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  • 1. Abrahamsson, C.
    et al.
    Nordstierna, L.
    Bergenholtz, J.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Magnetically induced structural anisotropy in binary colloidal gels and its effect on diffusion and pressure driven permeability2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 24, p. 4403-4412Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis, microstructure and mass transport properties of a colloidal hydrogel self-assembled from a mixture of colloidal silica and nontronite clay plates at different particle concentrations. The gel-structure had uniaxial long-range anisotropy caused by alignment of the clay particles in a strong external magnetic field. After gelation the colloidal silica covered the clay particle network, fixing the orientation of the clay plates. Comparing gels with a clay concentration between 0 and 0.7 vol%, the magnetically oriented gels had a maximum water permeability and self-diffusion coefficient at 0.3 and 0.7 vol% clay, respectively. Hence the specific clay concentration resulting in the highest liquid flux was pressure dependent. This study gives new insight into the effect of anisotropy, particle concentration and bound water on mass transport properties in nano/microporous materials. Such findings merit consideration when designing porous composite materials for use in for example fuel cell, chromatography and membrane technology. © 2014 the Partner Organisations.

  • 2. Acciaro, R.
    et al.
    Aulin, C.
    RISE, Innventia.
    Wågberg, L.
    Lindström, T.
    RISE, Innventia.
    Claesson, P.M.
    Varga, I.
    Investigation of the formation structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, no 4, p. 1369-1377Article in journal (Refereed)
  • 3. Aulin, C.
    et al.
    Netrval, J.
    Wågberg, L.
    Lindström, Tom
    RISE, Innventia.
    Aerogels from nanofibrillated cellulose with tunable oleophobicity2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 14, p. 3298-3305Article in journal (Refereed)
    Abstract [en]

    The formation of structured porous aerogels of nanofibrillated cellulose (NFC) by freeze-drying has been demonstrated. The aerogels have a high porosity, as shown by FE-SEM and nitrogen adsorption/desorption measurements, and a very low density (<0.03 g cm-3). The density and surface texture of the aerogels can be tuned by selecting the concentration of the NFC dispersions before freeze-drying. Chemical vapor deposition (CVD) of 1H,1H,2H,2H- perfluorodecyltrichlorosilane (PFOTS) was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids. An XPS analysis of the chemical composition of the PFOTS-modified aerogels demonstrated the reproducibility of the PFOTS-coating and the high atomic fluorine concentration (ca. 51%) in the surfaces. The modified aerogels formed a robust composite interface with high apparent contact angles (* ≫ 90°) for castor oil (γlv = 35.8 mN m-1) and hexadecane (γlv = 27.5 mN m-1).

  • 4. Bergström, L Magnus
    et al.
    Skoglund, Sara
    Danerlöv, Katrin
    YKI – Ytkemiska institutet.
    Garamus, Vasil M
    Pedersen, Jan Skov
    The growth of micelles, and the transition to bilayers, in mixtures of a single-chain and a double-chain cationic surfactant investigated with small-angle neutron scattering2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 22, p. 10935-10944Article in journal (Refereed)
    Abstract [en]

    Self-assembly in aqueous mixtures of a single-chain (DTAB) and a double-chain cationic surfactant (DDAB) has been investigated with small-angle neutron scattering (SANS). Small oblate spheroidal micelles formed by DTAB grow with respect to width and length to form mixed ellipsoidal tablet-shaped micelles as an increasing fraction of DDAB is admixed into the micelles. The growth behaviour of the micelles is rationalized from the general micelle model in terms of three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant ((k(c)) over bar kc). It is found that micelles grow with respect to width, mainly as a result of decreasing k(c)H(0), and in the length direction as a result of decreasing k(c). The micelles are still rather small, i.e. about 140 angstrom in length, as an abrupt transition to large bilayer aggregates is observed. The micelle-to-bilayer transition is induced by changes in aggregate composition and is observed to occur at a mole fraction of DDAB equal to about x = 0.48 in D2O, which is a significantly higher value than previously observed for the same system in H2O (x = 0.41). An abrupt micelle-to-bilayer transition is in agreement with predictions from the general micelle model, according to which an abrupt transition from micelles to bilayers is expected to occur at xi H-0 = 1/4, where x is the thickness of the self-assembled interface, and we may conclude that H-0(D2O) > H-0(H2O) for the system DDAB/DTAB in absence of added salt. Samples with bilayers are found to be composed of bilayer disks coexisting with vesicles. Disks are found to always predominate over vesicles with mass fractions about 70-90% disks and 10-30% vesicles. Micelles, disks and vesicles are observed to coexist in a few samples close to the micelle-to-bilayer transition.

  • 5. Bernin, D.
    et al.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Van Ruijven, M.
    Altskär, Annika
    SIK – Institutet för livsmedel och bioteknik.
    Strom, A.
    Rudemo, M.
    Microstructure of polymer hydrogels studied by pulsed field gradient NMR diffusion and TEM methods2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 12, p. 5711-5716Article in journal (Refereed)
    Abstract [en]

    The microstructure of various alginate gels have been studied by pulsed field gradient NMR (PFG NMR) and transmission electron microscopy (TEM). The reduced diffusivity of dendrimer diffusion within the gels has been obtained from PFG NMR diffusion experiments. The polymer strand radius, an important microstructural property, has been extracted from various diffusion models. The results agree well with the polymer strand radii obtained from image analysis of the corresponding TEM micrographs. © 2011 The Royal Society of Chemistry.

