Unusual Phase Behavior by Blending Star-Shaped Block Copolymer and Linear Block Copolymer*

Generally the block copolymer shows the arrangement of hexagonal patterns cylinder when volume fraction of one block is larger than that of the other. However, since all processes in the semiconductor business are geared to the rectilinear structure, it is needed to rework with time and money to apply block copolymer to the semiconductor business. Therefore, creating different structure from that of general block copolymer like square array structure or asymmetric lamellae has great significance in lithography applications.
Here, we synthesized star-shaped poly polystyrene-block-poly(4-thydroxystyrene) (PS-b-PHS) and linear polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) and blended them in various proportions to observe the structures. Because the molecular weight of the PS on the core of star polymer is much smaller than that of the PS in linear polymer, the spacing between cylinders is limited and the large configurational entropy is formed, which leads block copolymer to have different structure.