Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 17: Transport and Confinement I
CPP 17.6: Hauptvortrag
Dienstag, 1. April 2014, 11:15–11:45, ZEU 260
Molecular Dynamics simulations of the glass transition in 1,4-polybutadiene confined by graphite walls — •Wolfgang Paul1, Mathieu Solar1, and Kurt Binder2 — 1Institut für Physik, Martin-Luther-Universität, 06099 Halle — 2Institut für Physik, Johannes-Gutenberg-Universität, 55099 Mainz
We will discuss simulations of a chemically realistic representation of 1,4-polybutadiene (PBD) between graphite surfaces and discuss the influence of the walls on structure and dynamics in the polymer film. There have been many studies of polymers at interfaces and especially on the influence of interfaces on the glass transition in polymers, and with partially contradicting results. We will show that there are two influences of the wall on the structure in the adjacent melt. The first is a strong layering in the monomer density next to the wall, and the second is an orientation of the chains close to the wall and a layering in the centre of mass density of the chains.
Both structural effects give rise to significant modifications of the relaxation behaviour of the polymer next to the wall. We will discuss in detail how these can be identified in different experiments ranging from dielectric spectroscopy to nuclear magnetic resonance to neutron scattering. Determining the glass transition temperature of the confined system from the dielectric relaxation, we find that for this realistic polymer wall model it is independent of the thickness of the film studied down to about 1 nm.