Paper Number
NF16
Session
Non-Newtonian Fluid Mechanics & Flow Instabilities
Title
Visualization of chain dynamics of highly entangled shear-banding polymer solutions under large amplitude oscillatory shear (LAOS)
Presentation Date and Time
October 17, 2018 (Wednesday) 10:40
Track / Room
Track 7 / Plaza II
Authors
- Shin, Seunghwan (University of Minnesota, Department of Chemical Engineering and Materials Science)
- Dorfman, Kevin D. (University of Minnesota, Department of Chemical Engineering and Materials Science)
- Cheng, Xiang (University of Minnesota, Chemical Engineering and Materials Science)
Author and Affiliation Lines
Seunghwan Shin, Kevin D. Dorfman, and Xiang Cheng
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
Speaker / Presenter
Shin, Seunghwan
Text of Abstract
In contrast to well-entangled linear worm-like micelles, where the existence and the origin of shear-banding flows have been well established, the understanding of morphological and conformational changes that accompany shear banding in entangled polymer solutions is still far from complete. Here, we analyze the shear profiles and polymer dynamics of well-entangled double-stranded DNA (dsDNA) under LAOS by combining a custom planar Couette shear cell and a high-resolution confocal microscope. Under LAOS at sufficiently high Weissenberg number (Wi), the velocity profiles display clear evolution from linear to shear-banding flows. Interestingly, in the shear-banding flows, the edge disturbance exhibits an unexpectedly long penetration length that is an order of magnitude larger than the gap thickness. To further investigate the microscopic structural origin of the shear banding, we study the dynamics and distribution of individual dsDNA chains in the shear banding flows. Analysis of the dynamics of DNA chains reveals spatially distinctive features, which provide insights into the origin of the two co-existing bands.