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  • 1. Abrahamsson, Christoffer
    et al.
    Nordstierna, Lars
    Nordin, Matias
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. St. Petersburg State University, Russian Federation.
    Nyden, Magnus
    Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 437, p. 205-210Article in journal (Refereed)
    Abstract [en]

    The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed.

  • 2.
    An, Junxue
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Liu, Xiaoyan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Korchagina, Evgeniya
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 487, p. 88-96Article in journal (Refereed)
    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.

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

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

  • 4.
    Ankerfors, Caroline
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ondaral, Sedat
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ödberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Using jet mixing to prepare polyelectrolyte complexes: Complex properties and their interaction with silicon oxide surfaces2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 351, no 1, p. 88-95Article in journal (Refereed)
    Abstract [en]

    The influence of mixing procedure on the properties of polyelectrolyte complexes (PECs) was investigated using two complexation techniques, polyelectrolyte titration and jet mixing, the latter being a new method for PEC preparation. For the low-molecular-weight polyelectrolytes polyacrylic acid (PAA) and polyallyl amine hydrochloride (PAH), shorter mixing times produced smaller PECs, whereas for higher molecular weights of the same polyelectrolytes, PEC size first decreased with decreasing mixing time to a certain level, after which it started increasing again. This pattern was likely due to the diffusion-controlled formation of "pre-complexes", which, in the case of low-molecular-weight polymers, occurs sufficiently quickly to form stable complexes; when polyelectrolytes are larger, however, non-equilibrium pre-complexes, more prone to aggregation, are formed. Comparing the techniques revealed that jet mixing produced smaller complexes, allowing PEC size to be controlled by mixing time, which was not the case with polyelectrolyte titration. Higher polyelectrolyte concentration during jet mixing led to the formation of larger PECs. It was also demonstrated that PEC size could be changed after preparation: increasing the pH of the PEC dispersion led to an irreversible increase in PEC size, whereas lowering the pH did not influence PEC size. The adsorption behavior of PECs formed from weak polyelectrolytes on model substrates was studied using QCM-D, SPAR, and AFM imaging; the results indicated that increasing the pH increased the amount of PECs adsorbed to model surfaces. However, the amount of PECs adsorbed to the model surfaces was low compared with other systems in all studied cases.

  • 5.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindqvist, Josefina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Shchukarev, Andrei
    Umeå Universitet.
    Lindström, Tom
    Wetting kinetics of oil mixtures on fluorinated model cellulose surfaces2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, p. 556-567Article in journal (Refereed)
    Abstract [en]

    The wetting of two different model cellulose surfaces has been studied; a regenerated cellulose (RG) surface prepared by spin-coating, and a novel multilayer film of poly(ethyleneimine) and a carboxymethylated microtibrillated cellulose (MFC). The cellulose films were characterized in detail using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM indicates smooth and continuous films on a nanometer scale and the RMS roughness of the RG cellulose and MFC surfaces was determined to be 3 and 6 nm, respectively. The cellulose films were modified by coating with various amounts of an anionic fluorosurfactant, perfluorooctadecanoic acid, or covalently modified with pentadecafluorooctanyl chloride. The fluorinated cellulose films were used to follow the spreading mechanisms of three different oil mixtures. The viscosity and surface tension of the oils were found to be essential parameters governing the spreading kinetics on these surfaces. XPS and dispersive surface energy measurements were made on the cellulose films coated with perfluorooctadecanoic acid. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the contact angle of castor oil on the surface. A dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (theta(e) > 90 degrees) by castor oil.

  • 6. Bartenstein, J. E.
    et al.
    Liu, Xiaoyan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lange, K.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Briscoe, W. H.
    Polymersomes at the solid-liquid interface: Dynamic morphological transformation and lubrication2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 512, p. 260-271Article in journal (Refereed)
    Abstract [en]

    Polymersomes are hollow spheres self-assembled from amphiphilic block copolymers of certain molecular architecture. Whilst they have been widely studied for biomedical applications, relatively few studies have reported their interfacial properties. In particular, lubrication by polymersomes has not been previously reported. Here, interfacial properties of polymersomes self-assembled from poly(butadiene)-poly(ethylene oxide) (PBD-PEO; molecular weight 10,400 g mol−1) have been studied at both hydrophilic and hydrophobic surfaces. Their morphology at silica and mica surfaces was imaged with quantitative nanomechanical property mapping atomic force microscopy (QNM AFM), and friction and surface forces they mediate under confinement between two surfaces were studied using colloidal probe AFM (CP-AFM). We find that the polymersomes remained intact but adopted flattened conformation once adsorbed to mica, with a relatively low coverage. However, on silica these polymersomes were unstable, rupturing to form donut shaped residues or patchy bilayers. On a silica surface hydrophobized with a 19 nm polystyrene (PS) film, the polymer vesicles formed a more stable layer with a higher surface coverage as compared to the hydrophilic surface, and the interfacial structure also evolved over time. Moreover, friction was greatly reduced on hydrophobized silica surfaces in the presence of polymersomes, suggesting their potential as effective aqueous lubricants.

  • 7.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    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, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Garamus, Vasil M.
    GKSS Research Centre.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 1, p. 21-33Article in journal (Refereed)
    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.
    Bergström, L. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Explaining the growth behavior of surfactant micelles2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 440, p. 109-118Article in journal (Refereed)
    Abstract [en]

    The growth behavior of surfactant micelles has been investigated from a theoretical point of view. It is demonstrated that predictions deduced from the spherocylindrical micelle model, which considers micelles that are only able to grow in the length direction, are inconsistent with experimental measurements. Accordingly, the rise in aggregation numbers above a certain concentration, roughly corresponding to the second critical micelle concentration, appears to be much stronger than predicted by the spherocylindrical micelle model. On the other hand, predictions deduced from the general micelle model, which considers micelles that are able to grow with respect to both width and length, show excellent agreement with experimental observations. The latter theory is based on bending elasticity and it is demonstrated that the associated three parameters spontaneous curvature, bending rigidity and saddle-splay constant may all be determined for a micellar system from experimental measurements of the aggregation number as a function of surfactant concentration. The three parameters turn out to influence the appearance of a micellar growth curve rather differently. In accordance, the location of the second cmc is mainly determined by the saddle-splay constant and the bending rigidity. The shape of the growth curve, when going from the region of weakly growing micelles at low surfactant concentrations to strongly growing micelles above the second cmc, is mainly influenced by the bending rigidity.

