bonds, similar to those found in bones. Examination of PPEC adsorption to silica model surfaces indicated that,smaller PPECs adsorbed to a higher level than larger ones, due to the higher diffusion speed of smaller complexes. Adsorption studies of the same components as in the PPECs, but arranged in multilayers, that is, particle polyelectrolyte multilayers (PPEMs), indicated a stable, gradual build-up of material on the surface with smaller nanoparticles, whereas PPEMs comprising elongated nanoparticles appeared to be more loosely adsorbed onto the surface when the nanoparticles were in the outer layer, due to repulsive forces within the adsorbed layer. The AFM colloidal probe technique was used to study the interaction between surfaces treated with PPECs, multilayers, or polyelectrolyte complexes (PECs). The results showed that the expected long-range disentanglement could be achieved with PPECs but that the pull-off forces were generally low. Treatment with PPEMs comprising the same polymer and nanoparticle components produced higher pull-off values, together with disentanglement behaviour, possibly due to better contact between the surfaces. Adhesion experiments with polymer PECs showed significantly higher pull-off values than with the PPECs, probably due to polymer interdiffusion across the surface boundary.

  • 4.
    Ankerfors, Caroline
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    AFM adhesion imaging for comparison of polyelectrolyte complexes and polyelectrolyte multilayers2012Article in journal (Other academic)
  • 5.
    Ankerfors, Caroline
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    AFM adhesion imaging for the comparison of polyelectrolyte complexes and polyelectrolyte multilayers2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 32, p. 8298-8301Article in journal (Refereed)
    Abstract [en]

    The adhesion and topography of dry surfaces treated with polyelectrolyte complexes (PECs) and multilayers (PEMs) of PAH/PAA or CPAM/silica nanoparticles were studied using AFM adhesion mapping. PEMs gave higher adhesion than did PECs for the PAH/PAA system, but adhesion did not differ significantly between PEMs and PECs for the CPAM/silica system. The latter system displayed multiple release patterns, interpreted as disentanglements and tentatively ascribed to nanoparticle presence. AFM adhesion mapping is valuable for analysing PEC and PEM. The measurements should, however, be combined with separate force measurements for a more complete picture of the adhesion.

  • 6. Attard, Phil
    et al.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). Ytkemiska Institutet, Sweden.
    Thermal calibration of photodiode sensitivity for atomic force microscopy2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 11Article in journal (Refereed)
    Abstract [en]

    The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.

  • 7.
    Banerjee, Indradumna
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Salih, Tagrid
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Ramachandraiah, Harisha
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Erlandsson, Johan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, Superseded Departments (pre-2005), Chemistry.
    Araújo, A. C.
    Karlsson, M.
    Russom, Aman
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Slipdisc: A versatile sample preparation platform for point of care diagnostics2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 56, p. 35048-35054Article in journal (Refereed)
    Abstract [en]

    We report a microfluidic sample preparation platform called "Slipdisc" based on slipchip technology. Slipdisc is a rotational slipchip that uses a unique hand-wound clockwork mechanism for precise movement of specially fabricated polycarbonate discs. In operation, the microchannels and microchambers carved on the closely aligned microfluidic discs convert from continuous filled paths to defined compartments using the slip movement. The clockwork mechanism introduced here is characterised by a food dye experiment and a conventional HRP TMB reaction before measuring lactate dehydrogenase (LDH) enzyme levels, which is a crucial biomarker for neonatal diagnostics. The colorimetry based detection of LDH was performed with an unmodified camera and an image analysis procedure based on normalising images and observing changes in red channel intensity. The analysis showed a close to unity coefficient of determination (R2 = 0.96) in detecting the LDH concentration when compared with a standard Chemical Analyser, demonstrating the excellent performance of the slipdisc platform with colorimetric detection. The versatile point of care sample preparation platform should ideally be suited for a multitude of applications at resource-limited settings.

  • 8.
    Benselfelt, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Influence of Surface Charge Density and Morphology on the Formation of Polyelectrolyte Multilayers on Smooth Charged Cellulose Surfaces2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 4, p. 968-979Article in journal (Refereed)
    Abstract [en]

    To clarify the importance of the surface charge for the formation of polyelectrolyte multilayers, layer-by-layer (LbL) assemblies of polydiallyldimethylammonium chloride (pDADMAC) and polystyrenesulfonate (PSS) have been investigated on cellulose films with different carboxylic acid contents (20, 350, 870, and 1200 μmol/g) regenerated from oxidized cellulose. The wet cellulose films were thoroughly characterized prior to multilayer deposition using quantitative nanomechanical mapping (QNM), which showed that the mechanical properties were greatly affected by the degree of oxidation of the cellulose. Atomic force microscopy (AFM) force measurements were used to determine the surface potential of the cellulose films by fitting the force data to the DLVO theory. With the exception of the 1200 μmol/g film, the force measurements showed a second-order polynomial increase in surface potential with increasing degree of oxidation. The low surface potential for the 1200 μmol/g film was attributed to the low degree of regeneration of the cellulose film in aqueous media due to increasing solubility with increasing charge. The multilayer formation was characterized using a quartz crystal microbalance with dissipation (QCM-D) and stagnation-point adsorption reflectometry (SPAR). Extensive deswelling was observed for the charged films when pDADMAC was adsorbed due to the reduced osmotic pressure when ions inside the film were released, and the 1:1 charge compensation showed that all the charges in the films were reached by the pDADMAC. The multilayer formation was not significantly affected by the charge density above 350 μmol/g due to interlayer repulsions, but it was strongly affected by the salt concentration during the layer build-up.

  • 9.
    Benyahia Erdal, Nejla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Adolfsson, Karin H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Green Strategy to Reduced Nanographene Oxide through Microwave Assisted Transformation of Cellulose2018In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 6, no 1, p. 1245-1255Article in journal (Refereed)
    Abstract [en]

    A green strategy for fabrication of biobased reduced nanographene oxide (r-nGO) was developed. Cellulose derived nanographene oxide (nGO) type carbon nanodots were reduced by microwave assisted hydrothermal treatment with superheated water alone or in the presence of caffeic acid (CA), a green reducing agent. The carbon nanodots, r-nGO and r-nGO-CA, obtained through the two different reaction routes without or with the added reducing agent, were characterized by multiple analytical techniques including FTIR, XPS, Raman, XRD, TGA, TEM, AFM, UV-vis, and DLS to confirm and evaluate the efficiency of the reduction reactions. A significant decrease in oxygen content accompanied by increased number of sp2 hybridized functional groups was confirmed in both cases. The synergistic effect of superheated water and reducing agent resulted in the highest C/O ratio and thermal stability, which also supported a more efficient reduction. Interesting optical properties were detected by fluorescence spectroscopy where nGO, r-nGO, and r-nGO-CA all displayed excitation dependent fluorescence behavior. r-nGO-CA and its precursor nGO were evaluated toward osteoblastic cells MG-63 and exhibited nontoxic behavior up to 200 μg mL-1, which gives promise for utilization in biomedical applications.

