0000000000977099
AUTHOR
S. Krushev
The Role of Internal Rotational Barriers in Polymer Melt Chain Dynamics
We present molecular dynamics simulations on 1,4-polybutadiene comparing the dynamics of melt chains between chemically realistic models and a freely rotating chain version of one of the models. These models exhibit the same liquid structure, as measured by the structure factor, and meso- to large-scale chain structure, as measured by the Rouse-mode amplitudes. We show that in this case the Rouse-like chain dynamics as observable in the momentum transfer range of neutron spin-echo experiments is the same for the chains with and without torsion barriers. Our results bear on a recent comparative neutron spin-echo study of the chain dynamics of two polymers with similar chain structure which r…
Intramolecular caging in polybutadiene due to rotational barriers
We present molecular dynamics simulations of a chemically realistic model of 1,4-polybutadiene and a freely rotating chain model derived from the first model by neglecting all dihedral potentials. We show that the presence of energy barriers hindering dihedral rotation leads to an intermediate plateau regime in the tagged particle mean-squared displacement reminiscent of the cage effect underlying the mode-coupling description of the liquid-glass transition. This intramolecular caging, however, occurs already at temperatures well above the glass transition regime. Because of its different physical origin, it also does not comply with the theoretical predictions of the mode-coupling theory. …
Computer Simulation of Polymers: Physics and Methods from Specific to Universal
We will discuss in this contribution several aspects of the physics of polymers on different length and time scales and the simulation methods suited for their study. A Molecular Dynamics (MD) simulation of a chemically realistic model is needed to get quantitative insight into local relaxation processes. This study will also reveal the importance of four-particle correlations in polymer dynamics resulting from the presence of dihedral potentials along the chain. Universal largescale chain relaxation can be studied by realistic models as well, but in far better statistical accuracy by Monte Carlo (MC) simulations of a coarse-grained lattice model. Finally we will present considerations for …