Direct observation of HPL and DG structure in PS-b-PI thin film by transmission electron microscopy

The Hexagonal Perforated Lamellar (HPL) and double-gyroid (DG) structures of polystyrene-block-polyisoprene (PS-b-PT) thin films coated on mica and their coexistence were observed by Transmission Electron Microscopy (TEM). The TEM images show that PI domains are selectively stained and appear darker than the PS domains, and the layers of PS block are perforated by PI blocks. The glazing incidence small-angle X-ray scattering (GISAXS) patterns of PS-b-PT show a well-developed HPL and DG phases that are parallel to the substrate. The 3D images of the HPL structure obtained by TEMT shows that the perforations at the edge of the first layer reappears at the same position in the fourth layer. The coexistence of the two phases from the samples annealed at 120°C for 30h shows that the HPL and DG phase transition starts from the substrate.