Rheology of Soft Glassy Materials

Abstract

We attribute similarities in the rheology of many soft materials (foams, emulsions, slurries, etc.) to the shared features of structural disorder and metastability. A generic model for the mesoscopic dynamics of ``soft glassy matter'' is introduced, with interactions represented by a mean-field noise temperature $x$. We find power-law fluid behavior either with $(x<1)$ or without $(1<x<2)$ a yield stress. For $1<x<2$, both storage and loss modulus vary with frequency as ${\ensuremath{\omega}}^{x\ensuremath{-}1}$, becoming flat near a glass transition $(x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1)$. Values of $x\ensuremath{\approx}1$ may result from marginal dynamics as seen in some spin glass models.