  Nanolayered lamellae are common structures in nanoscience and nanotechnology,
but most are nearly symmetric in layer thickness. Here, we report on the
structure and mechanics of highly asymmetric and thermodynamically stable
soft--hard lamellar structures self-assembled from optimally designed
PS1-(PI-b-PS2)3 miktoarm star block copolymers. The remarkable mechanical
properties of these strong and ductile PS (polystyrene)-based nanomaterials can
be tuned over a broad range by varying the hard layer thickness while
maintaining the soft layer thickness constant at 13 nm. Upon deformation, thin
PS lamellae (\textless{}100 nm) exhibited kinks and predamaged/damaged grains,
as well as cavitation in the soft layers. In contrast, deformation of thick
lamellae (\textgreater{}100 nm) manifests cavitation in both soft and hard
nanolayers. In situ tensile-SAXS experiments revealed the evolution of cavities
during deformation and confirmed that the damage in such systems reflects both
plastic deformation by shear and residual cavities. The aspects of the
mechanics should point to universal deformation behavior in broader classes of
asymmetric hard--soft lamellar materials, whose properties are just being
revealed for versatile applications.
