title: Well-Ordered Nanoporous ABA Copolymer Thin Films via Solvent Vapor Annealing, Homopolymer Blending, and Selective Etching of ABAC Tetrablock Terpolymers.
abstract: Solvent vapor annealing treatments are used to control the orientation of nanostructures produced in thin films of a poly(styrene)-block-poly(isoprene)-block-poly(styrene)-block-poly((±)-lactide) (PS-PI-PS-PLA) and its blends with PLA homopolymer. The PS-PI-PS-PLA tetrablock terpolymer, previously determined to adopt a core(PLA)-shell(PS) cylindrical morphology in the bulk, gave perpendicular alignment of PLA cylinders over a limited range of thicknesses using a mixed solvent environment of tetrahydrofuran and acetone. On the other hand, perpendicular alignment was achieved regardless of film thickness by inclusion of 5 wt % homopolymer PLA in the PS-PI-PS-PLA tetrablock. Tapping mode atomic force microscopy (AFM) was used to visualize film surface morphologies. Subsequent reactive ion etching (RIE) and basic hydrolysis of PLA produced 15 nm pores in a PS-PI-PS triblock thin film matrix. Nanoporosity was confirmed by scanning electron microscopy (SEM) images and the vertical continuity of pores was confirmed by cross-sectional SEM analysis.
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Jackson
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Youngmin
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Madalyn R
authors.initials: MR
authors.lastname: Radlauer
authors.affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Hillmyer
keywords: homopolymer blending; nanoporous thin films; perpendicularly oriented cylinders; selective etching; solvent vapor annealing; tetrablock terpolymers