Soft Graphoepitaxy of Hexagonal PS-b-PDMS on Nanopatterned POSS Surfaces fabricated by Nanoimprint Lithography

Abstract

Directed self-assembly of block copolymer polystyrene-block-polydimethylsiloxane by combining graphoepitaxy using nanoimprinted polyhedral oligomeric silsesquioxanes thin films as substrates and solvent annealing resulted in the BCP microphase segregation. For this purpose, the substrates for graphoepitaxy were fabricated by patterning the soft material POSS as thin films on silicon with nanoimprint lithography. The directed self-assembly of PS-b-PDMS resulted in the microphase segregation of PDMS cylinders with 25 nm pore diameter imbedded in a PS matrix. By modulating the hydrophobicity of POSS substrates, it was possible to control the orientation of the PDMS cylinders. For more hydrophobic POSS surfaces, the cylinders oriented parallel to the side walls surfaces whereas in more hydrophilic POSS surfaces the cylinders were oriented perpendicular to the side walls.