0000000000121669
AUTHOR
Gary S. Grest
Relaxation of self-entangled many-arm star polymers
We present a description of the relaxation of star polymers based on the conformational scaling properties predicted by Daoud and Cotton and confirmed in our recent simulations. We identify three typical relaxation mechanisms. The first describes elastic deformation of the overall shape. Its relaxation time is nearly independent off. A second type of relaxation occurs via rotational diffusion. We predict that the relaxation time should scale with Nwlfz-v where Y is the correlation length exponent. A third relaxation process is the disentanglement of two or more arms. Here the longest relaxation time should increase exponentially with f llz. We measure various relaxation processes by molecul…
Dynamics of Dense Polymers: A Molecular Dynamics Approach
The physics of polymeric materials[1, 2] is one of the most challenging problems in condensed matter physics today. It is a problem of great interest both from a fundamental viewpoint and for their various technical applications. In addition to theortical and experimental approaches, computer simulations[3–11] have played an important role in our present understanding of polymers. For static properties Monte Carlo methods have been widely used and give excellent results for static critical exponents. To investigate dynamic properties three different methods — Monte Carlo (MC)[3–7], molecular dynamics (MD)[8, 9] and Brownian dynamics methods[10] — have been used. Detailed microscopic dynamic…
Crossover from Rouse to Reptation Dynamics: A Molecular-Dynamics Simulation
We present the results of an extensive molecular-dynamics simulation of a dense polymer system. We show for the first time that simulations are able to cover the whole regime from pure Rouse dynamics to reptation dynamics and give strong evidence of the latter. The mean square displacements clearly exhibit a ${t}^{\frac{1}{4}}$ power law. A mode analysis shows that the high-frequency modes follow the Rouse relaxation while those at lower frequency display reptation relaxation. Both quantities give the same entanglement length.
Computer Simulations for Polymer Dynamics
In this paper we review recent work on the dynamics of polymeric systems using computer simulation methods. For a two-dimensional polymer melt, we show that the chains segregate and the dynamics can be described very well by the Rouse model. This simulation was carried out using the bond fluctuation Monte Carlo method. For three-dimensional (3d) melts and for the study of hydrodynamic effects, we use a molecular dynamics simulation. For 3d melts our results strongly support the concept of reptation. A detailed comparison to experiment shows that we can predict the time and length scales for the onset of reptation for a variety of polymeric liquids. For a single chain, we find the expected h…