Research Projects

These are the projects the Müller-Plathe group is currently working on.

Coronavirus and Disinfectant

Picture: AK Müller-Plathe

The project investigates by molecular dynamics simulations the action of common disinfectants such as ethanol or isopropanol on the integrity of the external membrane of the coronavirus.

For further information go to: ccteamcov.blogspot

Disclaimer: We are using this channel instead of peer-reviewed publishing because of speed. We want to make results available to practitioners in time for them to be useful in the current crisis. Therefore, results may be preliminary, not quite converged or inaccurate. Still they might be useful, and they are the best we can do at the time. Use our results with care.

Mobility of polymer melts in confinement

RD_Simon Alberti_Projekt_DPD_NT
Picture: AK Müller-Plathe

The development of polymer nanocomposites is of great scientific interest and especially carbon nanotubes show promising properties, such as electrical and thermal conductivity, impact strength or viscoelasticity. Material properties strongly depend on the alignment of nanoparticles and polymers. We study entangled polymers in confinement in order to get an insight into the mobility behavior of the polymers. We use Dissipative Partivle Dynamics (DPD) as our coarse-grained simulation method together with a slip-springs model, which has been developed in our group. This model has shown to reproduce entangled dynamics of polymer chains. For soft-core methods, like DPD, polymer dynamics are generally greatly accelerated. The confinement in this work consists of nanotubes, arranged in a hexagonal array. These nanotubes are modeled as excluded volume through a repulsive potential and we analyze structural and dynamic properties of the polymers. Our model yields the potential to be further refined by a more structured nanotube model and a more detailed analysis of the chain movement. Moreover, irregular arrays or the dispersion of nanotubes under a flow of entangled polymers could then be studied in future projects.

For further information please contact Simon Alberti

Surpression of droplet rebound by polymer additives

RD_Eunsang Lee Project Picture
Picture: AK Müller-Plathe

When a water droplet impacts on a hydrophobic solid surface with a proper velocity, it rebounds back. Recent experiments revealed that adding a small amount of polymer in a water droplet suppresses the rebound without substantial change of its macroscopic rheological properties. We investigate in this project the anti-rebounding behavior of a dilute polymer solution via multi-body dissipative particle dynamics simulation. The rebounding tendency of a droplet is simulated and is interpreted in terms of non-equilibrium dynamics in non-linear response regime. The aim of this project is to establish a concrete relation between rebounding tendency and rheological properties of the polymer solutions.

For further information please contact Eunsang Lee

Multi-scale MD-FE coupled simulations of polymers

When simulating materials, one often encounters the situation that only in a small part of the material something “interesting” happens, but where the whole of the material needs to be described, as the less interesting regions influence directly or indirectly what is going on in the interesting region. An example is the failure of a polymer composite: When it breaks, complicated rearrangement of the polymer molecules take place near the crack tip. They are interesting from a fundamental and an application viewpoint. Away from the crack tip, the polymer is deformed under the load and this deformation will influence the processes at the crack tip. However, the deformation of the outer regions is not in itself interesting. Another example is the process of dry adhesion. For such cases, an algorithm is being developed by the Müller-Plathe group which allows us to conduct Molecular Dynamics – Finite Elements method (MD-FE) coupled Multi-scale Simulations.

For further information please contact Yash Jain

Molecular simulation of gecko inspired keratin

Picture: AK Müller-Plathe

Geckos multiscale adhesion apparatus is composed of hierarchical fibrils spanning from the nanoscale (spatulae) to the microscale (setae), allows walking on walls and even ceilings. The unique fibrillar structure, only found in geckos, is mainly composed of keratin-associated beta-proteins. A coarse-grained model based on the chemical amino acid composition was previously developed with the aim of reproducing linear mechanical properties. This project expands on the previous two-bead model by introducing different chemical moieties to allow the investigation of the effect of the amino acid composition onto the adhesion force. As the gecko walks on a substrate the amino acids on the surface of the spatulae are in close contact with the atoms of the substrate, the main driving force of the resulting dry adhesion is thought to be van der Waals interactions. With the new model this hypothesis will be tested. Additionally, the effect of humidity onto the adhesion force, due to an hypothesized underlying change in the secondary structure possible due to the relative long- timescales, will be examined.

For further information please contact Tobias Materzok

Coarse-grained simulation models with improved dynamics

Coarse-grained simulation models allow simulating large systems or on long time scales, such as simulations of a variety of polymers, surfactants and proteins. However, the dynamics of these models is accelerated compared to the parent atomistic models or experiments. An a-priori estimate of the acceleration would make predictions of realistic dynamical properties, such as diffusion coefficients and viscosities, possible. In this project, a recent and promising method to link the acceleration of dynamics, as one moves from atomistic to a coarse-grained model, to geometrical differences between the two models is under investigation. To this end, the decrease of molecular roughness is calculated by a numerical comparison of the molecular surfaces of both the atomistic and coarse-grained systems.

For further information please contact Melissa Meinel

Improved dynamics in hybrid particle-field simulations of polymers

RD_Zhenghao Wu_Project Picture
Picture: AK Müller-Plathe

One of the fundamental concepts in polymer dynamics is the entanglement. Referring to the case of polymer interpenetration, the term entanglement describes the topological interactions caused by the non-crossing nature of the chain. The recent developed hybrid particle-field (hPF-MD) simulation method enables efficient modeling of polymeric materials with detailed chemistry via employing soft potential of the density-functional-field. This soft potential allows chain crossing mutually, causing the artificial impacts on the dynamical behavior. The main aim of this project is to develop a novel hPF-MD based simulation approach for studying the dynamical properties of complex polymer systems such as polymer melts, polymer nanocomposites and polymer blends via combining with a multi-chain slip-spring model which mimics the topological confinement as transient mobile bonds between entanglement strands.

For further information please contact Zhenghao Wu

Heat transfer at the interface and miscibility of polymer blends

RD_Tianhang Zhou_Project Picture
Picture: AK Müller-Plathe

A. The interfacial thermal conductance at the interface is considered to play an important role in dictating the overall thermal conductivity of carbon-based nanocomposites. Molecular dynamics (MD) simulations can be used to investigate the mechanism of thermal energy transport over the interface between organic materials in solid and liquid phases and few-layer graphene at different temperatures under different heating modes.

B. Compared with synthesizing new polymers, it is an economical route to create high performance materials by polymer blending. Dissipative particle dynamics (DPD) can be used to examine the property of polymer blend system with different compatibilizers.

For further information please contact Tianhang Zhou