  • 10.
    Bruce, Carl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Javakhishvili, Irakli
    Technical University of Denmark.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Fogelström, Linda
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Hvilsted, Søren
    Technical University of Denmark.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Preparation and evaluation of well-defined di- and triblock copolymers based on poly[2-(dimethylamino)ethyl methacrylate] and poly(ε-caprolactone)2014In: ACS National Meeting, 2014Conference paper (Refereed)
    Abstract [en]

    In this work, di- and triblock copolymers based on poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(ε-caprolactone) (PCL) have been prepared. The PDMAEMA length was kept constant for both di- and triblock copolymers, while in the diblock copolymers the PCL length was varied in three different lengths, yielding three separate block copolymers. For the triblock blockcopolymers, on the other hand, also the PCL blocks were of the same length yielding one ABA- and one BAB-type block copolymer. In the next step, the PDMAEMA-part was quaternized to yield polyelectrolytes with either one or two charged block(s). In the final step, difference in adsorption behavior onto a negatively charged cellulose surface and subsequent alteration of surface properties was investigated. Overall, the polymers were evaluated in solid state, in solution, in water dispersion, and on cellulose surfaces with techniques including differential scanning calorimetry, size exclusion chromatography, dynamic light scattering and quartz crystal microbalance.

  • 11.
    Bruce, Carl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Fogelström, Linda
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Physical Tuning of Cellulose-Polymer Interactions Utilizing Cationic Block Copolymers Based on PCL and Quaternized PDMAEMA2013Conference paper (Refereed)
    Abstract [en]

    In this study, the aim was to prepare and evaluate a block copolymer that can be used as a compatibilizer in cellulose fiber-reinforced biocomposites. It is an amphiphilic block copolymer consisting of poly(ε-caprolactone) (PCL), prepared with  ring-opening polymerization (ROP)1, and a shorter segment of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) synthesized with atom transfer radical polymerization (ATRP)2. The PDMAEMA-part was prepared in one single length, while the PCL-part was varied in three different lengths. In the last synthesis step the PDMAEMA-part was quaternized, turning it into a cationically charged chain – a polyelectrolyte. The block copolymers were then able to form cationic micelles in water, from where they can adsorb, under mild conditions, to anionic surfaces such as silicon oxide and cellulose-model surfaces. A similar concept has been investigated earlier in a system fully prepared with ATRP3. Additionally, physical adsorption of micelles is a milder approach of attaching a polymer to a cellulose surface compared to more traditional covalent attachment4, making it an interesting option to use in industry. After adsorption, the surface had a more hydrophobic character shown with contact angle measurements, and with AFM force measurements, it was demonstrated that there is a clear entanglement behavior obtained between the block copolymers and a PCL surface at about 60 °C, which is of importance for the information regarding the adhesive interface in a future biocomposite.

  • 12.
    Bruce, Carl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Fogelström, Linda
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Physical Tuning of Cellulose-Polymer Interactions Utilizing Cationic Block Copolymers Based on PCL and Quaternized PDMAEMA2013Conference paper (Refereed)
    Abstract [en]

    In this study, the aim was to prepare and evaluate a block copolymer that can be used as a compatabilizer in cellulose fiber-reinforced biocomposites. It as an amphiphilic block copolymer consisting of poly(ε-caprolactone) (PCL), made with  ring-opening polymerization (ROP), and a shorter segment of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) that was synthesized with atom transfer radical polymerization (ATRP). The PDMAEMA-part was made in one single length, while the PCL-part was varied in three different lengths; in total were three block copolymers prepared. In the last step of the synthesis, the PDMAEMA-part was quaternized that turns it into a cationically charged chain – a polyelectrolyte. The block copolymers were then able to form cationic micelles in water, from where they can adsorb, under mild conditions, to anionic surfaces such as silicon oxide and cellulose-model surfaces. This provides the surface with a more hydrophobic character shown with contact angle measurements. Finally, with atomic force microscopy (AFM) force measurements, it was demonstrated that there is a clear entanglement behavior obtained between the block copolymers and a PCL surface at about 60 °C, which is of importance for the information regarding the adhesive interface in a future biocomposite.

  • 13.
    Bruce, Carl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Fogelström, Linda
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Preparation and evaluation of a block copolymer compatibilizer for biocomposite applications2012Conference paper (Refereed)
    Abstract [en]

    In this study, the concept of using a free polymer as a compatibilzer in biocomposite applications has been evaluated with focus on the polymer poly(ɛ-caprolactone) (PCL), commonly used in conventional grafting onto/from cellulose. A block copolymer consisting of PCL and a shorter segment of poly(di(methylamino)ethyl methacrylate) (PDMAEMA) was made combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The length of the PDMAEMA-part was kept constant, and the PCL-part was varied in three different lengths, yielding three separate block copolymers. As a final step, the PDMAEMA-part was quaternized, which resulted in cationically charged chains –polyelectrolytes. The charged part could then be used as an electrostatic linker allowing the PDMAEMA-PCL copolymer to be adsorbed onto negatively charged cellulose model surfaces. Finally, these cellulose model surfaces were evaluated regarding for example amount of polymer adsorbed and hydrophobic character, investigated with techniques such as quartz crystal microbalance (QCM) and contact angle measurements.

  • 14.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Naderi, A.
    Iruthayaraj, J.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Vareikis, A.
    Makuska, R.
    Interfacial properties of bottle-brush polyelectrolytes2007In: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007 / [ed] Makuska, R., Vilnius: VILNIUS UNIV. , 2007, p. 77-81Conference paper (Refereed)
    Abstract [en]

    This article is focused on interfacial properties of bottle brush polyelectrolytes, where side-chains are attached along a polymer backbone. This class of polymer has been much less studied than block copolymers, which is particularly true for bottle brush polyelectrolytes with a high graft density. We have explored how the graft density and charge density of such polymers affect surface properties, as well as some bulk properties. The adsorption of this class of polymer onto negatively charged silica and mica surfaces has been determined. On mica adsorption is driven by electrostatic forces whereas on silica both electrostatic forces and interactions between silica and ethylene oxide chains drive the adsorption. On silica the adsorbed amount is very sensitive to solution ionic strength and pH. We also report on surface interactions and frictional forces obtained between surfaces coated with bottle brush polyelectrolytes.

