Paper Number
SM44 

Session
Polymers Solutions, Melts and Blends

Title
Viscoelastic response of branched polyethylene combs: A molecular dynamics simulation insight

Presentation Date and Time
October 24, 2019 (Thursday) 8:40

Track / Room
Track 3 / Room 201

Authors (Click on name to view author profile)

  1. Wijesinghe, Sidath (Clemson University)
  2. Ge, Ting (Duke University, Department of Mechanical Engineering and Materials Science)
  3. Salerno, K. Michael (U S Army Research)
  4. Grest, Gary S. (Sandia National Laboratories)
  5. Perahia, Dvora (Clemson University)

Author and Affiliation Lines (in printed abstract book)
Sidath Wijesinghe1, Ting Ge2, K. Michael Salerno3, Gary S. Grest4, and Dvora Perahia1
1Clemson University, Durham, NC; 2Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708; 3U S Army Research, Aberdeen, MD; 4Sandia National Laboratories, Albuquerque, NM

Speaker / Presenter 
Perahia, Dvora

Text of Abstract
Polymers exhibit distinctive rheological behavior depending on their architecture. Addition of small number of branches is sufficient to affect the rheology of polymers compared to their linear counterpart with the same molecular weight. Here, using coarse grained molecular dynamics simulations we resolve the effects of the branch length and branch density on the viscoelastic response of entangled polyethylene (PE) melts with branch lengths above and below the entanglement length. The stress relaxation behavior is measured two ways, following a small step strain perturbation and determined from the stress autocorrelation function using the Green-Kubo relation. The stress relaxation functions were fit to the theoretical expression proposed by Likhtman and McLeish, which self-consistently combines reptation theory with contour length fluctuations and constraint release with. The entanglement molecular weight obtained from theses fits are compared to primitive path analysis. We find that the plateau moduli are sensitive to both branch length and branch density and decreases with decreasing branch length, consistent with reduction in entanglement length and increase in tube diameter. This study contributes to a molecular level insight into long-lived problems in viscoelastic responses of polymers. We kindly acknowledge NSF DMR 1611136.