Pattern formation and evolution in diblock copolymer thin films above the order-disorder transition

Research on diblock copolymer thin films has been devoted primarily toward understanding and controlling microstructural and topographical features at temperatures below the order-disorder transition (ODT), where ordered phas e separated structures exist. Recently, we showed that the topography of th in liquid diblock films above the ODT form a hierarchy of patterns, dependi ng on the film thickness. One of these topographies is a "spinodal-like" pa ttern. Through the use of a pair correlation analysis we show that the stru ctural evolution of this pattern is characterized by four stages. The first involves the amplification of surface perturbations, followed by the forma tion of an interconnected, "spinodal-like," pattern. The onset of the third stage is associated with the breakup of the interconnected pattern and the eventual formation of droplets of irregular shapes. The final stage involv es evolution toward the formation of circular droplets. (C) 2001 American I nstitute of Physics.