  • 9. Bergström, Lars Magnus
    Model calculations of the spontaneous curvature, mean and Gaussian bending constants for a thermodynamically open surfactant film2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 293, no 1, p. 181-193Article in journal (Refereed)
    Abstract [en]

    The spontaneous curvature (H-0), mean and Gaussian bending constants (k(c) and $(k) over bar $ (c)), as defined in the well-known Helfrich expression, have been calculated from a detailed model for a thermodynamically open surfactant layer. The effect of head group cross-section area, surfactant tail length and electrolyte concentration for monovalent ionic surfactants have been investigated. Geometrical packing constraints subjected to the aggregated hydrocarbon tails and electrostatics are found to be the dominant contributions to H-0, k(c) and (k) over bar (c). In addition, the transition from spherocylindrical micelles to vesicles were investigated in terms of the three parameters and the following simple expressions were derived as criteria for coexistence between micelles and vesicles H-0 = 1/4 xi and < N >(ves)/< N >(mic) = exp[4 pi(k(c) + (k) over bar (c))/kT], where xi is the thickness of the hydrocarbon part of the film and < N >(mic) and < N >(ves) the average aggregation numbers of micelles and vesicles, respectively. However, it is found that the ratio < N >(ves)/< N >(mic) is order of magnitudes too large for vesicles to form at all in charged single-surfactant systems where the surfactant head is of moderate size.

  • 10.
    Bergström, Lars Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Thermodynamics and bending energetics of toruslike micelles2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 327, no 1, p. 191-197Article in journal (Refereed)
    Abstract [en]

    The self-assembly of surfactants forming toruslike or toroidal micelles has been investigated from a theoretical point of view, in particular the structural behaviour and stability of tori in terms of the three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant (kc). It is demonstrated that the size of toruslike micelles increases with an increasing bending rigidity, but is independent of both spontaneous Curvature and saddle-splay constant. Similar to conventional micelles, toruslike micelles are found to be stable over bilayers as the spontaneous curvature times the surfactant layer thickness exceeds 1/4. Moreover, it is shown that toruslike micelles, in general, are favoured at the expense of long spherocylindrical micelles as a result of elimination of the unfavourable end-caps. However, conventional micelles that are able to grow with respect to both width and length (tablets) may be stable over tori as well as spheres in much wider regimes of different bending elasticity constants. As a result, toruslike micelles are predicted to be stable over conventional micelles, including rods, at large values of the effective bending constant k(eff) equivalent to 2k(c) +(k) over bar (c), i.e. in the same region where infinite cylinders are expected to be observed. This result is consistent with the fact that toruslike micelles have usually been observed to coexist with large networks of branched cylinders.

  • 11.
    Bergström, Lars Magnus
    KTH, Superseded Departments, Chemistry.
    Thermodynamics of unilamellar vesicles: Influence of mixing on the curvature free energy of a vesicle bilayer2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 240, no 1, p. 294-306Article in journal (Refereed)
    Abstract [en]

    The influence of mixing on the curvature free energy of a thermodynamically open, reversibly formed vesicle bilayer is investigated by deriving expressions for the various contributions to the Mayer bending constant k(bi) as functions of the structure of aggregated surfactants as well as the solution state (electrolyte concentration, average composition in the bilayers, etc). k(bi) is shown to be lowered in surfactant mixtures as a result of the fact that a mixed vesicle bilayer that is open in the thermodynamic sense may assume different compositions in the inner and outer monolayers. The net contribution of all terms related to surfactant mixing is to lower k(bi). The magnitude of this reduction increases with increasing asymmetry between the two surfactants with respect to charge number, head group size, and tail length. The reduction of k(bi) due to mixing is most pronounced for mixtures where the surfactant that carries charge or has the highest charge number has the larger head group and the smaller tail.

  • 12.
    Bergström, Lars Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Bramer, Tobias
    Synergistic effects in mixtures of oppositely charged surfactants as calculated from the Poisson-Boltzmann theory: A comparison between theoretical predictions and experiments2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 322, no 2, p. 589-595Article in journal (Refereed)
    Abstract [en]

    Critical micelle concentrations in mixtures of an anionic surfactant and a cationic amphiphilic drug have been investigated using a model-independent procedure to quantify observed synergistic effects. Experimental results were compared with a theory based on the Poisson-Boltzmann mean field approximation of a charged interface with a diffuse layer of counterions. Explicit expressions for the activity coefficients from which the critical micelle concentration can be calculated and quantitatively predicted have been derived and excellent agreement between experimental data and theory was obtained. As a result, we demonstrate that it is possible to rationalize and predict the magnitude of synergism in mixtures of oppositely charged surfactants in the presence of added salt.

  • 13.
    Bergström, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Garamus, V. M.
    Structural behaviour of mixed cationic surfactant micelles: A small-angle neutron scattering study2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 381, no 1, p. 89-99Article in journal (Refereed)
    Abstract [en]

    Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr]. =. 0.1. M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction . y=. 0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr]. =. 0.1. M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000. å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-splay constant, for DDAB/DTAB surfactant mixtures in presence of [NaBr]. =. 0.1. M, as compared to mixtures of CTAB/DTAB in [NaBr]. =. 0.1. M and DDAB/DTAB in absence of added salt.

  • 14.
    Besharat, Zahra
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mixed monolayers of alkane thiols with polar terminal group on gold: Investigation of structure dependent surface properties2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 484, no 279, p. 279-290, article id j.jcis.2016.08.053Article in journal (Refereed)
    Abstract [en]

    Adsorption of thiols with cationic or anionic terminal group on gold has been studied from mixed solutions of 11-Amino-1-undecanethiol (AUT) and 3-Mercaptopropionic acid (MPA) using Quartz Crystal Microbalance with Dissipation (QCM-D), X-ray Photoelectron Spectroscopy (XPS), atomic force microscopy (AFM) and contact angles. The goal is to probe the nature of such layers, and the additivity or otherwise of the pH responsiveness, with a view to evaluate their suitability as smart materials. For each of the two pure (unmixed) cases, ordered molecular monolayers are formed with sulfur binding to gold and the alkane chain pointing out from the surface as expected. Adsorption from the thiol mixtures, however, leads to a more complex behaviour. The surface concentration of thiols from the mixtures, as determined by QCM-D, is considerably lower than for the pure cases and it reaches a minimum at a 3:1 MPA/AUT relative concentration in the solution. The XPS results confirm a reduction in adsorbed amount in mixtures with the lowest overall intensity for the 3:1 ratio. Monolayers formed from mixtures display a wettability which is much lower and less pH sensitive. Collectively these results confirm that for adsorption from mixed systems, the configuration is completely different. Complex formation in the mixed solutions leads to the adsorption of molecules parallel to the surface in an axially in-plane configuration. This parallel layer of thiols is mechanically relatively robust to nano-shaving based on AFM measurements. These results will have a significant impact on the design of biomimetic surface coatings particularly when mixtures of oppositely charged molecules are present on the surface, as is commonly the case in biological, proteinaceous surfaces (e.g. hair and skin).

