摘要
This study demonstrates a new technique for controlled orientation of nanostructured block copolymer (BCP) thin films through solvent annealing using polystyrene-block-polydimethylsiloxane (PS-b-PDMS) as a representative BCP system. A two-step substrate functionalization of an intrinsic oxide layer (SiO 2 ) wafer is performed by using hydroxyl-terminated PS (PS-OH) followed by hydroxyl-terminated PDMS (PDMS-OH). By varying the grafting percentage of the PS and PDMS brushes on the substrate, it is possible to give different degrees of stretching and recoiling of grafted PS and PDMS, respectively, using PS-selective solvent for solvent annealing, resulting in roughness variation; that is termed a responsive functionalized substrate. With the appropriate roughness of the functionalized substrate under solvent annealing, the development of perpendicularly oriented cylinders of PDMS in the nanostructured PS-b-PDMS thin films can be driven from the bottom of the film. Moreover, by taking advantage of air plasma treatment, it is possible to generate a top-capped neutral layer on the film surface, giving induced perpendicular cylinders from the top surface of the thin film after solvent annealing. Consequently, it is possible to attain the formation of film-spanning perpendicular cylinders of PDMS in the PS-b-PDMS thin film under solvent annealing through the self-alignment process of the perpendicularly oriented cylinders from the top and the bottom surface of the thin film.