Block copolymers exhibit well-ordered nanostructures such as lamellar, hexagonally packed cylinder (HEX), sphere arranged in BCC lattice, double gyroid (DG), hexagonally perforated lamellar (HPL) and so on. These structures can transform from one to another upon changing temperature. The thermal phase transition of block copolymers often occurs epitaxially between the two phases. Many research results can be found in the literature for the epitaxial relationship, most of which are based on the small angle X-ray scattering (SAXS) method for the structural analysis. However, there is a limitation in the detailed analysis of the transitional relationship since the data acquired from SAXS measurements only provide with the averaged structural information only and it is difficult to extract the detailed structure near grain boundary between two ordered structures in real space.
In this study, we studied the epitaxial relationship involved in the thermal phase transition between the ordered structures of block copolymers in thin film by using transmission electron microtomography (TEMT) and grazing incidence SAXS (GISAXS). TEMT makes it possible to observe the 3-dimensional structure and it is possible to obtain the detailed transitional structure at the phase boundary.