Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 69
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Adhikari, Arindam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pani, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Deidinaitei, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 12, s. 4239-4247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 2.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dèdinaitè, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Winnik, Francoise M.
    Qiu, Xing-Ping
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Temperature-Dependent Adsorption and Adsorption Hysteresis of a Thermoresponsive Diblock Copolymer2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 15, s. 4333-4341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nonionic-cationic diblock copolymer, poly(2-isopropyl-2-oxazoline)(60)-b-poly((3-acrylamidopropyl)- trimethylammonium chloride)(17), (PIPOZ(60)-b-PAMPTMA(17)), was utilized to electrostatically tether temperature-responsive PIPOZ chains to silica surfaces by physisorption. The effects of polymer concentration, pH, and temperature on adsorption were investigated using quartz crystal microbalance with dissipation monitoring and ellipsometry. The combination of these two techniques allows thorough characterization of the adsorbed layer in terms of surface excess, thickness, and water content. The high affinity of the cationic PAMPTMA(17) block to the negatively charged silica surface gives rise to a high affinity adsorption isotherm, leading to (nearly) irreversible adsorption with respect to dilution. An increase in solution pH lowers the affinity of PIPOZ to silica but enhances the adsorption of the cationic block due to increasing silica surface charge density, which leads to higher adsorption of the cationic diblock copolymer. Higher surface excess is also achieved at higher temperatures due to the worsening of the solvent quality of water for the PIPOZ block. Interestingly, a large hysteresis in adsorbed mass and other layer properties was observed when the temperature was cycled from 25 to 45 degrees C and then back to 25 degrees C. Possible causes for this temperature hysteresis are discussed.

  • 3.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nilsson, Anki
    Holgersson, Jan
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Comparison of a Brush-with-Anchor and a Train-of-Brushes Mucin on Poly(methyl methacrylate) Surfaces: Adsorption, Surface Forces, and Friction2014Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, nr 4, s. 1515-1525Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfacial properties of two types of mucins have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. One is commercially available bovine submaxillary mucin, BSM, which consists of alternating glycosylated and nonglycosylated regions. The other one is a recombinant mucin-type fusion protein, PSGL-1/mIgG(2b), consisting of a glycosylated mucin part fused to the Fc part of an immunoglobulin. PSGL-1/mIgG(2b) is mainly expressed as a (timer upon production. A quartz crystal microbalance with dissipation was used to study the adsorption of the mucins to PMMA surfaces. The mass of the adsorbed mucin layers, including the adsorbed mucin and water trapped in the layer, was found to be significantly higher for PSGL-1/mIgG(2b) than for BSM. Atomic force microscopy with colloidal probe was employed to study interactions and frictional forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were Observed between PSGL-1/mIgG(2b) mucin layers, whereas a small adhesion was detected between BSM layers and attributed to bridging. Both mucin layers reduced the friction force between PMMA surfaces in aqueous solution. The reduction was, however, significantly more pronounced for PSGL-1/mIgG(2b). The effective friction coefficient between PSGL-1/mIgG(2b)-coated PMMA surfaces is as low as 0.02 at low loads, increasing to 0.24 at the highest load explored, 50 nN. In contrast, a friction coefficient of around 0.7 was obtained between BSM-coated PMMA surfaces. The large differences in interfacial properties for the two mucins are discussed in relation to their structural differences.

  • 4.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Korchagina, Evgeniya
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers2017Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 487, s. 88-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperatures <40 degrees C. A local force minimum at short separation develops at 40 degrees C and a strong attraction due to capillary condensation of a polymer-rich phase is observed close to the bulk phase separation temperature. The friction forces decrease in the cooling stage due to rehydration of the PIPOZ chain. A consequence of the adsorption hysteresis is that the friction forces measured at 25 degrees C are significantly lower after exposure to a temperature of 40 degrees C than prior to heating, which is due to higher polymer chain density on the surface after heating.

  • 5.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Linse, Per
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. SP Technical Research Institute of Sweden, Sweden .
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 10, s. 3039-3048Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic-nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 degrees C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

  • 6.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Zander, Thomas
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Linse, Per
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Winnik, Francoise M.
    Qiu, Xing-Ping
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Tethered Poly(2-Isopropyl-2-Oxazoline) Chai: Temperature Effects of Layer Structure and Interactions Probed by AFM Experiments and ModelingManuskript (preprint) (Övrigt vetenskapligt)
  • 7.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Iruthayaraj, Joseph
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Lundin, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Vareikis, Aušvydas
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    van der Wal, Albert
    Lever Faberage Europe Global Technology Centre, Unilever R and D.
    Furó, István
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Garamus, Vasil M.
    GKSS Research Centre.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, nr 1, s. 21-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PE045MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

  • 8.
    Beldowski, Piotr
    et al.
    UTP Univ Sci & Technol, Inst Math & Phys, Al Kaliskiego 7, PL-85796 Bydgoszcz, Poland..
    Weber, Piotr
    Gdansk Univ Technol, Atom & Opt Phys Div, Dept Atom Mol & Opt Phys, Fac Appl Phys & Math, Narutowicza 11-12, PL-80233 Gdansk, Poland..
    Dédinaité, Andra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Box 5607, SE-11486 Stockholm, Sweden..
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Box 5607, SE-11486 Stockholm, Sweden..
    Gadomski, Adam
    UTP Univ Sci & Technol, Inst Math & Phys, Al Kaliskiego 7, PL-85796 Bydgoszcz, Poland..
    Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment2018Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, nr 44, s. 8997-9004Artikel i tidskrift (Refereegranskat)
    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.

  • 9. Bełdowski, P.
    et al.
    Weber, P.
    Dédinaité, Andra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Research Institutes of Sweden, Box 5607, SE-114 86 Stockholm, Sweden.
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Research Institutes of Sweden, Box 5607, SE-114 86 Stockholm, Sweden.
    Gadomski, A.
    Correction: Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment (Soft Matter (2018) DOI: 10.1039/c8sm01388h)2018Ingår i: Soft Matter, Vol. 14, nr 47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Correction for 'Physical crosslinking of hyaluronic acid in the presence of phospholipids in an aqueous nano-environment' by Piotr Bełdowski et al., Soft Matter, 2018, DOI: 10.1039/c8sm01388h. 

