Preparation Of Polymeric Microspheres Grafted With Optically Active Helical Polymer Chains And Their Chiral Recognition Ability

Hollow/porous polymeric micro/nanospheres and helical polymers have recently attracted considerable attention due to their unique properties. By grafting helical chain to polymeric microspheres, it can not only help to resolve the application problem of helical polymer, but also achieve the functional modification of polymeric microspheres. Combining with the special properties of helical polymers, in particular the optical resolution and asymmetric catalysis properties, such hollow/ porous microspheres is expected to find lots of applications, such as chiral separation, controlled release, chiral catalysis and chiroptical materials. In this study, we fistly synthesized optically active helical N-propargylamide copolymers (OAHPs) containing specially designed C=C groups in pendent groups. Using OAHPs as macromonomer, we successfully prepared hollow/porous microspheres grafted with optically active helical chains by template polymerization and two-step swelling polymerization, respectively. The main works were as follows:Firstlty, a novel class of optically active N-propargylamide copolymers bearing C=C groups in side chains were synthesized with high yield (≥95%) and moderate molecular weights (10000-17000). The C=C side groups were characterized by FTIR and H1 NMR. All the copolymers adopted stable helices under the investigated conditions. The composition of the copolymers exerted large influence on their optical activity.Polymeric particles based on maleic anhydride (MAH) and vinyl acetate were prepared and used as the 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.Disersion polymerization was used to produce polystyrene microparticles. Using polystyrene particles as seed, OAHP as macromonomers, styrene as monomers, DVB as cross-linker, porous cross-linked polymeric microspheres. grated with optically active helical chains were prepared by two step swelling polymerization. The porous microspheres composition and microstructure were characterized with FTIR, CD, SEM and TEM measurements.