Preparation And Properties Of Optically Active Helical Substituted Polyacetylene/Silica Core-shell Microspheres

As a typical type of synthetic chiral polymers,optically active helical substituted polyacetylenes adopt predominantly one-handed helical structures which endow this type of polymers with significant optical activity.Therefore,they have shown great application prospects in chiral separation,chirally controlled release and enantioselective crystallization.As an important class of chiral materials,chiral substituted polyacetylene particles have excellent properties such as large specific surface area,regular morphology and the functionality of chiral polymers,and so they have attracted wide attention.However,the conjugated polymer structures generally lead to poor dispersibility,processability and thermal stability,which hinders the practical application of polyacetylenes.In order to handle above problems and construct novel chiral materials,we combine chiral helical substituted polyacetylene with high strength silica,from which silica@chiral polyacetylene core-shell particles were prepared.Silica@chiral polyacetylene core-shell particles combined advantage of chiral polyacetylene and silica,exhibiting great potential application values.The main research contents in this thesis are as follows:1.We established a new strategy to prepare optically active hybrid materials directly from achiral monomers,that is,helix-sense-selective surface grafting polymerization(HSSSGP).By this strategy,chiral polyacetylene/silica hybrid materials derived from chirally alkynylized silica(CA-SM)and achiral monomer M1 were prepared.SEM and TEM images demonstrated the formation of the core-shell hybrid architecture.CD and UV-vis absorption spectra ascertained the helical conformation of the polymers and the optical activity of the hybrid spheres thereof.The universality of HSSSGP was verified.Achiral monomer M2 with amide structure and achiral monomer M3 with benzene ring were subjected to HSSSGP with CA-SM as core.SEM and TEM images demonstrated the formation of core-shell hybrid architecture.Through CD and UV-vis absorption spectra measurement,it was found that only the core-shell particles derived from M2 and CA-SM exhibited optical activity.It shows that the HSSSGP strategy is only applicable to N-propargylamide monomers.2.SiO2-PGMA was obtained by grafting polyglycidyl methacrylate(PGMA)on the surface of silica microspheres via ATRP.By reacting SiO2-PGMA with excess propargylamine,a large number of alkynyl groups were introduced into the polymer chains.Next,the alkynyl microspheres and a chiral monomer M4 were subjected to solution polymerization to obtain hybrid material.The results of SEM,FT-IR and elemental analysis proved the successful preparation of core-shell particles.CD and UV-vis absorption spectra demonstrated that the core-shell particles possessed optical activity,and the optical activity was derived from the polyacetylene chains in the shell layer.Besides,the core-shell microsphere exhibited chiral recognition ability in enantioselective crystallization experiment.