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  • 151.
    Minelli, Caterina
    et al.
    National Physical Laboratory, UK.
    Bartczak, Dorota
    LGC Limited, UK.
    Peters, Ruud
    Wageningen University & Research, The Netherlands.
    Rissler, Jenny
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Undas, Anna
    Wageningen University & Research, The Netherlands.
    Sikora, Aneta
    National Physical Laboratory, UK.
    Sjöström, Eva
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Goenaga-Infante, Heidi
    LGC Limited, UK.
    Shard, Alexander G
    National Physical Laboratory, UK.
    Sticky Measurement Problem: Number Concentration of Agglomerated Nanoparticles2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 14, p. 4927-4935Article in journal (Refereed)
    Abstract [en]

    Measuring the number concentration of colloidal nanoparticles (NPs) is critical for assessing reproducibility, enabling compliance with regulation, and performing risk assessments of NP-enabled products. For nanomedicines, their number concentration directly relates to their dose. However, the lack of relevant reference materials and established traceable measurement approaches make the validation of methods for NP number concentration difficult. Furthermore, commercial products often exhibit agglomeration, but guidelines for dealing with nonideal samples are scarce. We have compared the performance of five benchtop measurement methods for the measurement of colloidal number concentration in the presence of different levels of agglomeration. The methods are UV-visible spectroscopy, differential centrifugal sedimentation, dynamic light scattering, particle tracking analysis, and single-particle inductively coupled plasma mass spectrometry. We find that both ensemble and particle-by-particle methods are in close agreement for monodisperse NP samples and three methods are within 20% agreement for agglomerated samples. We discuss the sources of measurement uncertainties, including how particle agglomeration affects measurement results. This work is a first step toward validation and expansion of the toolbox of methods available for the measurement of real-world NP products.

  • 152. Mizuno, Hiroyasu
    et al.
    Luengo, Gustavo S
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Interactions between crossed hair fibers at the nanoscale2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 24, p. 18909-18915Article in journal (Refereed)
    Abstract [en]

    The atomic force microscope fiber probe is used to directly measure the forces and friction between two human hairs under various conditions. It is shown that the forces between the hair fibers in solution can be well explained by a DLVO interaction and that cationic surfactant modifies the interactions in a manner entirely consistent with current views of adsorption behavior. A Coulombic attraction occurs between the crossed hair fibers in air due to the heterogeneity of the surface, and at shorter separations a clear dispersion interaction is observed. Exposure of the hair to a bleaching solution leads to the removal of the adhesion and solely a double-layer interaction. Two crossed hair fibers obey Amontons' classic law of friction, with a linear relation between applied load and frictional force, allowing the determination of a friction coefficient; positively charged surfactant adsorption is shown to reduce the friction coefficient between the fibers in a manner consistent with boundary lubrication by a palisade layer.

  • 153. Mol, L
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Forces in dimethyldodecylamine oxide- and dimethyldodecylphosphine oxide- water systems measured with an osmotic stress technique1993In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 9, p. 2926-2932Article in journal (Refereed)
    Abstract [en]

    The structural parameters of the hexagonal and lamellar phase of the dimethyldodecylamine oxide (DDAO)-water and the dimethyl-dodecylphosphine oxide (DDPO)-water systems have been determined using X-ray diffraction. In addition the relative vapour pressure of water in equilibrium with these phases was determined as a function of surfactant concentration and temperature. This allowed the determination of the swelling pressure in the lamellar phase. It was found that the swelling pressure was considerably higher in the DDAO-water system than in DDPO-water. For both surfactants, but most pronounced so for DDPO, the swelling pressure decreased with increasing temperature. The results obtained are discussed in the light of the ongoing debates about i) the relative importance of steric/protrusion forces and hydration forces between surfactant bilayers, and ii) the molecular origin of the temperature dependence of the interactions displayed in several non-ionic - water systems.

  • 154. Muller, D
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Hessing, J
    Olijve, J
    Mori, F
    Competitive adsorption of gelatin and sodium dodecylbenzenesulfonate at hydrophobic surfaces1998In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, p. 3107-3114Article in journal (Refereed)
    Abstract [en]

    The competitive adsorption of gelatin and sodium dodecylbenzenesulfonate (SDBS) at hydrophobic surfaces was investigated with surface and interfacial tension measurements, ellipsometry, surface plasmon resonance spectroscopy (SPR), and total internal reflectance fluorescence spectroscopy (TIRF). From both ellipsometry and SPR, initial additions of SDBS after gelatin preadsorption were found to result in a total adsorbed amount increase, as well as in a swelling of the adsorbed layer. At higher SDBS concentrations, both the total adsorbed amount and the amount of gelatin adsorbed decrease, which was observed from ellipsometry, SPR, and TIRF. From surface and interfacial tension measurements, it was found that the critical aggregation concentration (cac) for the SDBS-gelatin system decreases with decreasing pH. Analogous to this, ellipsometry, SPR, and TIRF indicate that the SDBS concentration required to cause a significant decrease in the gelatin adsorbed amount decreases with decreasing pH. The desorption therefore seems to be correlated to the SDBS binding to the adsorbed gelatin molecules rather than to purely competitive adsorption.

  • 155. Naderi, A
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Adsorption properties of polyelectrolyte-surfactant complexes on hydrophobic surfaces studied by QCM-D2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, p. 7639-7645Article in journal (Refereed)
    Abstract [en]

    Adsorption and deposition from turbid solutions are common in many industrial processes but notoriously difficult to investigate using standard optical techniques such as ellipsometry and reflectometry. In this report, we have addressed this problem by employing a quartz crystal microbalance with dissipation monitoring ability, QCM-D. The system under investigation consisted of a cationic polyelectrolyte, poly(vinylamine), PVAm, and an anionic surfactant, sodium dodecyl sulfate, SDS, which were mixed together in 10 mM NaCl solution. The polyelectrolyte and the surfactant readily associate in bulk solution, resulting in increased solution turbidity once large aggregates are formed. The solutions were placed in contact with a polystyrene surface, and the adsorption process was monitored by following the changes in the resonance frequency and dissipation factor. The results obtained can in most cases be evaluated using the Sauerbrey relation, but in some cases a more elaborate analysis is necessary. It is found that PVAm adsorbs to polystyrene in the absence of SDS. In the turbid region, deposition is observed, and the sensed mass exceeds the sum of that obtained for each of the components alone. On the other hand, at high SDS concentrations, the surfactant dominates in the adsorbed layer. Adsorption equilibrium is in most cases established within 1-2 h, the exception being found around the solution composition that results in the formation of charge-neutralized aggregates. In this case, a slow deposition of aggregates persists over prolonged times.

  • 156. Naderi, A
    et al.
    Iruthayaraj, J
    Pettersson, T
    Makuska, R
    Claesson, PM
    YKI – Ytkemiska institutet.
    Effect of polymer architecture on the adsorption properties of a nonionic polymer2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 6676-6682Article in journal (Refereed)
    Abstract [en]

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

  • 157. Naderi, A
    et al.
    Iruthayaraj, J
    Vareikis, A
    Makuska, R
    Claesson, PM
    YKI – Ytkemiska institutet.
    Surface properties of bottle-brush polyelectrolytes on mica: Effects of side chain- and charge density2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, p. 12222-12232Article in journal (Refereed)
    Abstract [en]

    Surface properties of a series of cationic bottle-brush polyelectrolytes with 45-unit-long poly(ethylene oxide) side chains were investigated by phase modulated ellipsometry and surface force measurements. The evaluation of the adsorbed mass of polymer on mica by means of ellipsometry is complex due to the transparency of mica and its birefringence and low dielectric constant. We therefore employed a new method to overcome these difficulties. The charge and the poly(ethylene oxide) side chain density of the bottle-brush polymers were varied from zero charge density and one side chain per segment to one charge per segment and no side chains, thus spanning the realm from a neutral bottle-brush polymer, via a partly charged brush polyelectrolyte, to a linear fully charged polyelectrolyte. The adsorption properties depend crucially on the polymer architecture. A minimum charge density of the polymer is required to facilitate adsorption to the oppositely charged surface. The maximum adsorbed amount and the maximum side chain density at the surface are obtained for the polymer with 50% charged segments and the remaining 50% of the segments carrying poly(ethylene oxide) side chains. It is found that brushlike layers are formed when 25-50% of the segments carry poly(ethylene oxide) side chains. In this paper, we argue that the repulsion between the side chains results in an adsorbed layer that is non-homogeneous on the molecular level. As a result, not all side chains will contribute equally to the steric repulsion but some will be stretched along the surface rather than perpendicular to it. By comparison with linear polyelectrolytes, it will be shown that the presence of the side chains counteracts adsorption. This is due to the entropic penalty of confining the side chains to the surface region.

