Symmetry-Breaking of Double Gyroid structures in Block Copolymer Films by Non-affine Distortion

In this study, we suggest that a solvent vapor annealing, which forms self-assembled gyroid structures in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films, causes unique structural distortion owing to unidirectional deformation upon deswelling processes. The rapid and spontaneous deswelling of the swollen PS-b-PMMA films immediately upon solvent vapor annealing lead to triclinic gyroid structures with different z-directional contraction ratios, maintaining the lateral dimensions. Our grazing-incidence X-ray scattering (GISAXS) analyses reveal several forbidden reflections such as {110} and {200} reflections that indicate a non-affine distortion generated during the deswelling process, where forbidden reflections for more contracted gyroid film are stronger than those for less contracted one. To closely observe the lattice distortion, we compute electron-density difference maps extracted from GISAXS patterns. Furthermore, a level-set approach, which is utilized to quantitate the structural characteristics of the two alternating PMMA channels, elucidate the inversion symmetry-breaking of gyroid structures, which enable us to exploit its possible application to optical Weyl photonic crystals.