  • 10.
    Bodvik, Rasmus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Karlson, Leif
    Bergström, Lars Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Baverback, Petra
    Pedersen, Jan Skov
    Edward, Katarina
    Karlsson, Göran
    Varga, Imre
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Aggregation and network formation of aqueous methylcellulose and hydroxypropylmethylcellulose solutions2010Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 354, nr 1-3, s. 162-171Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solution properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) have been investigated as a function of temperature and concentration using a broad range of experimental techniques. Novelties include the extensive comparison between MC and HPMC solutions as well as the combination of techniques, and the use of Cryo transmission electron microscopy (Cryo-TEM). The correlation between rheology and light scattering results clearly demonstrates the relation between viscosity change and aggregation. Cryo-TEM images show the network structures formed. Viscosity measurements show that for both MC and HPMC solutions sudden changes in viscosity occur as the temperature is increased. The onset temperature for these changes depends on polymer concentration and heating rate. For both MC and HPMC solutions the viscosity on cooling is very different compared to on heating, demonstrating the slow equilibration time. The viscosity changes in MC and HPMC solutions are dramatically different; for MC solutions the viscosity increases by several orders of magnitude when a critical temperature is reached, whereas for HPMC solutions the viscosity decreases abruptly at a given temperature, followed by an increase upon further heating. Light and (SAXS) small-angle X-ray scattering shows that the increase in viscosity, for MC as well as for HPMC solutions, is due to extensive aggregation of the polymers. Light scattering also provides information on aggregation kinetics. The SAXS measurements allow us to correlate aggregation hysteresis to the viscosity hysteresis, as well as to extract some structural information. Cryo-TEM images give novel information that a fibrillar network is formed in MC solutions, and the strong viscosity increase occurs when this network spans the whole solution volume. For HPMC solutions the behaviour is more complex. The decrease in viscosity can be related to the formation of compact objects, and the subsequent increase to formation of fibrillar structures, which are more linear and less entangled than for MC.

  • 11.
    Claesson, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Meszaros, R.
    Varga, Imre
    Association between Polyelectrolytes and Oppositely Charged Surfactants in Bulk and at Solid/Liquid Interfaces2007Ingår i: Colloid Stability and Application in Pharmacy: Volume 3, Weinheim: Wiley-VCH Verlagsgesellschaft, 2007, s. 337-395Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Mixtures of polyelectrolytes and oppositely charged surfactants find applications in many processes and products that are used in our daily life. Such systems also show many interesting features from a scientific point of view. Due to the combined technological relevance and scientific challenge, considerable research efforts have been made in this area in recent years. This has resulted in new theoretical approaches, the development of simulation methods and new experimental techniques and, of course, a large body of new findings. Together, these efforts have increased the understanding significantly, especially during the last 5 years. This chapter reviews some aspects of this topic, focusing on bulk association and association at solid/liquid interfaces. The review is focused on developments during the 21st century, even though in some cases a historical perspective is also offered.

  • 12.
    Claesson, Per M.
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner                               , Kemi.
    Dedinaite, Andra
    KTH, Tidigare Institutioner                               , Kemi.
    Kjellin, M.
    Legrand, J. F.
    Grillo, I.
    Mixtures of cationic polyelectrolyte and anionic surfactant studied with small-angle neutron scattering2000Ingår i: Journal of Physical Chemistry B, ISSN 1089-5647, Vol. 104, nr 49, s. 11689-11694Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Small-angle neutron scattering (SANS) data for solutions containing a highly charged cationic polyelectrolyte and an anionic surfactant are presented. The scattering data were obtained in pure D2O, emphasizing the scattering from the polyelectrolyte, and in a H2O/D2O mixture that contrast matches the polyelectrolyte. In the absence of surfactant, a broad scattering peak due to the mesh size of the polyelectrolyte solution is the most characteristic feature. This peak moves to larger q-values (smaller distances) as the polyelectrolyte concentration is increased, as expected for a semidilute polyelectrolyte solution. Addition of a small amount of surfactant reduces and finally removes this peak. Instead a sharp diffraction peak appears at high q-values. This Bragg peak corresponds to a characteristic distance of 37-39 Angstrom, and it is observed when either the polyelectrolyte or the surfactant is contrast matched by the solvent. Once this peak has appeared, its position does not change when the surfactant concentration is increased. The intensity of the peak grows, however, until a stoichiometric polyelectrolyte-surfactant complex has been formed. The Bragg peak remains in excess surfactant solution. These results are discussed in relation to the structure of the polyelectrolyte-surfactant aggregates and in connection with recent results from surface force and turbidity measurements using the same polyelectrolyte-surfactant pair.

  • 13.
    Claesson, Per M.
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Dedinaite, Andra
    KTH, Tidigare Institutioner                               , Kemi.
    Rojas, O. J.
    Polyelectrolytes as adhesion modifiers2003Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 104, s. 53-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorbed layers of polyelectrolytes have been studied with atomic force microscopy (AFM) and the interferometric surface force apparatus (SFA). Particular emphasis was put on determining the effect of the polyelectrolyte charge density on surface topography, and the effect of the polyelectrolyte coating on the adhesive properties. The AFM was employed to image individual polymer chains at low adsorption densities and to characterize the layer topography and coverage at higher adsorption densities. The adhesive properties between two polyelectrolyte-coated surfaces in air were determined as a function of the number of contacts made at any given spot. The data provide evidence for formation of electrostatic bridges, particularly when highly charged polyelectrolytes are used. Further, material transport between the surfaces is observed when the polyelectrolyte is either highly charged or have a very low charge density. For intermediate charge densities we could not observe any indication of material transfer. The adhesion between one polyelectrolyte-coated surface and one bare surface was initially higher than that between two polyelectrolyte-coated surfaces. However, due to material transfer between the two surfaces the adhesion decreased significantly with the number of times that the surfaces were driven into contact. For the polyelectrolytes of the lowest charge density the results suggest that entanglement effects contribute to the adhesive interaction. The modification of the adhesion by polyelectrolytes in practical systems such as in the case of dry-strength additives to improve paper resistance is also considered.

