Bjørn Hafskjold

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We use dissipative particle dynamics (DPD) and molecular models to simulate interacting oil/water/surfactant interfaces. The system comprises sections of two emulsion droplets separated by a film. The film is in equilibrium with a continuous phase, in analogy with the surface force apparatus. This is achieved by combining DPD with a Monte Carlo scheme to(More)
A binary isotope mixture of Lennard-Jones/spline particles at equilibrium was perturbed by a sudden change in the system's boundary temperatures. The system's response was determined by non-equilibrium molecular dynamics (NEMD). Three transient processes were studied: 1) The propagation of a pressure (shock) wave, 2) heat diffusivity and conduction, and 3)(More)
The effect of the surfactant chain length n on the bending modulus kappa of surfactant monolayers is simulated with a mesoscopic oil-water-surfactant model. We confirm a power law, kappa is proportional to np, as predicted by mean-field theory and found experimentally, and find p approximately 1.5 at a constant surface density and p approximately 1.0 at a(More)
We have used dissipative particle dynamics to simulate amphiphilic monolayers on the interface between oil and water. An ultralow interfacial tension is imposed by means of Monte Carlo to resemble the amphiphilic films that separate oil and water regions in microemulsions. We calculate the bending modulus by analyzing the undulation spectrum. By varying the(More)
– We study surfactants at the oil/water interface using Dissipative Particle Dynamics simulations at constant μsurfPT . The interfacial tension depends on the surfactant branching in a subtle way. For a given interfacial concentration, a double-tail surfactant is more efficient than its single-tail isomer only if the oil-head repulsion is sufficiently(More)
Pulsed field gradient stimulated echo (PFGSTE) nuclear magnetic resonance (NMR) has been applied to study the diffusion of toluene in porous semicrystalline polyethylene powder. A pulse sequence with unequal bipolar gradients that reduces effects from internal gradients was used. The effects of different diffusion regimens and restricted diffusion in this(More)
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