Control of molecular and microdomain orientation in a semicrystalline block copolymer thin film by epitaxy

Epitaxial crystallization is utilized to control both molecular chain orien tation and microdomain structure in a thin film of a semicrystalline triblo ck copolymer, composed of crystallizable polyethylene (PE) end blocks and a n amorphous ethylene-alt-propylene (PEP) midblock where the microphase sepa ration is driven by crystallization from a homogeneous melt, characterized by small-angle and wide-angle X-ray diffraction. Surface interaction due to a crystallographic matching of unit cells between the crystalline PE block and benzoic acid (BB) substrate induces high orientation of the crystallin e PE block, resulting in a well-ordered parallel lamellar microphase-separa ted structure. The excellent orientation induced by the surface interaction is evidenced by the selected area electron diffraction (SAD) pattern and b right-field (phase contrast) and dark-field (diffraction contrast) transmis sion electron microscope (TEM) images of the block copolymer thin film. The data clearly show that the chain axis ((c) over cap) of PE is parallel to the normal ((n) over cap) of the microphase-separated lamellar surfaces.