  The cubic blue phases of liquid crystals are fascinating and technologically
promising examples of hierarchically structured soft materials, comprising
ordered networks of defect lines (disclinations) within a liquid crystalline
matrix. We present the first large-scale simulations of their domain growth,
starting from a blue phase nucleus within a supercooled isotropic or
cholesteric background. The nucleated phase is thermodynamically stable; one
expects its slow orderly growth, creating a bulk cubic. Instead, we find that
the strong propensity to form disclinations drives the rapid disorderly growth
of a metastable amorphous defect network. During this process the original
nucleus is destroyed; re-emergence of the stable phase may therefore require a
second nucleation step. Our findings suggest that blue phases exhibit
hierarchical behavior in their ordering dynamics, to match that in their
structure.
