Shorttime elasticity of polymer melts: Tobolsky conjecture and heterogeneous local stiffness
Abstract
An extended MolecularDynamics study of the shorttime "glassy" elasticity exhibited by a polymer melt of linear fullyflexible chains above the glass transition is presented. The focus is on the infinitefrequency shear modulus $G_\infty$ manifested in the picosecond time scale and the relaxed plateau $G_p$ reached at later times and terminated by the structural relaxation. The local stiffness of the interactions with the first neighbours of each monomer exhibits marked distribution with average value given by $G_\infty$. In particular, the neighbourhood of the end monomers of each chain are softer than the inner monomers, so that $G_\infty$ increases with the chain length. $G_p$ is not affected by the chain length and is largely set by the nonbonding interactions, thus confirming for polymer melts the conjecture formulated by Tobolsky for glassy polymers.
 Publication:

Journal of Polymer Science B Polymer Physics
 Pub Date:
 October 2015
 DOI:
 10.1002/polb.23783
 arXiv:
 arXiv:1605.00878
 Bibcode:
 2015JPoSB..53.1401B
 Keywords:

 Condensed Matter  Soft Condensed Matter;
 Physics  Fluid Dynamics
 EPrint:
 18 pages, 6 figures