Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversel...

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Bibliographic Details
Published in:Physical review letters 2015-12, Vol.115 (25), p.258302-258302, Article 258302
Main Authors: Rokhlenko, Yekaterina, Gopinadhan, Manesh, Osuji, Chinedum O, Zhang, Kai, O'Hern, Corey S, Larson, Steven R, Gopalan, Padma, Majewski, Paweł W, Yager, Kevin G
Format: Article
Language:English
Subjects:
Alignment
Anisotropy
Asymptotic properties
Block copolymers
Chains
Magnetic permeability
NANOSCIENCE AND NANOTECHNOLOGY
Scattering
Self assembly
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Summary:We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ≈2×10^{-8}. From field-dependent scattering data, we estimate that grains of ≈1.2  μm are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.115.258302