  • 6.
    Bełdowski, Piotr
    et al.
    UTP University of Science and Technology, Poland.
    Weber, Piotr
    Gdansk University of Technology, Poland.
    Dedinaite, Andra
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Gadomski, Adam
    UTP University of Science and Technology, Poland.
    Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment2018In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, no 44, p. 8997-9004Article in journal (Refereed)
    Abstract [en]

    Hyaluronic acid and phospholipids are two components in the synovial joint cavity that contribute to joint lubrication synergistically. Molecular dynamics simulations were performed and hydrogen bonds in hyaluronic acid were analyzed to identify specific sites that are responsible for its physical cross-linking. Two molecular masses of hyaluronic acid, 10 kDa and 160 kDa, were considered. We use molecular dynamics simulations and the small world network approach to investigate dynamic couplings using a distance map applied to oxygen atoms in a chain of hyaluronic acid in the presence of phospholipids and water. The distance characterizing the coupling can be defined in various ways to bring out the most evident differences between various scenarios of the polymer chain conformation We show herein a physical distance understood as H-bond length and classes of these distances which are defined in a coarse-grained picture of the molecule. Simulation results indicate that addition of phospholipids has little influence on hyaluronic acid crosslinking. However, longer chains and addition of lipids promote appreciably long lasting (resilient) networks that may be of importance in biological systems. Specific sites for hydrogen bonding of phospholipids to hyaluronic acid have also been identified.

  • 7.
    Brandner, Birgit D
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Hansson, Petra M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Swerin, Agne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Claesson, Per M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Wåhlander, Martin
    Schoelkopf, Joachim
    Solvent segregation and capillary evaporation at a superhydrophobic surface investigated by confocal Raman microscopy and force measurements2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 3, p. 1045-1052Article in journal (Refereed)
    Abstract [en]

    Wetting of water, a 1 : 1 water/ethanol mixture and an aqueous dodecylbenzene sulfonic acid surfactant solution on hydrophobic and superhydrophobic surfaces were studied using confocal Raman microscopy. The superhydrophobic surfaces were prepared by immersion of a glass substrate in a silica particle/fluoropolymer formulation followed by silanization. Preparation of hydrophobic surfaces was done in the same way with the exception that the silica particles were excluded from the formulation. The hydrophobic and superhydrophobic surfaces were characterized with respect to surface roughness using AFM, and by contact angle measurements using different liquids. Confocal Raman microscopy measurements in a 1 : 1 water/ethanol mixture showed an enrichment of ethanol close to the superhydrophobic surface, which could not be observed for the hydrophobic surface. Unexpectedly, the Raman spectrum of a pure water film in close proximity to the superhydrophobic surface displayed some differences compared to that of bulk water and indicated a stronger hydrogenbonding close to the superhydrophobic surface. Evidence for capillary evaporation next to the superhydrophobic surface was also found, and this results in very long-range capillary attraction between one superhydrophobic surface and a hydrophobic colloidal probe as shown by AFM colloidal probe force measurements. Addition of a surfactant or ethanol suppresses capillary evaporation.

  • 8.
    Dedinaite, Andra
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Polymer och fiber.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Claesson, Per
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Low friction and high load bearing capacity layers formed by cationic-block-non-ionic bottle-brush copolymers in aqueous media2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 22, p. 5361-5371Article in journal (Refereed)
  • 9. Dunér, G
    et al.
    Thormann, E
    Dedinaite, Andra
    YKI – Ytkemiska institutet.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Matyjaszewski, K
    Tilton, RD
    Nanomechanical mapping of a high curvature polymer brush grafted from a rigid nanoparticle2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 32, p. 8312-8320Article in journal (Refereed)
    Abstract [en]

    Analysis of interaction forces when probing a silica core-polyelectrolyte brush shell nanoparticle, adsorbed on a silica substrate and bathed by aqueous electrolyte solution, with an ultrasharp atomic force microscopy (AFM) tip provides a spatially resolved map of heterogeneous mechanical properties across the nanoparticle. The deformation of the brush is mainly compressive when probed directly above the nanoparticle centre and mainly deflective when probed at a finite horizontal distance away from the centre. The brush is significantly stiffer against compression than against deflection, and ionization of the brush has a greater stiffening effect against compression than deflection. Whereas a height image of the core-shell nanoparticle was unremarkable, showing a monotonic decrease in height with increasing horizontal distance from the centre, brush deformation, energy dissipation and adhesion displayed local minima over the centre and maxima at a finite horizontal distance away from the centre, corresponding to a position near the rigid core nanoparticle edge. The different response to brush deformation depending on the angle of probing is relevant to the interactions of brush-decorated macroscopic surfaces with submicrometer roughness and to the interactions of brush-decorated nanoparticles with ultrafine structures in their environments.

  • 10.
    Dédinaité, A
    et al.
    YKI – Ytkemiska institutet.
    Pettersson, T
    Mohanty, B
    Claesson, PM
    YKI – Ytkemiska institutet.
    Lubrication by organized soft matter2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, 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.

