Magnetic Field Alignment of Coil-Coil Block Copolymers and Blends via Intrinsic Chain Anisotropy

Magnetic field alignment of block copolymers has typically relied on the presence of liquid crystalline (LC) or crystalline assemblies to provide sufficient magnetic anisotropy to drive alignment. Here we describe the field response of a wide variety of non-LC systems under magnetic fields, including coil-coil block copolymers like PS-b-P4VP, PS-b-PDMS, and PS-b-PMMA, blends of block copolymers of disparate morphologies and molecular weights, blends of block copolymers with homopolymers, and bottlebrush copolymers. Blends of PS-b-P4VP with poly(ethylene glycol) (PEG) provide a route to form size-selective nanoporous materials with aligned channels by preferential dissolution of PEG. PS-b-PMMA demonstrates an unusual field response which appears to be governed by anisotropic growth of grains coupled with confinement effects. We survey these various systems using in-situ X-ray scattering and transmission electron microscopy to study the phase behavior and temperature-, time- and field-dependent dynamics of alignment, highlighting fundamental insights and opportunities for novel applications.