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Block Copolymer Thin Films from Solutions with Different Solvent Quality

Block copolymers composed of chemically different components exhibit unique solution properties depending on the nature of solvent. In this work, by changing the solvent quality from neutral to selective solvent, its effects on the structure of block copolymer thin films are investigated. In a neutral solvent, the cylindrical microdomains exhibit typical morphology with parallel orientation due to selective interaction with substrate, while the micellar solution produces the spherical morphology. Unexpectedly, before the micelle forms, the orientation of cylinders is found to change to perpendicular orientation. Therefore, well-controlled solution processing can provide a very efficient way to produce well-controlled nanostructure without additional processes in practical applications.