  • 15.
    Dedinaite, Andra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mohanty, Biswaranjan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lubrication by organized soft matter2010In: SOFT MATTER, ISSN 1744-683X, Vol. 6, no 7, p. 1520-1526Article in journal (Refereed)
    Abstract [en]

    The AFM-colloidal probe technique has been used to explore surface interactions and friction forces between polyelectrolyte-coated surfaces immersed in aqueous solutions in the absence and presence of surfactant. It is found that the nature of the load bearing forces is decisive for the lubricating properties of the layers. Low frictional forces are obtained when the load is carried by a force that allows the interfacial layer to have a high fluidity, whereas attractive surface forces most often increase the friction. Highly charged polyelectrolytes and oppositely charged surfactants associate in bulk solution to form complexes with a well-defined internal structure. At the surface, similarly structured polyelectrolyte-surfactant layers are spontaneously formed. Such layers have a high load bearing capacity, and the friction coefficient is very low as long as the integrity of the layer remains intact. Interestingly, when the load is increased step-wise the friction force as a function of load displays some sharp peaks, which are identified as being due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces are obtained despite the presence of an adhesion between the layers. To maintain the favorable lubricating properties it is essential to have surfactants present in solution, whereas, after the initial adsorption step, there is no need to have the polyelectrolyte present in the bulk. The reason for this is the essentially irreversible adsorption of the polyelectrolyte.

  • 16.
    Fallqvist, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Fielden, Matthew
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Kroon, Martin
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Gad, Annica
    Karolinska Institutet, MTC.
    Experimental and computational assessment of F-actin influence in regulating cellular stiffness and relaxation behaviour of fibroblasts2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 59, p. 168-184Article in journal (Refereed)
    Abstract [en]

    In biomechanics, a complete understanding of the structures and mechanisms that regulate cellular stiffness at a molecular level remain elusive. In this paper, we have elucidated the role of filamentous actin (F-actin) in regulating elastic and viscous properties of the cytoplasm and the nucleus. Specifically, we performed colloidal-probe atomic force microscopy (AFM) on BjhTERT fibroblast cells incubated with Latrunculin B (LatB), which results in depolymerisation of F-actin, or DMSO control. We found that the treatment with LatB not only reduced cellular stiffness, but also greatly increased the relaxation rate for the cytoplasm in the peripheral region and in the vicinity of the nucleus. We thus conclude that F-actin is a major determinant in not only providing elastic stiffness to the cell, but also in regulating its viscous behaviour. To further investigate the interdependence of different cytoskeletal networks and cell shape, we provided a computational model in a finite element framework. The computational model is based on a split strain energy function of separate cellular constituents, here assumed to be cytoskeletal components, for which a composite strain energy function was defined. We found a significant influence of cell geometry on the predicted mechanical response. Importantly, the relaxation behaviour of the cell can be characterised by a material model with two time constants that have previously been found to predict mechanical behaviour of actin and intermediate filament networks. By merely tuning two effective stiffness parameters, the model predicts experimental results in cells with a partly depolymerised actin cytoskeleton as well as in untreated control. This indicates that actin and intermediate filament networks are instrumental in providing elastic stiffness in response to applied forces, as well as governing the relaxation behaviour over shorter and longer time-scales, respectively.

  • 17.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Mucin-electrolyte interactions at the solid-liquid interface probed by QCM-D2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 7, p. 3348-3357Article in journal (Refereed)
    Abstract [en]

    The interaction between mucin and ions has been investigated by employing the quartz crystal microbalance technique with measurement of energy dissipation. The study was partially aimed at understanding the adsorption of mucin on surfaces with different chemistry, and for this purpose, surfaces exposing COOH, OH, and CH3 groups were prepared. Mucin adsorbed to all three types of functionalized gold surfaces. Adsorption to the hydrophobic surface and to the charged hydrophilic surface (COOH) occured with high affinity despite the fact that in the latter case both mucin and the surface were negatively charged. On the uncharged hydrophilic surface exposing OH groups, the adsorption of mucin was very low. Another aim was to elucidate conformational changes induced by electrolytes on mucin layers adsorbed on hydrophobic surfaces from 30 mM NaNO3. To this end, we investigated the effect of three electrolytes with increasing cation valance: NaCl, CaCl2, and LaCl3. At low NaCl concentrations, the preadsorbed layer expands, whereas at higher concentrations of NaCl the layer becomes more compact. This swelling/compacting of the mucin layer is fully reversible for NaCl. When the mucin layer instead is exposed to CaCl2 or LaCl3, compaction is observed at I mM. For CaCl2, this process is only partially reversible, and for LaCl3, the changes are irreversible within the time frame of the experiment. Finally, mucin interaction with the DTAB cationic surfactant in an aqueous solution of different electrolytes was evaluated with turbidimetry measurements. It is concluded that the electrolytes used in this work screen the association between mucin and DTAB and that the effect increases with increasing cation valency.

  • 18. Gamstedt, E. Kristofer
    et al.
    Sandell, Robert
    Berthold, Fredrik
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterization of interfacial stress transfer ability of particulate cellulose composite materials2011In: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 43, no 11, p. 693-704Article in journal (Refereed)
    Abstract [en]

    Composites with cellulose reinforcements are steadily gaining increased use. The stress transfer ability between reinforcement and polymer matrix has a strong influence on mechanical properties like strength and fracture toughness. This work presents a method to assess the stress transfer ability between cellulose and polymer matrix from a model material with cellulose spheres embedded in a polymer matrix. Such a material show smaller variability compared with composites based on natural cellulose fibres, and is less cumbersome than single fibre tests with regard to interfacial characterization. Measured elastic moduli of particulate composites is compared with predicted values from a micromechanical model based on a composite sphere assembly in a self-consistent scheme with only a spring constant of an imperfect interface as fitting parameter expressed in Pa/m. This interface parameter is identified through inverse modelling and used to quantify stress-transfer ability of cellulose/polylactide and cellulose/polystyrene composite interfaces. A higher degree of interfacial interaction was found for the former. This ranking was corroborated by adhesive force measurements using a micrometre sized cellulose sphere attached to the end of a cantilever in an atomic force microscope. With the model microstructure of a cellulose-sphere composite, an interfacial efficiency parameter can be backed out from stiffness measurements to be used in e.g. ranking of different fibre surface treatments and choice of matrix in the development of stronger natural-fibre composites.

