Monte Carlo Simulation of Thin Film Polymer Melts

Abstract

We present Monte Carlo simulation data on conformations and dynamics of polymer melts confined in narrow slits of different widths and compare with data of bulk systems. We find that in confined geometries the chains swell laterally; they retain and even expand their spatially long-range correlations compared to bulk polymers and in contrast to the assumption of a complete screening of excluded volume. Long chains in bulk melts show entangled dynamics with a clear signature of a t^1/4-power law for the mean square displacements of innermost monomers at intermediate time scales. This behavior is gradually lost by confining the melts in slits with decreasing width. For ultra-thin films, the dynamics appears to follow a Rouse-like behavior over the entire subdiffusive regime. However, the terminal relaxation time is significantly increased compared to Rouse relaxation. This interesting observation was not reported previously and is the focus of our ongoing research.

Keywords:

• Polymer dynamics
• Entanglements
• Constrained Geometries
• Monte Carlo simulations

Notes

¹ It is not necessary to know the absolute time scale, as the universal properties of polymers lead to unique time ratios independent of the particular type of polymer or simulation model.

² Note that is determined by comparing diffusion with , whereas is determined from a comparison with b². Thus, we observe a slow down of by a factor of for and compared to the Rouse prediction for ideal chains and a slow down by a factor of about when considering the enlarged chain size.