Chiral, fluorescent microparticles constructed by optically active helical substituted polyacetylene: preparation and enantioselective recognition ability

Abstract

Microparticles simultaneously showing optical activity and fluorescence were prepared based on fluorescent, optically active helical polymers. Chiral and fluorescent substituted acetylene monomers (L- and D-CFM) were synthesized and then underwent precipitation polymerization in a solvent mixture of CHCl₃/n-heptane in the presence of a Rh catalyst at room temperature. The CHCl₃/n-heptane mixture at a suitable ratio provided spherical microparticles (L- and D-CFMPs) with uniform diameters of 910 nm in a high yield (ca. 90 wt%). The microparticles were comprised of polymer chains (number-average molecular weight, 8700 g mol⁻¹) that were found to adopt chiral helical structures, according to circular dichroism and UV-vis absorption spectroscopy. The fluorescence property was measured using fluorescent microscopy and spectroscopy. Remarkably, the novel microparticles exhibited enantioselective recognition ability towards alanine and phenylethylamine enantiomers. However, L- and D-CFMPs behaved differently in the enantioselective recognition processes. Possible mechanisms were proposed for the observed enantioselective recognition.