Hollow polymeric microspheres grafted with optically active helical polymer chains: Preparation and their chiral recognition ability

A novel class of hollow polymeric microspheres was prepared from optically active helical polymers. To prepare the hollow spheres, optically active helical N-propargylamide copolymers (OAHPs) containing specially designed C=C groups in pendent groups, were first synthesized and subsequently used as a macromonomer. Polymeric particles based on maleic anhydride (MAH) and vinyl acetate were prepared and used as sacrificial templates for the subsequent preparation of core/shell spheres, which were accomplished by using the system consisting of MAH, divinyl benzene and OAHP macromonomers. After extracting the core in the prepared core/shell particles, hollow microspheres grafted with optically active helical polymer chains were successfully obtained. The hollow particles were characterized with FTIR, field-emission SEM and TEM measurements. The size and the shell thickness of these hollow spheres were readily controllable. Circular dichroism (CD) spectra were recorded on the hollow spheres dispersed in THF. The intense CD effects indicated that the hollow spheres possessed high optical activity, arising from the helical polymer chains. The preferential adsorption of (R)-(+)-1-phenylethylamine to the (S)-form by the obtained hollow spheres clearly attested to the chiral recognition ability of the novel spheres.