Rearrangement Zone around a Crack Tip in a Double Self-Assembled Transient Network

Area of Science:

• Soft Matter Physics
• Rheology
• Materials Science

Background:

• Viscoelastic fluids composed of surfactant micelles and telechelic polymers exhibit tunable micelle morphology (spherical, rodlike, wormlike).
• These fluids form transient single or double networks depending on micelle entanglement and length.

Purpose of the Study:

• To investigate crack nucleation and propagation mechanisms in self-assembled viscoelastic fluids.
• To understand the role of micelle morphology and network structure on fracture behavior.

Main Methods:

• Experimental investigation of crack dynamics in viscoelastic fluids with varying micelle morphologies.
• Analysis of crack tip phenomena using birefringence to probe micelle alignment.

Main Results:

• Crack nucleation in single networks occurs when deformation rate matches the network relaxation time.
• Double networks exhibit significant micelle rearrangements during crack propagation.
• Birefringence at the crack tip reveals a characteristic alignment length (ξ) that increases with slower crack speeds, indicating enhanced ductility.

Conclusions:

• The study elucidates distinct crack propagation mechanisms in single and double network viscoelastic fluids.
• Micelle alignment and network ductility are key factors influencing fracture in these soft materials.