  • 158. Ng, Jovice BS
    et al.
    Kamali-Zare, Padideh
    Sörensen, Malin
    YKI – Ytkemiska institutet.
    Brismar, Hjalmar
    Hedin, Niklas
    Bergström, Lennart
    Intraparticle transport and release of dextran in silica spheres with cylindrical mesopores2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 1, p. 466-470Article in journal (Refereed)
    Abstract [en]

    The transport of oligomeric molecules in silica spheres with cylindrical mesopores has been quantified and related to the structural features of the spherical particles and the interactions at the solid-liquid interface. An emulsion-solvent evaporation method was used to produce silica spheres having cylindrical mesopores with an average pore diameter of 6.5 nm. The transport of dextran molecules (fluorescently tagged) with molecular weights of 3000 and 10 000 g/mol was quantified using confocal laser scanning microscopy (CLSM). The intraparticle concentration profiles in the dextrancontaining spheres were flat at all times, suggesting that the release is not isotropic and not limited by diffusion. The release of dextran into the solution is characterized by an initial burst, followed by long-term sustained release. The release follows a logarithmic time dependency, which was rationalized by coupling concentration-dependent effective diffusion constants with adsorption/desorption.

  • 159.
    Nuzzo, Marine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Lund University, Sweden.
    Sloth, Jakob
    GEA Process Engineering A/S, Denmark.
    Bergenstahl, Björn
    Lund University, Sweden.
    Millqvist-Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Phase segregation in individually dried particles composed of biopolymers2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 40, p. 10946-10954Article in journal (Refereed)
    Abstract [en]

    Mixing of two biopolymers can results in phase separation due to their thermodynamically incompatibility under certain conditions. This phenomenon was first reported when the solution was allowed to equilibrate, but it has later been observed also as a consequence of drying. The challenges of this study were to observe phase segregation by confocal Raman microscopy and LV-SEM on dried film, individually dried particles, and spray dried particles. The influence of the solid content and the phase ratio (composition) of a HPMC/maltodextrin mixture on the localization of the ingredients in the individually dried particles was investigated. We observed that phase segregation of HPMC and maltodextrin is induced by solvent evaporation in film drying, single particle drying, as well as spray drying. The phase ratio is an important parameter that influences the localization of the HPMC-enriched phase and maltodextrin-enriched phase, i.e., to the particle surface, to the core, or in a more or less bicontinuous pattern. The drying time, affected by the solids content, was found to control the level of advancement of the phase segregation.

  • 160. Olanya, G
    et al.
    Iruthayaraj, J
    Poptoshev, E
    Makuska, R
    Vareikis, A
    Claesson, PM
    YKI – Ytkemiska institutet.
    Adsorption characteristics of bottle-brush polymers on silica: Effect of side chain and charge density2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 10, p. 5341-5349Article in journal (Refereed)
    Abstract [en]

    The adsorption behavior of bottle-brush polymers with different charge/PEO ratio on silica was studied using optical reflectometry and QCM-D. The results obtained under different solution conditions clearly demonstrate the existence of two distinct adsorption mechanisms depending on the ratio of charge/PEO. In the case of low-charge density brush polymers (0-10 mol %), the adsorption occurs predominantly through the PEO side chains. However, the presence of a small amount of charge along the backbone (as low as 2 mol %) increases the adsorption significantly above that of the uncharged bottle-brush polymer in pure water. As the charge density of the brush polymers is increased to 25 mol % or larger the adsorption occurs predominantly through electrostatic interactions. The adsorbed layer structure was studied by measuring the layer dissipation using QCM-D. The adsorbed layer formed by the uncharged brush polymer dissipates only a small amount of energy that indicates that the brush lie along the surface, the scenario in which the maximum number of PEO side chains interact with the surface. The adsorbed layers formed by the low-charge density brush polymers (2-10 mol %) in water are more extended, which results in large energy dissipation, whereas those formed by the high-charge density brush polymers (50-100 mol %) have their backbone relatively flat on the surface and the energy dissipation is again low.

  • 161.
    Palmqvist, Lisa
    et al.
    RISE, Swerea, Swerea IVF.
    Holmberg, K.
    Chalmers University of Technology.
    Dispersant adsorption and viscoelasticity of alumina suspensions measured by quartz crystal microbalance with dissipation monitoring and in situ dynamic rheology2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 18, p. 9989-9996Article in journal (Refereed)
    Abstract [en]

    Adsorption behavior and water content of adsorbed layers of four dispersants for aqueous ceramic processing were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) on alumina surfaces. The dispersants were a poly(acrylic acid), a lignosulfonate, and two hydrophilic comb copolymers with nonionic polyoxyethylene chains of different molecular weights. A Voigt model was applied to analyze the viscoelastic behavior of the adsorbed dispersant layers. The results from QCM-D were compared with viscoelastic properties determined by in situ dynamic rheology measurements of highly concentrated alumina suspensions during slip casting. The QCM-D results showed that both the poly(acrylic acid) and the lignosulfonate adsorbed in low amounts and in a flat conformation, which generated thin, highly rigid layers less than 1 nm thick. The water content of these layers was found to be around 30% for the lignosulfonate and 35% for the poly(acrylic acid). High casting rate and strength in terms of storage modulus were observed in the final consolidate of the suspensions with the two polyelectrolytes. In contrast, the high molecular weight comb copolymer adsorbed in a less elastic layer with a thickness of about 6 nm, which is enough to provide steric stabilization. The viscous behavior of this layer was attributed to high water content, which was calculated to be around 90%. Such a water-rich layer gives a lubrication effect, which allows for reorientation of particles during the consolidation process, resulting in a high final strength of the ceramic material. During consolidation, the suspension showed a slow casting rate, most likely due to rearrangement facilitated by the lubricating layer. The short-chain comb copolymer adsorbed in a 1.5 nm thick, rigid layer and gave low final strength to the consolidated suspension. It is likely that the poor consolidation behavior is caused by flocculation due to insufficient stabilization of the dispersion. © 2008 American Chemical Society.

  • 162. Parker, JL
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Forces between hydrophobic silanated glass surfaces1994In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, p. 635-639Article in journal (Refereed)
    Abstract [en]

    A novel surface force apparatus has been utilized in order to determine the forces acting between two glass surfaces rendered hydrophobic by silanation. It was found that in pure water the long-range force is due to a repulsive double-layer force. At shorter separations the force is attractive and stronger than expected for a van der Waals attraction. When the pH is lowered to 2, the repulsive double-layer force is insignificant and the measured force is attractive at all separations. The measurable range is about 30 nm. The attractive force decays roughly exponentially with surface separation having a decay length of 5.6 nm, significantly larger than the electrostatic Debye length (3 nm). Thus we conclude that the origin of this attractive force is not electrostatic. The forces acting between one hydrophobic silanated glass surface and one untreated glass surface at distances greater than 3 nm are dominated by a repulsive double-layer force. At shorter separation the force turns attractive. The attractive force observed is slightly larger than that expected for a van der Waals force but significantly smaller than that observed between two hydrophobic surfaces or between mica and hydrophobized mica.

  • 163. Parker, JL
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wang, J-H
    Yasuda, HK
    Surface forces between plasma polymer films1994In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, p. 2766-2773Article in journal (Refereed)
    Abstract [en]

    The surface properties of two different plasma polymer coatings were investigated by means of ESCA wetting studies, and surface force measurements. The plasma polymer films formed from hexamethyldisiloxane (HMDSO) monomers were found to be very smooth. This made it possible to measure the attractive van der Waals interaction between HMDSO-coated sur,faces in air. When the HMDSO-coated surfaces were immersed in water, they initially appeared strongly hydrophobic with an advancing and recedingcontactangle of 109° and 98°, respectively. Nevertheless, nolongrange zhydrophobic"interaction was observed. The HMDSO coating became slightly more hydrophilic when kept in an aqueous phase for a prolonged time, indicating migration/reorientation of polar groups to the surface. Surface force me asurements in water cle arly de monstrat ed the appe arance of el ectro static charge s and extending polymer tails as a result of a prolonged exposure to water. Plasma polymer coatings of C2F4 or C2F6 deposited on top of a plasma polymer of CH4 were also studied. The forces between such a polymer and a glass surface are on the first approach in air characteristic of a van der Waals force. However, the attraction increases as the surfaces are brought together repeatedly. The increase in the long range attraction is a result of contact electrification due to electron transfer from glass to the fluorocarbon surface. It was found that in aqueous environment the C2F4 plasma polymer surface is significantly less smooth and less stable than the HMDSO plasma polymer surface.