  • 15.
    Bijelic, Goran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Shovsky, Alexander
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Makuska, Ricardas
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Adsorption characteristics of brush polyelectrolytes on silicon oxynitride revealed by dual polarisation interferometry2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, p. 189-197Article in journal (Refereed)
    Abstract [en]

    Adsorption properties of bottle-brush polyelectrolytes have been investigated using dual polarization interferometry (DPI), which provides real time monitoring of adsorbed layer thickness and refractive index. The adsorption on silicon oxynitride was carried out from aqueous solution with no added inorganic salt, and the adsorbed polyelectrolyte layer was subsequently rinsed with NaCl solutions of increasing concentration. The bottle-brush polyelectrolytes investigated in this study have different ratios of permanent cationic charged segments and uncharged PEO side chains. Both the cationic groups and the PEO side chains have affinity for silica-like surfaces, and thus contribute to the adsorption process that becomes rather complex. Adsorption properties in water, responses to changes in ionic strength of the surrounding medium, adsorption kinetics and the layer structure are all strongly dependent on the ratio between backbone charges and side chains. The results are interpreted in terms of competitive adsorption of segments with different chemical nature. The adsorption kinetics is relatively fast, taking only tens to hundreds of seconds when adsorbed from dilute 100 ppm solutions. The DPI technique was found to be suitable for studying such rapid adsorption processes, including determination of the initial adsorption kinetics. We expect that the effects observed in this study are of general importance for synthetic and biological polymers carrying segments of different nature.

  • 16.
    Blute, Irena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pugh, Robert J.
    van de Pas, John
    Callaghan, Ian
    Silica nanoparticle sols 1: Surface chemical characterization and evaluation of the foam generation (foamability)2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 313, no 2, p. 645-655Article in journal (Refereed)
    Abstract [en]

    Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5-40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pH(pzc) which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6-40 nm range) and (b) increased with particle concentration (within the range of 1-15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration.

  • 17.
    Blute, Irena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pugh, Robert J.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    van de Pas, John
    Callaghan, Ian
    Silica nanoparticle sols. Part 3: Monitoring the state of agglomeration at the air/water interface using the Langmuir-Blodgett technique2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, no 2, p. 584-591Article in journal (Refereed)
    Abstract [en]

    Langmuir-Blodgett films were prepared at the air/water interface from dispersions of hydrophilic and partially, hydrophobically modified industrially manufactured silica nanoparticles. The hydrophilic particles featured expanded, fairly easily compressible, surface pressure (pi)-area (A) isotherms with well defined collapse pressures which appeared to be caused by the formation of loosely structured agglomerates which exhibited elastic behavior at low surface pressure and inelastic behavior at high surface pressure. Lateral electrostatic interparticle interactions seemingly played an important role in this hydrophilic system. This contrasted with the hydrophobically modified particles which were more difficult to disperse in the ethanol/chloroform spreading solvent and appeared to be in the semi-agglomerated state at low surface pressures and exhibited a more difficult to compress compacted film. Both types of particulate films were shown to be sensitive to the spreading environment and changes in pH were found to increase particle agglomeration which drastically reduced the particulate area for the hydrophilic sol but less so, in the case of the moderately hydrophobically modified sol. In general, the LB technique proved to be a useful method to monitor changes in the state of aggregation of narrosized silica particles at the air/water interface. These results also appear to give some support of our ideas, presented in earlier publications [1,2] in which it was suggested that the major role of the hydrophobically modified hydrophilic particles in foaming was to produce an aggregated particulate film surrounding the air/water interface which provides a physical barrier preventing coalescence of bubbles.

  • 18.
    Burks, Terrance
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Avila, Marta
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Akhtar, F.
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Lansåker, P. C.
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Uheida, Abdusalam
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Studies on the adsorption of chromium(VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 425, p. 36-43Article in journal (Refereed)
    Abstract [en]

    Chromium (Cr) in the form of Cr(VI) is deemed toxic in water due to its mutagenic and carcinogenic properties. For the successful removal of Cr(VI), we demonstrate a novel adsorbent consisting of superparamagnetic iron oxide nanoparticles (SPION) functionalized with 3-Mercaptopropionic acid (3-MPA). Fourier transform infrared spectroscopy (FT-IR) confirmed the functionalization of nanoparticles and presence of sulfonate groups. Batch adsorption experiments showed that the functionalized adsorbent recovered 45 mg of Cr(VI)/g of 3-MPA coated SPION at initial concentration of 50 mg/L aqueous solution at pH 1 with less than 1% of Fe dissolution from SPION. The results from X-ray photoelectron spectroscopy confirmed that Cr(VI) chemisorbed onto the adsorbent. Hence, the XPS spectra did not indicate any reduction of Cr(VI) to Cr(III) upon adsorption. The adsorption data were better fitted for the Freundlich model. Moreover, the Cr(VI) adsorption kinetics on functionalized SPION followed a pseudo-second order rate, revealing chemisorption as the dominant mechanism. The high Cr(VI) removal, rapid adsorption kinetics and stability of adsorbent indicate that 3-MPA coated SPION could be an efficient adsorbent for the removal of Cr(VI).

  • 19.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Analysis of the aggregation-fragmentation population balance equation with application to coagulation2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, no 2, p. 428-441Article in journal (Refereed)
    Abstract [en]

    Coagulation of small particles in agitated suspensions is governed by aggregation and breakage. These two processes control the time evolution of the cluster mass distribution (CMD) which is described through a population balance equation (PBE). In this work, a PBE model that includes an aggregation rate function, which is a superposition of Brownian and flow induced aggregation, and a power law breakage rate function is investigated. Both rate functions are formulated assuming the clusters are fractals. Further, two modes of breakage are considered: in the fragmentation mode a particles splits into w ≥ 2 fragments of equal size, and in the erosion mode a particle splits into two fragments of different size. The scaling theory of the aggregation-breakage PBE is revised which leads to the result that under the negligence of Brownian aggregation the steady state CMD is self-similar with respect to a non-dimensional breakage coefficient θ. The self-similarity is confirmed by solving the PBE numerically. The self-similar CMD is found to deviate significantly from a log-normal distribution, and in the case of erosion it exhibits traces of multimodality. The model is compared to experimental data for the coagulationof a polystyrene latex. It is revealed that the model is not flexible enough to describecoagulation over an extended range of operation conditions with a unique set of parameters. In particular, it cannot predict the correct behavior for both a variation in the solid volume fraction of the suspension and in the agitation rate (shear rate).

