Helical polymer/Fe3O4 NPs constructing optically active, magnetic core/shell microspheres: preparation by emulsion polymerization and recycling application in enantioselective crystallization

Abstract

Hybrid materials combining chirality and magneticity are stimulating much interest in diverse research areas. This article reports the preparation of a new type of optically active, magnetic Fe₃O₄ NP@polyacetylene core/shell microspheres (Fe₃O₄@PA MPs) consisting of magnetic Fe₃O₄ NPs as the core and helical polyacetylene as the shell. The Fe₃O₄@PA MPs integrate two significant concepts, “macromolecular helicity-derived chirality” and “magneticity” in one single microsphere entity. The composite MPs were prepared by emulsion polymerization approach and characterized by TEM, XRD, FT-IR, VSM, TGA, circular dichroism and UV-vis absorption spectroscopy techniques. They simultaneously showed fascinating optical activity and considerable magneticity. The MPs were further used as a chiral additive to induce enantioselective crystallization of racemic threonine. L-Threonine was preferentially induced to form rectangular-shaped crystals with an enantiomeric excess up to 90% (after enantioselective crystallization twice). The microspheres can be recycled conveniently with the assistance of an external magnetic field, demonstrating the MPs’ significant potential applications in chiral fields.