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It is well-known that adsorption kinetics influences the damping coefficient of capillary waves. However, only a few kinetics studies of adsorption based on this effect have been published in the literature. We show that the method of low-frequency capillary waves has certain advantages as compared with other methods traditionally used for this purpose. It can be applied also to the investigation...
A regular solution theory for a system of molecules of different molecular sizes is used to derive parameters which can be related to the interaction between molecules of surface active compounds and water molecules in adsorbed films at the free water surface.
Curvature elasticity of monolayers can be described in terms of elastic moduli. These moduli depend on the position of the neutral surface (surface of inextension during pure bending). Based on a combination of a mean field theory of chain packing and a head group contribution for amphiphilic molecules, the position of the neutral surface is determined. The electrostatic part of charged molecuels...
Spread monolayers of nonadecylpyridine (NDP) were studied using subphases containing two different metal ions, Co2+ and Cu2+, at the same concentration, in order to investigate the interactions between the monolayer and the ions in the aqueous subphase and to deduce the behavior of NDP as a ligand. Surface pressure-area and surface potential-area isotherms were recorded at 20 °C. Langmuir-Blodgett...
The morphological structure of monolayers of straight-chain alcohols with 14 to 18 C-atoms are studied. Compression/decompression isotherms are illustrated by images taken with a Brewster angle microscope. Tetradecanol with a plateau region in the surface pressure-area isotherm exhibits circular domains during the phase transition. Decompression leads to the formation of a stable two-dimensional foam...
Surface modification techniques were developed to graft chemically poly(ethylene oxide) chains on mica and polyethylene substrates. The chemical composition of surface layer was characterized by X-ray photoelectron spectroscopy measurements. Static and dynamic wettability studies were performed to get information on the solid/liquid interaction. The wetting parameters indicate a strong influence of...
Langmuir films are formed by amphiphilic molecules. These molecules consist of a more or less structured head and one or more tails of different length. The hydrophilic heads are strongly attracted by the water surface, whereas the hydrophobic tails can move in the upper half space. We have carried out athermal MC simulations on a simple cubic lattice using periodic boundary conditions in x- and y...
Amphiphilic molecules consist of a hydrophilic head and one or more hydrophobic tails. The heads are strongly attracted by the water surface, whereas the tails can move in the upper half space. We investigated the behavior of a monomolecular film consisting of branched amphiphilic molecules in dependence on the head density and the side chain length. The Monte Carlo simulations were carried out on...
Static light-scattering measurements on aqueous solutions of charged polystyrenesulfonate (PSS) with five molecular weights between 1100 000 g/mol and 1 132 000 g/mol are presented. All experiments were performed in the dilute/semidilute regime at minimum ionic strengths (≈ 10−6 M) in order to maximize the electrostatic interaction between monomers of different polymers or monomers belonging to the...
Orientation behavior in external electric fields of rod-like fd-virus particles (length l=895 nm, diameter d=9 nm) in aqueous suspensions is examined by the electric birefringence mthod and static light-scattering measurements. In aqueous suspensions the negatively charged fd-particles are surrounded by a diffuse Debye cloud of counterions, which is characterized by the Debye-Hückel parameter κ. A...
The surface free energy of controlled porosity glasses was correlated with “geometrical” factors, i.e., specific surface area, mean pore diameter, and total pore volume. A new parameter related to the specific surface area was evaluated based on mean pore diameter and total pore volume and assuming various capillary models. Two CPG’s differing in their total pore volume were selected for further experiments
The electrophoretic mobility of ZrO2 particles stabilized with 3 mol % of yttria recorded at different pH is known to vary as a function of time. The cause of the shift in the surface charge was investigated since it is known to influence a range of important properties controlling the slip casting of ceramic green bodies. It was found that yttrium and some zirconium ions are leached out from the...
The Coulombic attraction theory of colloid stability, first proposed by Sogami in 1983, is shown to be well adapted to explain the existence and extent of both the one-phase (suspension) and two-phase (gel) regions of colloid stability which are observed in clay swelling. The central prediction of the Sogami theory is that there is a weak attractive tail in the thermodynamic electrostatic interaction...
The particle counter technique is used for studying the rate of aggregate fragmentation induced by polymer adsorption. The influeces of the hydrodynamic forces during aggregation and the degree of surface coverage before fragmentation were investigated. We determined that a scalling law a(x) ℞ xλ described the rate of break-up a(x) of aggregates of size x. Values...
The synthesis of stable cyclohexane magnetic fluids constituted by maghemite nanoparticles, coated by polystyrene chains (Mw=13 000) is described. α-Lithium poly(styrene) sulfonated polymer chains are adsorbed on the cationic nanoparticles of an aqueous magnetic fluid through electrostatic interactions between the anionic sulfonate group and the cationic surface. The colloidal solution obtained by...
Magnetic colloidal solutions are prepared by dispersion of surfactant coated magnetic nanoparticles in cyclohexane. The particles are maghemite grains, with a size distribution described by a lognormal law of parameters D0=6.5 nm, σ=0.35. The surfactant used to ensured the dispersion of particles is a phosphate ester of a long chain alkylphenol. The colloidal solution is characterized by...
We report an experimental study of the phase behaviour of a model hard sphere colloid + non-adsorbing polymer mixture — sterically stabilised PMMA and polystyrene in cis-decalin. The addition of non-adsorbing polymer to an otherwise stable colloidal suspension can induce phase instability. This is due to an entropic effect whereby the polymer induces an effective “depletion” attraction between the...
The total bare charges and electrophoretic mobilities of carboxylate latex and sulfate latex were measured as a function of pH and salt concentration. Titration curves fall together in a master curve, if the surface pH is calculated from the surface potential using a Gouy-Chapman model with small modifications. Carboxylate latex shows a spectrum of intrinsic dissociation constants with a linear increase...
The influence of the surface active substances of the cationic (n-dodecyl amine sulphate S+) + anionic type (sodium n-dodecyl sulphate S−) on the characteristics of the negative silver iodide sols was investigated. Surfactants were present at the moment of silver iodide formation, and act markedly at very low concentrations. In order to obtain new data about interaction between S+ + S− and AgI-I−,...
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