  • 11.
    Dédinaité, Andra
    YKI – Ytkemiska institutet.
    Biomimetic lubrication2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 2, p. 273-284Article in journal (Refereed)
    Abstract [en]

    The lubrication of synovial joints is extremely efficient, allowing smooth motion to be performed between relatively soft and vulnerable cartilage surfaces for close to 100 years. A failure of this system leads to significant pain and loss of life quality. The ultrastructure of cartilage is complex and of functional significance. The molecules that are involved in the lubrication process are of many types, and they associate with each other in a complex fashion. This review focuses on the lubricating molecules, both biolubricants and biomimetic ones that share some features of the biolubricants. It discusses the conditions that must be fulfilled for achieving low friction in aqueous media and emphasizes the importance of load bearing capacity and self-healing ability.

  • 12.
    Dédinaité, Andra
    et al.
    YKI – Ytkemiska institutet.
    Thormann, Esben
    Olanya, Geoffrey
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Nyström, Bo
    Kjøniksen, Anna-Lena
    Friction in aqueous media tuned by temperature-responsive polymer layers2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 11, p. 2489-2498Article in journal (Refereed)
    Abstract [en]

    An atomic force microscope colloidal probe technique has been employed to probe normal and friction forces between silica surfaces coated with adsorbed layers of a diblock copolymer of the composition poly(N-isopropylacrylamide)48-block-poly(3-acrylamidopropyl)trimethylammonium chloride)20, abbreviated PNIPAAM48-b-PAMPTMA(+)20. The interactions between the PNIPAAM48-b- PAMPTMA(+)20-coated surfaces across a 0.1 mM NaCl (pH 6) solution at 25 _x0002_C are purely repulsive, due to a combination of steric and electrostatic double-layer forces. However, when the temperature is increased to 35 _x0002_C, and subsequently to 45 _x0002_C, an attractive force develops at short separations due to the unfavourable PNIPAAM–water interaction at these temperatures. The temperature-dependent polymer–water interaction has implications for the friction force between the layers. At 25 _x0002_C a frictional force that increases linearly with increasing load is observed once the surfaces are brought into close contact. At higher temperatures significantly higher friction forces appear as a consequence of attractive segment–segment interactions. Further, a clearly expressed hysteresis between friction forces encountered on loading and unloading is detected. Our results demonstrate that both normal and friction forces between surfaces can be controlled by temperature changes when temperatureresponsive polymers are employed, and friction forces can be adjusted as required from low to high.

  • 13. Fransson, S.
    et al.
    Peleg, O.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Kroger, M.
    Modelling and confocal microscopy of biopolymer mixtures in confined geometries2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 12, p. 2713-2722Article in journal (Refereed)
  • 14.
    Li, Gen
    et al.
    KTH Royal Institute of Technology, Sweden.
    Dobryden, Illia
    KTH Royal Institute of Technology, Sweden.
    Salazar-Sandoval, Eric Johansson
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Johansson, Mats
    KTH Royal Institute of Technology, Sweden.
    Claesson, Per M
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Load-dependent surface nanomechanical properties of poly-HEMA hydrogels in aqueous medium.2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 38, p. 7704-7714Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of hydrogels are of importance in many applications, including scaffolds and drug delivery vehicles where the release of drugs is controlled by water transport. While the macroscopic mechanical properties of hydrogels have been reported frequently, there are less studies devoted to the equally important nanomechanical response to local load and shear. Scanning probe methods offer the possibility to gain insight on surface nanomechanical properties with high spatial resolution, and thereby provide fundamental insights on local material property variations. In this work, we investigate the local response to load and shear of poly(2-hydroxyethyl methacrylate) hydrogels with two different cross-linking densities submerged in aqueous solution. The response of the hydrogels to purely normal loads, as well as the combined action of load and shear, was found to be complex due to viscoelastic effects. Our results show that the surface stiffness of the hydrogel samples increased with increasing load, while the tip-hydrogel adhesion was strongly affected by the load only when the cross-linking density was low. The combined action of load and shear results in the formation of a temporary sub-micrometer hill in front of the laterally moving tip. As the tip pushes against such hills, a pronounced stick-slip effect is observed for the hydrogel with low cross-linking density. No plastic deformation or permanent wear scar was found under our experimental conditions.

  • 15. Liu, C
    et al.
    Wang, M
    An, J
    Thormann, E
    Dedinaite, Andra
    YKI – Ytkemiska institutet.
    Hyaluronan and phospholipids in boundary lubrication2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 40, p. 10241-10244Article in journal (Refereed)
    Abstract [en]

    Hyaluronan has been found to play an important role in boundary lubrication in joints, but model experiments have shown that free hyaluronan is reluctant to stay between surfaces. We show that hyaluronan, when assisted by a phospholipid bilayer, can act as a boundary lubricant, even at pressures well above those leading to breakdown of cartilage.