  • 20.
    Colson, Jerome
    et al.
    Univ Nat Resources & Life Sci Vienna, Dept Mat Sci & Proc Engn, Inst Wood Technol & Renewable Mat, Konrad Lorenz Str 24, A-3430 Tulin, Austria..
    Pettersson, Torbjörn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Asaadi, Shirin
    Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, Vuorimiehentie 1, Espoo 02150, Finland..
    Sixta, Herbert
    Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, Vuorimiehentie 1, Espoo 02150, Finland..
    Nypelo, Tiina
    Chalmers Univ Technol, Dept Chem & Chem Technol, Kemigarden 4, S-41296 Gothenburg, Sweden..
    Mautner, Andreas
    Univ Vienna, Fac Chem, Inst Mat Chem & Res, Wahringer Str 42, A-1090 Vienna, Austria..
    Konnerth, Johannes
    Univ Nat Resources & Life Sci Vienna, Dept Mat Sci & Proc Engn, Inst Wood Technol & Renewable Mat, Konrad Lorenz Str 24, A-3430 Tulin, Austria..
    Adhesion properties of regenerated lignocellulosic fibres towards poly (lactic acid) microspheres assessed by colloidal probe technique2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 532, p. 819-829Article in journal (Refereed)
    Abstract [en]

    In the field of polymer reinforcement, it is important to understand the interactions involved between the polymer matrix and the reinforcing component. This paper is a contribution to the fundamental understanding of the adhesion mechanisms involved in natural fibre reinforced composites. We report on the use of the colloidal probe technique for the assessment of the adhesion behaviour between poly(lactic acid) microspheres and embedded cross-sections of regenerated lignocellulosic fibres. These fibres consisted of tailored mixtures of cellulose, lignin and xylan, the amount of which was determined beforehand. The influence of the chemical composition of the fibres on the adhesion behaviour was studied in ambient air and in dry atmosphere. In ambient air, capillary forces resulted in larger adhesion between the sphere and the fibres. Changing the ambient medium to a dry nitrogen atmosphere allowed reducing the capillary forces, leading to a drop in the adhesion forces. Differences between fibres of distinct chemical compositions could be measured only on freshly cut surfaces. Moreover, the surface energy of the fibres was assessed by inverse gas chromatography. Compared to fibres containing solely cellulose, the presence of lignin and/or hemicellulose led to higher adhesion and lower surface energy, suggesting that these chemicals could serve as natural coupling agents between hydrophobic and hydrophilic components.

  • 21.
    Duner, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Iruthayaraj, Joseph
    Daasbjerg, Kim
    Pedersen, Steen Uttrup
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 385, p. 225-234Article in journal (Refereed)
    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.

  • 22.
    Dunér, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Quartz Crystal Microbalance with Dissipation (QCM-D) studies of the viscoelastic response from a continuously growing grafted polyelectrolyte layer2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 408, p. 229-234Article in journal (Refereed)
    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.

  • 23. Ederth, T.
    et al.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Forces between carboxylic acid surfaces in divalent electrolyte solutions2000In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 229, no 1, p. 123-128Article in journal (Refereed)
    Abstract [en]

    The behavior of self-assembled monolayers of thiohexadecanoic acid adsorbed onto gold interacting in asymmetric 2:1 electrolytes has been studied with direct force measurements. The effects of two divalent cations (Mg2+ and Ca2+) were studied at concentrations ranging from 1 mu M to 10 mM. As compared to interactions in the presence of Na+, the divalent ions adsorb strongly to the surfaces, with the effect of lowering the surface potential and decreasing the double-layer repulsion. At concentrations above 10 mu M, the Ca2+ ions were found to adsorb stronger than Mg2+. Ca2+ ions cause charge reversal at high concentrations, and the net interactions at 10 mM were attractive over the measurable range.

  • 24.
    Ederth, Thomas
    et al.
    KTH, Superseded Departments, Chemistry.
    Tamada, K.
    Claesson, Per
    KTH, Superseded Departments, Chemistry.
    Valiokas, R.
    Colorado, R.
    Graupe, M.
    Shmakova, O. E.
    Lee, T. R.
    Force measurements between semifluorinated thiolate self-assembled monolayers: Long-range hydrophobic interactions and surface charge2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 235, no 2, p. 391-397Article in journal (Refereed)
    Abstract [en]

    Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated head groups but varying hydrocarbon spacer lengths, were investigated: CF3(CF2)(9)(CH2)(x)SH, where x = 2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different, The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces, The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed.

  • 25.
    Eita, Mohamed
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Arwin, Hans
    Granberg, Hjalmar
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Addition of silica nanoparticles to tailor the mechanical properties of nanofibrillated cellulose thin films2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 363, no 2, p. 566-572Article in journal (Refereed)
    Abstract [en]

    Over the last decade, the use of nanocellulose in advanced technological applications has been promoted both due the excellent properties of this material in combination with its renewability. In this study, multilayered thin films composed of nanofibrillated cellulose (NFC), polyvinyl amine (PVAm) and silica nanoparticles were fabricated on polydimethylsiloxane (PDMS) using a layer-by-layer adsorption technique. The multilayer build-up was followed in situ by quartz crystal microbalance with dissipation, which indicated that the PVAm-SiO(2)-PVAm-NFC system adsorbs twice as much wet mass material compared to the PVAm-NFC system for the same number of bilayers. This is accompanied with a higher viscoelasticity for the PVAm-SiO(2)-PVAm-NFC system. Ellipsometry indicated a dry-state thickness of 2.2 and 3.4 nm per bilayer for the PVAm-NFC system and the PVAm-SiO(2)-PVAm-NFC system, respectively. Atomic force microscopy height images indicate that in both systems, a porous network structure is achieved. Young's modulus of these thin films was determined by the Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) technique. The Young's modulus of the PVAm/NFC films was doubled, from 1 to 2 GPa, upon incorporation of silica nanoparticles in the films. The introduction of the silica nanoparticles lowered the refractive index of the films, most probably due to an increased porosity of the films.

  • 26.
    Eita, Mohamed
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    El Sayed, Ramy
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Optical properties of thin films of zinc oxide quantum dots and polydimethylsiloxane: UV-blocking and the effect of cross-linking2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 387, p. 135-140Article in journal (Refereed)
    Abstract [en]

    Thin films of polydimethylsiloxane (PDMS) and ZnO quantum dots (QDs) were built up as multilayers by spin-coating. The films are characterized by a UV-blocking ability that increases with increasing number of bilayers. Photoluminescence (PL) emission spectra of the thin films occur at 522 nm, which is the PL wavelength of the ZnO QDs dispersion, but with a lower intensity and a quantum yield (QY) less than 1% that of the dispersion. Cross-linking has introduced new features to the absorption spectra in that the absorption peak was absent. These changes were attributed to the morphological and structural changes revealed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR), respectively. TEM showed that the ZnO particle size in the film increased from 7 (+/- 2.7) nm to 16 (+/- 7.8) upon cross-linking. The FTIR spectra suggest that ZnO QDs are involved in the cross-linking of PDMS and that the surface of the ZnO QDs has been chemically modified.