  • 164. Parker, JL
    et al.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Time-dependent adhesion between glass surfaces in dilute surfactant solutions1993In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 9, p. 1965-1967Article in journal (Refereed)
    Abstract [en]

    Measurements of surface forces between glass surfaces in very dilute cationic surfactant solutions at pH 10 are presented. As the surfaces approach the forces are purely repulsive and correspond exactly to the interaction of glass surfaces in aqueous solution at the same pH. However, a small adhesion is observed on separation, the magnitude of which is dependent on the time the surfaces are left in contact. The adhesion arises due to adsorption of surfactant in a narrow gap around the contact area and is induced by the favorable interaction of hydrophobic tails across the gap. The time dependence of the adhesion suggests that the adsorption is diffusion limited.

  • 165. Paulson, O
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    The flotation of inherently hydrophobic particles in aqueous solutions of inorganic electrolytes1996In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 12, p. 4808-4813Article in journal (Refereed)
    Abstract [en]

    The flotation of graphite particles in aqueous solutions of inorganic electrolytes was shown to depend on both the nature of the cation/anion pair and the range of the bubble/particle electrostatic interaction. For several electrolytes, as the Debye length of the solution approached the decay length of the hydrophobic attraction, then flotation began to occur. Using earlier reported data (7), it was also possible to relate the flotation to s urface tension/electrolyte concentration gradients and bubble co al es cence behaviour of the different electrolyte solutions. Higher flotation recoveries were attributed to an increase in the collision probability between the graphite particles and higher concentration of smaller non-coalescing bubbles and also from the increase in stability of the froth. However, it has been shown from previous studies that the gas solubility decreased with increasing electrolyte concentration, and depended on the hydration entropy of the cation (7). This phenomenon was explained terms of competitive utilization of water molecules in the hydration of cations and a consequent loss or gain in gas solubility. Although a reduction in the electrostatic interactions between particle and bubble assisted flotation, in addition, we propose that the increase flotation performance results from the inhibition of coalescence of bubbles which is also linked with dissolved gas concentration gradients in the electrolyte solutions.

  • 166. Persson, CM
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Johansson, I
    Interfacial behavior of n-Octylß-D-glucopyranoside compared to that of a technical mixture consisting of octyl glucosides2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, p. 10227-10235Article in journal (Refereed)
    Abstract [en]

    The difference in interfacial behavior between a technical mixture consisting of n-octyl glucopyranosides, having between 1 and 7 glucose units in the polar headgroup, and n-octylß-D-glucopyranoside was investigated using a range of methods. The forces acting between two hydrophobic solid surfaces across surfactant solutions were determined with a surface force apparatus. It was found that adsorption of the technical mixture generated a long-range repulsive force of electrostatic nature. At shorter separations a local minimum in the force curve (located on the repulsive side) was observed. Further in a steric repulsion dominated the interaction. In contrast, adsorption of pure n-octylß-D-glucopyranoside did not generate any long-range electrostatic double-layer force and an attractive force was present between the monolayer-coated surfaces close to contact. Wetting experiments showed that the technical mixture was a better wetting agent of hydrophobic surfaces (lower contact angle and higher wetting tension). The adsorption to air-liquid interfaces was also investigated by surface tension measurements and by measuring the forces acting across single foam films. The latter measurements were carried out using a thin film balance employing the porous frit technique. The technical mixture was more efficient in generating long-range electrostatic forces whereas the pure n-octylß-D-glucopyranoside was more efficient in generating stable Newton black films. Pyrene fluorescence measurements revealed that the micelles formed by the technical mixture continuously change its average composition with concentration toward structures with a more hydrophobic micellar core

  • 167. Persson, CM
    et al.
    Kjellin, URM
    Eriksson, JC
    YKI – Ytkemiska institutet.
    Surface pressure effect of poly(ethylene oxide) and sugar headgroups in liquid-expanded monolayers2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, p. 8152-8160Article in journal (Refereed)
    Abstract [en]

    Surface tension isotherms were recorded for six different but chemically closely related surfactants. The surfactants studied have three types of headgroups, tetra(ethylene oxide) (E4), penta(ethylene oxide) (E5), and maltopyranoside (Mal). For each headgroup, two hydrocarbon chain lengths were investigated, decyl (C10) and dodecyl (C12). By utilizing the Gibbs surface tension equation, surface pressure versus molecular area isotherms as well as the corresponding adsorption isotherms were generated for all six surfactants. By considering the various contributions to the free energy of the interface, theoretical surface pressure isotherms have been derived which are compared with the experimental ones in the molecular area interval especially studied here, from 60 Å2/molecule down to the molecular area obtained at the critical micelle concentration. Mainly two contributions to the free energy give rise to changes of the surface pressure with the area/molecule. The first contribution is related to restricting the hydrocarbon chain configurations, and the second one to the interactions between the polar groups and the surrounding solvent, water. It was found that the surface pressure effect of the maltoside headgroup is close to the one calculated for hard disks whereas the ethylene oxide headgroup behaves more like short polymer chains for which the Flory-Huggins theory is approximately valid. Surprisingly, we have found that the shorter carbon chain (C10) generates a higher surface pressure than the longer one (C12)

  • 168.
    Persson, CM
    et al.
    YKI – Ytkemiska institutet.
    Kumpulainen, AJ
    YKI – Ytkemiska institutet.
    Eriksson, JC
    YKI – Ytkemiska institutet.
    Adsorption of n-decyl-β-D-glucopyranoside and n-decyl-β-D-maltopyranoside mixtures at the liquid-vapor interface2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, p. 6110-6114Article in journal (Refereed)
    Abstract [en]

    Surface tension isotherms were recorded for mixtures of n-decyl-β-D-glucopyranoside (Glu) and n-decyl-β-D-maltopyranoside (Mal) and for the pure components. By use of conventional surface thermodynamics, the adsorbed amounts of Glu and Mal were calculated for different compositions and overall concentrations. The critical micelle concentrations (cmc's) of the pure components and the mixtures were between 2 and 2.2 mM. It was found that the molecule with the smaller headgroup, Glu, packs more tightly at the liqud-vapor interface at cmc, 37.5 Å2/molecule as compared to 48.1 Å2/molecule for Mal. The transition from a two-dimensional ideal solution state to a liquid-expanded state was investigated in detail. This transition occurs from an area/molecule of ~450-550 to ~150-200 Å2/molecule and at very low values of the surface pressure, ~1 mN/m. For a 1:1 mixture of Mal and Glu, an excess of the larger molecule, Mal, was found at the interface in a small concentration interval just after the ideal Henry's law region. At higher concentrations Glu adsorbs more readily, and at the cmc Glu occupies 73% of the interface. The observed adsorption behavior, surface pressure behavior, and the relative amounts of the two surfactants at the interface for the different mixtures are indicative of a hard disk behavior of the two sugar headgroups.

  • 169. Pettersson, T
    et al.
    Naderi, A
    Makuska, R
    Claesson, PM
    YKI – Ytkemiska institutet.
    Lubrication properties of bottle-brush polyelectrolytes: An AFM study on the effect of side chain and charge density2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 7, p. 3336-3347Article in journal (Refereed)
    Abstract [en]

    The effect of side chain to charge ratio on the frictional properties of adsorbed layers formed by bottle-brush polyelectrolytes with poly(ethylene oxide) side chains has been investigated. The brush polyelectrolytes were preadsorbed from 0.1 mM NaNO3 solutions onto mica and silica surfaces; the interfacial friction was then measured in polyelectrolyte-free solutions via AFM (with the silica surface acting as the colloidal probe). It was concluded that the decisive factor for achieving favorable lubrication properties is the concentration of nonadsorbing poly(ethylene oxide) side chains in the interfacial region. However, contrary to what may be expected, the results showed that an ideal brush layer structure with the adsorbed polymers adopting comb-like conformation is not necessary for achieving a low coefficient of friction in the asymmetric mica-silica system. In fact, the lowest coefficient of friction (<0.01) under applied pressures as high as 30 MPa was observed for a system with a side chain to charge ratio of 9:1, incapable of forming brush-like layers.

