Optically Active, Magnetic Microparticles: Constructed by Chiral Helical Substituted Polyacetylene/Fe3O4 Nanoparticles and Recycled for Uses in Enantioselective Crystallization

This paper reports a novel category of optically active magnetic microparticles (OAMMPs), which are exclusively constructed by helical polymer chains and Fe3O4 nanoparticles. The resulting microparticles exhibit remarkable optical activity and magnetic property, according to circular dichroism (CD) and UV–vis spectroscopy and vibrating sample magnetometry characterizations. Alkynyl-modified Fe3O4 nanoparticles are employed as a comonomer to fabricate the microparticles. The OAMMPs are further used as a chiral additive to induce enantioselective crystallization of racemic alanine. l-Alanine is preferentially induced to crystallize, forming rod-like crystals, according to CD and scanning electron microscopy characterizations. Also remarkably, the particles possess rapid magnetic responsivity, making it possible to be recycled and reused. The initially induced crystals are further enantioselectively crystallized twice and thrice, and the enantiomeric excess can be increased to 90%. Recyclability of the particles is also clearly verified. The present study not only provides a novel type of advanced functional materials but also creates a “green” strategy for chiral resolution and purification.