Accordion-like Oscillation of Contracted and Stretched Helices of Polyacetylenes Synchronized with the Restricted Rotation of Side Chains

Optically Active Porous Microspheres Consisting of Helical Substituted Polyacetylene Prepared by Precipitation Polymerization without Porogen and the Application in Enantioselective Crystallization

A novel chiral acetylenic monomer derived from cholic acid was synthesized and structurally characterized. The monomer underwent precipitation polymerization in tetrahydrofuran/n-heptane mixed solvent with [Rh(nbd)Cl]₂ as catalyst. Without adding porogen, porous microspheres were successfully prepared in a high yield (>80 wt %). The formation mechanism of the porous structure was proposed. Circular dichroism and UV-vis absorption spectra demonstrated that the porous microspheres possessed optical activity. The optical activity was originated in the chiral helical conformations of substituted polyacetylene forming the microspheres. The porous microspheres were further used as specific chiral additive to induce enantioselective crystallization of racemic BOC-alanine, in which BOC-l-alanine was preferentially induced forming rod-like crystals with e.e. of 69%. This strongly indicates the significant potential applications of the porous microspheres in chiral technologies. The present study also provides a new approach to prepare chiral porous polymer microspheres.

Configuration and conformation of poly(3-carbazolylacetylene) including cis and trans radicals revealed by ESR spectroscopy

π-Conjugated cis and trans radicals of poly(N-isobutyl-3-carbazolylacetylene) were stereospecifically prepared using the [Rh(norbornadiene)Cl]₂-NEt₃ catalyst, and their geometric structures were determined using the electron spin resonance (ESR) method.

Chiral functionalization of graphene oxide by optically active helical-substituted polyacetylene chains and its application in enantioselective crystallization

This article reports an original, versatile strategy to chirally functionalize graphene oxide (GO) with optically active helical-substituted polyacetylene. GO was first converted into alkynyl-GO containing polymerizable -C≡C moieties, which took part in the polymerization of another chiral acetylenic monomer, yielding the expected GO hybrid covalently grafted with chiral helical polyacetylene chains. Transmission electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyses verified the successful attachment of substituted polyacetylene chains on GO by covalent chemical bonding. Moreover, circular dichroism effects and UV-vis absorption demonstrated that the GO hybrid possessed fascinating optical activity. It also largely improved the dispersibility of GO in tetrahydrofuran. The GO-derived hybrid was further used as a chiral inducer toward enantioselective crystallization of alanine enantiomers. l-Alanine was preferably induced to crystallize, forming rodlike crystals.

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

The precipitation polymerization for constructing chiral, magnetic microspheres based on substituted polyacetylene and Fe₃O₄ nanoparticles: preparation and application in enantioselective crystallization.