We investigate the nucleation and propagation of cracks in self-assembled viscoelastic fluids, which are made of surfactant micelles reversibly linked by telechelic polymers. The morphology of the micelles can be continuously tuned, from spherical to rod-like to wormlike, thus producing transient double networks when the micelles are sufficiently long and entangled, and transient single networks otherwise. For a single network, we show that cracks nucleate when the sample deformation rate involved is comparable to the relaxation time scale of the network. For a double network, by contrast, significant rearrangements of the micelles occur as a crack nucleates and propagates. We show that birefringence develops at the crack tip over a finite length, ξ, which corresponds to the length scale over which micelles alignment occur. We find that ξ is larger for slower cracks, suggesting an increase of ductility.
@article{arxiv.1607.02271,
title = {Rearrangement zone around a crack tip in a double self-assembled transient network},
author = {Guillaume Foyart and Christian Ligoure and Serge Mora and Laurence Ramos},
journal= {arXiv preprint arXiv:1607.02271},
year = {2016}
}