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ICS-3 Vortrag: Herr Jonas Riest,
Universität Wien, Computational Physics

"Elastic properties of single particle systems: A molecular dynamics study"

06.Nov.2012 10:30
Seminarraum A1-A3, Building 04.6


In the last years, many experimental studies that focused on the investigation of the  elastic properties of single particle systems,  lead to the understanding of biological processes, to the design of target-oriented drugs as well as to the study of crystallization relating such processes to the elastic single particle deformations.

Such investigations  opened the path for  a deeper analysis of the relation between the macroscopic properties of  materials and the microscopic properties of the constituent particles. In this work, we focus on  the characterization of spherical polymer brushes by means of Molecular Dynamics simulations.

First we discuss the properties of spherical polymer brushes in the absence of an external field, and we show that the latter are characterized by a density decay that differs from the typical star-polymer case.

As a first step, we use the properties of free brushes  as a characterization of the shape of the polymer brush;  by using as a reference point the free brush, we implement an  “up-bottom” linear elastic theory  from the macroscopic  to the microscopic case to describe the elastic single particle properties. By determining  the elastic moduli of a microscopic object we obtain interesting physical insights on the properties of the single particle, e.g.  we discover that   the  Poisson’s ratios, in contrast to the macroscopic case, are not constant when computed on the microscopic level. Due to the radial inhomogeneity on the microscopic level, Poisson's ratios appear to be dependent on the compression strength. Nevertheless, the Poisson’s ratios of the polymer brushes studied have values in the interval 0 < ν < 1/2 for a broad range of parameters. This is the expected interval observed for  isotropic and homogenous materials. In addition we determine the Young’s modulus of spherical polymer brushes for a broad configuration of parameters.

This work is the basis for upcoming studies of the elastic properties of one-particle systems.