  • 14.
    Claesson, Per M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Poptoshev, Evgeni
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Polyelectrolyte-mediated surface interactions2005Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114, s. 173-187Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The current understanding of interactions between surfaces coated with polyelectrolytes is reviewed. Experimental data obtained with various surface force techniques are reported and compared with theoretical predictions. The majority of the studies concerned with interactions between polyelectrolyte-coated surfaces deal with polyelectrolytes adsorbed to oppositely charged surfaces, and this is also the main focus of this review. However, we also consider polyelectrolytes adsorbed to uncharged surfaces and to similarly charged surfaces, areas where theoretical predictions are available, but relevant experimental data are mostly lacking. We also devote sections to interactions between polyelectrolyte brush-layers and to interactions due to non-adsorbing polyelectrolytes. Here, a sufficient amount of both theoretical and experimental studies are reported to allow us to comment on the agreement between theory and experiments. A topic of particular interest is the presence of trapped non-equilibrium states that often is encountered in experiments, but difficult to treat theoretically.

  • 15.
    Dedinaite, Andra
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Bastardo Zambrano, Luis Alejandro
    Oliveira, C. P.
    Pedersen, J. S.
    Claesson, Per M
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Vareikis, A.
    Makuska, R.
    Solution properties of bottle-brush polyelectrolytes2007Ingår i: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007    , 2007, s. 112-116Konferensbidrag (Refereegranskat)
    Abstract [en]

    Aqueous solution properties of bottle brush polyelectrolytes, where side-chains are attached to a polymer backbone, have been studied. The side chains consist of 45 units long poly(ethylene oxide) groups and the backbone is of the methacrylate type. Small-angle X-ray scattering (SAXS) was used to elucidate the solution conformation of this class of polymer and how it is affected by the side chain density and charge density. The effect of temperature on the solution conformation, and in particular the side chain extension, has also been quantified. At higher concentrations the interactions between the polymer chains in solution affects the scattering, and it is shown that this interaction is well described by a model originally developed for wormlike micelles.

  • 16.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Campbell, B.
    Interactions between mica surfaces across triglyceride solution containing phospholipid and polyglycerol polyricinoleate2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 5, s. 2248-2253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results obtained by direct measurements of the forces acting between polar mica surfaces interacting across solutions of triolein containing phosphatidylethanolamine (PE), polyglycerol polyricinoleate (PGPR), and a PE/PGPR mixture are presented. It was shown that PE adsorbed on mica from anhydrous triolein and thus rendered the surface nonpolar. The change in ordering of the liquid triolein molecules induced by bringing two such surfaces together gives rise to a structural force with two force barriers. In contrast, the adsorption of PGPR from anhydrous triolein resulted in a steric force barrier with a range of 120 Angstrom. It was also found that from the mixture of PE and PGPR in triolein both additives adsorbed as a complex on mica surfaces. The presence of these aggregates on the surfaces gave rise to a very long-range strong repulsive force. We discuss the implication of the measured forces to colloidal stability of particle dispersion in nonpolar media and compare the efficiency of additives as dispersion stabilizers. We also show that the presence of water has an effect on the adsorbed layer structures. When PE is used as a dispersing agent, water induces formation of aggregates, which would provide strong repulsive barriers between the particles. In contrast, when PGPR is used as additive, water preferentially adsorbs on the polar mica surface and at water saturation gives rise to a capillary formation around the surface contact position. Finally, when a mixture of PE and PGPR is used, water is found to result in formation of a viscous, sticky, adsorbed layer that would flocculate the particles.

  • 17.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Claesson, Per M
    KTH, Tidigare Institutioner                               , Kemi.
    Interfacial properties of aggregates formed by cationic polyelectrolyte and anionic surfactant2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 4, s. 1951-1959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interactions between mica surfaces across aqueous solutions containing mixtures of a highly positively charged polyelectrolyte and an anionic surfactant were studied by use of a surface force apparatus. The investigation was carried out with a constant polyelectrolyte concentration (20 ppm) and a wide range of surfactant concentrations [0-1 times the critical micelle concentration (cmc)]. The chemical composition of the adsorbed polyelectrolyte-surfactant layers was analyzed by x-ray photoelectron spectroscopy (XPS). The properties of polyelectrolyte-surfactant aggregates formed in bulk were studied by measurements of turbidity and electrophoretic mobility. The aggregates formed at low surfactant concentrations (<0.04 times cmc) were positively charged, whereas at higher surfactant concentrations the aggregates carried a net negative charge. It was shown that polyelectrolyte-surfactant aggregates rapidly adsorb on negatively charged mica surfaces regardless of the sign of their charge. At surfactant concentrations up to 0.01 times cmc, the polyelectrolytes adsorb on mica surfaces with loops acid tails stretching out into solution and repulsive steric forces are generated. The thickness of the layer decreases with time and we suggest that this conformational change is accompanied by some expulsion of surfactant from the adsorbed layers. Thick adsorbed layers were formed in the surfactant concentration range 0.02-0.1 times cmc. In this concentration regime the measurement of equilibrium forces was inaccessible due to a very slow layer relaxation. During compression the forces were repulsive and during separation an attraction developed. We attribute this to formation of interlayer surfactant bridges. Finally, at high surfactant concentrations (greater than or equal to 0.4 times cmc) highly negatively charged aggregates adsorb on the surfaces in rather thin layers, resulting in purely repulsive forces of mixed electrostatic and steric origin.

  • 18.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Claesson, Per M
    KTH, Tidigare Institutioner                               , Kemi.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner                               , Kemi.
    Polyelectrolyte-surfactant layers: Adsorption of preformed aggregates versus adsorption of surfactant to preadsorbed polyelectrolyte2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 12, s. 5257-5266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The character of adsorbed layers containing both polyelectrolyte and surfactant depends on the type of polyelectrolyte used and the surfactant concentrations, as demonstrated by several recent studies. However, the layer properties also depend on the experimental pathway. This shows that the adsorbed layers can be trapped in quasi-equilibrium states and that the true equilibrium is reached only after experimentally inaccessible time scales. This has to be kept in mind when comparing different results reported in the literature. The present article highlights these effects using a system consisting of a highly charged cationic polyelectrolyte, poly{(propionyloxy)ethyl}trimethylammonium chloride (PCMA), and an anionic surfactant, sodium dodecyl sulfate (SDS). The adsorbed layer properties were determined using mainly surface force measurements and atomic force microscope (AFM) imaging. We also present some small-angle neutron scattering data for bulk PCMA-SDS complexes formed between the polyelectrolyte and the surfactant. They demonstrate the presence of a characteristic correlation length of about 37-39 Angstrom. A similar characteristic length scale is also observed in some of the adsorbed layers, both employing the AFM and the surface force apparatus. It may be interpreted as the distance between surfactant loaded polyelectrolyte chains.