  • 19. Grygiel, Konrad
    et al.
    Wicklein, Bernd
    Zhao, Qiang
    Eder, Michaela
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Bergstroem, Lennart
    Antonietti, Markus
    Yuan, Jiayin
    Omnidispersible poly(ionic liquid)-functionalized cellulose nanofibrils: surface grafting and polymer membrane reinforcement2014In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 83, p. 12486-12489Article in journal (Refereed)
    Abstract [en]

    We report a facile one-step route to graft poly(ionic liquid)s (PILs) onto cellulose nanofibrils (CNFs). The dispersibility of the PIL-functionalized CNFs in water and various organic solvents could be tuned by the choice of the PIL-binding anion. We demonstrate that such omnidispersible PIL@CNF hybrids can be used to reinforce porous poly(ionic liquid) membranes.

  • 20.
    Gustafsson, Emil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Direct adhesive measurements between wood biopolymer model surfaces2012Conference paper (Other academic)
  • 21.
    Gustafsson, Emil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Direct Adhesive Measurements between Wood Biopolyrner Model Surfaces2012In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 10, p. 3046-3053Article in journal (Refereed)
    Abstract [en]

    For the first time the dry adhesion was measured for an all-wood biopolymer system using Johnson-Kendall-Roberts (JKR) contact mechanics. The polydimethylsiloxane hemisphere was successfully surface-modified with a Cellulose I model surface using layer-by-layer assembly of nanofibrillated cellulose and polyethyleneimine. Flat surfaces of cellulose were equally prepared on silicon dioxide substrates, and model surfaces of glucomannan and lignin were prepared on silicon dioxide using spin-coating. The measured work of adhesion on loading and the adhesion hysteresis was found to be very similar between cellulose and all three wood polymers, suggesting that the interaction between these biopolymers do not differ greatly. Surface energy calculations from contact angle measurements indicated similar dispersive surface energy components for the model surfaces. The dispersive component was dominating the surface energy for all surfaces. The JKR work of adhesion was lower than that calculated from contact angle measurements, which partially can be ascribed to surface roughness of the model surfaces and overestimation of the surface energies from contact angle determinations.

  • 22.
    Gustafsson, Emil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Marais, Andrew
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    The use of thin, tailored Layer-by-Layer (LbL) films to improve the mechanical properties of fibrous networks2012Conference paper (Other academic)
  • 23.
    Hajian, Alireza
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH.
    Lindström, Stefan B.
    Linköping University.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH.
    Hamedi, Mahiar M.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH.
    Understanding the Dispersive Action of Nanocellulose for Carbon Nanomaterials2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 3, p. 1439-1447Article in journal (Refereed)
    Abstract [en]

    This work aims at understanding the excellent ability of nanocelluloses to disperse carbon nanomaterials (CNs) in aqueous media to form long-term stable colloidal dispersions without the need for chemical functionalization of the CNs or the use of surfactant. These dispersions are useful for composites with high CN content when seeking water-based, efficient, and green pathways for their preparation. To establish a comprehensive understanding of such dispersion mechanism, colloidal characterization of the dispersions has been combined with surface adhesion measurements using colloidal probe atomic force microscopy (AFM) in aqueous media. AFM results based on model surfaces of graphene and nanocellulose further suggest that there is an association between the nanocellulose and the CN. This association is caused by fluctuations of the counterions on the surface of the nanocellulose inducing dipoles in the sp2carbon lattice surface of the CNs. Furthermore, the charges on the nanocellulose will induce an electrostatic stabilization of the nanocellulose–CN complexes that prevents aggregation. On the basis of this understanding, nanocelluloses with high surface charge density were used to disperse and stabilize carbon nanotubes (CNTs) and reduced graphene oxide particles in water, so that further increases in the dispersion limit of CNTs could be obtained. The dispersion limit reached the value of 75 wt % CNTs and resulted in high electrical conductivity (515 S/cm) and high modulus (14 GPa) of the CNT composite nanopapers.

  • 24. Hassanzadeh, Salman
    et al.
    Feng, Zhaoxuan
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    A proof-of-concept for folate-conjugated and quercetin-anchored pluronic mixed micelles as molecularly modulated polymeric carriers for doxorubicin2015In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 74, p. 193-204Article in journal (Refereed)
    Abstract [en]

    Pluronic, F127 (PEG-PPO-PEG, Mn = 12,500 g/mol) and reverse pluronic, 10R5 (PPO-PEG-PPO, Mn = 2000 g/mol) were molecularly modulated to reach multifunctional mixed micelle systems aiming to overcome some of the inherent weaknesses of pluronic based drug delivery systems. Targeting function was introduced by covalent attachment of folic acid to F127 (F127-FA), while quercetin was anchored to 10R5 (P-Q). The successful syntheses were evidenced by H-1 NMR, FTIR, DSC and UV-Vis. The proof-of-concept for the mixed micelles prepared from the drug anchored pluronics was demonstrated through reduced CMCs, slower release rates and increased Doxorubicin (DOX) encapsulation capacity from similar to 19% to similar to 43%. Quercetin therefore boosted the interactions of DOX with the hydrophobic core of the micelles. This was further evidenced by colloidal probe AFM which demonstrated almost doubled adhesion forces between the DOX coated probe and the quercetin modified pluronic as compared to the plain pluronic. The pre-biological essay of the DOX-modulated mixed micelle demonstrates promising properties. In addition quercetin has previously been proposed as combinatory drug to DOX enhancing its therapeutic function and reducing the side effects to normal cells.

  • 25.
    Holmboe, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Petterson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Effects of the injection grout Silica sol on Bentonite2011In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 36, no 17/18, p. 1580-1589Article in journal (Refereed)
    Abstract [en]

    Silica sol, i.e., colloidal SiO2, may be used as a low-pH injection grout for very fine fractures in the construction of deep geological repositories for radioactive waste in Sweden and in Finland. If the bentonite barrier encounters SiO2-colloid particles under conditions favorable for aggregation, there is concern that it will modify the bentonite barrier at the bentonite/bedrock interface. In this study qualitative experiments were performed with mixed dispersions of SiO2-colloids and bentonite or homo-ionic Na/Ca-montmorillonite. Samples were prepared at different colloid concentrations and treated under various conditions such as low and high ionic strength (0.3 M NaCl), as well as dehydration and redispersing. Free swelling and settling experiments were performed in order to qualitatively compare the conditions in which SiO2-colloids affect the bulk/macro properties of bentonite. In order to study specific SiO2-colloid/montmorillonite interactions and preferred type of initial aggregation, dilute dispersions of homo-ionic montmorillonite dispersions mixed with varying concentrations of SiO2-colloids were prepared and selected samples were characterized by PCS, SEM/EDS, AFM and PXRD. The results from this study show that bentonite and montmorillonite particles can be modified by SiO2-colloids when mixed in comparable amounts, due to dehydration or high ionic strength. Some indications for increased colloidal stability for the SiO2-colloid modified clay particles were also found. From the AFM investigation it was found that initial attachment of the SiO2-colloids in Na+ dominated samples seemed to occur on the edges of the montmorillonite layers. In Ca2+ dominated samples not subjected to excess NaCl, SiO2-colloid sorption onto the faces of the montmorillonite layers was also found. In all, contact between the bentonite barrier and ungelled Silica sol should preferably be avoided.

