Paper Number
SM25                         My Program 

Session
Polymer Solutions Melts Blends

Title
How do polymers stretch in capillary-driven extensional flows?

Presentation Date and Time
October 15, 2024 (Tuesday) 1:50

Track / Room
Track 4 / Waterloo 6

Authors (Click on name to view author profile)

  1. Calabrese, Vincenzo (Okinawa Institute of Science and Technology)
  2. Shen, Amy Q. (Okinawa Institute of Science and Technology Graduate Univers, Micro,Bio,Nanofluidics Unit)
  3. Haward, Simon J. (Okinawa Institute of Science and Technology Graduate Univers, Micro,Bio,Nanofluidics Unit)

Author and Affiliation Lines (in printed abstract book)
Vincenzo Calabrese, Amy Q. Shen and Simon J. Haward
Micro,Bio,Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate Univers, Onna-son, Okinawa 904-0495, Japan

Speaker / Presenter 
Calabrese, Vincenzo

Keywords
experimental methods; non-Newtonian fluids; polymers

Text of Abstract
Measurements of the capillary-driven thinning and breakup of fluid filaments are widely used to extract extensional rheological properties of complex materials. For viscoelastic fluids like polymer solutions, the longest relaxation time of the polymer is inferred from the decay rate of the filament diameter in the elastocapillary thinning regime. This determination depends on several assumptions concerning the polymeric response to the flow that are derived from constitutive models, but are hard to test experimentally. By comparing the response of fluids in capillary thinning with that in a microfluidic extensional flow (in which the polymeric dynamics can be readily assessed), we show experimentally that these assumptions are likely only valid for highly extensible polymers but do not hold in general. For polymers with relatively low extensibility, such as polyelectrolytes in salt-free media, conventional extrapolation of the longest relaxation time from capillary thinning techniques leads to a significant underestimation. We explain this discrepancy by considering the macromolecular dynamics occurring in the initial Newtonian-like thinning regime prior to the onset of elastocapillarity.