Paper Number
SM38 

Session
Polymers Solutions, Melts and Blends

Title
Tight-links in extensional flows of nonconcatenated ring polymers

Presentation Date and Time
October 23, 2019 (Wednesday) 3:45

Track / Room
Track 3 / Room 201

Authors (Click on name to view author profile)

  1. O'Connor, Thomas C. (Sandia National Laboratories, Harry S. Truman Fellow)
  2. Grest, Gary S. (Sandia National Laboratories)
  3. Ge, Ting (Duke University, Department of Mechanical Engineering and Materials Science)
  4. Rubinstein, Michael (Duke University)

Author and Affiliation Lines (in printed abstract book)
Thomas C. O'Connor1, Gary S. Grest2, Ting Ge3, and Michael Rubinstein3
1Harry S. Truman Fellow, Sandia National Laboratories, Albuquerque, NM; 2Sandia National Laboratories, Albuquerque, NM; 3Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708

Speaker / Presenter 
Grest, Gary S.

Text of Abstract
Non-concatenated ring polymers do not entangle like linear polymers, and they tend to have a much lower Newtonian viscosity than linear melts of similar molecular weight. However, recent experiments show that ring melts are extraordinarily sensitive to extensional flow, exhibiting a large rise in viscosity even for Weissenberg numbers Wi well below 1. Here, we explain the origin of this massive rise in viscosity through thorough molecular dynamics simulations of non-concatenated ring melts in uniaxial extensional flows. Ring melts of three molecular weights are elongated for constant Rouse Wi from 0.1 to 25 and compared to analogous data for linear melts. Simulations confirm that strong extension-rate thickening occurs for all Wi and we find it coincides with the extreme elongation of a minority population of rings that grows with Wi. The large susceptibility of rings to extension is due to a flow-induce formation of “tight-links” that connect two or more rings into supramolecular daisy-chains while flow persists. Links are pulled tight and stabilized by flow and can form spontaneously after flow begins. Once linked, the composite rings act like much larger molecules and experience much larger drag forces than individual rings, driving their strong elongation.