  • 27.
    Ejenstam, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Rodriguez-Meizoso, I.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    The effect of superhydrophobic wetting state on corrosion protection - The AKD example2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 412, p. 56-64Article in journal (Refereed)
    Abstract [en]

    Corrosion is of considerable concern whenever metal is used as construction material. In this study we address whether superhydrophobic coatings could be used as part of an environmentally friendly corrosion-protective system, and specific focus is put on how the wetting regime of a superhydrophobic coating affects corrosion inhibition. Superhydrophobic alkyl ketene dimer (AKD) wax coatings were produced, using different methods resulting in hierarchical structures, where the coatings exhibit the same surface chemistry but different wetting regimes. Contact angle measurements, ESEM, confocal Raman microscopy, open circuit potential and electrochemical impedance spectroscopy were used to evaluate the surfaces. Remarkably high impedance values of 1010Ωcm2 (at 10-2Hz) were reached for the sample showing superhydrophobic lotus-like wetting. Simultaneous open circuit potential measurements suggest that the circuit is broken, most likely due to the formation of a thin air layer at the coating-water interface that inhibits ion transport from the electrolyte to the metal substrate. The remaining samples, showing superhydrophobic wetting in the rose state and hydrophobic Wenzel-like wetting, showed less promising corrosion-protective properties. Due to the absence of air films on these surfaces the coatings were penetrated by the electrolyte, which allowed the corrosion reaction to proceed.

  • 28.
    Ekholm, P.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Auflem, I. H.
    Department of Chemical Engineering, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Sjöblom, J.
    Department of Chemical Engineering, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Kornfeldt, A.
    ABB Corporate Research, Västerås, Sweden.
    A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 247, no 2, p. 342-350Article in journal (Refereed)
    Abstract [en]

    The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quarts crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.

  • 29.
    Enarsson, Lars-Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Conformation of preadsorbed Polyelectrolyte Layers on Silica studied by secondary Adsorption of Colloidal Silica2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 325, no 1, p. 84-92Article in journal (Refereed)
    Abstract [en]

    The conformation of cationic polyelectrolytes preadsorbed on macroscopic silica surfaces was studied before and after addition of colloidal silica (CS) and compared to the fixation capacity of CS. The Study included two polyelectrolytes of equal charge density, cationic polyacrylamide and cationic dextran. Adsorbed amounts were determined with stagnation point adsorption reflectometry (SPAR) and quartz crystal microgravimetry (QCM). Unsaturated layers of polyelectrolyte were formed in SPAR by stopping the adsorption at a fractional coverage relative to saturation adsorption. These layers were probed by secondary saturation adsorption of colloidal silica (CS). At low salt concentrations a high fractional coverage of polyelectrolyte was required to attain adsorption of CS, while significant adsorption of CS was found also for low fractional coverages of polyelectrolyte at salt concentrations above 10 mM NaCl. Saturation adsorption of cationic polyacrylamide (CPAM) and cationic dextran (Cdextran) onto the silica surface was found to be similar, while the secondary adsorption of CS was significantly higher onto preadsorbed CPAM compared with Cdextran. The QCM and SPAR data together indicated that the adsorbed layer of Cdextran was thinner than CPAM, and that a loose, expanded layer was formed after adsorption of CS on CPAM but not on Cdextran.

  • 30. Eriksson, Malin
    et al.
    Notley, Shannon
    Pelton, Robert
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    The role of polymer compatibility in adhesion between surfaces saturated with modified dextrans2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 310, no 1, p. 312-320Article in journal (Refereed)
    Abstract [en]

    Wet and dry adhesion between dextran-coated surfaces were measured aiming to understand the influence of polymer compatibility. The wet adhesion measurements were performed using the atomic force microscope (AFM) colloidal probe technique whereas the dry adhesion measurements were performed using the micro adhesion measurement apparatus (MAMA). Two types of dextrans were used, one cationically modified dextran (DEX) and one that was both cationically and hydrophobically modified (HDEX), leading to three different combinations of polymer-coated surfaces; (1) DEX:DEX, (2) HDEX:DEX, and (3) HDEX:HDEX. DEX increased dry adhesion more than HDEX did, which likely is due to differences in the ability to form specific interactions, especially hydrogen bonding. HDEX gave strong wet adhesion, probably due to its poorer solvency, while DEX contributed to reducing the wet adhesion due to its hydrophilicity. All combinations showed a steric repulsion on approach in aqueous media. Furthermore, when HDEX was adsorbed on either or both surfaces a long range attractive force between the surfaces was detected outside this steric regime.

  • 31.
    Eriksson, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Notley, Shannon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    The influence on paper strength properties when building multilayers of weak polyelectrolytes onto wood fibres2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 292, no 1, p. 38-45Article in journal (Refereed)
    Abstract [en]

    Polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) have been used to build up polyelectrolyte multilayers (PEM) on wood fibres and on silicon oxide surfaces, under various pH conditions. Consecutive adsorption onto silicon oxide surfaces of PAH and PAA were studied using stagnation point adsorption reflectometry, and the results showed a steady build-up of multilayers. Furthermore, by altering pH, the build-up of the multilayer could be made either linear or exponential in terms of adsorbed amount. Nitrogen analysis of sheets prepared from modified fibres showed that the adsorbed amount of PAH increased throughout PEM build-up, the amount of increase depending on pH during adsorption. Strength measurements of the sheets, i.e., stress at break and strain at break, showed significant improvements ranging from 60 to 200%, depending on both pH during adsorption and type of polyelectrolyte in the outer layer. A good correlation between the adsorbed amount of PAH and the improved strength properties of the paper was also found.

  • 32. Estephan, Elias
    et al.
    Saab, Marie-belle
    Larroque, Christian
    Martin, Marta
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gergely, Csilla
    Peptides for functionalization of InP semiconductors2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 337, no 2, p. 358-363Article in journal (Refereed)
    Abstract [en]

    The challenge is to achieve high specificity in molecular sensing by proper functionalization of micro/nano-structured semiconductors by peptides that reveal specific recognition for these structures. Here we report on surface modification of the InP semiconductors by adhesion peptides produced by the phage display technique. An M13 bacteriophage library has been used to screen 10(10) different peptides against the InP(0 0 1) and the InP(1 1 1) surfaces to finally isolate specific peptides for each orientation of the InP. MALDI-TOF/TOF mass spectrometry has been employed to study real affinity of the peptide towards the InP surfaces. The peptides serve for controlled placement of biotin onto InP to bind then streptavidin. Our Atomic Force Microscopy study revealed a total surface coverage of molecules when the InP surface was functionalized by its specific biotinylated peptide (YAIKGPSHFRPS). Finally, fluorescence microscopy has been employed to demonstrate the preferential attachment of the peptide onto a micro-patterned InP surface. Use of substrate specific peptides could present an alternative solution for the problems encountered in the actually existing sensing methods and molecular self-assembly due to the unwanted unspecific interactions.

