Alignment of perpendicular lamellae in block copolymer thin films by shearing

Saswati Pujari, Michael A. Keaton, Paul M. Chaikin, Richard A. Register

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Lamellar block copolymers, with the lamellae standing perpendicular to the substrate, are attractive candidates as templates for nanostructure array fabrication. However, no process currently exists to impose long-range in-plane alignment of such perpendicular lamellae on simple unpatterned substrates - to align the lamellar normal over macroscopic distances. Here, we have generated such aligned films of perpendicular lamellae in a polystyrene- poly(methylmethacrylate) diblock, PS-PMMA, by neutralizing the substrate with a random terpolymer brush and shearing the film with a moving polydimethylsiloxane (PDMS) pad in contact with the film surface. At sufficiently high shear stresses, the lamellae align over the entire (cm2) area of the pad; the perpendicular orientation of the lamellae is preserved, although for films thicker than the lamellar spacing, a "capping layer" of PS forms in contact with the PDMS pad. However, when compared with typical shear-aligned block copolymers having a morphology of in-plane cylinders, a significantly higher stress is required to align the lamellar PS-PMMA, and the orientational order is poorer and the dislocation density higher; a limiting order parameter ψ2 ≈ 0.8 is achieved at high stresses.

    Original languageEnglish (US)
    Pages (from-to)5358-5363
    Number of pages6
    JournalSoft Matter
    Volume8
    Issue number19
    DOIs
    StatePublished - May 21 2012

    ASJC Scopus subject areas

    • Chemistry(all)
    • Condensed Matter Physics

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