  • 170. Pezron, I
    et al.
    Pezron, E
    Claesson, PM
    YKI – Ytkemiska institutet.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Temperature-dependent forces between hydrophilic mica surfaces coated with ethyl(hydroxyethyl)cellulose1991In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 7, p. 2248-2252Article in journal (Refereed)
    Abstract [en]

    The forces acting between hydrophilic mica surfaces across 0.1wt% aqueous ethyl(hydroxyethyl)cellulose (EHEC) solutions have been investigated with a surface force apparatus. It was found that EHEC adsorbs rather weakly onto these surfaces, and that the adsorbed polymers at low temperatures (20°C) are easily squeezed out from between the surfaces on compression. The force distance curve is purely repulsive at this temperature, and up to the point where EHEC molecules are squeezed out from between the surfaces, all forces were found to be reversible on compression/decom-pression. Hence, up to this point the experiments were performed under close to quasi-equilibrium conditions. The adsorbed amount increases with temperature and it becomes more difficult to remove the polymers from between the surfaces by applying a compressive force. At a temperature of 45°C, which is 6° above the cloud point, a weak attractive force was experienced on separating the polymer coated surfaces from contact. On diluting the solution to roughly 10-4 wt%, some of the adsorbed polymers desorb. A comparison with the forces acting between EHEC coated mica and EHEC coated hydrophobic surfaces demonstrates the importance of the surface-polymer interaction.

  • 171.
    Plunkett, MA
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Ernstsson, M
    Rutland, MW
    YKI – Ytkemiska institutet.
    Comparison of the adsorption of different charge density polyelectrolytes: A quartz crystal microbalance and XPS study2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, p. 4673-4681Article in journal (Refereed)
    Abstract [en]

    The adsorption of a series of six cationic polyelectrolytes onto a gold surface was monitored via a quartz crystal microbalance with dissipation (QCM-D). The series of polyelectrolytes were chemically similar but differing in the ratio of two randomly ordered constituent monomers, one of which was charged, the other neutral. Thus the series of polyelectrolytes differed systematically in their charge densities, ranging from a high charge density (100% of monomers charged) to a low charge density (1% charged). It was determined that high charge density polyelectrolytes adsorbed in a relatively flat and rigid layer, while the low charge density polyelectrolyte, as expected, adsorbed in a much more extended structure that coupled strongly to the bulk solvent. By comparison to X-ray photoelectron spectroscopy results, we have also calculated the relative solvent mass hydrodynamically coupled to the adsorbed polymer, which ranges from almost 80% solvent for the 1% charged case down to close to zero for the 100% charged case. Since the QCM-D results are measured relative to uncoated gold in aqueous solution, the latter results should be interpreted as showing that the amount of water hydrodynamically coupled to gold and that coupled to gold coated with the 100% charged polyelectrolyte is very similar. It is believed that this systematic study on the effect of polyelectrolyte structure on the measured dissipation change in the QCM-D may serve as a first guide when inferring structural and viscoelastic information based solely on the QCM-D technique for other similar systems. In addition, a preliminary study on the ability of one polymer to replace another preadsorbed polymer layer was conducted that showed that a steric layer was able to prevent the adsorption of a thermodynamically more favorable polymer. In the reverse case, greater exchange was possible

  • 172. Plunkett, MA
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Adsorption of a cationic polyelectrolyte followed by surfactant-induced swelling, studied with a quartz crystal microbalance2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 1274-1280Article in journal (Refereed)
    Abstract [en]

    The adsorption and subsequent surfactant-induced swelling of a 10% charged cationic polyelectrolyte (AM-MAPTAC-10), on a gold surface, was monitored by means of a quartz crystal microbalance with dissipation (QCM-D). This instrument gives information on the total adsorbed amount including any adsorbed solvent and on the manner of adsorption. In this case the total adsorbed amount from a 20 ppm AM-MAPTAC-10 solution registered by the QCM-D device was approximately 0.6 g cm-2. X-ray photoelectron spectroscopy results showed that the polyelectrolyte adsorbed mass was 0.16 g cm-2; thus the water trapped within the polyelectrolyte layer constitutes about 70% of the mass measured by the quartz crystal microbalance. The adsorption process was found to be rather complex, though the time evolution of the adsorbed mass indicated that the majority of the process was diffusion controlled. Toward the end of the adsorption process, the rate of adsorption drops off and the dissipation rate increases, indicating that as the surface becomes crowded the layer extends further in the direction normal to the surface. The effect of addition of sodium dodecyl sulfate (SDS) to a preadsorped AM-MAPTAC-10 layer was also investigated. It was found that some swelling of the preadsorbed layer occurred once the bulk surfactant concentration reached 20% of the critical micelle concentration (cmc). Between 60% of the cmc and twice the cmc, the adsorbed layer swelled significantly and desorption started to occur. Rinsing the surface with the surfactant-free electrolyte solution results in a rapid decrease in dissipation and adsorbed mass indicating the removal of the surfactant but not the polyelectrolyte.

  • 173.
    Plunkett, MA
    et al.
    YKI – Ytkemiska institutet.
    Feiler, A
    Rutland, MW
    YKI – Ytkemiska institutet.
    Atomic force microscopy measurements of adsorbed polyelectrolyte layers 2: Effect of composition & substrate on structure, forces and friction2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, p. 4180-4187Article in journal (Refereed)
    Abstract [en]

    An investigation on the effect of the conformation of preadsorbed polyelectrolyte layers of acrylamide-1% [3-(2-methylpropionamide)propyl]trimethylammonium chloride on the normal and lateral interactions between surfaces has been conducted. It was shown that when bridging mechanisms increased the adhesion, huge increases in the friction were also seen. When the polymer adsorbed in an extended layer, it resulted in a steric repulsion in the direction normal to the interface. However, the resulting friction measurements were shown to be far more complicated. For example, in cases where the integrity of the polymer layer was maintained under compression, the layer was able to act as a lubricant; however when the layer integrity was affected by the load and shear rate, then friction increased due to energy losses resulting from disrupting the polymer conformation. The conformation was controlled by varying both the polymer charge density and the nature of the surface. The interaction between the polyelectrolyte and gold proved to be significantly stronger than that with silica, rendering the polymer layer more resistant to damage under shear and, consequently, a significantly different friction-load relationship. The dynamics of the interactions were also investigated and were highly dependent on the polyelectrolyte-surface interaction. As an aside, a novel observation of interference effects between cantilever and substrate is also made

  • 174.
    Plunkett, MA
    et al.
    YKI – Ytkemiska institutet.
    Wang, Z
    Rutland, MW
    YKI – Ytkemiska institutet.
    Johannsmann, D
    Adsorption of pNIPAM layers on hydrophobic gold surfaces, measured in-situ by QCM and SPR2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, p. 6837-6844Article in journal (Refereed)
    Abstract [en]

    In situ surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) measurements have been employed to measure the adsorption kinetics and absolute adsorbed amount of the poly(N-isopropyl acrylamide) (pNIPAM) from bulk aqueous solution onto a hydrophobized gold substrate. The adsorption was carried out at 31° C, which is just below the lower critical solution temperature of pNIPAM in water. We find that the shift in the coupling angle of the surface plasmon (proportional to the "optical thickness") and the shift in the resonance frequency of the quartz crystal (proportional to the "acoustic thickness") increase in parallel for most of the adsorption. Also, the change of dissipation is proportional to the change in frequency. These observations suggest that the buildup of the polymer layer proceeds via growth in thickness rather than by densification of a layer with constant thickness. We interpret this finding in the sense that the dense high-temperature phase wets the hydrophobic gold surface. The wetting layer has a fixed density and grows in thickness. In addition, the QCM has been used to study the temperature-induced conformational change for pNIPAM around the critical temperature. It was found that the technique was able to monitor additional adsorption that occurs when crossing the critical point, which was due to bulk phase separation. Desorption was also noted when crossing the critical point from the opposite direction, and for the given system the process was entirely reversible

  • 175. Poptoshev, E
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Forces between glass surfaces in aqueous polyethylenimine solutions2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 2590-2594Article in journal (Refereed)
    Abstract [en]

    Interaction forces between flame-polished glass surfaces were measured in a range of aqueous solutions of a branched cationic polyelectrolyte, polyethylenimine (PEI) MW≈70 000 g/mol. Short incubation in 1 ppm PEI solution leads to neutralization of the glass negative surface charge. At this point the interaction forces are dominated by a bridging attraction detectable at separations below 10 nm. Prolonged incubation in the same solution results in charge reversal. Upon increasing the bulk polymer concentration, an additional adsorption takes place, and the magnitude of the observed charge reversal increases. In 50 ppm PEI an additional electrosteric force is present at short distances, and the force measured on approach remains repulsive at all separations. The pull-off forces measured on separation were shown to be dependent on the time the two surfaces spent in contact and increased with increasing contact time. In addition, the concentration dependence of the pull-off force in PEI solutions was compared to two linear, highly charged polyelectrolytes polyvinylamine (PVAm) and poly([2-(propionyloxy)ethyl]trimethylamonium chloride) (PCMA). It was found that the two linear polyelectrolytes induce lower adhesion between glass surfaces than PEI. Further, for the linear polyelectrolytes the adhesion force was not strongly influenced by the polyelectrolyte concentration for concentrations higher than 2 ppm. In contrast, PEI generates higher adhesive forces at low bulk concentrations, which then sharply decrease upon increasing the PEI concentration. These differences are discussed in terms of both the PEI highly branched structure and the fact that the PEI charge is concentration dependent due to changes in solution pH.