  • 19.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Ernstsson, M.
    Chitosan-SDS interactions at a solid-liquid interface: Effects of surfactant concentration and ionic strength2003Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, nr 32, s. 8181-8188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of ionic strength on adsorption of chitosan on mica as well as the impact of addition of an anionic surfactant, SDS, on the adsorbed chitosan layers is explored. It is demonstrated by chemical surface analysis (ESCA) and surface force measurements (SFA) that an elevated salt concentration leads to larger adsorbed amounts and thicker adsorption layers of this cationic polyelectrolyte. It is also shown that in contrast to the bulk, the binding of oppositely charged surfactant to the polyelectrolyte adsorbed on a negatively charged surface is facilitated by elevated ionic strength. Thus, the association process in bulk and at solid-liquid interfaces is rather different. The main point of difference is that at the solid-liquid interface one also has to consider interactions between the polyelectrolyte and the surface as well as between the surfactant and the surface.

  • 20.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Meszaros, R.
    Claesson, Per M
    KTH, Tidigare Institutioner, Kemi.
    Effect of sodium dodecyl sulfate on adsorbed layers of branched polyethylene imine2004Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, nr 31, s. 11645-11653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of an anionic surfactant, sodium dodecyl sulfate, SDS, on the properties of adsorbed layers of a cationic highly branched polyelectrolyte, polyethylene,imine, PEI, has been investigated using surface force measurements, atomic force microscopy, and ESCA. The strategy used was to preadsorb PEI on negatively charged muscovite mica surfaces from a 20 ppm polyelectrolyte solution in 10 mM NaCl. The adsorption of PEI under these conditions gives rise to a strong recharging of the surface, i.e. after adsorption of PEI the surface carries a net positive charge. This conclusion was supported by ESCA measurements. Despite the high molecular weight of PEI (1.8 x 10(5) g/mol), the adsorbed layer is found to be very flat, and a repulsive double-layer force dominates at large separations. At smaller separation a strong attractive force is the main feature. Addition of SDS to a concentration of 0.01 cmc results in a nearly complete removal of the double-layer force, an increase in compressed layer thickness, and an increase in the magnitude of the adhesion force. Hence, significant SDS incorporation in the adsorbed layer occurs already at this low surfactant concentration. A recharging of the layer occurs at higher surfactant concentrations. At 0.5 cmc, the compressed thickness of the adsorbed layer is increased significantly and the adhesion between the surfaces has disappeared. We argue that each layer now is coated with an outer SDS layer oriented with the polar groups toward solution. In fact, there are striking similarities between the interfacial association between SDS and PEI and the adsorption of an ionic surfactant to an oppositely charged mineral surface. AFM imaging reveals that the adsorbed PEI layer is somewhat nonhomogeneous and contains polyelectrolyte patches. These surface features are smoothed out by addition of SDS to a concentration of 6 mM (1 cmc in 10 mM NaCl). ESCA measurements showed that exposure of the preadsorbed PEI layer to SDS concentrations around the cmc resulted in a limited desorption; about 15% of the initially adsorbed polyelectrolyte was removed after 16 h.

  • 21.
    Dedinaite, Andra
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mohanty, Biswaranjan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Claesson, Per M
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Lubrication by organized soft matter2010Ingår i: SOFT MATTER, ISSN 1744-683X, Vol. 6, nr 7, s. 1520-1526Artikel i tidskrift (Refereegranskat)
    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.

  • 22.
    Dobryden, Illia
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Ruiz, Maria Cortes
    CUNY City Coll, Dept Chem Engn, Grove Sch Engn, New York, NY 10031 USA..
    Zhang, Xuwei
    Univ Montreal, Dept Chem, CP 6128 Succursale Ctr Ville, Montreal, PQ H3C 3J7, Canada..
    Dédinaité, Andra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Div Biosci & Mat, SE-11486 Stockholm, Sweden..
    Wieland, D. C. Florian
    Helmholtz Zentrum Geesthacht, Inst Mat Res, Max Planck Str 1, D-21502 Geesthacht, Germany..
    Winnik, Francoise M.
    Univ Helsinki, Dept Chem, POB 55, FI-00014 Helsinki, Finland.;NIMS, Int Ctr Mat Nanoarchitecton MANA, 1-1 Namiki, Tsukuba, Ibaraki 3050044, Japan..
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Div Biosci & Mat, SE-11486 Stockholm, Sweden..
    Thermoresponsive Pentablock Copolymer on Silica: Temperature Effects on Adsorption, Surface Forces, and Friction2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 3, s. 653-661Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of hydrophilic or amphiphilic multiblock copolymers provides a powerful means to produce well-defined "smart" surfaces, especially if one or several blocks are sensitive to external stimuli. We focus here on an A-B-A-B-A copolymer, where A is a cationic poly((3acrylamido-propyl)-trimethylammonium chloride) (PAMPTMA) block containing 15 (end blocks) or 30 (middle block) repeat units and B is a neutral thermosensitive water-soluble poly(2-isopropyl-2-oxazoline) (PIPOZ) block with 50 repeat units. X-ray reflectivity and quartz crystal microbalance with dissipation monitoring were employed to study the adsorption of PAMPTMA(15)-PAMPTMA(30)-PIPOZ(50)-PAMPTMA(15) on silica surfaces. The latter technique was employed at different temperatures up to 50 degrees C. Surface forces and friction between the two silica surfaces across aqueous pentablock copolymer solutions at different temperatures were determined with the atomic force microscopy colloidal probe force and friction measurements. The cationic pentablock copolymer was found to have a high affinity to the negatively charged silica surface, leading to a thin (2 nm) and rigid adsorbed layer. A steric force was encountered at a separation of around 3 nm from hard wall contact. A capillary condensation of a polymer-rich phase was observed at the cloud point of the solution. The friction forces were evaluated using Amontons' rule modified with an adhesion term.

