Encoding Textures into Liquid-Crystalline Materials Using Structured Magnetic Fields

Liquid-crystalline block copolymer (LCBCP) systems self-assemble into microphase-separated structures that are magnetically anisotropic and can be aligned by the imposition of a sufficiently strong magnetic field. The balance between magnetostatics, elasticity, and interfacial block interactions governs the resultant morphology. We propose a methodology for using microstructured magnetic materials, appropriately patterned, to precisely control LCBCPs using spatially varying magnetic fields. Here we show that these fields can govern the local orientational order in LCBCPs. We simulate the field patterns created when a unique geometry of ferromagnetic material embedded into and around LCBCPs is brought into the presence of a weak background magnetic field. Then, we use software based on the tensorial Landau-de Gennes theory to describe how variations in the field and the newly imposed boundary conditions, alter the local nematic director orientation of the mesogenic and elastic components of the LCBCP. These steps allow us to engineer ferromagnetic inclusions to program methodical arrangements of mesophase grain orientation (textures) into these LC systems. We anticipate that these bespoke textures in the LCBCP systems can be coupled to thermomechanical, thermochromic, and optical abilities and will enable a new paradigm for geometric actuation in soft stimuli-responsive materials. This development will lay the groundwork for the invention of materials with tunable properties for industries like soft robotics, smart wearables, and photonics.