  • 176. Poptoshev, E
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Weakly charged polyelectrolyte adsorption to glass and cellulose studied by surface force technique2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 1184-1189Article in journal (Refereed)
    Abstract [en]

    Interaction forces were measured between glass surfaces and between one glass and one cellulose surface in the presence of a 10% charged, random copolymer of acrylamide and cationic [(3-(2-methylpropionamide) propyl] trimethylammonium chloride (AM-MAPTAC-10), using a non interferometric surface force technique (MASIF). Adsorption to glass from 1 ppm solution leads to neutralization of the substrate negative surface charge. When the bulk polymer concentration is increased to 50 ppm, a weak charge reversal occurs as indicated by the reappearance of the double-layer force. Throughout the concentration range studied here (1-50 ppm), the forces measured on approach between two glass surfaces could be adequately described by the DLVO theory. The interactions between one glass and one model cellulose surface under the same conditions follow a different pattern. AM-MAPTAC-10 adopts an extended conformation upon adsorption to cellulose and steric repulsion is generated when the thick adsorbed layer is compressed. The different structure of the adsorbed layers on cellulose is explained in terms of its lower surface charge density compared to glass. This leads to fewer attachment spots on the solid surface and an increased amount of polymer loops and tails proturding into solution, i.e. thicker adsorbed layers are formed and the resulting system is sterically stabilised.

  • 177.
    Poptoshev, E
    et al.
    YKI – Ytkemiska institutet.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Surface forces in aqueous polyvinylamine solutions. 2. Interactions between glass and cellulose2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, p. 1987-1992Article in journal (Refereed)
    Abstract [en]

    The forces acting between one surface coated with Langmuir-Blodgett cellulose films and one glass surface have been measured using the MASIF surface force technique. This study is mainly concerned with the effects due to addition of cationic polyvinylamine and changes in ionic strength. The results have implications for the interactions between cellulose and mineral surfaces in the papermaking process. The cellulose surface is weakly negatively charged at pH 5.5-6.0. Polyvinylamine adsorbs to both glass and cellulose surfaces, which first causes charge neutralization and subsequently a charge reversal upon increasing the polymer concentration. The cellulose films swell upon immersion in aqueous solutions as evidenced by the appearance of a short-range steric force barrier. The dynamics of the swelling process was found to be dependent on the ionic strength of the solution. It was found that an increased ionic strength accelerates the swelling, which can be attributed to an increase in surface charge density and hence an increase in the short-range repulsion between individual cellulose chains. The results obtained in this study are consistent with those obtained for the interaction between two glass surfaces in polyvinilamine solutions as described in a previous report. However, the long-range (bridging) attraction observed between two glass surfaces immersed in the polyvinylamine solution was absent between one glass and one cellulose surface. We attribute this to the lower surface charge density of the cellulose surface.

  • 178. Poptoshev, E
    et al.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Surface forces in aqueous polyvinylamine solutions. I. Glass surfaces1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, p. 7789-7794Article in journal (Refereed)
    Abstract [en]

    A noninterferometric surface force apparatus has been used to measure interactions between glass spheres in dilute aqueous polyvinylamine solutions at two different salt concentrations. Close to the substrate charge neutralization point, an attractive interaction is present mainly because of bridging of the extending polymer tails. Additional adsorption leads to an overcompensation of the glass negative surface charge, and the interaction at this point is dominated by a long-range double-layer repulsion. The results from fitting the Derjaguin-Landau-Verwey-Overbeek theory to the measured force curves demonstrate that the degree of overcompensation increases with polyelectrolyte concentration and increasing ionic strength of the solution (addition of indifferent electrolyte). An increase in ionic strength results in the screening of the electrostatic forces which leads to: (i) a reduced free energy cost of creating a charged interface, (ii) a decreased repulsion between protonated amine groups along the polymer backbone and a corresponding increased chain flexibility, (iii) a reduced electrostatic attraction between the polyelectrolyte and the surface. The first effect is apparently is the most important in the present case.

  • 179. Poptoshev, E
    et al.
    Um, S-U
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Influence of surface aging on the drainage of foam films stabilized by aqueous solutions of ethyl hydroxyethyl cellulose1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, p. 3905-3908Article in journal (Refereed)
    Abstract [en]

    The drainage times of microscopic horizontal foam films stabilised by dilute aqueous solutions of ethyl (hydroxyethyl) cellulose (EHEC) was shown to be dependent on the ageing effects (conformation changes of the adsorbed macromolecules) occuring in the freshly creates air/solution interface. At low polymer concentration (5 ppm), the films drained fairly rapidly from thickeness of about 400 to 300 nm with drainage times about 5 to 6 times greater than theoretical values calculated using the Reynolds equation. However, at higher polymer concentrations (100 ppm) at extended surface ageing (15 to 180 minutes) the films drainage times were shown to increase drastically giving values 50 times greater than theoretical values. Although these ageing effects could not be directly related to surface tension data, diffusion coefficient were calculated from interfacial tension profiles using classical diffusion theory. As the concentration of polymer increased, the diffusion coefficient were shown to decrease and were considerably smaller than previously reported experimentally values determined in bulk solution by NMR. This difference between experimental and theoretical results endorsed a kinetic rather than a diffusion or mass transport model for the transfer of EHEC molecules to the interface. The increase in drainage times with extended ageing times could be explained by the gradual formation of a steric energy barrier caused by configuration changes of the adsorbed polymer. This propably involved the progressive extension of the EHEC tails into the aqueous phase increasing the disjoining pressure, decreasing the drainage rate and producing thick stable films.

  • 180.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Foaming in chemical surfactant free aqueous dispersions of anatase (titanium dioxide) particles2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 15, p. 7972-7980Article in journal (Refereed)
    Abstract [en]

    Steady-state dynamic aqueous foams were generated from surfactant free dispersion of aggregated anatase nanoparticles (in the micron size range). In order to tune the particle surfaces, to ensure a critical degree of hydrophobicity (so that they disperse in water and generate foam), the particles were subjected to low temperature plasma treatment in the presence of a vapour phase silane coupling agents. From ESCA it was shown that hydrophobization of the surface only occured at a small number of sites. Foamability (foam generation) experiments were carried out under well defined conditions, at a range of gas flow rates using the Bikermann Foaming Column (1). The volume of the steadystate foams were determined under constant gas flow conditions but on removing the gas flow, transient foams with short decay times (< 5 s) were observed. The foamability of the steady state foams was found to be dependent on (a) the time of plasma treatment of the particles (surface hydrophobicity), (b) the particle concentration in the suspension and (c) the state of dispersion of the particles. High foamability was promoted in the pH regions where the charged particles were less hydrophobic and more highly dispersed. In the pH regions where the particles were more hydrophobic and colloidally unstable, the foamability was considerably reduced.

