Using self-assembled monolayers exposed to X-rays to control the wetting behavior of thin films of diblock copolymers

The wetting behavior of thin films of symmetric poly(styrene-bloch-methyl m ethacrylate) was investigated on self-assembled monolayers (SAMs) of octade cyltrichlorosilane (OTS) that were chemically modified by exposure to X-ray s in the presence of air. The concentration of aldehyde and hydroxyl groups on the surface of exposed OTS increases with increasing dose. The polarity and surface tension of the SAMs were tuned to control the wetting behavior of the polymer films. Symmetric, neutral, and asymmetric wetting of the fi lms were observed for doses of 400-1000, 1200, and 1400-2000 mJ/cm(2), resp ectively. The wetting behavior was qualitatively described by estimating th e interfacial energies between each block of the copolymer and exposed SAMs and the surface tensions of both blocks using the Fowkes-van Oss-Chaudhury -Good model of surface tension. These results lay the foundation for contro lling the morphology of thin films of block copolymers over macroscopic dim ensions by nanopatterning substrates with regions of different wetting beha vior using advanced lithography.