  • 23.
    Duner, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Iruthayaraj, Joseph
    Daasbjerg, Kim
    Pedersen, Steen Uttrup
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica2012Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 385, s. 225-234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Amine functionalities have been introduced on glassy carbon surfaces through electrografting of 4-(2-aminoethyl)benzenediazonium tetrafluoroborate. The grafted layers were characterized by ellipsometry and by nanomechanical mapping in air and aqueous solutions using the atomic force microscopy Peak-Force QNM mode. The layer was found to be 2.5 nm thick with low roughness, comparable to that of the glassy carbon substrate. However, small semi-spherical features were observed in the topographical image, indicating a clustering of the grafted amine compound. The nanomechanical mapping also demonstrated some swelling of the layer in water and pointed toward an important contribution of electrostatic interactions for the tip-surface adhesion. The forces between an aminated glassy carbon surface and a mu m-sized silica particle in aqueous solutions were measured at different ionic strength and pH-values. The results demonstrate that an attractive double-layer force predominates at large separations, and that the surface charge densities increase as the separation between the surfaces decreases. The degree of charge regulation on the aminated glassy carbon is significant. The relatively low surface charge density of the aminated glassy carbon is attributed to significant incorporation of counterions in the water-rich grafted layer.

  • 24.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Acid dissorciation constant gradients in a thick viscoelastic film determined by dissipation monitoring using quartz crystal microbalanceManuskript (preprint) (Övrigt vetenskapligt)
  • 25.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Frequency and dissipation measurements of in situ grafted poly(acrylic acid): a study of sensitivity and signal-to-noise ratio from thin to thick viscoelastic regimeManuskript (preprint) (Övrigt vetenskapligt)
  • 26.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Quartz Crystal Microbalance with Dissipation (QCM-D) studies of the viscoelastic response from a continuously growing grafted polyelectrolyte layer2013Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 408, s. 229-234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poly(acrylic acid) was grown from substrates by photopolymerization, and the grafting process was monitored in situ by Quartz Crystal Microbalance with Dissipation (QCM-D) measurements in a 1:1 v/v mixture of water/ethanol. The polymerization process was monitored into the thick film region, where the change in frequency and dissipation with increasing film mass changes sign as predicted by the Voigt viscoelastic model. Our experimental data are compared with predictions of this model, and satisfactory agreement is found for low overtone numbers. The Voigt model was applied to analyze the measured changes in frequency, Delta f, and dissipation, Delta D, in order to extract information on layer thickness, shear elasticity, mu, and shear viscosity, eta, of the growing film. The increasing rate of changes in Delta f and Delta D observed after about 150 s of polymerization was found to correlate with an increasing growth rate of the film thickness. For longer polymerization times a close to linear increase in thickness with time was observed. The sensitivity, defined as the derivatives of Delta f and Delta D with respect to thickness, depends on overtone number and is different for the frequency and dissipation signals - facts that should be considered when investigating small changes in thick films used in e.g. sensor applications.

  • 27.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Matyjaszewski, Krzysztof
    Tilton, Robert D.
    Nanomechanical mapping of a high curvature polymer brush grafted from a rigid nanoparticle2012Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, nr 32, s. 8312-8320Artikel i tidskrift (Refereegranskat)
    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.

  • 28.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Determination of grafting density of poly(acrylic acid) in a grafting: from approach using quartz crystal microbalance with dissipationManuskript (preprint) (Övrigt vetenskapligt)
  • 29.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Friction between Surfaces—Polyacrylic Acid Brush and Silica—Mediated by Calcium Ions2010Ingår i: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 31, s. 1285-1287Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With this letter, we report how friction can be controlled by inducing physical bonds solely within a polyelectrolyte brush layer, while keeping repulsive interactions between the brush layer and the bare surface that slides above. Our results imply that the nature of the bare surface is of minor importance as long as the repulsive surface interaction is maintained.

  • 30.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Biomimetic lubrication2012Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, nr 2, s. 273-284Artikel, forskningsöversikt (Refereegranskat)
    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.

  • 31.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Interfacial properties of mucins2010Ingår i: Encyclopedia of Surface and Colloid Science: Second Edition, Tailor and Francis , 2010, 2, s. 1-17Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Mucins are a very abundant class of glycoproteins present on most internal interfaces in most organisms in the animal kingdom. They fulfill many functions related to hydration, lubrication, and protection and also in recognition events and cell signaling. Despite the great importance of mucins, it is fair to say that even today the understanding of the interfacial properties of mucins is limited. One reason for this is the great variation in mucin structure. Mucins can be secreted or they can be membrane‐bound, their molecular weight can be vastly different, and their charge density varies, but most importantly, the unlimited number of ways that the carbohydrate moieties can be assembled provides a structural variation that is enormous. Thus, different mucins behave differently in solution, they aggregate differently, and they have very different interfacial properties. This has yet not been investigated in a systematic manner and thus the structure–property relations are not fully clear. However, different mucins do show general structural similarities, and some general features of their interfacial properties also display similarities. This review seeks to elucidate these similarities and tries to relate them to common physical chemical characteristics, which are also key elements for their functions in living organisms.

  • 32.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Monolayer Properties Probed by Surface Forces Measurements2007Ingår i: Advanced chemistry of monolayers at interfaces: trends in methodology and technology, Elsevier, 2007, s. 23-53Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In a review like this it is impossible to refer to even a small fraction of all the interesting work that has been done with the SFA. Anyway, I hope to have illustrated some selected areas in which the SFA has played a major role for increasing our understanding. It is fascinating to see how the development of the "basic SFA" is continued in many laboratories. One clear focus of modern developments is towards studies of dynamic phenomena, another is to combine the SFA with spectroscopy in order to gain further molecular understanding of matter in confinement. The coming years will be exciting and promise new developments that will allow us to develop our understanding of colloids, biophysical systems and complex liquids at and between interfaces.

  • 33.
    Dédinaité, Andra
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Iruthayaraj, Joseph
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Gorochovceva, Natalija
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Interfacial Properties of Chitosan-PEO graft Oligomers: Surface Competition with Unmodified Chitosan Oligomers2006Ingår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 132, s. 124-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oligomers of chitosan carrying 45 units long poly(ethylene oxide), PEO, chains grafted to the C-6 position of the sugar units were prepared using a novel synthesis route. The graft density was high, close to one poly(ethylene oxide) chain grafted to each sugar unit of the chitosan oligomer but a small fraction of unreacted chitosan remained in the sample. The molecular weight distribution of the sample was determined using GPC. The interfacial properties of the chitosan-PEO graft oligomers were evaluated using X-ray photoelectron spectroscopy and surface force measurements. It was found that the small fraction of unreacted chitosan was significantly enriched at the solid-solution interface on negatively charged muscovite mica surfaces. The interactions between chitosan-PEO oligomer coated surfaces were found to be dominated by the extended PEO chains, and at high coverage the measured forces were consistent with those expected for polymer brushes. Addition of salt up to 10 mM did not result in any significant desorption of preadsorbed oligomer layers.

