Molecular dynamics simulations on the glass transition in  thin polymer films and the film formation process by spin coating

Simone Peter is a PhD student in the POLYFILM Network working at the Instut Charles Sadron (Strasbourg),  in the group Theory and Simulation of Polymers. I got  my master in physics from  the Technical University of Vienna. My master thesis dealt with the application of time-dependent density functional theory to the calculation of transition amplitudes in helium excited by femto-second laser pulses. I participated in a student exchange program during my studies and spent a year at the University of Pittsburgh.

During my PhD thesis we would like to investigate the glass transition in confinement using numerical simulations. A simple generic flexible bead spring model is used to simulate the polymer melt which retains only the most prominent features of polymers.

We study free standing and supported polymer films of different thickness at low temperature and constant pressure using the method of molecular dynamics.   We investigate changes of static and dynamic properties in the films upon confinement.  We find a depression of the glass transition temperature with respect to the bulk, which is caused by faster monomer dynamics close to the interfaces.

Another aspect of the project focuses on the film formation process. In experiments polymer films are usually prepared by the spin-coating technique. This process is based on the very fast evaporation of the solvent  upon which the film vitrifies rapidly (cf. sketch below). This might leave the films in a non-equilibrium state containing residual stresses. In order to study this phenomenon we include the solvent explicitly in the simulations. This allow us to observe the behavior of the system upon solvent evaporation. We attempt to characterize the influence of the production history on the properties of the resulting films.