Conditions for the coexistence of liquid-like and solid-like behaviors in viscoelastic liquids

Abstract

Viscoelastic liquids at small scales and in the presence of strong gradients are known to exhibit anomalous behaviors. Despite recent advances, our understanding of the phenomena is far from complete. For example, it is not clear what causes the molecules in molecular liquids to act in a collective manner and why similar dynamic heterogeneity takes place in gels and polymers? Furthermore, we would like to know why particles in suspensions experience clustering? The "ordered" liquid is a liquid, and yet it exhibits some properties of a viscoelastic solid-like material. We conjecture that the liquid-like and solid-like behaviors can coexist but only in the presence of the dynamics heterogeneity. In liquids, the heterogeneity is an internal constraint. In amorphous viscoelastic solids, it destroys the solid-like microstructural organization. Thus, the two behaviors may converge and become indistinguishable. The transitional behavior occurs in the absence of an abrupt configurational change. For this reason, these transitions cannot be viewed as the first order phase transformations. © 2014 AIP Publishing LLC.