Rokhlenko Yekaterina, Gopinadhan Manesh, Osuji Chinedum O, Zhang Kai, O'Hern Corey S, Larson Steven R, Gopalan Padma, Majewski Paweł W, Yager Kevin G
Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, USA.
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
Phys Rev Lett. 2015 Dec 18;115(25):258302. doi: 10.1103/PhysRevLett.115.258302.
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.
我们利用原位X射线散射研究了本征链磁化率各向异性在嵌段共聚物磁场定向自组装中的作用。在冷却通过无序-有序转变时，观察到层状中间相的取向，所产生的取向有序度与冷却速率成反比。我们讨论了驱动取向的磁化率各向异性Δχ的起源，并使用粗粒化分子动力学对表面束缚链的构象进行采样来计算其大小，发现Δχ≈2×10⁻⁸。根据与场相关的散射数据，我们估计在取向过程中存在约1.2μm的晶粒。这些结果表明，本征各向异性足以支持强场诱导的中间相取向，并为嵌段共聚物中取向有序的场控制提出了一种通用策略。
