Reducing Substrate Pinning of Block Copolymer Microdomains with a Buffer Layer of Polymer Brushes

• Published in: Macromolecules Vol. 33; no. 3; pp. 857 - 865
• Main Authors: Harrison, Christopher, Chaikin, Paul M, Huse, David A, Register, Richard A, Adamson, Douglas H, Daniel, Abishai, Huang, E, Mansky, P, Russell, T. P, Hawker, Craig J, Egolf, David A, Melnikov, Ilarion V, Bodenschatz, Eberhard
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.02.2000
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis; Triblock copolymer; Domain structure; Order parameter; SBS; Morphology; Temperature effect; Experimental study; Cylindrical shape; Correlation length; Thin film
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma991551g

We study the range of orientational order of a single layer of cylindrical block copolymer microdomains annealed on several types of substrates. The orientational persistence length or nematic correlation length (ξ) is evaluated using recently developed imaging and analysis methods to measure the grain size of the block copolymer microdomains. We show that the substrate can lower ξ for block copolymers with a majority component that interacts strongly with the substrate, but this can be mitigated by attaching a buffer layer of polystyrene brushes to the substrate. In addition, we show that, for a block copolymer where the block that strongly interacts with the substrate is the minority component, the microdomain correlation length does not increase when substrates are treated with this buffer layer. We suggest that in this case the brushes do not increase ξ not only because of the lower volume fraction of the strongly interacting component but also because there are block copolymer wetting layers at the free and substrate interfaces that decouple the microdomains from the substrate in a similar manner as the polystyrene brushes.