Measuring Flow Boundary Conditions and Nano-Scale Coating Processes During Sharkskin Melt Fracture

Published

October 16, 2008

Author(s)

Kalman Migler

Abstract

Micelles formed of amphiphilic diblock copolymers may have applications in drug delivery and in understanding the physics of biological structures. Wormlike micelles, in particular, provide an opportunity to study the behavior of semiflexible rods in elongational flows. We utilize microfluidic devices coupled with fluorescence microscopy to study the dynamics of wormlike micelles formed from amphiphilic diblock copolymers. Individual micelles are imaged in a planar elongational flow generated by a simple cross-flow device with dimensions of the order of 100 microns. A sharp transition is seen between the regime where Brownian motion dominates the micellar dynamics and where the micelles stretch with the flow. For a solvent viscosity, hs = 4 cP, this transition occurs in the range of elongation rates, 0.5 < e < 2.5 s-1. At elongation rates above the transition, most of the micelles stretch with the fluid elements. Only two main classes of stretching conformations are seen: uniform and folded. This is fewer than the number of classes seen in experiments with DNA molecules, which are more flexible than the micelles used in this study. The dynamics of the micelles are also compared to those from Brownian dynamics simulations of bead-spring chains in planar elongation. The behavior of the bead-spring chains qualitatively matches the dynamics of the micelles, e.g., there is an abrupt transition between dynamics dominated by Brownian forces to flow-dominated dynamics and similar stretching configurations are seen.

Proceedings Title

International Conference on Rheology | 14th | | International Congress on Rheology

Conference Dates

August 22-27, 2004

Conference Location

Seoul, 1, KO

Conference Title

International Congress of Rheology

Pub Type

Conferences

Keywords

extrusion, flow instabilities, fluoropolymers, polyethylene, polymer processing, sharkskin

Citation

Migler, K. (2008), Measuring Flow Boundary Conditions and Nano-Scale Coating Processes During Sharkskin Melt Fracture, International Conference on Rheology | 14th | | International Congress on Rheology, Seoul, 1, KO (Accessed April 24, 2024)