Banding in entangled polymer fluids under oscillatory shearing

Area of Science:

• Polymer physics
• Rheology
• Soft matter science

Background:

• Entangled polymer solutions exhibit complex flow behaviors.
• Understanding polymer chain dynamics under shear is crucial for material science.

Purpose of the Study:

• To report and characterize a novel flow phenomenon in entangled polymer solutions.
• To investigate the mechanisms of chain disentanglement under large-amplitude oscillatory shear.

Main Methods:

• Imposing large-amplitude oscillatory shear on entangled polymer solutions.
• Applying shear frequencies higher than the overall chain relaxation rate.
• Observing the resulting polymer chain orientation and entanglement distribution.

Main Results:

• A previously undescribed flow phenomenon was observed.
• Inhomogeneous spatial disentanglement of polymer chains occurred.
• A distinct layer with reduced chain entanglement formed, absorbing imposed strain.
• The bulk of the polymer sample remained largely undeformed and entangled.

Conclusions:

• This study reveals a new nonlinear viscoelastic response in entangled polymers.
• The formation of an entanglement-depleted layer is a key mechanism for stress dissipation.
• This finding has implications for processing and understanding complex fluid dynamics.