Magnetoviscosity of dipolar colloidal fluids (Dr Patrick Ilg)
The viscosity of dipolar colloidal fluids (ferrofluids) can be manipulated by varying an external magnetic field. Current constitutive models suffer from the lack of knowledge about the relevant microstructure. Our simulations provide information on the field- and flow-induced structural changes and will allow us to formulate improved constitutive equations for dipolar colloidal fluids.
Field-dependent mechanical properties of ferrogels (Dr Patrick Ilg)
When magnetic particles are brought into polymer gels, their soft solid-like behaviour responds strongly to external fields. From a theoretical point of view, the coupling of the translational and rotational dynamics of the magnetic particles to the polymer matrix is largely unknown. From detailed microscopic simulations we want to extract information on how to modify the classical Brownian Dynamics of the particles when they move not through a simple liquid but through a viscoelastic environment.
Rheology of supercooled liquids (Dr Patrick Ilg)
The viscosity of liquids increases enormously when cooled down towards the glass transition without apparent change of their microstructure. By analysing the underlying potential energy landscape of a binary Lennard-Jones system, we identify cooperative rearranging regions that grow in size upon cooling. Our simulation results help to improve and provide a microscopic basis of current theories of the dynamics and rheology of glassy systems.
Polymer brushes under shear (Dr Patrick Ilg)
Polymer brushes are very effective in lubricating surfaces. We use nonequilibrium molecular dynamics simulations in order to investigate the effect of semi-flexibility as well as different polymer architectures on the resulting coefficient of friction of the polymer-coated surface.
Complex fluid-fluid interfaces (Dr Patrick Ilg)
Fluid-fluid interfaces can be stabilised by adsorbed multi-block copolymers that self-assemble into complex microstructures. We study the influence of the microstructure on the stability and surface rheology with a multi-scale approach, combining molecular simulations and non-equilibrium thermodynamics modelling.
Atomistic simulation of nanostructured polymeric and surfactant materials (Dr Zuowei Wang)
Molecular dynamics simulations at the atomistic level can provide microscopic understanding of physical properties of soft matter materials that are generally hard to achieve in experiments. This type of simulation also constructs the basis for developing more coarse-grained computational models.
The systems we are working on include polymer melts, surfactant micelles, polymer-drug conjugates, etc. The simulation results are directly compared with experimental measurements and contribute to the development of coarse-grained models in the group.
Field-theoretic simulations for block copolymers
Monte Carlo field-theoretic simulation is a novel and very promising technique for studying the fluctuation effects in block copolymers. In opposite to the chain-based simulation methods, the field-theoretic approach allows to consider very large polymerisation indexes.
Mathematically, the technique is related to the well-known self-consisted field theory, but instead of using the mean-field approximation, it exactly describes the composition fluctuations, which are particularly important in the proximity of the order-disorder transition and in the disordered phase. We focus on the fluctuation corrections to the mean-field predictions for the disordered-state structure factor and the order-disorder transition in a symmetric diblock-copolymer melt.