Preparation And Application Of CeO₂@Polysiloxane Core-shell Microspheres

Core-shell microspheres are defined as composite spherical particls with core-shell structure.Core-shell microspheres are fabricated by mean of coating single-layer or multi-layer organic shell or inorganic shell on the surfaces of the core microspheres.Core-shell microsphers have many excellent physical and chemical properties because of their unique chemical structures and geometric shapes,easily-controlled particle size and adjustable surface properties.In this paper,highly monodisperse polysilsesquioxane microspheres were prepared by one-step reaction using the aqueous solution of organosilane.Then monodisperse CeO₂@polysilsesquioxane core-shell spheres were fabricated by a facile chemical precipitation technique.Our researchs open up new opportunities for the preparation of composites with multifunction.Highly monodisperese poly?methylsilsesquioxane??PMSQ?microspheres,poly?vinylsilsesquioxane??PVSQ?microspheres and poly?phenylsilsesquioxane??PPSQ?microspheres were prepared by one-step approach with methyltrimethoxysilane?MTMS?,vinyltrimethoxysilane?VTMS?and phenyltrimmethoxysilane?PTMS?as raw materials in aqueous medium.The strucuture of microspheres were characterized by FT-IR and XRD,the thermal stability of spheres were investigated by TGA,the morphology and size distribution were analyzed by SEM and DLS.The results incated that the order of the particle size is as follows: PPSQ>PVSQ>PMSQ,PMSQ microsphere and PVSQ microsphere possess better thermal stability than PPSQ microsphere.The size of microspheres could be adjusted by controlling the reaction temperature and the concentration of organosilane precursor and the ammonia catalyst.Highly monodisperse CeO₂@PMSQ core-shell microspheres have been successfully prepared by a facile chemical precipitation technique.Struct ures and properties of CeO₂@PMSQ core-shell were analyzed by FT-IR,XRD,SEM,XPS and UV-Vis,etc.It was confirmed that PMSQ microspheres was uniformly coated by CeO₂ nanoparticles with about 8 nm of crystallite diameter,and forming a complete core-shell structure.The UV-Vis result shows that CeO₂@PMSQ microspheres exhibit strong absorption in the ultraviolet region.Then the CeO₂@PMSQ was incorporated in polyvinyl alcohol?PVA?matrix to fabricate CeO₂@PMSQ/PVA composite films by casting homogeneous solutions.The thermal and optical properties of composite films was investigated by TG and UV-Vis.The results revealed the high UV-shielding efficiency of the composites: for a film containing 2.5 wt% of CeO₂@PMSQ microspheres,about 80% of UV light at wavelengths between 200 nm and 360 nm was absorbed while the optical transparency in the visible region still keep very high.The addition of CeO₂@PMSQ microspheres can improve the thermal stability of PVA films.CeO₂@PMSQ/silicone composites was prepared by solution blend.The obscure interface between CeO₂@PMSQ core-shell microspheres and silicone resin was observed by SEM,which implied that CeO₂@PMSQ had a good compatibility with the silicone matrix.For the composite containing 0.1 wt% of CeO₂@PMSQ particles,the light transmittance over 72% at 800 nm while the light transmittance is 320 nm at 350 nm,which indicated that CeO₂@PMSQ/silicone composites own good UV-shielding performance.