  • 26.
    Karabulut, Erdem
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ankerfors, Mikael
    Material Processes, Innventia AB, Stockholm, Sweden.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Adhesive Layer-by-Layer Films of Carboxymethylated Cellulose Nanofibril Dopamine Covalent Bioconjugates Inspired by Marine Mussel Threads2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 6, p. 4731-4739Article in journal (Refereed)
    Abstract [en]

    The preparation of multifunctional films and coatings from sustainable, low-cost raw materials has attracted considerable interest during the past decade. In this respect, cellulose-based products possess great promise due not only to the availability of large amounts of cellulose in nature but also to the new classes of nanosized and well-characterized building blocks of cellulose being prepared from trees or annual plants. However, to fully utilize the inherent properties of these nanomaterials, facile and also sustainable preparation routes are needed. In this work, bioinspired hybrid conjugates of carboxymethylated cellulose nanofibrils (CNFC) and dopamine (DOPA) have been prepared and layer-by-layer (LbL) films of these modified nanofibrils have been built up in combination with a branched polyelectrolyte, polyethyleneimine (PEI), to obtain robust, adhesive, and wet-stable nanocoatings on solid surfaces. It is shown that the chemical functionalization of CNFCs with DOPA molecules alters their conventional properties both in liquid dispersion and at the interface and also influences the LbL. film formation by reducing the electrostatic interaction. Although the CNFC-DOPA conjugates show a lower colloidal stability in aqueous dispersions due to charge suppression, it was possible to prepare the LbL films through the consecutive deposition of the building blocks. Adhesive forces between muttilayer films prepared using chemically functionalized CNFCs and a silica probe are much stronger in the presence of Fe3+ than those between a multilayer film prepared from unmodified nanofibrils and a silica probe. The present work demonstrates a facile way to prepare chemically functionalized cellulose nanofibrils whereby more extended applications can produce novel cellulose-based materials with different functionalities.

  • 27.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden.
    Yu, Shun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Pendergraph, Samuel Allen
    RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden..
    Pettersson, Torbjörn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Hellwig, Johannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed)
    Abstract [en]

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

  • 28.
    Kaufman, E. D.
    et al.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Belyea, J.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Johnson, M. C.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Nicholson, Z. M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Ricks, J. L.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Shah, P. K.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Bayless, M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Feldötö, Zsombor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Franzen, S.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Probing Protein Adsorption onto Mercaptoundecanoic Acid Stabilized Gold Nanoparticles and Surfaces by Quartz Crystal Microbalance and ζ-Potential Measurements2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 11, p. 6053-6062Article in journal (Refereed)
    Abstract [en]

    The adsorption characteristics of three proteins [bovine serum albumin (BSA), myoglobin (Mb), and cytochrome c (CytC)] onto self-assembled monolayers of mercaptoundecanoic acid (MUA) on both gold nanoparticles (AuNP) and gold surfaces (Au) are described. The combination of quartz crystal microbalance measurements with dissipation (QCM-D) and pH titrations of the zeta-potential provide information on layer structure, surface coverage, and potential. All three proteins formed adsorption layers consisting of an irreversibly adsorbed fraction and a reversibly adsorbed fraction. BSA showed the highest affinity for the MUA/Au, forming an irreversibly adsorbed rigid monolayer with a side-down orientation and packing close to that expected in the jamming limit. In addition, BSA showed a large change in the adsorbed mass due to reversibly bound protein. The data indicate that the irreversibly adsorbed fraction of CytC is a monolayer structure, whereas the irreversibly adsorbed Mb is present in form of a bilayer. The observation of stable BSA complexes on MUA/AuNPs at the isoelectric point by zeta-potential measurements demonstrates that BSA can sterically stabilize MUA/AuNP. On the other hand, MUA/AuNP coated with either Mb or CytC formed a reversible flocculated state at the isoelectric point. The colloidal stability differences may be correlated with weaker binding in the reversibly bound overlayer in the case of Mb and CytC as compared to BSA.

  • 29.
    Lars, Wågberg
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ankerfors, Caroline
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Johansson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Molecular engineering of surfaces with polyelectrolyte complexes and layer-by-layer technology: Influence of structure and molecular composition2011In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, American Chemical Society (ACS), 2011, Vol. 241Conference paper (Other academic)
  • 30.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Cross-linked barrier films with low sensitivity to relative humidity fabricated from nanofibrillated cellulose2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 256-CELL-Article in journal (Other academic)
  • 31.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Improved barrier films of cross-linked cellulose nanofibrils: a microscopy study2014In: Green materials, ISSN 2049-1220, Vol. 2, no 4, p. 163-168Article in journal (Refereed)
    Abstract [en]

    It is highly desirable to replace gas barriers of aluminium and non-renewable plastics in order to lower our ecological footprint. One interesting candidate is films made from cellulose nanofibrils (CNFs), which after cross-linking have been shown to have competitive barrier properties even at a high relative humidity (80% RH). This work presents studies at even higher relative humidity (90% RH) and microscopic studies of what happens when unmodified and cross-linked CNF films are exposed to water. The microscopy techniques used were scanning electron microscopy of dry and wet cross-sections of films after freeze-drying and atomic force microscopy in the dry state and in the wet state shortly after wetting. Both techniques clearly revealed that the cross-links prevent the CNFs from separating from each other and hence prevent the films from swelling, so that the free-volume-sensitive gas permeability is maintained at a low level.

  • 32. Lidenmark, Cecilia
    et al.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Karlsson, Ola J.
    Notley, Shannon M.
    Norgren, Magnus
    Edlund, Håkan
    The adhesive behavior of extracted latex polymers towards silicon oxide and cellulose2013In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 44, p. 250-258Article in journal (Refereed)
    Abstract [en]

    The objective with this work is to compare the adhesive behavior for latex polymers of different glass transition temperatures (T-g) at different length scales and with different contact times. This is accomplished by two techniques: AFM colloidal probe force measurements and JKR-measurements. The aim is to compare the results from these two techniques and relate them to the interaction of the latex polymers towards oxidized silicon wafers and silica/cellulose probes. Theory suggests that altering the short timeframes used in the colloidal probe technique does not affect the ranking of the adhesion for the different polymers, but for the macroscopic JKR-technique it influences the measured work of adhesion. It is therefore important to let the system reach a steady state before assuming complete spreading and adhesion. AFM and JKR measurements showed the same trends where the polymer with lowest content of styrene has the lowest T-g and the highest adhesion, due to the larger polymer chain mobility.

