title: Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy.
abstract: 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.
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Yekaterina
authors.initials: Y
authors.lastname: Rokhlenko
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Manesh
authors.initials: M
authors.lastname: Gopinadhan
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Chinedum O
authors.initials: CO
authors.lastname: Osuji
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Corey S
authors.initials: CS
authors.lastname: O'Hern
authors.affiliation: Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Larson
authors.affiliation: Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Padma
authors.initials: P
authors.lastname: Gopalan
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Paweł W
authors.initials: PW
authors.lastname: Majewski
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Yager