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

Abstract

AbstractThis 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.