  • 33.
    Mizuno, Hiroyasu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Kjellin, M.
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Wallqvist, V.
    Fielden, M.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Friction measurement between polyester fibres using the fibre probe SPM2006In: Australian journal of chemistry (Print), ISSN 0004-9425, E-ISSN 1445-0038, Vol. 59, no 6, p. 390-393Article in journal (Refereed)
    Abstract [en]

    An SPM has been used to measure frictional interactions between two crossed fibres for the first time. The preparation of the surfaces is briefly described, but the crucial element is that the fibre attached to the AFM cantilever is glued parallel to the long axis. The fibres consist of polyester and frictional forces were measured both in air and solutions of cationic surfactant C(14)TAB. The friction coefficients reduce markedly with increasing concentration of surfactant which is ascribed to the formation of a boundary lubricating film between the surfaces. On removal of the solution, the subsequent friction coefficient in air was reduced by more than a factor of two compared to its value before immersion.

  • 34.
    Mizuno, Hiroyasu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Kjellin, Mikael
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Wallqvist, Viveca
    Fielden, Matthew
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    COLL 385-Friction measurement between polyester fibres using fibre probe SPM2008In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235, p. 385-COLL-Article in journal (Other academic)
  • 35.
    Naderi, Ali
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Effect of Polymer Architecture on the Adsorption Properties of a Nonionic Polymer2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 13, p. 6676-6682Article in journal (Refereed)
    Abstract [en]

    The adsorption of a linear- and bottle-brush poly(ethylene oxide (PEO))-based polymer, having comparable molecular weights, was studied by means of quartz crystal microbalance with dissipation monitoring ability (QCM-D) and AFM colloidal probe force measurements. The energy dissipation change monitored by QCM-D and the range of the steric forces obtained from force measurements demonstrated that linear PEO forms a more extended adsorption layer than the bottle-brush polymer, despite that the adsorbed mass is higher for the latter. Competitive adsorption studies revealed that linear PEO is readily displaced from the interface by the bottle-brush polymer. This was attributed to the higher surface affinity of the latter, which is governed by the number of contact points between the polymers and the interface, and the smaller loss of conformational entropy.

  • 36. Naderi, Ali
    et al.
    Lindstrom, Tom
    Pettersson, Torbjorn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    The state of carboxymethylated nanofibrils after homogenization-aided dilution from concentrated suspensions: a rheological perspective2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2357-2368Article in journal (Refereed)
    Abstract [en]

    The rheological properties of a carboxymethylated (D. S. & 0.1) nanofibrillated cellulose (NFC) were investigated at different solid contents. The critical overlap concentration was determined to be in the range between 0.04 and 0.07 % (w/w) using shear stress versus shear rate measurements. From the critical overlap concentration using the simple Mason excluded volume formalism, the apparent aspect ratio was estimated to be 75 [ at a critical overlap concentration of 0.04 % (w/w)]. The aspect ratio of the NFC system was also estimated by using the EinsteinSimha equation together with the intrinsic viscosity value of the system (corrected for the electroviscous effects). The obtained value was found to be around 80, which is in good agreement with the value obtained from the excluded volume calculation. Further, by combining oscillatory measurements and the equation of Shankar et al. the apparent fibril length was determined to be 4 mu m. As the production of NFC through homogenization occurs at concentrations far above the critical overlap concentration an NFC-gel is constituted by a severely entangled structure. The disentanglement of the fibrils is therefore difficult and the employed dilution method was found not to lead to fully liberated nanofibrils, which was also indicated by atomic force microscopy-imaging.

  • 37. Naderi, Ali
    et al.
    Lindström, Tom
    Sundström, Jonas
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Flodberg, Göran
    Erlandsson, Johan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Microfluidized carboxymethyl cellulose modified pulp: a nanofibrillated cellulose system with some attractive properties2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1159-1173Article in journal (Refereed)
    Abstract [en]

    A method (Ankerfors and Lindstrom in Method for providing nanocellulose comprising modified cellulose fibers, 2009) was employed to physically attach anionic carboxymethyl cellulose (CMC) chains onto wood pulp, upon which it was fibrillated by a microfluidizer-type homogenizer at high applied pressures and at dilute conditions [< 3 % (w/w)]. It was found that the CMC-modified pulp can be fibrillated at the same consistencies as many of the commercially available NFC products. The NFC manufacturing process was also deemed to be energy efficient, as it lacked the need for mechanical pre-treatment, which is often a prerequisite for the production of many existing NFC systems. The CMC-based NFC was studied with respect to the rheological characteristics, and was also characterized using AFM-imaging. Further, The NFC was made into films, and its tensile strength was determined together with its barrier properties. In general, the rheological characteristics (viscosity and storage modulus) together with the tensile strength and oxygen barrier properties of the films were improved with increasing the number of passes through the microfluidizer. The fibrillated CMC-modified pulp was found to be as efficient as other NFC systems when employed as dry strength additive. The employment of the investigated material, which can be produced at acceptable costs and through environmentally benign and industrially relevant processes can, hence, potentially lead to significant future savings in the energy consumption levels in the paper and cardboard manufacturing processes, which have been recognized as major application areas of NFC products.

  • 38.
    Nordgren, Niklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sandell, Robert
    Berthold, Fredrik
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gamstedt, Kristofer
    Characterization of interfacial stress transfer ability of particulate cellulose composite materials2012Conference paper (Other academic)
  • 39.
    Nugroho, Robertus Wahyu N.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Force interactions of grafted polylactide particles2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
  • 40.
    Nugroho, Robertus Wahyu Nayan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Force Interactions of Nonagglomerating Polylactide Particles Obtained through Covalent Surface Grafting with Hydrophilic Polymers2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 26, p. 8873-8881Article in journal (Refereed)
    Abstract [en]

     Nonagglomerating polylactide (PLA) particles with various interaction forces were designed by covalent photografting. PLA particles were surface grafted with hydrophilic poly(acrylic acid) (PAA) or poly(acrylamide) (PAAm), and force interactions were determined using colloidal probe atomic force microscopy. Long-range repulsive interactions were detected in the hydrophilic/hydrophilic systems and in the hydrophobic/hydrophilic PLA/PLA-g-PAAm system. In contrast, attractive interactions were observed in the hydrophobic PLA/PLA and in the hydrophobic/hydrophilic PLA/PLA-g-PAA systems. AFM was also used in the tapping mode to determine the surface roughness of both neat and surface-grafted PLA film substrates. The imaging was performed in the dry state as well as in salt solutions of different concentrations. Differences in surface roughness were identified as conformational changes induced by the altered Debye screening length. To understand the origin of the repulsive force, the AFM force profiles were compared to the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory and the Alexander de Gennes (AdG) model. The steric repulsion provided by the different grafted hydrophilic polymers is a useful tool to inhibit agglomeration of polymeric particles. This is a key aspect in many applications of polymer particles, for example in drug delivery.