  • 16.
    Lopez-Sanchez, Patricia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience. University of Queensland, Australia.
    Schuster, Erich
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Wang, Dongjie
    University of Queensland, Australia.
    Gidley, Michael J.
    University of Queensland, Australia.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    Diffusion of macromolecules in self-assembled cellulose/hemicellulose hydrogels2015In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, no 20, p. 4002-4010Article in journal (Refereed)
    Abstract [en]

    Cellulose hydrogels are extensively applied in many biotechnological fields and are also used as models for plant cell walls. We synthesised model cellulosic hydrogels containing hemicelluloses, as a biomimetic of plant cell walls, in order to study the role of hemicelluloses on their mass transport properties. Microbial cellulose is able to self-assemble into composites when hemicelluloses, such as xyloglucan and arabinoxylan, are present in the incubation media, leading to hydrogels with different nano and microstructures. We investigated the diffusivities of a series of fluorescently labelled dextrans, of different molecular weight, and proteins, including a plant pectin methyl esterase (PME), using fluorescence recovery after photobleaching (FRAP). The presence of xyloglucan, known to be able to crosslink cellulose fibres, confirmed by scanning electron microscopy (SEM) and 13C NMR, reduced mobility of macromolecules of molecular weight higher than 10 kDa, reflected in lower diffusion coefficients. Furthermore PME diffusion was reduced in composites containing xyloglucan, despite the lack of a particular binding motif in PME for this polysaccharide, suggesting possible non-specific interactions between PME and this hemicellulose. In contrast, hydrogels containing arabinoxylan coating cellulose fibres showed enhanced diffusivity of the molecules studied. The different diffusivities were related to the architectural features found in the composites as a function of polysaccharide composition. Our results show the effect of model hemicelluloses in the mass transport properties of cellulose networks in highly hydrated environments relevant to understanding the role of hemicelluloses in the permeability of plant cell walls and aiding design of plant based materials with tailored properties.

  • 17. Moglianetti, M
    et al.
    Campbell, RA
    Nylander, T
    Varga, I
    Mohanty, B
    Claesson, PM
    YKI – Ytkemiska institutet.
    Interaction of sodium dodecyl sulfate and high charge density comb polymers at the silica/water interface2009In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 5, no 19, p. 3646-3656Article in journal (Refereed)
    Abstract [en]

    The structures of interfacial layers formed from mixtures of comb polymers, comprising a high charge density cationic backbone and poly(ethylene oxide) (PEO) side-chains, with the anionic surfactant sodium dodecyl sulfate (SDS) at the silica/water interface, have been determined using neutron reflectivity measurements. The use of mixtures in which only the isotopic composition of the surfactant is changed has made it possible to determine the interfacial volume fraction profiles for both the polymer and the surfactant. For the polymer with 90% of the segments charged and 10% of the segments carrying PEO side-chains, there are four regimes of interfacial behavior with increasing surfactant composition of the bulk solution. First there is adsorption of surfactant to the polymer-covered surface, then, slightly above polymer charge stoichiometry, there is adsorption of near-neutral polymer/surfactant complexes followed by the adsorption of polymer/surfactant aggregates, with a well-defined internal structure. If the concentration of SDS is increased directly from below polymer charge stoichiometry to above the cmc, micelles or polymer/micelle complexes interact with the pre-existing polymer layer. Increasing the fraction of segments carrying PEO side-chains to 25% suppresses the formation of charge-neutral polymer/surfactant complexes at the interface. There is an increase in the adsorption of surfactant, which interacts with the pre-existing layer of polymers. This results in the surface aggregation of SDS and a swelling of the PEO side-chains from a mushroom to a brush-like configuration.

  • 18.
    Niga, Petru
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Hansson-Mille, Petra
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Swerin, Agne
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Schoelkopf, Joachim
    Omya International AG, Switzerland.
    Gane, Patrick
    Omya International AG, Switzerland; Aalto University, Finland.
    Dai, Jing
    KTH Royal Institute of Technology, Sweden.
    Furó, Istvan
    KTH Royal Institute of Technology, Sweden.
    Campbell, Richard
    Institut Laue-Langevin, France; University of Manchester, UK.
    Johnson, Magnus
    KTH Royal Institute of Technology, Sweden.
    Propofol adsorption at the air/water interface: a combined vibrational sum frequency spectroscopy, nuclear magnetic resonance and neutron reflectometry study2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 1, p. 38-46Article in journal (Refereed)
    Abstract [en]

    Propofol is an amphiphilic small molecule that strongly influences the function of cell membranes, yet data regarding interfacial properties of propofol remain scarce. Here we consider propofol adsorption at the air/water interface as elucidated by means of vibrational sum frequency spectroscopy (VSFS), neutron reflectometry (NR), and surface tensiometry. VSFS data show that propofol adsorbed at the air/water interface interacts with water strongly in terms of hydrogen bonding and weakly in the proximity of the hydrocarbon parts of the molecule. In the concentration range studied there is almost no change in the orientation adopted at the interface. Data from NR show that propofol forms a dense monolayer with a thickness of 8.4 Å and a limiting area per molecule of 40 Å2, close to the value extracted from surface tensiometry. The possibility that islands or multilayers of propofol form at the air/water interface is therefore excluded as long as the solubility limit is not exceeded. Additionally, measurements of the 1H NMR chemical shifts demonstrate that propofol does not form dimers or multimers in bulk water up to the solubility limit.

