Three-Dimensional Observations of Grain Boundary Morphologies in a Cylinder-Forming Block Copolymer

The grain boundary morphology of a cylinder-forming poly(styreneblock-isoprene) (SI) diblock copolymer was investigated using transmission electron microtomography (TEMT). The three-dimensional (3D) morphologies of the grain boundaries between the two grains with different orientation angle, α, were investigated. In the present study, two kinds of grain boundary morphologies, α ≃ 90° and α ≃ 120°, were examined in 3D. It was found that, in the case of α ≃ 90°, most of the cylindrical domains bent at the grain boundary in order not to intersect each other, while the cylindrical domains were found to be smoothly connected and were continuous in the case of α ≃ 120°. The observed morphologies indicated that the chain conformation inside the cylindrical microdomains plays more significant role than the segmental interaction between the two blocks.