In this collaborative project with Michelin, we develop new simulation codes to study dense polymer systems. The company is particularly interested in block copolymers as molecularly designed novel composite materials, and their rheological properties, like the frequency-dependent shear modulus. To study these materials by simulation, one needs a molecular model in order to capture nonlinear response and the effect of entanglements. The generation of equilibrated model samples is however tricky and computationally demanding. We implemented a novel hierarchical equilibration strategy for homopolymer melts, and work to generalise this to polymer blends and block copolymers. These latter systems are even more demanding, due to their microstructure. For further details, see the "E-CAM Case Study" below.
List of Tasks
- Modules for equilibrating simple homopolymer melts (done, see list below)
- Modules for equilibrating homopolymer melts with attractive interactions, with the goal to handle gas-vapour coexistence (work in progress)
- Modules for equilibrating binary polymer blends (future work)
- Modules for equilibrating block copolymers (future work)
- Modules for studying linear and nonlinear frequency-dependent response of polymer systems to shear (future work)
List of Modules
To study the properties of polymer melts by numerical simulations, equilibrated configurations must be prepared. However, the relaxation time for high molecular weight polymer melts is huge and increases, according to reptation theory, with the third power of the molecular weight. Hence, an effective method for decreasing the equilibration time is required. The hierarchical strategy is a particularly suitable way to do this. The following modules are part of a suite of programs which realize this method within the framework of the simulation package ESPResSO++.
Description: In contrast to simple Molecular Dynamics, which is based only on pairs of particles, the hierarchical strategy needs to allow tuples of arbitrary size. This module provides this more general data structure. The list can contain both real and ghost particles.
Description: This module provides the potentials and thermostat for the molecular dynamics simulation of softblobs.
Description: This module provides a steepest-descent method which is a typical energy minimization method.
Description: This module provides the C++ class for applying a suitable constraint that conserves the position of the center of mass of an arbitrary number particles.
Description: This module provides the C++ class for applying a suitable constraint that conserves the radius of gyration of an arbitrary number particles.
Description: This module provides a python script which performs coarse-graining (CG) procedure from microscopic model to softblob model.
Description: This module provides a python script which performs fine-graining (FG) procedure in which each CG polymer chain is replaced with a more FG chain, by dividing a CG blob into several FG blobs.
Description: This module provides a python script which performs a reinsertion procedure in which atomistic monomers are reinserted into softblobs and monomers are treated as mass points without non-bonded interaction.
Feedback control mechanism: A Component of the Hierarchical Equilibration Strategy for Polymer Melts
Description: This module provides a python script which performs the feedback control mechanism in which monomers are reinserted into softblobs and repulsive non-bonded interactions are gradually introduced according to the feedback control mechanism.
List of publications