  • 19.
    Nordgren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Non-ionic assembly of nanofibrillated cellulose and polyethylene glycol grafted carboxymethyl cellulose and the effect of aqueous lubrication in nanocomposite formation2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 31, p. 7448-7457Article in journal (Refereed)
  • 20. Pääkkö, M.
    et al.
    Vapaavuori, J.
    Silvennoinen, R.
    Kosonen, H.
    Ankerfors, Mikael
    RISE, STFI-Packforsk.
    Lindström, Tom
    RISE, STFI-Packforsk.
    Berglund, L. A.
    Ikkala, O.
    Long and entangled native cellulose i nanofibers allow flexible aerogels and hierarchically porous templates for functionalities2008In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 4, no 12, p. 2492-2499Article in journal (Refereed)
    Abstract [en]

    Recently it was shown that enzymatic and mechanical processing of macroscopic cellulose fibers lead to disintegration of long and entangled native cellulose I nanofibers in order to form mechanically strong aqueous gels (Pääkkö¶ et al., Biomacromolecules, 2007, 8, 1934). Here we demonstrate that (1) such aqueous nanofibrillar gels are unexpectedly robust to allow formation of highly porous aerogels by direct water removal by freeze-drying, (2) they are flexible, unlike most aerogels that suffer from brittleness, and (3) they allow flexible hierarchically porous templates for functionalities, e.g. for electrical conductivity. No crosslinking, solvent exchange nor supercritical drying are required to suppress the collapse during the aerogel preparation, unlike in typical aerogel preparations. The aerogels show a high porosity of ˜98% and a very low density of ca. 0.02 g cm -3. The flexibility of the aerogels manifests as a particularly high compressive strain of ca. 70%. In addition, the structure of the aerogels can be tuned from nanofibrillar to sheet-like skeletons with hierarchical micro- and nanoscale morphology and porosity by modifying the freeze-drying conditions. The porous flexible aerogel scaffold opens new possibilities for templating organic and inorganic matter for various functionalities. This is demonstrated here by dipping the aerogels in an electrically conducting polyaniline-surfactant solution which after rinsing off the unbound conducting polymer and drying leads to electrically conducting flexible aerogels with relatively high conductivity of around 1 ח 10-2 S cm-1. More generally, we foresee a wide variety of functional applications for highly porous flexible biomatter aerogels, such as for selective delivery/separation, tissue-engineering, nanocomposites upon impregnation by polymers, and other medical and pharmaceutical applications.

  • 21. Rousseau, D
    et al.
    Smith, P
    YKI – Ytkemiska institutet.
    Microstructure of fat bloom development in plain and filled chocolate confections2008In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 4, p. 1706-1712Article in journal (Refereed)
    Abstract [en]

    Temperature-controlled environmental scanning electron microscopy was used to examine the microstructural changes in plain solid chocolate and its counterpart stored against a tricaprylin-based filling cream. Sample storage at 26 C for 40 days led to significant changes in microstructure as a function of time. Surface imperfections (pores, pits, etc.) initially present on the filled confection disappeared within two days whereas those on the control did not throughout the storage period. Morphological changes on the surface of the control were dominated by the growth of needle-like crystals whereas spherulites appeared on the filled chocolate, with large crystals (upwards of 100 microns in length, in some cases) observed in both cases. From a microstructural perspective, both diffusion and capillarity appear to have a part in fat bloom initiation and propagation, though temperature and the presence of a filling fat strongly dictate which mechanism will dominate.

  • 22.
    Röding, Magnus
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Shape-dependent effective diffusivity in packings of hard cubes and cuboids compared with spheres and ellipsoids2017In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 13, no 46, p. 8864-8870Article in journal (Refereed)
    Abstract [en]

    We performed computational screening of effective diffusivity in different configurations of cubes and cuboids compared with spheres and ellipsoids. In total, more than 1500 structures are generated and screened for effective diffusivity. We studied simple cubic and face-centered cubic lattices of spheres and cubes, random configurations of cubes and spheres as a function of volume fraction and polydispersity, and finally random configurations of ellipsoids and cuboids as a function of shape. We found some interesting shape-dependent differences in behavior, elucidating the impact of shape on the targeted design of granular materials.

  • 23.
    Röding, Magnus
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden; University College London, Australia.
    Schuster, Erich
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Logg, Katarina
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Lundman, Malin
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    Bergström, Per
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    Hanson, Charlotta
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Computational high-throughput screening of fluid permeability in heterogeneous fiber materials2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 29, p. 6293-6299Article in journal (Refereed)
    Abstract [en]

    We explore computational high-throughput screening as a design strategy for heterogeneous, isotropic fiber materials. Fluid permeability, a key property in the design of soft porous materials, is systematically studied using a multi-scale lattice Boltzmann framework. After characterizing microscopic permeability as a function of solid volume fraction in the microstructure, we perform high-throughput computational screening of in excess of 35000 macrostructures consisting of a continuous bulk interrupted by spherical/elliptical domains with either lower or higher microscopic permeability (hence with two distinct microscopic solid volume fractions and therefore two distinct microscopic permeabilities) to assess which parameters determine macroscopic permeability for a fixed average solid volume fraction. We conclude that the fractions of bulk and domains and the distribution of solid volume fraction between them are the primary determinants of macroscopic permeability, and that a substantial increase in permeability compared to the corresponding homogenous material is attainable.

