| Abstract
| - Segment distribution of styrene in an alternating lamellarstructure of styrene−2-vinylpyridine diblock copolymer was investigated by neutron reflection.Block copolymers having threetypes of deuterium-labeled styrene block chains consisting of fullylabeled, partially junction-labeled,and partially end-labeled block chains were used in this study.The degree of junction and end labelingwas varied to obtain a more complete picture of segment distribution.Spin-coated thin films of theseblock copolymers on silicon wafers exhibited lamellar structures whichwere oriented preferentially parallelto the silicon surface. Our results indicate that thepoly(2-vinylpyridine) block chain exists at thesiliconsurface, while polystyrene appears at the air surface in all of thefilm specimens. The segment distributionat the interface between polystyrene and poly(2-vinylpyridine)lamellae could be well described by anerror function. The thickness of the lamellar interface (definedas a full-width half-maximum value ofthe error function) is evaluated to be about 4.5 nm, suggesting thatthe blocks are strongly segregated.Accordingly, the segments of a block chain in the vicinity of thechemical junction point between twoblock chains are determined to be strongly localized near the lamellarinterface. However, the free endsare broadly distributed throughout the lamellar microdomain with theirnet maximum distribution atthe center of each microdomain. Such an end-segment distributionof the block chains is shown to beconsistent with predictions from a mean field theory.
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