Hierarchical morphology of ABC mikto-arm terpolymer*

The morphology of a ABC mikto-arm terpolymer consisting of polystyrene, polyisoprene and poly(2-vinylpyridine) (PS-PI-P2VP) was studied by combining small angle neutron and X-ray scattering (SANS and SAXS) with transmission electron microscopy (TEM). Because of the complex electron density differences between each block, SAXS is limited to the observation of interferences arising from all three phases, leading to ambiguity in the determination of the morphology. To overcome this ambiguity, SANS and resonance soft x-ray scattering was used to elucidate the morphology by isotopic labeling of the PS with deuterium and by varying the x-ray energy to change the electron density of each component. The experimentally determined morphology was compared to simulations where the key input parameters are the segmental interactions between the components. The morphology determined is a new complex lamellae structure.