  A promising approach to the fabrication of materials with nanoscale features
is the transfer of liquid-crystalline structure to polymers. However, this has
not been achieved in systems with full three-dimensional periodicity. Here we
demonstrate the fabrication of self-assembled three-dimensional nanostructures
by polymer templating blue phase I, a chiral liquid crystal with cubic
symmetry. Blue phase I was photopolymerized and the remaining liquid crystal
removed to create a porous free-standing cast which retains the chiral
three-dimensional structure of the blue phase, yet contains no chiral additive
molecules. The cast may in turn be used as a hard template for the fabrication
of new materials. By refilling the cast with an achiral nematic liquid crystal,
we created templated blue phases which have unprecedented thermal stability in
the range -125 to 125 [degrees symbol]C, and that act both as mirrorless lasers
and switchable electro-optic devices. Blue-phase templated materials will
facilitate advances in device architectures for photonics applications in
particular.