  • 33.
    Feldötö, Zsombor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Braesch-Andersen, Sten
    Mabtech AB, Sweden.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Institute for Surface Chemistry, Sweden.
    Adsorption of IgG on/in a PAH/PSS Multilayer Film: Layer Structure and Cell Response2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 354, no 1, p. 31-37Article in journal (Refereed)
    Abstract [en]

    The binding of immunogloblulins (IgG) (mouse monoclonal recognizing IFN gamma) on precoated polystyrene or silica surfaces by the layer-by-layer technique has been investigated with QCM-D and DPI. The aim of the work was to increase the sensitivity of the conventional enzyme-linked immunosorbent spot (ELISpot) assay. The polyelectrolytes used to build the multilayers were poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) alternately adsorbed from 150 mM NaCl. The multilayer build up is linear and the internal structure of the PAH/PSS multilayer is compact and rigid as observed by low relative water content (20-25%) and high layer refractive index (n similar to 1.5) after the formation of five bilayers. Incorporation of IgG within the PAH/PSS multilayer did not give rise to overcharging and did not affect the linear build up. ELISpot test on PAH/PSS multilayer modified polystyrene wells showed that the cytokine response was significantly smaller than on the regular PVDF backed polystyrene wells. This may be due to the compact and rigid nature of the PAH/PSS multilayer, which does not allow formation of the kind of three dimensional support needed to achieve bioactive IgG binding to the surface. Immunological tests of the polyelectrolyte multilayers in the absence of IgG showed that PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view.

  • 34.
    Fernandes, Ricardo Madeira F.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. University of Porto, Portugal.
    Buzaglo, M.
    Regev, O.
    Furó, I.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Marques, E. F.
    Mechanical agitation induces counterintuitive aggregation of pre-dispersed carbon nanotubes2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 493, p. 398-404Article in journal (Refereed)
    Abstract [en]

    Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10–60 s, power density ∼0.002 W mL−1), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (∼1 W mL−1) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1–102 μm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (∼0.03 W mL−1), the flocs break down and re-dispersal occurs. Molecular insight for the mechanism behind this surprising phenomenon is put forth.

  • 35.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Degueldre, Claude
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Frick, Sabrina
    Determining pseudo-equilibrium of montmorillonite colloids in generation and sedimentation experiments as a function of ionic strength, cationic form, and elevation2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 335, no 1, p. 54-61Article in journal (Refereed)
    Abstract [en]

    Colloid generation and sedimentation experiments were carried out on Na- and Ca-montmorillonite in order to verify whether pseudo-equilibrium concentrations are reached at the same level in both types of experiments. The size and concentration of colloidal Na- and Ca-montmorillonite particles were monitored as a function of time and distance from the colloid bed in different ionic strength solutions. A stable pseudo-equilibrium concentration was reached after time in generation and sedimentation experiments. The colloid concentration decreased sharply at distances near to the colloid source. Na-montmorillonite concentration at pseudo-equilibrium (roughly quantified at distances ≥7 cm from the colloid source) was 5.2 ± 0.5, 0.5 ± 0.1, and 0.2 ± 0.1 mg L-1 in 0.001, 0.01, and 0.1 M NaCl solution, respectively, while the Ca-montmorillonite concentration was 0.4 ± 0.2 mg L-1 in 0.001 M NaCl.

  • 36.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Temperature effect on the stability of bentonite colloids in water2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 298, no 2, p. 694-705Article in journal (Refereed)
    Abstract [en]

    The stability of natural bentonite suspensions has been investigated as a function of temperature at pH 9 and ionic strength 10-3 M. The sedimentation rate of the particles is directly related to their stability. The sedimentation kinetics was determined by examining the variation of particle concentration in solution with time. The observed kinetics for sedimentation is discussed quantitatively in terms of the potential energy between particles. The ζ-potential of the particles was measured and the DLVO theory was used to calculate attractive and repulsive potentials. Experimental observations are consistent with DLVO model predictions and show that the stability of bentonite colloids increases with temperature. Differences with other colloidal systems can be attributed to the temperature dependence of the surface charge of bentonite particles.

  • 37.
    García García, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Kinetic determination of critical coagulation concentrations for sodium- and calcium-montmorillonite colloids in NaCl and CaCl2 aqueous solutions2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 315, no 2, p. 512-519Article in journal (Refereed)
    Abstract [en]

    The stability of the sodium and calcium forms of montmorillonite was studied at different NaCl and CaCl2 concentrations. The aggregation kinetics was determined from the decrease in particle concentration with time at different electrolyte concentrations. The DLVO theory defines the critical coagulation concentration (CCC) value as the electrolyte concentration that balances the attractive and repulsive potential energies between the particles, making aggregation diffusion-controlled. Therefore CCC values were obtained by extrapolation of the aggregation rate constants measured as a function of ionic strength to conditions where the rate constant value is determined by diffusion only. When the electrolyte was CaCl2, the CCC value was found to be approximately two orders of magnitude lower than the CCC values obtained using NaCl as electrolyte.

  • 38. Gilanyi, Tibor
    et al.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Stubenrauch, Cosima
    Meszaros, Robert
    Adsorption of alkyl trimethylammonium bromides at the air/water interface2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, no 2, p. 395-401Article in journal (Refereed)
    Abstract [en]

    A number of features of the adsorption of alkyl trimethylammonium bromides with n(c) = 10, 12, 14, and 16 at the air/water interface were studied. First, the adsorption isotherms were calculated front experimental surface tension vs concentration curves by means of the Gibbs equation. Second, a novel method was used to estimate the adsorption free energy change. From the analysis of these data it was concluded that the hydrophobic driving force for the adsorption first increases with increasing adsorbed amount and then levels off in a plateau, which holds true for all four homologues. This peculiar behavior was interpreted by the formation of a thin liquid-like alkane film at the air/water interface once a certain adsorbed amount is exceeded. The hydrophobic contribution to the standard free energy change of adsorption was compared with those values previously determined for alkyl sulfate homologues. This comparison suggests that the alkyl trimethylammonium type surfactants behave as if their alkyl chain was approximately one methylene group shorter than those of the corresponding alkyl sulfates.

