Directed self-assembly of thin block copolymer films under controlled atmosphere

Abstract

We have developed a simple and fast methodology to control the orientation of cylindrical microdomains in thin block copolymer films under controlled atmosphere conditions. Asymmetric block copolymers of polystyrene and polyethylene oxide) (PS-b-PEO) were dissolved in toluene and spin coated with less than one minute exposure to different solvent vapors and controlled humidity. The specific choice of solvents was based on the polymer solubility parameters and the solvent vapor pressure. By controlling the spin coating environment we were able to produce cylinders with orientations ranging from parallel to perpendicular with respect to the substrate. Orientation was apparently controlled by the preferential affinity of the vapor atmosphere. A combinatorial gradient technique was employed to investigate the mechanism of solvent-induced microdomain orientation. © 2007 Materials Research Society.