Hollow Two‐Layered Chiral Nanoparticles Consisting of Optically Active Helical Polymer/Silica: Preparation and Application for Enantioselective Crystallization

Abstract

This article reports for the first time a novel category of hollow organic@inorganic hybrid two‐layered nanoparticles (NPs), in which the inner layer is formed by optically active helical polyacetylene, and the outer layer by silica. Such NPs show remarkable optical activity and are successfully used for enantioselective crystallization. To prepare such NPs, n‐butyl acrylate undergoes radical polymerization to first form poly(n‐butyl acrylate) (PBA) cores two shells by catalytic polymerization of substituted acetylene and sol–gel approach of TEOS (tetraethyl orthosilicate), respectively. Removal of the PBA cores provides the expected hollow core/shell NPs. The intense dircular dichroism (CD) effects demonstrate that the hollow chiral NPs possess considerable optical activity, arising from the helical substituted polyacetylenes forming the inner layer. The hollow NPs are further used as chiral templates to induce enantioselective crystallization of racemic alanines, demonstrating the significant potential applications of the hollow chiral NPs in chiral technologies. Also of particular significance is the detailed process of the induced crystallization observed by TEM. The strategy for preparing the hollow hybrid chiral NPs should be highlighted since it combines free radical polymerization and catalytic polymerization with sol–gel process in a single system, by which numerous advanced materials will be accessible.

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.…”

Optically Active Helical Substituted Polyacetylenes Showing Reversible Helix Inversion in Emulsion and Solution State

“…[2][3][4][5] However, we found that two polymers derived from a pair of enantiomeric monomers (as structurally shown in Scheme 1 ) showed the opposite phenomenon. In more detail, the two polymers also adopted helical conformations when existing in the form of nanoparticles.…”

“…The polymer solution was prepared following in Scheme 1 ). According to the methodology created by us, [ 2 , 3 ] M 1 and M 2 underwent emulsion polymerization in aqueous media, with Triton X-100 as surfactant and (nbd) Rh + B − (C 6 H 5 ) 4 as catalyst. The detailed preparing processes and experimental conditions were introduced earlier.…”

Optically Active Hybrid Materials Constructed from Helically Substituted Polyacetylenes

“…[31] Following the same concept, that is, the seed emulsion polymerization strategy presented in Figure 1, we prepared hollow core/shell NPs through a three-step, onepot process, as illustrated in Figure 2. The three steps include the successive emulsion polymerization of BA (step one), emulsion polymerization of SA (step two), and then the solgel process of TEOS (step three) in the same polymerization system.…”