  • 24.
    Schellmann, Kathrin
    et al.
    University of Stuttgart, Germany.
    Preisig, Natalie
    University of Stuttgart, Germany.
    Claesson, Per
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Stubenrauch, Cosima
    University of Stuttgart, Germany.
    Effects of protonation on foaming properties of dodecyldimethylamine oxide solutions: A pH-study2015In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, no 3, p. 561-571Article in journal (Refereed)
    Abstract [en]

    The critical micelle concentration (cmc), the surface excess (Γ), as well as the micelle aggregation number (m) of the surfactant dodecyldimethylamine oxide (C12DMAO) have been reported to strongly depend on the pH-value of the aqueous surfactant solution. At high ionic strength, the cmc displays a minimum, while both Γ and m have a maximum at a pH-value close to the pKa of the surfactant. These experimental observations have been explained as being due to specific hydrogen bonds between the head groups, which are formed once the surfactant is partly or fully protonated. This investigation addresses the question of whether the pH also affects the foaming properties of C12DMAO solutions. To answer this question we measured the foamability and the foam stability of C12DMAO solutions at a fixed C12DMAO concentration of 5 cmc for five different pH-values, namely pH = 2, 3, 5, 8, and 10. We found that the foamability is hardly affected by the pH-value, while the foam stability strongly depends on the pH. As is the case for the above mentioned properties, the foam stability also displays an extremum in the studied pH-range, namely a maximum at pH = 5. We discuss our results in terms of the hydrogen bond hypothesis and show that this hypothesis indeed is in line with the observed trend for the foam stability. Moreover, we discuss that hydrogen bond formation may rationalize how the molecular structure of a surfactant affects foam stability.

  • 25.
    Schuster, Erich
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Eckardt, Johanna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Larsson, A.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Microstructural, mechanical and mass transport properties of isotropic and capillary alginate gels2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 2, p. 357-366Article in journal (Refereed)
    Abstract [en]

    Macroscopically homogeneous and inhomogeneous calcium alginate gels are formed via internal or external addition of various amounts of calcium to an alginate solution. The externally formed gels contain parallel aligned capillary structures. The mechanical and mass transport properties and the microstructure of the differently set gels were characterized by rheological measurements, fluorescence recovery after photobleaching (FRAP) and transmission electron microscopy (TEM). TEM images show a zone of distorted anisotropic gel structure in the vicinity of the capillaries as well as indications of a lower degree of void connectivity. The diffusion rates of dextran at large distances from the capillaries were fast and capillary gels showed a plastic behaviour in comparison to the internally set gels. The results presented show large functional differences between the internally and externally set gels, which cannot be explained by the presence of capillaries alone. © 2014 The Royal Society of Chemistry.

  • 26.
    Schuster, Erich
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Sott, Kristin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Smisdom, Nick
    Hasselt University, Belgium; Flemish Institute for Technological Research, Belgium.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Hermansson, Anne-Marie
    Chalmers University of Technology, Sweden.
    Interplay between flow and diffusion in capillary alginate hydrogels2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 17, p. 3897-3907Article in journal (Refereed)
    Abstract [en]

    Alginate gels with naturally occurring macroscopic capillaries have been used as a model system to study the interplay between laminar flow and diffusion of nanometer-sized solutes in real time. Calcium alginate gels that contain homogeneously distributed parallel-aligned capillary structures were formed by external addition of crosslinking ions to an alginate sol. The effects of different flow rates (0, 1, 10, 50 and 100 μl min-1) and three different probes (fluorescein, 10 kDa and 500 kDa fluorescein isothiocyanate-dextran) on the diffusion rates of the solutes across the capillary wall and in the bulk gel in between the capillaries were investigated using confocal laser scanning microscopy. The flow in the capillaries was produced using a syringe pump that was connected to the capillaries via a tube. Transmission electron microscopy revealed an open aggregated structure close to the capillary wall, followed by an aligned network layer and the isotropic network of the bulk gel. The most pronounced effect was observed for the 1 nm-diameter fluorescein probe, for which an increase in flow rate increased the mobility of the probe in the gel. Fluorescence recovery after photobleaching confirmed increased mobility close to the channel, with increasing flow rate. Mobility maps derived using raster image correlation spectroscopy showed that the layer with the lowest mobility corresponded to the anisotropic layer of ordered network chains. The combination of microscopy techniques used in the present study elucidates the flow and diffusion behaviors visually, qualitatively and quantitatively, and represents a promising tool for future studies of mass transport in non-equilibrium systems.

  • 27. Stubenrauch, C
    et al.
    Shrestha, LK
    Varade, D
    Johansson, I
    Olanya, G
    YKI – Ytkemiska institutet.
    Aramaki, K
    Claesson, P
    YKI – Ytkemiska institutet.
    Aqueous foams stabilized by n-dodecyl-β-D-maltoside, hexaethyleneglycol monododecyl ether, and their 1 : 1 mixture2009In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 5, no 16, p. 3070-3080Article in journal (Refereed)
    Abstract [en]

    Aqueous foams stabilized by the non-ionic surfactants n-dodecyl-β-D-maltoside (β-C12G2) and hexaethyleneglycol monododecyl ether (C12E2) as well as by their 1 : 1 mixture were studied as a function of the total surfactant concentration from 0.1 to 10 cmc. Foamability and foam stability were measured with home-built winding equipment, the commercially available FoamScan, and a home-built foam conductivity apparatus (FCA), respectively. It was found that the foamability increases with increasing surfactant concentration for both the single and the mixed surfactant systems. On the other hand, at a fixed relative surfactant concentration (c/cmc) the foamability of β-C12G2 solutions was found to be much higher than that of C12E6 solutions, while the 1 : 1 mixture behaves like the pure C12E6.Measurements at different gas (N2) flow rates have shown that the foamability decreases non-linearly with decreasing N2 flow rate, which shows that foam generation and foam breakdown occur simultaneously. Regarding foam stability it was found that it also increases with increasing surfactant concentration. As was the case for the foamability, the stability of foams stabilized by β-C12G2 was much higher than that of foams stabilized by C12E6, while the foam stability of the 1 : 1 mixture was comparable to that of the pure C12E6. The foam results are discussed in the light of static surface tensions, dynamic surface tensions, and surface elasticities, which were measured for the single and the mixed surfactant systems.

