Helix-sense-selective surface grafting polymerization for preparing optically active hybrid microspheres†
Chiral hybrid micro/nanomaterials have attracted great interest and have been extensively studied due to their intriguing properties and promising applications which cannot be achieved with each of the single components. Preparation of chiral materials from low-cost and abundant achiral monomers is significant for both chiral and materials science. This paper reports an unprecedented strategy, helix-sense-selective surface grafting polymerization (HSSSGP), for fabricating optically active hybrid spheres. Chiral and meanwhile polymerizable acetylenic moieties were first introduced onto silica microspheres’ surface, which then worked as a chiral acetylenic comonomer undergoing co-polymerization with an achiral monomer. The surface chirality efficiently transferred from the pre-chiralized silica microspheres to the resulting polymer shell through helix-sense-selective polymerization, thereby providing optically active hybrid microspheres consisting of a silica core grafted with an optically active shell consisting of chiral helical polyacetylene. Scanning electron microscopy and transmission electron microscopy images demonstrate the formation of a core–shell hybrid architecture. CD and UV-vis absorption spectra ascertain the helical conformation of the polymers and the optical activity of the hybrid spheres thereof. This study establishes an effective and straightforward alternative for making use of achiral monomers to construct chiral hybrid materials.