# Multi-Scale Approach in Soft Matter

**Armand Soldera**

University of Sherbrooke

Friday, November 25, 2011

1:30 PM @ Stirling A

## Abstract:

To describe the vast domain of relaxation times related to the different phase transitions occurring in soft matter, molecular modeling was revealed to be a strongly beneficial tool to complement existing theoretical models. In fact, among the different kinds of simulations, the coarse-grained approach remains the most appropriate technique to deal with the time spreading phenomenon usually related to phase transitions. Alternatively, atomistic simulation is more appropriate for treating the effect of small variations in the molecular architecture of the repeat unit. This technique is unfortunately not available when electronic effects intervene, involving the use of quantum calculations, ab initio calculations. These different kinds of calculation are referred as the multi-scale approach. Its aim is to carry out, through a bottom-up procedure (see Fig. ÂƒÃ±), series of calculations at different levels of approximation. Each level must be used efficiently to probe molecular events occurring during a phase transition. It is then possible to gain a better understanding of the underlying microscopic aspects of a particular property. The challenge is to reveal the perplexing link between molecular structure and macroscopic phenomenon. Ultimately, it is used to guide the design of new molecules and new materials. In this presentation, new membranes are thus designed from ab initio (change occurring after adding water molecules) and mesoscopic (through the study of the spinodal transition) calculations. Glass transition, melting, liquid crystal transitions are explored using atomistic simulations.