Effects of Annealing Solventson the Morphology ofBlock Copolymer-Based Supramolecular Thin Films.

We report a strategy that combines supramolecular assemblyandsolvent annealing to manipulate the microdomain orientation in blockcopolymer thin films. In supramolecular thin films formed by polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) with3-pentadecylphenol (PDP) hydrogen-bonded onto P4VP blocks, where PSblocks phase-separate into cylindrical microdomains, we found thatthe orientation of PS cylinders can be controlled by using differenttypes of solvents to anneal the films. As films are annealed underthe vapors of solvents bearing no oxygen atoms, such as chloroform,PS cylinders are perpendicular to the surface, while under those ofsolvents bearing oxygen, such as THF, PS cylinders are parallel tothe surface. Furthermore, the orientation is switchable upon the alternateuse of different types of solvents. The 1H NMR measurementsshowed that the strengths of hydrogen bonds between PDP and P4VP aregreatly weakened in oxygen-bearing solvents due to the competitionof the highly electronegative oxygen atoms. We thus suggest that thebinding capability of PDP onto P4VP is the key to determine whetherthe supramolecules can be assembled in the vapors of different typesof solvents, which in turn, regulates the orientation of PS cylinders. [ABSTRACT FROM AUTHOR]