  We use large-scale molecular dynamics simulations of a simple glass-forming
system to investigate how its liquid-gas phase separation kinetics depends on
temperature. A shallow quench leads to a fully demixed liquid-gas system
whereas a deep quench makes the dense phase undergo a glass transition and
become an amorphous solid. This glass has a gel-like bicontinuous structure
that evolves very slowly with time and becomes fully arrested in the limit
where thermal fluctuations become negligible. We show that the phase separation
kinetics changes qualitatively with temperature, the microscopic dynamics
evolving from a surface tension-driven diffusive motion at high temperature to
a strongly intermittent, heterogeneous and thermally activated dynamics at low
temperature, with a logarithmically slow growth of the typical domain size.
These results shed light on recent experimental observations of various porous
materials produced by arrested spinodal decomposition, such as nonequilibrium
colloidal gels and bicontinuous polymeric structures, and they elucidate the
microscopic mechanisms underlying a specific class of viscoelastic phase
separation.
