Research

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

Coarse-grained polymer models with improved dynamic properties

Multiscale methods make possible to capture polymer features of various length and time scales. In particular, coarse-grained (CG) modeling allows simulating larger systems and/or longer time intervals in comparison with atomistic simulations. However, the dynamics of CG models is artificially accelerated and thus the dynamical properties obtained from CG simulations cannot be related to their atomistic or experimental values. This means that CG diffusion coefficients, for instance, exceed their atomistic or experimental counterparts by one to two orders of magnitude, and CG viscosities are too low by the same amount. The aim of this project is to predict a priori, for a given CG scheme, how much the mobility of the system will be enhanced artificially. Two methods are currently under investigation, namely excess entropy scaling, and time scale separation.

For further information please contact Gustavo Rondina

Coarse-grained molecular approach to mechanical properties and adhesion mechanism of gecko setae

Geckos have a special ability to climb up walls and walk even upside down on ceilings due to fiber structure called seta on its toe pads. The seta is divided into number of spatulas. The origin of the adhesion is inter-molecular force between spatulas and a wall, however the microscopic mechanisms of the adhesion have not been clarified yet. In addition, elasticity of seta also plays an important role for the adhesion. Purposes of our research are to understand microscopic detailed mechanisms of the adhesion and stiffness of a seta. Coarse-grained (CG) models are suitable for our purpose because the CG models are intermediate length scale of chemical microscopic analysis and biological macroscopic measurements, and hence have an ability to connect both data.

For further information please contact Kenkoh Endoh

Droplet evaporation of plymer-containing nanodroplets

Droplet evaporation has been the object of intense research due to its role in promising new applications such as surface coating, nanopatterning and manipulation of macromolecules. The main goal of this project is to develop the coarse-grained simulation models for examining main parameters (polymer chain length, surface nanostructure, initial polymer concentration, etc.) influence on the droplet evaporation of polymer solution, including the pattern of deposits left behind and the molecular processes leading to these shapes. Additionally, dynamical wetting of polymer solution droplets will be studied.

For further information please contact Hari Krishna Chilukoti

Free energy based coarse-grain models

(i) A method to derive free energy based coarse-grain potentials for a given solid-liquid system is developed by combing the Dry-surface approach (to calculate the work of adhesion) and Conditional reversible work (to derive the coarse-grain potential) methods.
(ii) Study on the chain-length dependence of simple n-alkane systems on graphite is being done to understand the thermodynamics of the low energy solid-liquid interfaces.
(iii) My main objective is to study the formation of percolation networks of nano-materials in a polymer matrix and also to understand the fundamentals of thermal percolation at the molecular level.

For further information please contact Vikram Reddy Ardham

Curved Solid-Liquid Interfaces

The solid-liquid interfacial free energy determines numerous properties of technologically important phenomena from crystal nucleation and growth to wetting. Since precise and valid experimental measurements of interfacial free energy are rare, much effort has been given to the development of simulation methods to compute this quantity for interfaces between solid and fluid phases. So far these efforts to determine interfacial free energy have been primarily restricted to the planar interface; however, there are many physically relevant systems in which interfacial curvature is relevant, for example, in the formation of critical nuclei in nucleation or the solvation or wetting of hydrophobic nanoscale particles. Therefore, the main objective of this project is to develop a method for computing the solid-liquid interfacial excess free energy by using the curved surface of a solid.

For further information please contact Shubhadip Das

Improved dynamics in self-consistent field molecular dynamics simulations of polymers

There is a long-standing research interest in multiscale simulations of polymers and nanocomposites. Furthermore there is a need for methods, which are fast and accurate at the same time. The Self Consistent Field Molecular Dynamics (MD-SCF) method evaluates the non-bonded interactions with density fields resulting in a tunable coarse grained resolution at low computational costs. The lack of hard-core repulsions and entanglements though, leads to chain crossing. By combining Slip-Springs, temporary bonds between chains, with DPD we had been successful to repair the entanglement deficit. Our goal is to combine MD-SCF with Slip-Springs to a new method which restores the entanglement dynamics.

For further information please contact Andreas Kalogirou

Polymer chain collapse upon rapid solvent exchange

A recent and promising method to synthesize nanoparticles of defined size and structure is the so-called flash nanoprecipitation method, where a polymer is dissolved in a solvent and precipitated by rapid mixing of the solvent with a non-solvent. Computer simulations of this process necessitate different prerequisites such as the use of an explicit solvent model and fast solvent exchange. We created a model system to answer this while still incorporating solvent dynamics, such as diffusion, using Dissipative Particle Dynamics (DPD). A polymer chain which is suddenly exposed to large amounts of non-solvent will collapse to a globule. If multiple chains are present in the system, they will eventually form a nanoparticle. The aim of this project is to study the collapse behaviour of isolated chains and polymer solutions in dependence of e.g. chain length, polymer concentration, and solvent quality.

For further information please contact Jurek Schneider

Structure and dynamics of self-assembled monolayers on metal surfaces

Self-assembled monolayers (SAMs) provide an excellent way to understand the fundamental principle governing self-assembly process starting from two to three-dimensional assemblies. They can be easily modified to take into account the various specific interactions that occur in nature and elucidate the effect caused by these interactions on self-assembly and interfacial phenomena. They can also be prepared easily in very less time and have vast potential applications in the field of corrosion prevention; chemical and biochemical sensing; electro-optic devices and many more. This project focuses on getting better understanding of the change in structure and dynamics of SAMs due to the variations in chemical nature of the SAM and its effect on the self-assembly and interfacial phenomena.

For further information please contact Saurav Prasad