Heterogeneous diffuse interfaces: A new mechanism for arrested coarsening in binary mixtures

Abstract

We discuss the dynamics of binary fluid mixtures in which surface tension density is allowed to become locally negative within the interface, while still preserving positivity of the overall surface tension (heterogeneous diffuse interface). Numerical simulations of two-dimensional Ginzburg-Landau phase field equations implementing such mechanism and including hydrodynamic motion, show evidence of dynamically arrested domain coarsening. Under specific conditions on the functional form of the surface tension density, dynamical arrest can be interpreted in terms of the collective dynamics of metastable, non-linear excitations of the density field, named compactons, as they are localized to finite-size regions of configuration space and strictly zero elsewhere. Aside from compactons, the heterogeneous diffuse interface scenario appears to provide a robust mechanism for the interpretation of many aspects of soft-glassy behaviour in binary fluid mixtures.

Morphology formation in binary mixtures upon gradual destabilisation

“…In the classical picture, a homogeneous mixture of unlike molecules is initially stable, but upon a sudden temperature quench spontaneously demixes to form a phase-separated morphology that subsequently coarsens and arrests. Phenomenological phase-field models are highly successful in explaining how coarsening and arresting are affected by viscoelastic effects [6], hydrodynamics [7,8], chemical reactions [9,7,10,8], turbulent flow [11], and the presence of a surfactant [12]. However, there is limited understanding of how the early-stage structure development is affected by the physical properties of the molecules and by the processing conditions [13,14,15,16,17,18,19,20,21].…”