seed projects

Michelle Calabrese: Controlling polymer self-assembly with magnetic fields

Commercial block polymers (BCPs) self-assemble in aqueous conditions into micelles, cubic, hexagonal, and lamellar phases, among others, and are used in applications ranging from drug delivery to flexible electronics. Directing or altering this self-assembly with external magnetic fields has typically required large field strengths (≥5 T); the addition of liquid-crystalline (LC) blocks, rod-like blocks, or aromatic rings to facilitate ordering; substantial chain anisotropy; or combinations therein. We have recently shown that BCP ordering can be controlled with directional precision using direct fields of low strengths (B ≤0.5 T), where the assembly kinetics are controlled via the field strength. In this project, we are focusing on tailoring self-assembly and kinetics with time-dependent magnetic fields of various forms (oscillatory, step, etc.). The application of direct magnetic fields in these BCPs can increase ordering and/or produce new structures not seen through traditional self-assembly. With this basis, we will explore how transient fields of varying strengths can be employed to further enhance ordering, direct morphology selection, and tailor phase spacing. The application of orthogonal shear fields will also be examined as a method to accelerate the assembly kinetics. Finally, assembled materials will be crosslinked to preserve the morphology for use in wide-ranging applications.

Funded by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013