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Issue 19, 2012
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Alignment of perpendicular lamellae in block copolymer thin films by shearing

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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.

Graphical abstract: Alignment of perpendicular lamellae in block copolymer thin films by shearing

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Publication details

The article was received on 05 Feb 2012, accepted on 22 Mar 2012, published on 03 Apr 2012 and first published online on 03 Apr 2012


Article type: Paper
DOI: 10.1039/C2SM25270H
Citation: Soft Matter, 2012,8, 5358-5363
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    Alignment of perpendicular lamellae in block copolymer thin films by shearing

    S. Pujari, M. A. Keaton, P. M. Chaikin and R. A. Register, Soft Matter, 2012, 8, 5358
    DOI: 10.1039/C2SM25270H

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