  • 41.
    Olin, Pontus Hans
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Influence of tilt angle and droplet size on the sliding rate of water droplets on superhydrophobic surfaces2012Conference paper (Other academic)
  • 42.
    Olin, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Stefan B.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Water Drop Friction on Superhydrophobic Surfaces2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 29, p. 9079-9089Article in journal (Refereed)
    Abstract [en]

    To investigate water drop friction on superhydrophobic surfaces, the motion of water drops on three different superhydrophobic surfaces has been studied by allowing drops to slide down an incline and capturing their motion using high-speed video. Two surfaces were prepared using crystallization of an alkyl ketene dimer (AKD) wax, and the third surface was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of the water droplets on these superhydrophobic surfaces was measured as a function of droplet size and inclination of the surface. For small capillary numbers, we propose that the energy dissipation is dominated by intermittent pinning-depinning transitions at microscopic pinning sites along the trailing contact line of the drop, while at capillary numbers exceeding a critical value, energy dissipation is dominated by circulatory flow in the vicinity of the contacting disc between the droplet and the surface. By combining the results of the droplet acceleration with a theoretical model based on energy dissipation, we have introduced a material-specific coefficient called the superhydrophobic sliding resistance, b(sh). Once determined, this parameter is sufficient for predicting the motion of water drops on superhydrophobic surfaces of a general macroscopic topography. This theory also infers the existence of an equilibrium sliding angle, beta(eq), at which the drop acceleration is zero. This angle is decreasing with the radius of the drop and is in quantitative agreement with the measured tilt angles required for a stationary drop to start sliding down an incline.

  • 43.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wear studies of superhydrophobic coatings of wax and polymers sprayed from rapid expansion of supercritical solutions (RESS)Manuscript (preprint) (Other academic)
  • 44.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tuominen, Mikko
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    The effect of different wear on superhydrophobic wax coatings2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 2, p. 195-203Article in journal (Refereed)
    Abstract [en]

    Wear resistance of superhydrophobic coatings made by spraying a crystallizing wax from supercritical carbon dioxide solutions was evaluated using several methods. Scratch tests were performed using a tip in contact with the surface using atomic force microscope (AFM). Compression tests were performed by applying different loads on a rubber stamp placed on the surface. Frictional wear was evaluated by stroking an index finger over the surfaces while measuring applied load and friction. The wetting properties of the coatings were subsequently evaluated as advancing and receding water contact angles, superhydrophobic sliding resistance according to a recently developed method and surface roughness, coating morphology was studied using scanning electron microscopy and optical profilometry. Scratching with tip of an AFM cantilever with a force of 12 nN removed major fraction of the wax coating from underlying silica substrate whereas subjecting the surfaces to a compressive load up to 59 kPa did not significantly influence the superhydrophobicity of the coatings. Frictional wear measurements indicate that superhydrophobic properties were immediately lost after pressing and moving a finger over the coating, as movement of the finger destroyed the fine surface structure. Nevertheless, the surfaces could withstand up to 200000 falling water drops without losing their superhydrophobicity.

  • 45.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Tuominen, Mikko
    SP Kemi, Material och Ytor, Drottning Kristinas väg 45, SE-114 86 Stockholm.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wear studies of superhydrophobic coatings of wax sprayed from rapid expansion of supercritical solutions (RESS)Manuscript (preprint) (Other academic)
    Abstract [en]

    The wear resistance of superhydrophobic coatings made by spraying a wax from supercritical carbon dioxide solutions have been evaluated by different methods. Scratch tests were performed by using the tip of the cantilever in an atomic force microscope (AFM) by applying an increasing load force on the tip during the measurement. Compression tests were also performed by applying different loads onto a rubber stamp that was placed on the surfaces. In addition to this, frictional wear was evaluated by moving an index finger over the surface using a device that measured the applied load and frictional forces. The wetting properties of the exposed coatings were subsequently evaluated in terms of advancing and receding water contact angles, the superhydrophobic sliding resistance parameter and the surface roughness (RMS). The morphology of the coatings was studied by scanning electron microscopy and optical profilometry. Scratching, with the AFM, at load forces of 12 nN was enough to fully remove the coating from the underlying silica substrate. Results also show that the surfaces remained superhydrophobic after being exposed to compression loads up to 59 kPa. The frictional wear measurments showed that the superhydrophobic properties were immediately lost after pressing and moving a finger over the coating since the lateral movement destroyed the fine surface structure.  Finally it was found that the surfaces could stand up to 200 000 falling water drops without losing its superhydrophobicity.

  • 46.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lubrication and Surface Properties of Adsorbed Layers of Polyelectrolytes and Proteins2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Friction forces between protein / polyelectrolyte layers, adsorption properties of proteins, and conformational changes due to variation in electrolyte concentration have been investigated. The aim was to obtain better understanding of adsorbed layer properties, with focus on the relation between layer structure and lubrication capabilities. The major techniques used were AFM (atomic force microscope) with colloidal probe for normal force and friction measurements together with QCM-D (quartz crystal microbalance with dissipation) for measurement of adsorption and conformational changes of adsorbed layers.

    A comparison between some techniques for calibration of the AFM instrument for friction measurements was made to find the most suitably one for colloidal probe friction measurements in aqueous solutions. It is suggested that the normal and torsional Sader methods are preferred in combination with torsional detector sensitivity measurement, for which one new methodology has been proposed.

    Adsorption was studied for bovine serum albumin, cytochrome c, myoglobin and mucin, whereas conformational changes of the adsorbed layer were monitored only for mucin. It was found that it was essential to take into account bulk density and viscosity changes for correct interpretations of QCM data when studying the effect of changes in electrolyte type and concentration on preadsorbed layers of mucin, and also when having different (high) concentrations of proteins in the measuring solution. The adsorbed amount of proteins appears to depend on the strength of the surface attachment, in such a manner that a too high affinity reduces the adsorbed amount.