  • 39.
    Gustafsson, Jon Petter
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 244, no 1, p. 102-112Article in journal (Refereed)
    Abstract [en]

    To describe the binding of protons and metals to humic substances, the Stockholm Humic Model (SHM) has been developed. The model employs a discrete-site approach similar to that of Model V/VI, although it has another electrostatic submodel, based on the Basic Stern concept. An empirical set of equations has been introduced to account for the extra screening of charge inside the gel-like structures of the humic substances. Six adjustable parameters are needed to describe proton binding to humic or fulvic acids. To simulate metal binding, equilibrium constants are defined for mono- and bidentate coordination and an extra parameter, Delta LK2, accounts for binding-site heterogeneity. It is shown that the SHM appears to be able to describe proton binding well; the quality of the fits is similar to those obtained by Model V/VI and the NICA-Donnan model. The SHM was capable of correctly describing metal binding and competitive interactions over a wide range of conditions, although the model performance was not very convincing concerning the ionic strength dependence of metal binding and stepwise proton-metal exchange stoichiometries.

  • 40. Gärdlund, Linda
    et al.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Norgren, Magnus
    New insights into the structure of polyelectrolyte complexes2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 2, p. 237-246Article in journal (Refereed)
    Abstract [en]

    The formation of polyelectrolyte complexes (PECs) from oppositely charged linear polyelectrolytes (PELs) was studied using static light scattering at various salt concentrations. The PELs used were poly(allylamine hydro chloride) (PAH) and the two polyanions poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Physical characteristics such as the radii of gyration, molecular weights, and water contents of the PECs were determined at various molar mixing ratios. Despite relatively small differences in chemical structure between PAA and PMAA, fairly large differences were detected in these physical characteristics. Generally, PECs comprising PMAA were larger and contained more water. Moreover, by using cryogenic transmission electron microscopy, transmission microscopy and atomic force microscopy, shape and structure of the prepared PECs were investigated both in solution and after drying. The PECs were found to be spherical in solution and the shape was retained after freeze-drying. PECs adsorbed on silica surfaces and dried in air at room-temperature still showed a three-dimensional structure. However, the relatively low aspect ratios indicated that the PECs collapsed significantly due to interactions with the silica during adsorption and drying. At intermediate ionic strengths (1-10 mM), stagnation point adsorption reflectometry (SPAR) showed that the adsorption oflow charged cationic PAH-PAA PECs on silica surfaces increased if the pH value was increased from pH 5.5 to 7.5.

  • 41.
    Hansson, Petra M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hormozan, Yashar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Brandner, Birgit D.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hydrophobic pore array surfaces: Wetting and interaction forces in water/ethanol mixtures2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 396, p. 278-286Article in journal (Refereed)
    Abstract [en]

    Interactions between and wetting behavior of structured hydrophobic surfaces using different concentrations of water/ethanol mixtures have been investigated. Silica surfaces consisting of pore arrays with different pore spacings and pore depths were made hydrophobic by silanization. Their static and dynamic contact angles were found to be independent of the pore depth while fewer pores on the surface, i.e. a closer resemblance to a flat surface, gave a lower contact angle. As expected, a higher amount of ethanol facilitated wetting on all the surfaces tested. Confocal Raman microscopy measurements proved both water and ethanol to penetrate into the pores. AFM colloidal probe force measurements clearly showed that formation of air cavitation was hindered between the hydrophobic surfaces in presence of ethanol, and an increase in ethanol concentration was followed by a smaller jump-in distance and a weaker adhesion force. On separation, an immediate jump-out of contact occurred. The measured forces were interpreted as being due to capillary condensation of ethanol between the surfaces giving rise to very unstable cavities immediately rupturing on surface separation.

  • 42. Harbottle, David
    et al.
    Bueno, Pablo
    Isaksson, Rebecka
    KTH, School of Chemical Science and Engineering (CHE).
    Kretzschmar, Ilona
    Coalescence of particle-laden drops with a planar oil-water interface2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 362, no 1, p. 235-241Article in journal (Refereed)
    Abstract [en]

    The coalescence mechanism of a particle-laden drop resting at an oil-water interface has been studied. Two mechanisms for drop coalescence are observed; (i) complete coalescence, in which the drop experiences total coalescence in one event, and (ii) partial coalescence, where a drop is observed to separate during coalescence, producing a smaller secondary drop that rebounds and comes to rest at the planar oil-water interface. For particle-laden drops of approximately 4 mm in diameter, we show the critical condition for partial to complete coalescence to be dependent on the particle concentration, and the interparticle interaction energy. Colloidal silica spheres dispersed in 10(-4) M KNO(3) electrolyte solution are highly charged and remain dispersed in the drop. By increasing the solids concentration, we measure the transition from partial to complete coalescence at 20 wt.%. However, this critical condition can be reduced by increasing the interparticle interaction energy. In 1 M KNO(3) electrolyte solution, the particle surface charge is sufficiently screened such that particle clusters readily form in the water drop. With particle clustering, transition from partial to complete coalescence is measured at 8 wt.% solids.

  • 43. He, M.
    et al.
    Jiang, H.
    Wang, R.
    Xie, Y.
    Zhao, Weifeng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan Univ, Peoples R China.
    Zhao, C.
    A versatile approach towards multi-functional surfaces via covalently attaching hydrogel thin layers2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 484, p. 60-69Article in journal (Refereed)
    Abstract [en]

    In this study, a robust and straightforward method to covalently attach multi-functional hydrogel thin layers onto substrates was provided. In our strategy, double bonds were firstly introduced onto substrates to provide anchoring points for hydrogel layers, and then hydrogel thin layers were prepared via surface cross-linking copolymerization of the immobilized double bonds with functional monomers. Sulfobetaine methacrylate (SBMA), sodium allysulfonate (SAS), and methyl acryloyloxygen ethyl trimethyl ammonium chloride (METAC) were selected as functional monomers to form hydrogel layers onto polyether sulfone (PES) membrane surfaces, respectively. The thickness of the formed hydrogel layers could be controlled, and the layers showed excellent long-term stability. The PSBMA hydrogel layer exhibited superior antifouling property demonstrated by undetectable protein adsorption and excellent bacteria resistant property; after attaching PSAS hydrogel layer, the membrane showed incoagulable surface property when contacting with blood confirmed by the activated partial thromboplastin time (APTT) value exceeding 600 s; while, the PMETAC hydrogel thin layer could effectively kill attached bacteria. The proposed method provides a new platform to directly modify material surfaces with desired properties, and thus has great potential to be widely used in designing materials for blood purification, drug delivery, wound dressing, and intelligent biosensors.

