Hollow spherical micro/meso-porous silica structure by nanospherical sacrificial polystyrene templates

Abstract

In this study, spherical polystyrene (PS) nanoparticles having a negative surface charge were synthesized by polymerization of a miniemulsion containing styrene monomer, normal hexadecane (HD) as hydrophobic agent, sodium dodecyl sulfate (SDS) as anionic emulsifier, sodium bicarbonate (NaHCO3) as buffer, and water soluble potassium persulfate (KPS) as initiator. The effects of three important parameters (surfactant, cosurfactant, and initiator) on particle size and size distribution were contemporaneously investigated. The particle size and size distribution was measured using dynamic light scattering (DLS). Transmission electron microscopy (TEM) images were also taken from the corresponding latexes to confirm the results. The produced polystyrene particles were coated by silica via sol-gel process in which tetraethyl orthosilicate (TEOS) precursor, ethanol, hydrochloric acid, and water were employed to carry out hydrolyzation/condensation process. Using ultra-high speed centrifugation, a closely packed assembly of particles resulted which were subjected to calcination process to form hallow spherical micro/meso-porous silica structure. The average pore diameters of the micro and meso pores were 2–3 nm and 25–30 nm, respectively, as determined by nitrogen sorption isotherms. The specific surface of the porous sample was also measured by Brunauer, Emmett, and Teller (BET) method to be 554.74 m2/g that is well suited for catalyst support applications. In the end, the produced catalyst support was used to form ziegler-natta catalyst. By using the produced catalyst via prepolymerization and slurry polymerization at 70℃, polypropylene was polymerized from propylene.