Dislocation-Induced Defect Formation in a Double-Gyroid Network

Double-gyroid (DG)-structured materials are promising for various applications owing to their unique 3D network structures. However, defects in DG structures affect material properties. In this study, structural defects in a self-assembled DG structure of polystyrene-block-polyisoprene were observed using three-dimensional transmission electron microtomography (3D-TEM). The 3D-TEM image clearly indicates various point and line defects, i.e., dislocations, contained in the DG structure. Dislocations in the DG structure were characterized crystallographically. Regions distant from the dislocation contained the combined defects of broken struts (network breaks) and joints between nonintersecting gyroid networks (network bridges) without any periodicity; these were expected to be derived from local structural fluctuations. However, many point defects were found periodically near the dislocation, suggesting that point defects were formed because of lattice distortion induced by the dislocation. This study reveals that several defect formation mechanisms coexist in self-assembled DG structures.