The pliable morphology of block copolymer crystals

Block copolymers form soft crystals of ‘mesoatomic’ building blocks comprised of many thousands of molecules, whose sub-unit-cell configurations couple strongly to sub- and super-strate boundary conditions and symmetries. High-fidelity 3D tomographic structural information from both the near-surface as well as interior regions is key to understanding the properties of a given polymer structure. BCPs having a tubular network morphology are particularly attractive for applications ranging from photonic crystals to 3D batteries. Additionally, such complex 3D structures are quite sensitive to confinement by interfaces. We study the 3D domain morphology of a solution-cast block copolymer double gyroid. Analysis reveals that the morphology reconstructs in the near surface regions as well as with non-affine deformation of the sub-unit-cell symmetry in the interior region. Such strongly pliable morphological behavior has strong implications for properties, raising the question as to whether highly perfect cubic self assembled BCP structures are possible.