  • 181. Reimhult, K
    et al.
    Petersson, K
    Krozer, A
    RISE, Swedish ICT, Acreo.
    QCM-D analysis of the performance of blocking agents on gold polystyrene surfaces2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 16, p. 8695-8700Article in journal (Refereed)
  • 182. Rippner, B
    et al.
    Boschkova, K
    Claesson, PM
    YKI – Ytkemiska institutet.
    Arnebrant, T
    Interfacial films of poly(ethylene oxide)-poly(butylene oxide) block copolymers characterized by disjoining pressure measurements, in situ ellipsometry, and surface tension measurements2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 5213-5221Article in journal (Refereed)
    Abstract [en]

    Interactions between two air-water interfaces stabilized by poly(ethylene oxide)-poly(butylene oxide) block copolymers were investigated by employing the microinterferometric thin-film balance technique. A series of three block copolymers, two linear diblock copolymers, B8E41 and E106B16, and one linear triblock copolymer, E21B8E21, were investigated. In particular the range of the steric forces operating across the thin foam films was quantified. As expected, higher concentrations were required of the triblock copolymer than for the diblocks for the formation of a stable foam film. Despite the low polydispersity of the sample (Mw/Mn = 1.03), effects due to polydispersity on the concentration dependence of the disjoining pressure isotherm were noted. Furthermore, the adsorption at the air-water interface was determined by surface tension measurements. It was noted that long equilibrium times are required to obtain (quasi) equilibrium surface tension data. Time-resolved ellipsometry was used to follow the adsorption rates and determine the amounts adsorbed in situ at hydrophobic solid surfaces. The adsorbed amount at the solid-liquid interface determined by ellipsometry was similar to that at the air-water interface estimated from the surface tension isotherm provided polydispersity effects on the surface tension isotherm were taken into account. Moreover, interactions in foam films formed from mixtures of the diblock copolymer, B8E41, and a cationic surfactant, hexadecyltrimethylammonium bromide, were studied. Both electrostatic double-layer forces and, at shorter range, steric forces were present, demonstrating the formation of a mixed layer at the interface.

  • 183. Rippner Blomqvist, B
    et al.
    Benjamins, J-W
    YKI – Ytkemiska institutet.
    Nylander, T
    Arnebrant, T
    Ellipsometric characterization of ethylene oxide-butylene oxide diblock copolymer adsorption at the air-water interface2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, p. 5061-5068Article in journal (Refereed)
    Abstract [en]

    Ellipsometry was used to determine the adsorbed layer thickness (d) and the surface excess (adsorbed amount, ¡) of a nonionic diblock copolymer, E106B16, of poly(ethylene oxide) (E) and poly(butylene oxide) (B) at the air-water interface. The results were obtained (i) by the conventional ellipsometric evaluation procedure using the change of both ellipsometric angles and ¢ and (ii) by using the change of ¢ only and assuming values of the layer thickness. It was demonstrated that the calculated surface excesses from the different methods were in close agreement, independent of the evaluation procedure, with a plateau adsorption of about 2.5 mg/m2 (400 Å2/molecule). Furthermore, the amount of E106B16 adsorbed at the air-water interface was found to be almost identical to that adsorbed from aqueous solution onto a hydrophobic solid surface. In addition, the possibility to use combined measurements with H2O or D2O as substrates to calculate values of d and ¡ was investigated and discussed. We also briefly discuss within which limits the Gibbs equation can be used to determine the surface excess of polydisperse block copolymers

  • 184. Rippner Blomqvist, B
    et al.
    Ridout, MJ
    Mackie, AR
    Wärnheim, T
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wilde, P
    Disruption of visco-elastic β-lactoglobulin surface layers at the air-water interface by non-Ionic polymeric surfactants2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, p. 10150-10158Article in journal (Refereed)
    Abstract [en]

    Non-equilibrium interfacial layers formed by competitive adsorption of β-lactoglobulin and the non-ionic triblock co-polymer PEO99-PPO65-PEO99 (F127) to the air-water interface were investigated in order to explain the influence of polymeric surfactants on protein film surface rheology and foam stability. Surface dilatational and shear rheological methods, surface tension measurements, dynamic thin-film measurements, diffusion measurements (from fluorescence recovery after photo bleaching) and determinations of foam stability were used as methods. The high surface visco-elasticity, both the shear and dilatational, of the protein films was significantly reduced by co-adsorption of polymeric surfactant. The drainage rate of single thin films, in presence of β-lactoglobulin, increased with the amount of added F127, but equilibrium F127 films were found to be thicker than β-lactoglobulin films, even at low concentration of the polymeric surfactant. It is concluded that the effect of the non-ionic triblock copolymer on the interfacial rheology of £]-lactoglobulin layers is similar to that of low molecular weight surfactants. They differ however in that F127 increase the thickness of thin liquid films. In addition, the significant destabilising effect of low molecular weight surfactants on protein foams is not found in the investigated system. This is explained as due to that long-range steric forces start to stabilise the foam films at low concentrations of F127.

  • 185. Rippner Blomqvist, B
    et al.
    Wärnheim, T
    Claesson, PM
    YKI – Ytkemiska institutet.
    Surface rheology of PEO-PPO-PEO triblock copolymers at the air-water interface: Comparison of spread and adsorbed layers2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, p. 6373-6384Article in journal (Refereed)
    Abstract [en]

    The dilatational rheological properties of monolayers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-type block copolymers at the air-water interface have been investigated by employing an oscillating ring trough method. The properties of adsorbed monolayers were compared to spread layers over a range of surface concentrations. The studied polymers were PEO26-PPO39-PEO26 (P85), PEO103- PPO40-PEO103 (F88), and PEO99-PPO65-PEO99 (F127). Thus, two of the polymers have similar PPO block size and two of them have similar PEO block size, which allows us to draw conclusions about the relationship between molecular structure and surface dilatational rheology. The dilatational properties of adsorbed monolayers were investigated as a function of time and bulk solution concentration. The time dependence was found to be rather complex, reflecting structural changes in the layer. When the dilatational modulus measured at different concentrations was replotted as a function of surface pressure, one unique master curve was obtained for each polymer. It was found that the dilatational behavior of spread (Langmuir) and adsorbed (Gibbs) monolayers of the same polymer is close to identical up to surface concentrations of 0.7 mg/m2. At higher coverage, the properties are qualitatively alike with respect to dilatational modulus, although some differences are noticeable. Relaxation processes take place mainly within the interfacial layers by a redistribution of polymer segments. Several conformational transitions were shown to occur as the area per molecule decreased. PEO desorbs significantly from the interface at segmental areas below 20 Å2, while at higher surface coverage, we propose that segments of PPO are forced to leave the interface to form a mixed sublayer in the aqueous region.

  • 186. Rojas, OJ
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Berglund, KD
    Tilton, RD
    Coadsorption and surface forces for selective surfaces in contact with aqueous mixtures of oppositely charged surfactants and low charge density polyelectrolytes2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, p. 3221-3230Article in journal (Refereed)
    Abstract [en]

    The coadsorption of a positively charged polyelectrolyte (with 10% of the segments carrying a permanent positive charge, AM-MAPTAC-10) and an anionic surfactant (sodium dodecyl sulfate, SDS) on silica and glass surfaces has been investigated using optical reflectometry and a noninterferometric surface force technique. This is a selective coadsorption system in the sense that the polyelectrolyte does adsorb to the surface in the absence of surfactant, whereas the surfactant does not adsorb in the absence of polyelectrolyte. It is found that the total adsorbed amount goes through a maximum when the SDS concentration is increased. Maximum adsorption is found when the polyelectrolyte/surfactant complexes formed in bulk solution are close to the charge neutralization point. Some adsorption does occur also when SDS is present in significant excess. The force measured between AM-MAPTAC-10-coated surfaces on approach in the absence of SDS is dominated at long range by an electrostatic double-layer force. Yet, layers formed by coadsorption from solutions containing both polyelectrolyte and surfactant generate long-range forces of an electrosteric nature. On separation, adhesive interactions are found only when the adsorbed amount is low, i.e., in the absence of SDS and in a large excess of SDS. The final state of the adsorbed layer is found to be nonhysteretic, i.e., independent of the history of the system. The conditions for formation of long-lived trapped adsorption states from mixed polymer-surfactant solutions are discussed.

  • 187. Rojas, OJ
    et al.
    Ernstsson, M
    Neuman, RD
    Claesson, PM
    YKI – Ytkemiska institutet.
    Effect of polyelectrolyte charge density on the adsorption and desorption behavior on mica2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 1604-1612Article in journal (Refereed)
    Abstract [en]

    The XPS (ESCA) method was employed to quantitatively determine polyelectrolyte adsorption on the mica basal plane from low ionic strength solutions. Particular emphasis was given to the effect of the polyelectrolyte charge density. By combining the results obtained from XPS and surface force measurements it was possible to analyze the cation exchange at the surface that occurs as a result of polyelectrolyte adsorption. AFM-imaging was used to obtain information on the structure of the adsorbed layer when the polyelectrolyte coverage was low. Further, the desorption of preadsorbed polyelectrolyte layers by addition of inorganic salt and by addition of an anionic surfactant was investigated by XPS and some complementary surface force measurements. The results demonstrate that the lower the polyelectrolyte charge density is, the easier it is to remove the polyelectrolyte from the surface. The surfactant, which by itself does not adsorb to the mica surface, is more efficient in this respect than the inorganic salt. This observation can be rationalized by considering that the surfactant and polyelectrolyte form complexes with each other. Thus, the surfactant brings negative charges into the adsorbed layer that reduces the affinity to the surface. However, high-charge-density polyelectrolytes are removed to a very limited degree even when the surfactant concentration is above the critical micellar concentration, which is explainable by the poor solubility of the polyelectrolyte-surfactant complexes formed.