    Friction properties in aqueous solution have been studied for adsorbed layers of PEO45MEMA:METAC co-polyelectrolytes, with varying density of grafted PEO45 side chains and varying charge density, as well as for a naturally occurring polyelectrolyte (chitosan) and the glycoprotein mucin. These polymers were used to cover a wide range of different types of adsorbed layers and interactions to gain a better understanding of friction mechanisms and demands on layer properties for achieving favourable lubrication. It was found that the common features of low friction layers are that no attractive forces are present, and that excluded volume and / or electrostatic forces counteract chain interpenetration under load.

  • 47.
    Pettersson, Torbjörn
    KTH, Superseded Departments, Chemistry.
    Wetting and levelling of toner during fusing of electrophotographic prints2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This licentiate thesis comprises two studies dealing withthe fusing step in electrophotographic printing. The firststudy addresses the development of a method for monitoringwetting/spreading of single toner particles in-situ on a heatedsubstrate. The method employs imaging from above and thus makesit possible to use toner particles of realistic size (around 10µm in this case). The results of this first study clearlyshow that high energy substrates not only exhibit far greatertoner particle spreading, and work of adhesion generated by it,but also a strong dependence on the toner type. For the Xeikontoners used the cyan and black spread far more than themagenta, with yellow clearly the lowest. Conversely, low energysubstrates exhibit limited spreading and lack of sensitivity totoner type. The results permitted the proposal of a simplegeneralised law to describe thespreading kinetics. Thisempirical relation was able to fit all experimental resultswith the bare minimum of input information from the equilibriumstate. The method provides a readily visualisable and flexiblemeans for more systematic design of toner-substrateinteractions in electrophotography. A broad range of differenttoner particles can be rapidly screened in contact with modeland real substrates, and the spreading then correlated toelectrophotographic runnability, print quality and durabilityissues.

    The second study is based on evaluation of print qualityfrom trials on a Xeikon digital press with varying fusingconditions. The study illustrated the utility of white-lightinterferometric profilometry in quantifying the thickness andsurface roughness spectrum of toner layers transferred andfused on two different paper substrates (coated and uncoated).These measurements generate increased insight into themechanisms giving rise to toner print quality. Significantdifferences in surface roughness behaviour were observedbetween different toner colour combinations as a function oftemperature settings and both paper type and fusing units(radiant and heated roll). The correlation between gloss andprint surface roughness at micron length scales extends tolonger length scales with increasing toner film thickness andon use of the heated roll glossing unit. These observationsfacilitate a more systematic approach to designing fusing unitsto avoid typical problems such as gloss variations inelectrophotographic prints.

  • 48.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dėdinaitė, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Normal and Friction Forces between Mucin and Mucin-Chitosan Layers in Absence and Presence of SDS2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 324, no 1-2, p. 246-256Article in journal (Refereed)
    Abstract [en]

    Employing the colloidal probe AFM technique we have investigated normal and friction forces between flat mica surfaces and silica particles coated with mucin and combined mucin-chitosan layers in presence and absence of anionic surfactant, SDS, in 30 mM NaCl solution. We have shown that the normal interactions between mucin coated mica and silica surfaces are dominated by long-range steric repulsion on both compression and decompression. Friction forces between such mucin layers are characterized by a low effective friction coefficient, mu(eff) = 0.03 +/- 0.02, which is lower than the value of 0.13 +/- 0.02 observed when chitosan layers were adsorbed. Forces between combined mucin-chitosan layers have Adsorption of chitosan on mucin results in considerable compaction of the layer, also been measured. and development of attractive forces detectable on separation. Friction between mucin-chitosan layers in 30 mM NaCl solution is high, with mu(eff) approximate to 0.4. Adsorption of additional mucin to this layer results in no improvement with respect to lubrication as compared to the mucin-chitosan layer, and mu(eff) approximate to 0.4 is We argue that the layers containing both mucin and chitosan are not strictly layered but rather observed. As a result attractive interactions between oppositely charged moieties of sialic acid strongly entangled. residues from mucin and amine groups from chitosan residing on the opposing surfaces contribute to the increased friction. The effects of SDS on normal and friction forces between combined mucin-chitosan layers were also investigated. The relation between surface interactions and friction properties is discussed.

  • 49.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Feldötö, Zsombor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dėdinaitė, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    The Effect of Salt Concentration and Cation Valency on Interactions Between Mucin-Coated Hydrophobic Surfaces2008In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 134, p. 1-10Article in journal (Refereed)
    Abstract [en]

    The AFM colloidal probe technique has been utilized in order to investigate the forces acting between preadsorbed mucin layers on uncharged, hydrophobic mercaptohexadecane-coated gold surfaces. Layers with some highly extended tails are formed when the adsorption proceeds from 25 ppm mucin solution in 30 mM NaNO3. The effects of salt concentration and cation valency on the interactions have been explored using NaCl, CaCl2, and LaCl3 in the concentration range 1–100 mM. It will be shown that the results in NaCl, where the tail length decreases as the salt concentration is increased, can be rationalized by considering the polyelectrolyte nature of mucin and the screening of intralayer electrostatic interactions between charged groups, mainly anionic sialic acid. When multivalent cations are present in solution a significant compaction of the mucin layer occurs even at low concentrations (1 mM), suggesting binding of these ions to the anionic sites of mucin. The results are discussed in relation to previous data from quartz crystal microbalance measurements on the same systems.

  • 50.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Fogden, A.
    YKI, Ytkemiska Institutet.
    Leveling during toner fusing: Effects on surface roughness and gloss of printed paper2006In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 50, no 2, p. 202-215Article in journal (Refereed)
    Abstract [en]

    The results of digital printing trials using a Xeikon press on uncoated and coated paper were analyzed using interferometric profilometry to characterize printed paper topography and toner film thickness. Solid print areas were fused at various temperatures, including radiant fusing with and without heated rolls. The overall surface roughness of the prints is slightly higher on the coated than uncoated paper, but is mainly dictated by transferred toner amount and fusing conditions. Increased toner coverage degree, or layer thickness, gives reduced surface roughness, provided the applied fusing power suffices. Increase in radiant fusing temperature yields a decrease in overall print roughness, however, this decrease is more pronounced on coated paper and higher toner amounts. Bandpass analysis of print surface roughness shows that short-scale roughness at or below the lateral length scales of toner particle dimensions always decreases with increasing radiant fusing temperature, whereas roughness contributions at wavelengths above 10 mu m can increase, with this transition value being shorter on coated paper and at lower toner amounts. Print gloss after radiant fusing is strongly correlated to print roughness on wavelengths up to this transition length scale, and the correlation can extend to order 100 mu m if complemented by heated roll fusing.

12 1 - 50 of 78
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