  • 44.
    Hedberg, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lowe, Troy
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Interactions between surfactants and silver nanoparticles of varying charge2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 369, no 1, p. 193-201Article in journal (Refereed)
    Abstract [en]

    The interaction between silvernanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant–Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.

  • 45.
    Heydari, Golrokh
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sedighi Moghaddam, Maziar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden..
    Tuominen, Mikko
    Fielden, Matthew
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Haapanen, Janne
    Makela, Jyrki M.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wetting hysteresis induced by temperature changes: Supercooled water on hydrophobic surfaces2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 468, p. 21-33Article in journal (Refereed)
    Abstract [en]

    The state and stability of supercooled water on (super)hydrophobic surfaces is crucial for low temperature applications and it will affect anti-icing and de-icing properties. Surface characteristics such as topography and chemistry are expected to affect wetting hysteresis during temperature cycling experiments, and also the freezing delay of supercooled water. We utilized stochastically rough wood surfaces that were further modified to render them hydrophobic or superhydrophobic. Liquid flame spraying (LFS) was utilized to create a multi-scale roughness by depositing titanium dioxide nanoparticles. The coating was subsequently made non-polar by applying a thin plasma polymer layer. As flat reference samples modified silica surfaces with similar chemistries were utilized. With these substrates we test the hypothesis that superhydrophobic surfaces also should retard ice formation. Wetting hysteresis was evaluated using contact angle measurements during a freeze-thaw cycle from room temperature to freezing occurrence at -7 degrees C, and then back to room temperature. Further, the delay in freezing of supercooled water droplets was studied at temperatures of -4 degrees C and -7 degrees C. The hysteresis in contact angle observed during a cooling-heating cycle is found to be small on flat hydrophobic surfaces. However, significant changes in contact angles during a cooling-heating cycle are observed on the rough surfaces, with a higher contact angle observed on cooling compared to during the subsequent heating. Condensation and subsequent frost formation at sub-zero temperatures induce the hysteresis. The freezing delay data show that the flat surface is more efficient in enhancing the freezing delay than the rougher surfaces, which can be rationalized considering heterogeneous nucleation theory. Thus, our data suggests that molecular flat surfaces, rather than rough superhydrophobic surfaces, are beneficial for retarding ice formation under conditions that allow condensation and frost formation to occur. 

  • 46. Horvath, Elisabet
    et al.
    Lindström, Tom
    THe influence of colloidal interactions on fiber network strength2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 309, no 2, p. 511-517Article in journal (Refereed)
    Abstract [en]

    Various forces govern the fiber–fiber interaction in a flowing suspension, causing fibers to create flocs. The aim with this investigation was to examine the influence of colloidal interactions on the fiber network strength by varying surface charge density, electrolyte concentration, and type of counterion. This was accomplished by comparing surface force measurements, utilizing colloidal probe microscopy (CPM), with the apparent yield stress, using a parallel plate rheometer. Results show that by increasing the charge density by grafting carboxymethyl cellulose (CMC) to the surface, a large electrosteric repulsion is created, which gives weaker network strength. Increasing the electrolyte concentration decreases the repulsion. The network strength was, however, not affected by electrolyte concentration for untreated fibers whereas a high electrolyte concentration increased the yield stress for CMC-treated fibers. The change of counterions affect the repulsion, causing a change in network strength due to differences in the surface swelling of cellulose.

  • 47.
    Huang, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Shandong University, China.
    Dobryden, Illia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ihrner, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Ma, Houyi
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden.
    Temperature-dependent surface nanomechanical properties of a thermoplastic nanocomposite2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 494, p. 204-214Article in journal (Refereed)
    Abstract [en]

    In polymer nanocomposites, particle-polymer interactions influence the properties of the matrix polymer next to the particle surface, providing different physicochemical properties than in the bulk matrix. This region is often referred to as the interphase, but detailed characterization of its properties remains a challenge. Here we employ two atomic force microscopy (AFM) force methods, differing by a factor of about 15 in probing rate, to directly measure the surface nanomechanical properties of the transition region between filler particle and matrix over a controlled temperature range. The nanocomposite consists of poly(ethyl methacrylate) (PEMA) and poly(isobutyl methacrylate) (PiBMA) with a high concentration of hydrophobized silica nanoparticles. Both AFM methods demonstrate that the interphase region around a 40-nm-sized particle located on the surface of the nanocomposite could extend to 55–70 nm, and the interphase exhibits a gradient distribution in surface nanomechanical properties. However, the slower probing rate provides somewhat lower numerical values for the surface stiffness. The analysis of the local glass transition temperature (Tg) of the interphase and the polymer matrix provides evidence for reduced stiffness of the polymer matrix at high particle concentration, a feature that we attribute to selective adsorption. These findings provide new insight into understanding the microstructure and mechanical properties of nanocomposites, which is of importance for designing nanomaterials.

  • 48. Jiang, Ping-Li
    et al.
    Hou, Rui-Qing
    Chen, Cheng-Dong
    Sun, Lan
    Dong, Shi-Gang
    Pan, Jin-Shan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lin, Chang-Jian
    Controllable degradation of medical magnesium by electrodeposited composite films of mussel adhesive protein (Mefp-1) and chitosan2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 478, p. 246-255Article in journal (Refereed)
    Abstract [en]

    To control the degradation rate of medical magnesium in body fluid environment, biocompatible films composed of Mussel Adhesive Protein (Mefp-1) and chitosan were electrodeposited on magnesium surface in cathodic constant current mode. The compositions and structures of the films were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and infrared reflection absorption spectroscopy (IRAS). And the corrosion protection performance was investigated using electrochemical measurements and immersion tests in simulated body fluid (Hanks' solution). The results revealed that Mefp-1 and chitosan successfully adhered on the magnesium surface and formed a protective film. Compared with either single Mefp-1 or single chitosan film, the composite film of chitosan/Mefp-1/chitosan (CPC (chitosan/Mefp-1/chitosan)) exhibited lower corrosion current density, higher polarization resistance and more homogenous corrosion morphology and thus was able to effectively control the degradation rate of magnesium in simulated body environment. In addition, the active attachment and spreading of MC3T3-E1 cells on the CPC film coated magnesium indicated that the CPC film was significantly able to improve the biocompatibility of the medical magnesium.

  • 49.
    Karlsson, Rose-Marie Pernilla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden.
    Yu, Shun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Pendergraph, Samuel Allen
    RISE Bioecon, Box 5604, S-11486 Stockholm, Sweden..
    Pettersson, Torbjörn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Hellwig, Johannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed)
    Abstract [en]

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

  • 50.
    Krivosheeva, Olga
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Adsorption of Mefp-1: Influence of pH on adsorption kinetics and adsorbed amount2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 379, p. 107-113Article in journal (Refereed)
    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.

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