  • 188. Rojas, OJ
    et al.
    Macakova, L
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Emmer, Å
    Claesson, PM
    YKI – Ytkemiska institutet.
    Fluorosurfactant self-assembly at solid/liquid interfaces2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 8085-8095Article in journal (Refereed)
    Abstract [en]

    Fluorosurfactants have some unique properties that are advantageously used in a range of applications. Their solutions are commonly in contact with solid surfaces onto which the molecules adsorb. Despite this, the adsorption behavior of fluorosurfactants at solid/liquid interfaces is not sufficiently understood, and there is a need for more information. In this study we focus on cationic fluorosurfactant adsorption on negatively charged hydrophilic surfaces, especially with respect to the adsorbed layer structure, long-range interactions and adhesion forces. To this end we combined results obtained from bimorph and interferometric surface force instruments and ellipsometry techniques. The initial adsorption to the oppositely charged surfaces occurs due to the electrostatic attraction between the charged headgroups and the surface. Further adsorption, driven by hydrophobic interactions, occurs readily as the surfactant concentration is increased. Surface force and ellipsometric experiments indicate that the surfactants self-assemble in the form of bilayer aggregates. The thickness of the bilayer aggregates was found to be consistent with the molecular structure. Further, ellipsometric measurements indicate that no complete bilayers were formed but rather that bilayer aggregates were present on the surface even at concentrations well above the cmc. Surface force data for low fluorosurfactant concentrations demonstrate that upon compression the bilayer aggregates assembled on the isolated surfaces are transformed and as a result monolayer structures build up between the surfaces in contact. The force required to attain bilayer-bilayer contact increases with the surfactant bulk concentration due to an increase in the repulsive double-layer force. The force required to drive out surfactant molecules to achieve monolayer-monolayer contact also increases with surfactant concentration. Above the cmc some additional aggregates are present on top of the bilayer aggregates coating the surface. The adhesion found between the monolayer aggregates is an order of magnitude larger than between the bilayer aggregates. However, it is an order of magnitude lower than the corresponding value for Langmuir-Blodgett monolayer films of similar fluorosurfactants.

  • 189. Rojas, OJ
    et al.
    Stubenrauch, C
    Schultze-Schlarmann, J
    Claesson, PM
    YKI – Ytkemiska institutet.
    Interactions between non-polar surfaces coated with the non-ionic surfactant n-dodecyl-β-D-maltoside β-C12G22005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, p. 11836-11843Article in journal (Refereed)
    Abstract [en]

    The forces acting between nonpolar surfaces coated with the nonionic surfactant n-dodecyl-β-D-maltoside (β-C12G2) were investigated at concentrations below and above the critical micelle concentration. The long-range and adhesive forces were measured with a bimorph surface force apparatus (MASIF). It was found that the effect of hydrodynamic interactions had to be taken into account for an accurate determination of the short-range static interactions. The results were compared with disjoining pressure versus thickness curves that were obtained earlier with a thin film pressure balance (TFPB). This comparison led to the conclusion that the charges observed at the air-water interface are not due to charged species present in the surfactant sample. In addition, it was observed that the stability of thin liquid films crucially depends on the surfactant's bulk concentration (c) and thus on the packing density in the adsorbed layer. The force barrier preventing removal of the surfactant layer from between two solid-liquid interfaces increases with increasing c, while for foam films it is the stability of the Newton black film that increases with c. Finally, the results obtained for β-C12G2 were compared with those obtained for the homologue n-decyl-β-D-maltoside (β-C12G2) as well as with those obtained for nonionic surfactants with polyoxyethylene moieties as polar groups

  • 190. Ruths, M
    et al.
    Lundgren, SM
    YKI – Ytkemiska institutet.
    Danerlöv, K
    YKI – Ytkemiska institutet.
    Persson, K
    YKI – Ytkemiska institutet.
    Friction of fatty acids in nanometer-sized contacts of different adhesive strength2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 1509-1516Article in journal (Refereed)
    Abstract [en]

    The effects of adhesion, contact area, and pressure on the lubricating properties of self-assembled monolayers on steel have been investigated with friction force microscopy. The adsorbed molecules were fatty acids with varying degrees of unsaturation (0-2 double bonds; stearic, oleic, and linoleic acid) and a rosin acid (dehydroabietic acid), adsorbed from n-hexadecane solution. The friction of these loose-packed monolayers was studied in dry N2 gas and in ethanol. Low adhesion (in ethanol) resulted in a linear increase in friction force at low loads, that is, F = L, whereas higher adhesion (in N2 gas) gave an apparent area-dependence at low loads of the form F = ScA, where Sc is the critical shear stress. A recent model for the contact mechanics of a compliant elastic film confined between stiffer substrates was applied to the data obtained in dry N2. Using this approach, we obtained interfacial energies of the compliant monolayers in good agreement with van der Waals-Lifshitz theory. With a low monolayer elastic modulus of = 0.2 GPa, we obtained a slightly higher value of Sc for stearic acid than that established for more close-packed stearic acid monolayers. An increase of and Sc was found with increasing degree of unsaturation of the fatty acid.

  • 191.
    Rutland, M
    et al.
    YKI – Ytkemiska institutet.
    Waltermo, Å
    Claesson, P
    YKI – Ytkemiska institutet.
    pH-dependent interactions of mica surfaces in aqueous dodecylammonium/dodecylamine solutions1992In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 8, p. 176-183Article in journal (Refereed)
    Abstract [en]

    The adsorption of a hydrolyzable surfactant, dodecylammonium chloride, and interactions between layers thereof, has been studied at a surfactant concentration of 10-4 M as a function of pH using the surface force apparatus. At low pH the surfaces undergo charge reversal as dodecylammonium ions adsorb to form a sparse monolayer. At pH 8-9, adsorption of neutral dodecylamine molecules becomes important, rendering the monolayer more compact with a thickness close to the length of an extended molecule. A hydrophobic attraction is observed between the surfactant monolayers. At pH 9.5-10.3, a bilayer forms on each surface. The double layer force decreases gradually with incrasing pH and disappears at pH 10.3. At this and slightly higher pH values a multilayer gradually builds up on the surface. At pH values around 12 the multilayer buildup is prevented by a recharging of the adsorbed layer. Both the adsorption behavior and the interactions between the layers are reversible with respect to changes in the pH. The structure of the adsorbed surfactant layer on mica is compared to that on other surfaces.

  • 192.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Monolayer study by VSFS: In situ response to compression and shear in a contact2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 11, p. 3075-3085Article in journal (Refereed)
  • 193.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    New insight on the friction of natural fibers. Effect of sliding angle and anisotropic surface topography2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 19, p. 5857-5862Article in journal (Refereed)
  • 194.
    Rutland, MW
    et al.
    YKI – Ytkemiska institutet.
    Parker, JL
    Surface forces between silica surfaces in cationic surfactant solutions: Adsorption and bilayer formation at normal and high pH1994In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, p. 1110-1121Article in journal (Refereed)
    Abstract [en]

    Forces have been measured between glass surfaces in CTAB solutions at pH 10 and the adsorption, inferred from the fitted surface potentials and the measured adhesion, has been shown to be strongly dependent on the surface charge and the competing ions. At very low CTAB concentrations adsorption can only be detected after the surfaces are left in contact, and this results in a time dependent adhesion consistent with diffusion controlled adsorption of CTAB in the annulus around the contact area. At slightly higher concentrations (between 3 and 6 x10-6 M) a hydrophobic monolayer forms and purely attractive hydrophobic interactions are measured indicating that the surfaces are close to electro neutrality. This concentration is much lower than that required to achieve neutral surfaces at pH 5.6 for glass or for mica surfaces. It is argued that after charge reversal the forces can be fitted with DLVO theory, assuming a plane of charge away from the surface. Bilayer formation occurs at the CMC (1x10-3 M) for low pH and below the CMC at elevated pH. The density of surfactant in the outer layer of the bilayer on silica at normal and elevated pH is much lower than that on mica at a comparable bulk CTAB concentration. As a result it is possible to disrupt the bilayers and push the surfaces into a hydrophobic contact. The thickness of the bilayer and the surface charge density obtained from fitting the force law as well as the nature of the force law during compression of the bilayer leads to the conclusion that CTAB adsorbs to glass as patches of bilayers or surface aggregates. Dynamic rearrangements within the surface layer have also been observed.

