Chiral Microspheres Consisting Purely of Optically Active Helical Substituted Polyacetylene: The First Preparation via Precipitation Polymerization and Application in Enantioselective Crystallization

Abstract

This article reports on a novel type of microspheres (∼720 nm in diameter) prepared via precipitation polymerization and constructed by optically active helical substituted polyacetylene (PSA). The microspheres were obtained in high yield (>80%), with regular morphology and narrow size distribution. PSA forming the microspheres was found to adopt helices with predominant one-handed screw sense, according to circular dichroism and UV−vis absorption spectroscopies and specific optical rotation measurements. The helical conformations of PSA endowed the microspheres thereof with considerable optical activity. The chiral microspheres feature in combining in one entity the advantages of both chiral polymers and the micrometer-sized particles in scale and spherical morphology and thus are expected to find some significant applications. This is well exemplified by successful induction of enantioselective crystallization with the chiral microspheres. Such chiral microspheres efficiently induced enantioselective crystallization of alanine enantiomers: (S)-PSA preferably induced L-alanine to form octahedral crystals while (R)-PSA toward D-alanine forming needle-like crystals, with a remarkably high ee (85%). This is the first precipitation polymerization of substituted acetylenes for preparing chiral polymeric microspheres. The present chiral microspheres represent a new type of advanced functional chiral materials.

Particles of polyacetylene and its derivatives: preparation and applications

“…[19][20][21][22][23][24][25][26][27][28][29] Polymer particles based on chirally helical substituted polyacetylenes also have been prepared and performed interesting optical activity. Such optically active polymer particles were majorly reported by Deng group [43][44][45][46] and are also included in this review article.…”

“…For acetylene and the derivatives, it has kept remarkably challenging to perform their precipitation 40 polymerizations. However, recently Zhang et al 44 carried out precipitation polymerizations of acetylenic monomers, by which regular polymer particles were obtained.…”

“…The ee for the process can be up to 80%. Zhang et al 44 prepared optically 90 active particles consisting of helical polyacetylene, which also performed enantioselective crystallization ability. In the enantioselective crystallization, special chiral interactions maybe occurred between the surfaces of the optically active particles and the target chiral compounds.…”

Optically Active Hybrid Materials Constructed from Helically Substituted Polyacetylenes

“…To circumvent this limitation, we specifically established precipitation methodology. [16] Although the approach of precipitation polymerization has been extensively used in vinyl monomers for preparing polymer particles, it has never been used in the case of acetylic monomers. We established the first precipitation polymerization protocol for preparing optically active polymeric particles constructed from HSPA.…”

“…We established the first precipitation polymerization protocol for preparing optically active polymeric particles constructed from HSPA. [16] Based on this methodology and the preceding CMPs, we made special efforts to prepare hybrid particles simultaneously showing optical activity and magneticity through a precipitation polymerization technique. Initially, we considered it extremely hard to prepare chiral magnetic composite particles by using HSPAs through the precipitation polymerization route because, before polymerization, the preformed Fe 3 O 4 NPs should be homogenously dispersed in the polymerization system of acetylenic monomer.…”