Optically active helical polyacetylene/Fe3O4 composite microspheres: prepared by precipitation polymerization and used for enantioselective crystallization

This article reports the first coordination-precipitation polymerizations for preparing chiral, magnetic composite microspheres consisting of helical substituted polyacetylene and Fe3O4 nanoparticles. The microspheres were obtained in high yield (>85%) and characterized by XRD, FT-IR, SEM, TEM, CD and UV-vis absorption techniques. TEM and SEM images showed that the microspheres were approx. 600 nm in average diameter and possessed a spherical morphology with a rough surface. CD and UV-vis absorption spectra demonstrated that the polyacetylene chains constructing the microspheres adopted helical structures of a predominantly one handed screw nature, which enabled the microspheres to show remarkable optical activity. The microspheres also performed desirable magneticity. They were further used as chiral selectors efficiently inducing enantioselective crystallization of D-and L-alanine as model chiral enantiomers. Moreover, the microspheres can be easily restored under the assistance of an external magnetic field. The coordination-precipitation polymerizations provide a versatile platform for preparing advanced chiral and non-chiral, magnetic hybrid microspheres.