Below are some ongoing projects:
My main occupation is developing computational methods for studying the microscopic origins of elasticity in cross-linked polymer materials using Molecular Dynamics simulations on supercomputers. This activity is funded by Continental. (Collaboration: Continental researchers, Ralf Everaers ENS Lyon)
Mapping of KG polymers to real polymers
With recent progress we now know how to convert a given real polymer species into the equivalent KG polymer model, and vise versa convert KG units sigma, epsilon, and tau into SI units. (Collaboration: Continental researchers, Ralf Everaers ENS Lyon)
Damage and wear in polymer materials
How can we develop methods for breakable bonds and use them utilize them to study damage mechanisms in polymer materials. (Ph.D. Student: Igor Gula)
Mori-Zwanzig based coarse-graining
Structure based coarse-graining is routinely used to develop coarse-grained models that reproduce static structural properties of a more detailed model of e.g. biophysical systems. However, dynamic non-equilibrium behaviour is also of significant interest. Currently only one method exists for systematically deriving coarse-grained equations of motion: Mori- Zwanzig theory was developed more than 50 years ago. Despite this fact it has yet to be used as a basis for deriving coarse-grained Molecular Dynamics models. (Collaboration Ass. Prof. K. Debrabant, Ph.D. Student: Nicky Mattson)
Computational fast generic polymer models
The Kremer-Grest polymer model was proprosed in 1986 and have been the defacto standard model for MD simulations ever since. Recently we characterized the dynamics of KG melts as function of chain stiffness. With this benchmark we can tell how many wall hours of simulation (on some standard hardware) are required to reach e.g. the entanglement or disentanglement time for a given polymer melt state. With this insight its quite relevant to ask whether we can optimize the model wrt. this benchmark to invent generic polymer models that are computationally cheaper.
Can we utilize segmental-repulsive interactions in the contect of DPD simulations to make computationally effective models of gels of very stiff polymers.
Casin gel formation
When acid is added to skimmed milk, the casein micelles can aggregate to form a network. We are developing models based on granular particles to simulate the self-assembly of such network structures. The resulting structures will be compared to experimental results.
Damage in elastic materials
We aim to simulate continuum models (inspired from peridynamics) of elastic material, but where these materials can break. How is the material properties related to the force field we simulate, and secondly what is the physics of fracture initiation and growth in these materials.
Diffusion in 2D solids at an solid/liquid or liquid/liquid interface
Recent theory suggests logarithmic dependence on the mean-square displacements under certain assumptions we plan to test these. (ISA student, and F. Lo Verso, SDU)
Redistribution of hydrophobic pharmacuticals between oil droplets
Naively one would expect hydrophobic agents would stay well partitioned in oil droplets or micelles in a aqueous solution, however, experiments suggests they are rather rapidly distributed if a mixture of loaded and unloaded droplets is prepared. We will study if this redistribution process follows a type of Ostwald ripening dynamics. (with F. Lo Verso and J. Kunche SDU)
Chemically modified DNA molecules (LNA - Locked nucleic acids) offers a promise as probes for detecting specific mutations. In order to optimize the pharmaceutical application of such probes, molecules we need to understand and predict their hybridization behaviour (melting temperature) and sequence specificity. This is currently being studied by developing a Poland-Scheraga type model of the thermodynamics of DNA/LNA hybrid hybridization. (Collaboration Ass. Prof. I. Kira Astakhova, Students: Peter Reinholdt, Erik Kjellgren, Oliver Glue)
Small-angle Neutron and X-ray Scattering techniques (SANS/SAXS) are ideal techniques for investigating nano-structures in soft-condensed matter and biological matter. However, to analyze the results of such experiments detailed knowledge is required about the scattering form and structure factors. I have developed a formalism for predicting the scattering from a large class of structures comprising polymers, and geometric objects. Currently this is being expanded by developing theory for the scattering from self-avoiding random walks.