Pilot Project on Rheological Properties of New Composite Materials

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.

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++.

Hierarchical Strategy for Simple One-Component Polymer Melts: fixed-local-tuple

Status:Delivered

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.

Hierarchical Strategy for Simple One-Component Polymer Melts: md-softblob

Status:Delivered

Description: This module provides the potentials and thermostat for the molecular dynamics simulation of softblobs.

Hierarchical Strategy for Simple One-Component Polymer Melts: Minimize Energy

Status:Delivered

Description: This module provides a steepest-descent method which is a typical energy minimization method.

Hierarchical Strategy for Simple One-Component Polymer Melts: contrain-com

Status:Delivered

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.

Hierarchical Strategy for Simple One-Component Polymer Melts: constrain-rg

Status:Delivered

Description: This module provides the C++ class for applying a suitable constraint that conserves the radius of gyration of an arbitrary number particles.

Coarse-Graining: A Component of the Hierarchical Equilibration Strategy for Polymer Melts

Status:Delivered

Description: This module provides a python script which performs coarse-graining (CG) procedure from microscopic model to softblob model.

Fine-graining: A Component of the Hierarchical Equilibration Strategy for Polymer Melts

Status:Delivered

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.

Reinsertion: A Component of the Hierarchical Equilibration Strategy for Polymer Melts

Status:Delivered

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

Status:Delivered

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