  • 195.
    Rödner, SC
    et al.
    YKI – Ytkemiska institutet.
    Wedin, P
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    Effect of electrolyte and evaporation rate on the structural features of dried silica monolayer films2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 9327-9333Article in journal (Refereed)
    Abstract [en]

    The structural features of colloidal monolayers formed from dilute silica suspensions dried on a glass substrate have been studied using optical microscopy and image analysis. We determined the size of the hexagonally ordered domains from the pair correlation function and the defect population using an analysis based on Delaunay triangulation. The addition of small amounts of salt resulted in drastic structural changes, which was attributed to the loss of colloidal stability as the suspension dries and the electrolyte concentration increases. The size of the ordered domains decreased exponentially with increasing amounts of added salt and the concentration of large defects increased suggesting that aggregation and particle adhesion to the substrate inhibit rearrangement and ordering. The evaporation rate was controlled by varying the relative humidity; we found that colloidal monolayers with the largest ordered domains and the lowest concentration of stacking faults were formed at intermediate relative humidity.

  • 196. Saigal, T
    et al.
    Riley, JK
    Golas, PL
    Bodvik, R
    Claesson, Per M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Matyjaszewski, K
    Poly(ethylene oxide) star polymer adsorption at the silica/aqueous interface and displacement by linear poly(ethylene oxide)2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 12, p. 3999-4007Article in journal (Refereed)
    Abstract [en]

    Multiarm star copolymers with approximately 460 poly(ethylene oxide) (PEO) arms that have a degree of polymerization N = 45 were synthesized via atom transfer radical polymerization (ATRP) of PEO-methacrylate macromonomers in the presence of divinyl benzene cross-linkers. These are an example of molecular or nanoparticulate brushes that are of interest as steric stabilizers or boundary lubrication agents when adsorbed from solution to a solid/aqueous interface. We use ellipsometry to measure adsorption isotherms at the silica/aqueous interface for PEO star polymers and linear PEO chains having molecular weights comparable either to the star polymer or to the individual arms. The compactness of the PEO star polymers (molecular weight 1.2 × 106) yields a saturation surface excess concentration that is approximately 3.5 times greater than that of the high molecular weight (1 × 106) linear PEO. Adsorption of low molecular weight (6000) linear PEO was below the detection limit. Competitive adsorption experiments were conducted with ellipsometry, complemented by independent quartz crystal microbalance with dissipation (QCM-D) measurements. Linear PEO (high molecular weight) displaced preadsorbed PEO star polymers over the course of approximately 1.5 h, to form a mixed adsorbed layer having not only a significantly lower overall polymer surface excess concentration, but also a significantly greater amount of hydrodynamically entrapped water. Challenging a preadsorbed linear PEO (high molecular weight) layer with PEO star polymers produced no measurable change in the overall polymer surface excess concentration, but changes in the QCM-D energy dissipation and resonance frequency suggested that the introduction of PEO star polymers caused a slight swelling of the layer with a correspondingly small increase in entrapped water content.

  • 197. Samoshina, Y
    et al.
    Nylander, T
    Claesson, PM
    YKI – Ytkemiska institutet.
    Schillén, K
    Iliopoulos, I
    Lindman, B
    Adsorption and aggregation of cationic amphiphilic polyelectrolytes on silica2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, p. 2855-2864Article in journal (Refereed)
    Abstract [en]

    The adsorption of two cationic amphiphilic polyelectrolytes, which are copolymers of two charged monomers, triethyl(vinylbenzyl)ammonium chloride and dimethyldodecyl(vinylbenzyl)ammonium chloride (which is the amphiphilic one) with different contents of amphiphilic groups (40% (40DT) and 80% (80DT)), onto the hydrophilic silica-aqueous solution interface has been studied by in situ null ellipsometry and tapping mode atomic force microscopy (AFM). Adsorption isotherms for both polyelectrolytes were obtained at 25° C and at different ionic strengths, and the adsorption kinetics was also investigated. At low ionic strength, thin adsorbed layers were observed for both polyelectrolytes. The adsorption increases with polymer concentration and reaches, in most cases, a plateau at a concentration below 50 ppm. For the 80DT polymer, at higher ionic strength, an association into aggregates occurs at concentrations at and above 50 ppm. The aggregates were observed directly by AFM at the surface, and by dynamic light scattering in the solution. The adsorption data for this case demonstrated multilayer formation, which correlates well with the increase in viscosity with the ionic strength observed for 80DT.

  • 198. Schantz, S
    et al.
    Carlsson, HT
    Andersson, T
    Erkselius, S
    Larsson, A
    YKI – Ytkemiska institutet.
    Karlsson, OJ
    Poly(methyl methacrylate-co-ethyl acrylate) latex particles with poly(ethylene glycol) grafts: Structure and film formation2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, p. 3590-3602Article in journal (Refereed)
    Abstract [en]

    Water-based copolymer dispersions were prepared using methyl methacrylate (MMA), ethyl acrylate (EA) (MMA:EA = 1:2) and a series of nonionic polymerizable surfactants, i.e., “surfmers” based on poly(ethylene glycol)-(meth)acrylates. The latexes were compared with the behavior of a conventionally stabilized (nonionic nonylphenol ethoxylate, NP100 with 84 ethylene oxide units) dispersion with the same MMA-EA composition (PMMAEA). A number of techniques were employed in order to characterize structure, dynamics and film formation properties: solution/solid-state NMR, dynamic/static light scattering (DLS/SLS), differential scanning calorimetry (DSC), tensile/shear mode dynamic mechanical thermal analysis (DMTA) and atomic force microscopy (AFM). The surfmers were found to be miscible with the MMA-EA copolymer at room temperature, with 46–85 mol % of the reacted surfmer detected at the particle surfaces, the remaining part being buried in the particle bulk. In contrast, the NP100 surfactant formed a separate interphase between the copolymer particles with no mixing detected at room temperature or at 90°C. For a 4.0 % dry weight concentration, NP100 phase separated and further crystallized at room temperature over a period of several months. Composition fluctuations related to a limited blockiness on a length scale above ~2 nm were detected for PMMAEA particles, whereas the surfmer particles were found to be homogeneous also below this limit. On a particle-particle level the dispersions tended to form colloidal crystals unless hindered by a broadened particle size distribution or, in the case of PMMAEA, by the action of NP100. Finally, a surface roughness (Rq) master plot was constructed for data above the glass transition temperature (Tg) from Tg+11 °C to Tg+57 °C and compared with the complex shear modulus over 11 frequency decades. Shift factors from the two methods obeyed the same Williams3 Landel-Ferry (WLF) temperature dependence, thus connecting the long-time surface flattening process to the rheological behavior of the copolymer.

  • 199.
    Sedighi Moghaddam, Maziar
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Swerin, Agne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Claesson, Per
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Multicycle wilhelmy plate method for wetting properties, swelling and liquid sorption of wood2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 39, p. 12145-12153Article in journal (Refereed)
  • 200. Sennerfors, T
    et al.
    Bogdanovic, G
    Tiberg, F
    YKI – Ytkemiska institutet.
    Formation, chemical composition, and structure of polyelectrolyte-nanoparticle multilayer films2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 6410-6415Article in journal (Refereed)
    Abstract [en]

    The buildup and structure of multilayer films containing cationic polyelectrolyte and silica nanoparticles have been studied by means of ellipsometry, atomic force microscopy, and X-ray photoelectron spectroscopy. Emphasis was placed on the effect of ionic strength on the adsorption behavior and structure formation. Consecutive exposure of a silica substrate to low ionic strength solutions containing polyelectrolyte and nanoparticles resulted in the formation of stable adsorbed films with a reproducible stratified multilayer structure. The films formed in high ionic strength solutions were initially much thicker but also clearly less stable. A significant desorption was observed to take place in conjunction with the second exposure to silica nanoparticles. The effect of electrolyte concentration is discussed in terms of a salt-induced glass-liquid transition, above which the relaxation rate in the adsorbed composite film increases and thereby hinders the formation of multilayer structures

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