  • 28. Ture, H.
    et al.
    Gällstedt, M.
    RISE, Innventia.
    Kuktaite, R.
    Johansson, E.
    Hedenqvist, M.S.
    Protein network structure and properties of wheat gluten extrudates using a novel solvent-free approach with urea as a combined denaturant and plasticiser2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, no 19, p. 9416-9423Article in journal (Refereed)
  • 29. Varga, Imre
    et al.
    Mezei, Amalia
    Meszaros, Robert
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Controlling the interaction of poly(ethylene imine) adsorption layers with oppositely charged surfactant by tuning the structure of the preadsorbed polyelectrolyte layer2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 22, p. 10701-10712Article in journal (Refereed)
    Abstract [en]

    This study contributes to the understanding of how the structure of preadsorbed polyelectrolyte layers affects their interaction with oppositely charged surfactants. The adsorbed amount, and thus the adsorption layer structure of poly(ethylene imine), (PEI), was tuned by the pH (4, 6 and 9) of the PEI adsorption. Following the PEI adsorption, each adsorption layer was rinsed with 10 mM NaCl solution (pH(Rinse) = 6) to establish identical conditions for further SDS binding. The structure of the PEI adsorption layers was investigated in situ by dual polarization interferometry (DPI). By comparing the DPI results with ellipsometry results and by performing DPI and ellipsometry simulations it could be demonstrated the first time that PEI forms a vertically inhomogeneous adsorption layer that can be described as having a compact bottom part, which contains PEI molecules with a large number of surface contacts, and a swollen outer part, which includes loosely bound PEI molecules that extend far into the bulk phase. The pH of the adsorption controls not only the adsorbed mass but also the structure of the adsorbed layer, which can be further tuned by changing the pH of the rinsing solution. To investigate how the structure of the preadsorbed PEI layer affects its interfacial association with SDS, the preadsorbed polymer layers were rinsed with SDS solutions under identical conditions (10 mM NaCl, pH(Rinse) = 6). It was found that the structure of the preadsorbed PEI layer has a profound effect on the PEI/surfactant interaction. For instance, when the outer part of the PEI layer contained a sufficient amount of polymer segments, desorption of PEI could be prevented. In contrast, when the outer part of the PEI layer was depleted in polymer segments complete desorption could be achieved provided the polymer layer was rinsed with a high concentration (similar to cmc) surfactant solution under continuous flow.

  • 30.
    Wassen, Sofia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Geback, T.
    Bernin, D.
    Schuster, E.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Probe diffusion in phase-separated bicontinuous biopolymer gels2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 41, p. 8276-8287Article in journal (Refereed)
    Abstract [en]

    Probe diffusion was determined in phase separated bicontinuous gels prepared by acid-induced gelation of the whey protein isolate-gellan gum system. The topological characterization of the phase-separated gel systems is achieved by confocal microscopy and the diffusion measurements are performed using pulsed field gradient (PFG) NMR and fluorescence recovery after photo-bleaching (FRAP). These two techniques gave complementary information about the mass transport at different time- and length scales, PFG NMR provided global diffusion rates in the gel systems, while FRAP enabled the measurements of diffusion in different phases of the phase-separated gels. The results revealed that the phase-separated gel with the largest characteristic wavelength had the fastest diffusion coefficient, while the gel with smaller microstructures had a slower probe diffusion rate. By using the diffusion data obtained by FRAP and the structural data from confocal microscopy, modelling through the lattice-Boltzmann framework was carried out to simulate the global diffusion and verify the validity of the experimental measurements. With this approach it was found that discrepancies between the two experimental techniques can be rationalized in terms of probe distribution between the different phases of the system. The combination of different techniques allowed the determination of diffusion in a phase-separated biopolymer gel and gave a clearer picture of this complex system. We also illustrate the difficulties that can arise if precautions are not taken to understand the system-probe interactions.

  • 31.
    Wassen, Sofia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    van Bemmel, K.
    Schuster, E.
    Rondeau, E.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Effects of confinement on phase separation kinetics and final morphology of whey protein isolate-gellan gum mixtures2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 9, p. 2738-2749Article in journal (Refereed)
    Abstract [en]

    The final microstructure of a phase separating and gelling biopolymer mixture is affected by physical confinement, because the structure evolution is limited by the surrounding surfaces. Here, we used various confining geometries such as microdroplets, parallel cover glasses, and networks of cellulose fibers to analyze the structure evolution and final morphology of mixtures of whey protein isolate (WPI) and gellan gum. The results were evaluated by confocal laser scanning microscopy (CLSM) and 2D fast Fourier transform (FFT) image analysis. This showed that the final morphology within the restricted geometry is determined by the characteristic wavelength of the bicontinuous bulk microstructure in relation to the dimensions of the confinements. The growth of the characteristic wavelength in the WPI-gellan gum system has two different regimes, which are similar in the bulk phase and large microdroplets. The growth is then kinetically trapped by the gelation. In microdroplets with a smaller dimension than the characteristic bulk wavelength, the growth of the spinodal structure is observed to collapse as the characteristic wavelength approaches the microdroplet diameter. This results in a core-shell structure with WPI present at the interface. Furthermore, 3D reconstructions of CLSM images from the parallel glass confinement showed that the bicontinuous structure is converted to columnar structures interconnecting two wetting layers at the glass surfaces. Similar columnar structures are observed between cellulose fibers. The present findings demonstrate that it is important to understand the impact of confinement on phase separation and gelation in order to control the final microstructure. © 2013 The Royal Society of Chemistry.