  • 34.
    Dédinaité, Andra
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Olanya, Geoffrey
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nystrom, Bo
    Kjoniksen, Anna-Lena
    Zhu, Kaizheng
    Friction in aqueous media tuned by temperature-responsive polymer layers2010Ingår i: SOFT MATTER, ISSN 1744-683X, Vol. 6, nr 11, s. 2489-2498Artikel i tidskrift (Refereegranskat)
    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)trimethyla mmonium chloride)(20), abbreviated PNIPAAM(48)-b-PAMPTMA(+)(20). The interactions between the PNIPAAM(48)-b-PAMPTMA(+)(20)-coated surfaces across a 0.1 mM NaCl (pH 6) solution at 25 degrees C are purely repulsive, due to a combination of steric and electrostatic double-layer forces. However, when the temperature is increased to 35 degrees C, and subsequently to 45 degrees 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 degrees 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 temperature-responsive polymers are employed, and friction forces can be adjusted as required from low to high.

  • 35.
    Feldötö, Zsombor
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Mucin-electrolyte interactions at the solid-liquid interface probed by QCM-D2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 7, s. 3348-3357Artikel i tidskrift (Refereegranskat)
    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.

  • 36. Gorochovceva, N.
    et al.
    Naderi, A.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Makuska, R.
    Chitosan-N-poly(ethylene glycol) brush copolymers: Synthesis and adsorption on silica surface2005Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 41, nr 11, s. 2653-2662Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chitosan-N-poly(ethylene glycol) brush copolymers with different degree of substitution (DS) were synthesized via reductive amination of chitosan by rnethoxy poly(ethylene glycol) (MPEG) aldehyde. Chitosan-N-MPEG copolymers were high-molecular-weight products with desirable DS; solubility and solution viscosity of those copolymers depended on the method of the synthesis of MPEG aldehyde and on DS. Synthesis of MPEG aldehyde by the use of TEMPO radical/BAIB was not suitable because of partial oxidation of methoxy groups of MPEG resulting in bifunctional PEG derivatives leading to cross-linking. Adsorption studies of chitosan-N-MPEG graft copolymers oil silica surface show that these polymers adsorb in highly hydrated layers.

  • 37. Krivorotova, T.
    et al.
    Makuska, R.
    Naderi, Ali
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Synthesis and interfacial properties of novel cationic polyelectrolytes with brush-on-brush structure of poly(ethylene oxide) side chains2010Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 46, nr 2, s. 171-180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Novel cationic polyelectrolytes with a brush-on-brush structure of poly(ethylene oxide) (PEO) side chains and a charge-containing polyacrylate backbone were synthesized. The PEO side chains were not directly attached to the backbone but via polymethacrylate spacers, thus locating the PEO chains a distance away from the charged units of the backbone. The cationic brush-on-brush polyelectrolytes with high density of PEO chains showed a strong affinity to silica surfaces, provided the backbone charge density was high enough. The adsorption of these polymers was studied by QCM-D giving very high sensed mass, 20 mg/m(2). It was shown by direct force measurements that protective surface layers were formed by the novel polyelectrolytes, generating strongly repulsive steric forces, which provided an effective barrier against flocculation. The adsorbed layer was sufficiently robust to withstand sliding experiments under a pressure of up to 35 MPa. The friction force in water was very low. and the lubrication was characterized by a friction coefficient in the range of 0.02-0.06.

  • 38.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Adsorption of Mefp-1: Influence of pH on adsorption kinetics and adsorbed amount2012Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 379, s. 107-113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive proteins have received considerable attention due to their ability to bind strongly to many surfaces under water. Key structural features of these proteins include a large number of 3,4-dihydroxyphenyl-L-alanin (DOPA) and positively charged lysine residues. We elucidate the effects of solution pH, in the pH range 3-9, on adsorption kinetics, adsorbed amount, and layer structure on silicon oxynitride by employing Dual Polarization Interferometry. As a comparison, the cationic globular protein lysozyme was also investigated. The zeta-potential of the silicon oxynitride substrate was determined as a function of pH, and the isoelectric point was found to be below pH 3. Mefp-1 is positively charged at pH < 10, and thus, the protein is expected to have an electrostatic attraction for the surface at all pH values investigated. The adsorbed amount and the initial adsorption rate were found to increase with solution pH, and no significant desorption occurred due to rinsing with pure water. The layer thickness after rinsing was 3-4 nm, except at pH 3, where the adsorption was limited to a small amount. Covalent cross-linking of the Mefp-1 layer with NaIO4 resulted in a small but significant compaction and increase in refractive index of the layer. The results are discussed in terms of the role of DOPA and electrostatic interactions for the adsorption of Mefp-1 to silicon oxynitride. (C) 2012 Elsevier Inc. All rights reserved.

  • 39.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Salt- and pH-induced desorption: Comparison between non-aggregated and aggregated mussel adhesive protein, Mefp-1, and a synthetic cationic polyelectrolyte2013Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 408, s. 82-86Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive proteins are of great interest in many applications due to their ability to bind strongly to many types of surfaces under water. Effective use such proteins, for instance the Mytilus edulis foot protein - Mefp-1, for surface modification requires achievement of a large adsorbed amount and formation of a layer that is resistant towards desorption under changing conditions. In this work we compare the adsorbed amount and layer properties obtained by using a sample containing small Mefp-1 aggregates with that obtained by using a non-aggregated sample. We find that the use of the sample containing small aggregates leads to higher adsorbed amount, larger layer thickness and similar water content compared to what can be achieved with a non-aggregated sample. The layer formed by the aggregated Mefp-1 was, after removal of the protein from bulk solution, exposed to aqueous solutions with high ionic strength (up to 1 M NaCl) and to solutions with low pH in order to reduce the electrostatic surface affinity. It was found that the preadsorbed Mefp-1 layer under all conditions explored was significantly more resistant towards desorption than a layer built by a synthetic cationic polyelectrolyte with similar charge density. These results suggest that the non-electrostatic surface affinity for Mefp-1 is larger than for the cationic polyelectrolyte.

