The directed assembly of polystyrene-block-poly(methyl methacrylate) films on a variety of photolytically nanopatterned siloxane-modified surfaces was investigated. The amount of siloxane removal is related to the exposure dose of a 157 nm laser. The modified surfaces were imaged using a 157 nm interference exposure system to lithographically define areas of different surface energies to direct the assembly of the diblock copolymer films. The analysis of the surface energy aerial image provided insights into the exposure doses required to result in defect-free films. While the slope of the surface energy aerial image was not found to be important by itself, in concert with the difference in high and low surface energy regions, as well as the maximum value of the low surface energy region, it provided insight into conditions needed to direct self-assembly of the block copolymer films. Preliminary investigations concerning the extension of this methodology to 193 nm showed that the polar surface energy of arylsiloxane-modified surfaces can also be affected by 193 nm exposure.