Thin Film Nanostructures Prepared via Self-Assembly of Partly Labile Protected Block Copolymers for Hybrid Patterning Strategies

Thin nanostructured block copolymer films were prepared using dilute solutions of partly tert-butoxycarbonyl (BOC)- and tert-butyl (TBU)-protected block copolymers based on 4-hydroxystyrene with varying block ratios. AFM measurements showed different nanostructures and morphologies of the films dependent on the block composition of the employed block copolymers. The nanostructure observed in thin films was compared to that of the bulk samples which was analyzed in detail by temperature-dependent SAXS measurements. In order to improve the regularity of the nanostructures of the as-prepared films, different film preparation techniques, film preparation parameters. and solvents were applied, and their impact on the film morphology was investigated. A complete removal of the BOC protecting groups in a block copolymer film was achieved by heating of a film at 190 degrees C. This process gave rise to the transformation of a partly BOC-protected block copolymer into the homopolymer poly(4-hydroxy styrene), and thus a switching of the thin film morphology occurred which was investigated by AM FI-IR, ellipsometry, and contact angle measurements.