  • 40.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Linder, Markus B.
    Tilton, Robert D.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Kinetic and Equilibrium Aspects of Adsorption and Desorption of Class II Hydrophobins HFBI and HFBII at Silicon Oxynitride/Water and Air/Water Interfaces2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 8, s. 2683-2691Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrophobins are relatively small globular proteins produced by filamentous fungi. They display unusual high surface activity and are implied as mediators of attachment to surfaces, which has resulted in high scientific and technological interest. In this work we focus on kinetic and equilibrium aspects of adsorption and desorption properties of two representatives of class II hydrophobins, namely HFBI and HFBII, at a negatively charged hydrophilic solid/water interface and at the air/water interface. The layers formed at the air/liquid interface were examined in a Langmuir trough, whereas layers formed at the solid/liquid interface were studied using dual polarization interferometry (DPI) under different flow conditions. For comparison, another globular protein, lysozyme, was also investigated. It was found that both the adsorbed amount and the adsorption kinetics were different for HFBI and HFBII, and the adsorption behavior of both hydrophobins on the negatively charged surface displayed some unusual features. For instance, even though the adsorption rate for HFBI was slowed down with increasing adsorbed amount as expected from packing constraints at the interface, the adsorption kinetics curves for HFBII displayed a region indicating adsorption cooperativity. Further, it was found that hydrophobin layers formed under flow partly desorbed when the flow was stopped, and the desorption rate for HFBII was enhanced in the presence of hydrophobins in solution.

  • 41.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sababi, Majid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nanostructured Composite Layers of Mussel Adhesive Protein and Ceria Nanoparticles2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 30, s. 9551-9561Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive proteins are known for their high affinity to a range of different surfaces, and they therefore appear as ideal candidates for producing thin inorganic-organic composite films with high robustness. In this work we explore the possibility of making cohesive films utilizing layer-by-layer deposition of the highly positively charged mussel adhesive protein, Mefp-1, and negatively charged ceria nanoparticles. This particular material combination was chosen due to recent findings that such films provide good corrosion protection. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used for following the film formation process in situ on silica surfaces. A close to linear growth of the film with number of deposited layers was found for up to 18 deposition steps, the highest number of depositions investigated in this work. The Mefp-1 concentration during film deposition affected the film properties, where a higher protein concentration resulted in a stiffer film. It was also found that the added mass could be amplified by using a Mefp-1 solution containing small aggregates. The surface nanomechanical properties of dried multilayer films were investigated using peak force QNM (quantitative nanomechanical mapping) in air. Homogeneous surface coverage was found under all conditions explore, and the Young's modulus of the outer region of the coating increased when a higher Mefp-1 concentration was used during film deposition. The nature of the outermost surface layer was found to significantly affect the surface nanomechanical properties. The abrasion resistance of the coating was measured by using controlled-force contact mode AFM.

  • 42.
    Liu, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wang, Min
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    An, Junxue
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Hyaluronan and phospholipids in boundary lubrication2012Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, nr 40, s. 10241-10244Artikel i tidskrift (Refereegranskat)
    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.

  • 43.
    Liu, Xiaoyan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Nylander, Tommy
    Dabkowska, Aleksandra P.
    Skoda, Maximilian
    Makuska, Ricardas
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Association of anionic surfactant and physisorbed branched brush layers probed by neutron and optical reflectometry2015Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 440, s. 245-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pre-adsorbed branched brush layers were formed on silica surfaces by adsorption of a diblock copolymer consisting of a linear cationic block and an uncharged bottle-brush block. The charge of the silica surface was found to affect the adsorption, with lower amounts of the cationic polyelectrolyte depositing on less charged silica. Cleaning under basic conditions rendered surfaces more negatively charged (more negative zeta-potential) than acid cleaning and was therefore used to increase polyelectrolyte adsorption. The structure of adsorbed layers of the diblock copolymer was as determined by neutron reflectometry found to be about 70 nm thick and very water rich (97%). Interactions between the anionic surfactant sodium dodecylsulfate (SDS) and such pre-adsorbed diblock polymer layers were studied by neutron reflectometry and by optical reflectometry. Optical reflectometry was also used for deducing interactions between the individual blocks of the diblock copolymer and SDS at the silica/aqueous interface. We find that SDS is readily incorporated in the diblock copolymer layer at low SDS concentrations, and preferentially co-localized with the cationic block of the polymer next to the silica surface. At higher SDS concentrations some desorption of polyelectrolyte/surfactant complexes takes place.

  • 44.
    Liu, Xiaoyan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Visnevskij, C.
    Makuska, R.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Electrostatically anchored branched brush layers2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 44, s. 15537-15547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel type of block copolymer has been synthesized. It consists of a linear cationic block and an uncharged bottle-brush block. The nonionic bottle-brush block contains 45 units long poly(ethylene oxide) side chains. This polymer was synthesized with the intention of creating branched brush layers firmly physisorbed to negatively charged surfaces via the cationic block, mimicking the architecture (but not the chemistry) of bottle-brush molecules suggested to be present on the cartilage surface, and contributing to the efficient lubrication of synovial joints. The adsorption properties of the diblock copolymer as well as of the two blocks separately were studied on silica surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and optical reflectometry. The adsorption kinetics data highlight that the diblock copolymers initially adsorb preferentially parallel to the surface with both the cationic block and the uncharged bottle-brush block in contact with the surface. However, as the adsorption proceeds, a structural change occurs within the layer, and the PEO bottle-brush block extends toward solution, forming a surface-anchored branched brush layer. As the adsorption plateau is reached, the diblock copolymer layer is 46-48 nm thick, and the water content in the layer is above 90 wt %. The combination of strong electrostatic anchoring and highly hydrated branched brush structures provide strong steric repulsion, low friction forces, and high load bearing capacity. The strong electrostatic anchoring also provides high stability of preadsorbed layers under different ionic strength conditions.

  • 45.
    Liu, Xiaoyan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Visnevskij, Ceslav
    Makuska, Ricardas
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Low friction and high load bearing capacity layers formed by cationic-block-non-ionic bottle-brush copolymers in aqueous media2013Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, nr 22, s. 5361-5371Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient lubricants should be able to build surface layers that result in low friction and high load bearing capacity. In this work we show how this can be achieved in aqueous media by means of adsorption of a diblock copolymer consisting of a cationic anchor block without side chains and an uncharged and hydrophilic bottle-brush block that protrudes into solution. Surface and friction forces were measured between negatively charged silica surfaces coated with adsorbed layers of the cationic diblock copolymer, utilizing the atomic force microscope colloidal probe technique. The interactions between the surfaces coated with this copolymer in water are purely repulsive, due to a combination of steric and electrostatic double-layer forces, and no hysteresis is observed between forces measured on approach and separation. Friction forces between the diblock copolymer layers are characterized by a low friction coefficient, mu approximate to 0.03-0.04. The layers remain intact under high load and shear due to the strong electrostatic anchoring, and no destruction of the layer was noted even under the highest pressure employed (about 50 MPa). Addition of NaCl to a concentration of 155 mM weakens the anchoring of the copolymer to the substrate surface, and as a result the friction force increases.

