Paper Number
PO30 

Session
Poster Session

Title
Block copolymer worms under flow: Shear and stretch

Presentation Date and Time
October 12, 2022 (Wednesday) 6:30

Track / Room
Poster Session / Riverwalk A

Authors (Click on name to view author profile)

  1. Calabrese, Vincenzo (Okinawa Institute of Science and Technology)
  2. Gyorgy, Csilla (The Univeristy of Sheffield)
  3. Haward, Simon J. (Okinawa Institute of Science and Technology)
  4. Neal, Thomas J. (The University of Sheffield)
  5. Armes, Steven P. (The University of Sheffield)
  6. Shen, Amy Q. (Okinawa Institute of Science and Technology)

Author and Affiliation Lines (in printed abstract book)
Vincenzo Calabrese1, Csilla Gyorgy2, Simon J. Haward1, Thomas J. Neal2, Steven P. Armes2 and Amy Q. Shen1
1Okinawa Institute of Science and Technology, Okinawa, Japan; 2The Univeristy of Sheffield, Sheffield, United Kingdom

Speaker / Presenter 
Calabrese, Vincenzo

Keywords
colloids; suspensions

Text of Abstract
We investigate the shear and extensional flow behaviour of two semi-flexible worm-like nanoparticles (WLNP) with comparable cross-sectional diameters, similar persistence lengths and differing contour lengths. By measuring the flow-induced birefringence (FIB) in two contrasting microfluidic devices, we perform an experimental quantification of the role of shearing and planar extensional flows for aligning short, stiff WLNP (S-WLNP) and relatively long, flexible WLNP (L-WLNP). We show that shear and extensional flows each induce alignment of both types of WLNP. However, extensional deformations are 9.5× and 4× more effective than shear deformations at inducing alignment of the L-WLNP and S-WLNP, respectively. The difference between shear and extensional deformations for WLNP alignment is explained based on the ratio of extensional and shear viscosity of the solvent fluid (Trouton ratio of the solvent) and a structural parameter related to the WLNP extensibility and flexibility. Under shear flow, these WLNP dispersions display shear-thinning behaviour, with an exponential reduction in viscosity with increasing alignment. Under extensional flow, we suggest that the WLNP alignment causes extensional-thinning, making WLNP ideal additives in formulations exposed to extensional-dominated flows, such as during jetting, spraying and printing