  • 32.
    Wieland, D. C. Florian
    et al.
    Helmholtz-Zentrum Geesthacht, Germany.
    Degen, Patrick
    Technical University of Dortmund, Germany.
    Zander, Thomas
    Helmholtz-Zentrum Geesthacht, Germany.
    Gayer, Sören
    Helmholtz-Zentrum Geesthacht, Germany.
    Raj, Akanksha
    KTH Royal Institute of Technology, Sweden.
    An, Junxue
    RISE, SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Dédinaité, Andra A.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. KTH Royal Institute of Technology, Sweden.
    Willumeit-Römer, Regine
    Helmholtz-Zentrum Geesthacht, Germany.
    Structure of DPPC-hyaluronan interfacial layers-effects of molecular weight and ion composition2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 3, p. 729-740Article in journal (Refereed)
    Abstract [en]

    Hyaluronan and phospholipids play an important role in lubrication in articular joints and provide in combination with glycoproteins exceptionally low friction coefficients. We have investigated the structural organization of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) Langmuir layers at the solution-air interface at different length scales with respect to the adsorption of hyaluronan (HA). This allows us to assemble a comprehensive picture of the adsorption and the resulting structures, and how they are affected by the molecular weight of HA and the presence of calcium ions. Brewster angle microscopy and grazing incident diffraction were used to determine the lateral structure at the micro- and macro scale. The data reveals an influence of HA on both the macro and micro structure of the DPPC Langmuir layer, and that the strength of this effect increases with decreasing molecular weight of HA and in presence of calcium ions. Furthermore, from X-ray reflectivity measurements we conclude that HA adsorbs to the hydrophilic part of DPPC, but data also suggest that two types of interfacial structures are formed at the interface. We argue that hydrophobic forces and electrostatic interactions play important rules for the association between DPPC and HA. Surface pressure area isotherms were used to determine the influence of HA on the phase behavior of DPPC while electrophoretic mobility measurements were used to gain insight into the binding of calcium ions to DPPC vesicles and hyaluronan.

  • 33.
    Zander, Thomas
    et al.
    Institute of Materials Research, Germany.
    Wieland, Florian
    Institute of Materials Research, Germany.
    Raj, Akanksha
    KTH Royal Institute of Technology, Sweden.
    Salmen, Paul
    Fakultät Physik/DELTA, Germany.
    Dogan, Susanne
    Fakultät Physik/DELTA, Germany.
    Dėdinaitė, Andra
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Garamus, Vasil
    Institute of Materials Research, Germany.
    Schreyer, Andreas
    Institute of Materials Research, Germany.
    Claesson, Per M
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Willumeit-Römer, Regine
    Institute of Materials Research, Germany.
    Influence of high hydrostatic pressure on solid supported DPPC bilayers with hyaluronan in the presence of Ca2+ ions2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 36, p. 7295-7304Article in journal (Refereed)
    Abstract [en]

    The molecular mechanisms responsible for outstanding lubrication of natural systems, like articular joints, have been the focus of scientific research for several decades. One essential aspect is the lubrication under pressure, where it is important to understand how the lubricating entities adapt under dynamic working conditions in order to fulfill their function. We made a structural investigation of a model system consisting of two of the molecules present at the cartilage interface, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and hyaluronan, at high hydrostatic pressure. Phospholipid layers are found at the cartilage surfaces and are able to considerably reduce friction. Their behavior under load and varied solution conditions is important as pressures of 180 bar are encountered during daily life activities. We focus on how divalent ions, like Ca2+, affect the interaction between DPPC and hyaluronan, as other investigations have indicated that calcium ions influence their interaction. It could be shown that already low amounts of Ca2+ strongly influence the interaction of hyaluronan with DPPC. Our results suggest that the calcium ions increase the amount of adsorbed hyaluronan indicating an increased electrostatic interaction. Most importantly, we observe a modification of the DPPC phase diagram as hyaluronan absorbs to the bilayer which results in an Lα-like structure at low temperatures and a decoupling of the leaflets forming an asymmetric bilayer structure.

  • 34. Zhou, Q.
    et al.
    Malm, E.
    Nilsson, Helena
    RISE, Innventia.
    Larsson, Per Tomas
    RISE, Innventia.
    Iversen, Tommy
    RISE, Innventia.
    Berglund, L. A.
    Bulone, V.
    Nanostructured biocomposites based on bacterial cellulosic nanofibers compartmentalized by a soft hydroxyethylcellulose matrix coating2009In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Soft Matter, Vol. 5, no 21, p. 4124-4130Article in journal (Refereed)
    Abstract [en]

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

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