Molecular Simulations Provide a Critical Observation for Understanding Polymer Flow
Left frame: Snapshots of the simulated entangled polymers in the equilibrium state (upper) and immediately after the uniaxial stretching (bottom). Right frame: Corresponding simulated small-angle scattering spectra, where Q1 is along the stretching direction. (hi-res image)
Large-scale non-equilibrium molecular dynamics simulations demonstrate key shortcomings of the conventional “tube model” for polymer flow.
Significance and Impact
The tube theory of Doi and Edwards has been thought to properly describe nonlinear rheology of entangled polymers, a key element for polymer processing.
–The chain retraction hypothesis of the classical tube model is tested by large-scale non-equilibrium molecular dynamics (NEMD) simulations using ORNL’s Titan supercomputer.
–Both NEMD simulations and previous SANS results disagree with key structural features of the model.
–The results are critical for improving our understanding of polymer flow.
W.-S. Xu, J.-M.Y. Carrillo, C. N. Lam, B. G. Sumpter, Y. Wang, "Molecular dynamics investigation of a relaxation mechanism of entangled polymers after a large step deformation," ACS Macro Letters7, 190 (2018). DOI: 10.1021/acsmacrolett.7b00900