Nanostructure Analysis by Electron Tomography

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The aim of this study was to clarify the complex nanostructures such as self-assembled microdomain structures of block copolymers and composite structures in nanotechnology materials, which had never been understood from the two-dimensional images obtained by transmission electron microscopy (TEM), by means of three-dimensional observation by electron tomography. For such a purpose we developed and improved the techniques in electron tomography. In 2002, we investigated a tetrablock quaterpolymers consisting of polystyrene (PS), polyisoprene (PI), poly(dimethyl siloxane) (PDMS) and poly(2-vinyl pyridine)(P2VP) provided by Prof. Hadjichristidis in University of Athens. Electron tomography revealed that the micro-domain structure of this polymer had the triple-coaxial cylinders of P2VP core and PDMS and PI shells packed hexagonally in PS matrix. In 2003, we investigated a 3-Miktoarm star polymer consisting of PS, PI and PDMS by using combined electron tomography and energy-filtering TEM. Electron tomography revealed that the star polymer formed cylindrical microdomains with complex-shaped cross-sections. In addition to the study of multicomponent systems, we also investigated two-component systems. We first observed 3D arrangement of spherical microdomains in BCC lattice for a PS-b-PI-b-PS triblock copolymer as well as its transition from spherical microdomains to cylindrical microdomains. Furthermore, we clarified the hexagonally perforated layer (HPL) structure, defects and grain boundary structures in PS-b-PI diblock copolymer/homoPS blends as well as nano-composites such as Gyroid network structures incorporating Pd nonoparticles. We also developed 3D noise filter (median filter) for the 3D tomography data.