  • 46.
    Lundin, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Macakova, L.ubica
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Interactions between Chitosan and SDS at a Low-Charged Silica Substrate Compared to Interactions in the Bulk: The Effect of Ionic Strength2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 8, s. 3814-3827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of ionic strength on association between the cationic polysaccharide chitosan and the anionic surfactant sodium dodecyl sulfate, SDS, has been studied in bulk solution and at the solid/liquid interface. Bulk association was probed by turbidity, clectrophoretic mobility, and surface tension measurements. The critical aggregation concentration, cac, and the saturation binding of surfactants were estimated from surface tension data. The number of associated SDS molecules per chitosan segment exceeded one at both salt concentrations. As a result, a net charge reversal of the polymer-surfactant complexes was observed, between 1.0 and 1.5 mM SDS, independent of ionic strength. Phase separation occurs in the SDS concentration region where low charge density complexes form, whereas at high surfactant concentrations (up to several multiples of cmc SDS) soluble aggregates are formed. Ellipsometry and QCM-D were employed to follow adsorption of chitosan onto low-charged silica substrates, and the interactions between SDS and preadsorbed chitosan layers. A thin (0.5 nm) and rigid chitosan layer was formed when adsorbed from a 0.1 mM NaNO3 solution, whereas thicker (2 nm) chitosan layers with higher dissipation/unit mass were formed from solutions at and above 30 mM NaNO3. The fraction of solvent in the chitosan layers was high independent of the layer thickness and rigidity and ionic strength. In 30 mM NaNO3 Solution, addition of SDS induced a collapse at low concentrations, while at higher SDS concentrations the viscoelastic character of the layer was recovered. Maximum adsorbed mass (chitosan + SDS) was reached at 0.8 times the cmc of SDS, after which surfactant-induced polymer desorption occurred. In 0.1 mM NaNO3. the initial collapse was negligible and further addition of surfactant lead to the formation of a nonrigid, viscoelastic polymer layer until desorption began above a surfactant concentration of 0.4 times the cmc of SDS.

  • 47. McNamee, Cathy E.
    et al.
    Yamamoto, Shinpei
    Kappl, Michael
    Butt, Hans-Jürgen
    Higashitani, Ko
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Surface and friction forces between grafted polysaccharide layers in the absence and presence of surfactant2011Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 364, s. 351-358Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyzed the interaction between chemically grafted polysaccharide layers in aqueous solutions. To fabricate such layers, an end-terminated dextran silane coupling agent was synthesized and the polydextran was grafted to oxidized silicon wafers and to silica particles. This resulted in the formation of a 28 nm thick layer (in air) and a grafted amount of 40 mg/m2 as determined by ellipsometry. The physical properties of the grafted layer were investigated in aqueous solutions by atomic force microscope imaging and colloidal probe force measurements. Surface and friction forces were measured between one bare and one polydextran coated silica surface. A notable feature was a bridging attraction due to affinity between dextran and the silica surface. Surface interactions and friction forces were also investigated between two surfaces coated with grafted polydextran. Repulsive forces were predominant, but nevertheless a high friction force was observed. The repulsive forces were enhanced by addition of sodium dodecyl sulfate (SDS) that associates with the tethered polydextran layers. SDS also decreased the friction force. Our data suggests that energy dissipation due to shear-induced structural changes within the grafted layer is of prime importance for the high friction forces observed, in particular deformation of protrusions in the surface layer.

  • 48.
    Naderi, Ali
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Bergström, Lars Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Trapped non-equilibrium states in aqueous solutions of oppositelycharged polyelectrolytes and surfactants: effects of mixing protocoland salt concentration2005Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 253, nr 1-3, s. 83-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The very slow equilibration time in oppositely charged systems makes it necessary to control not only the concentration of the species but also the details of the mixing process. This has been demonstrated for processes occurring at interfaces where order of addition effects can be of great importance. In this investigation we set out to study the bulk properties of aqueous mixtures of a highly charged cationic polyelectrolyte mixed with an anionic surfactant with the aim to learn if long-lived non-equilibrium states were formed also in this case, and thus if the details of the mixing procedure would affect the structure of the aggregates formed. For simplicity we chose two mixing protocols, denoted “PTS” and “STP”. In the PTS-method the polyelectrolyte is added to the surfactant solution whereas in the STP-method the surfactant is added into the polyelectrolyte solution. The properties of the mixtures in aqueous solutions, with different NaCl concentrations and as a function of time, were followed by conducting turbidity, electrophoretic mobility and dynamic light scattering measurements. The results demonstrate that the mixing protocol indeed has a great impact on the size of the aggregates initially formed and that this size difference persists for long times. Hence, trapped non-equilibrium states do play an important role also in the bulk solution. We found that in excess surfactant solutions the smaller aggregates formed by the STP-method are more resistant than the larger ones formed by the PTS-method to colloidal instability induced by electrolytes (NaCl). Based on our results we suggest that for producing small and stable polyelectrolyte–surfactant aggregates in systems with excess surfactant, the surfactant should be added last, while the opposite should be applied for systems with excess polyelectrolyte.

  • 49.
    Paulraj, Thomas
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Wennmalm, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Wieland, D.C. Florian
    Dédinaité, Andra
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Pomorski, T. Günther
    Cárdenas, M.
    Svagan, Anna Justina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Assembly of Primary Cell-Wall inspired Microcontainers, Plantosomes, as a step towards a Synthetic Plant-CellManuskript (preprint) (Övrigt vetenskapligt)
  • 50.
    Pettersson, Torbjörn
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dėdinaitė, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Normal and Friction Forces between Mucin and Mucin-Chitosan Layers in Absence and Presence of SDS2008Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 324, nr 1-2, s. 246-256Artikel i tidskrift (Refereegranskat)
    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.

12 1 - 50 av 69
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf