Preparation of carboxyl-functionalized polystyrene/silica composite nanoparticles

摘要

This paper describes the synthesis of carboxylfunctionalized polystyrene/silica (PS/SiO2) composite nanoparticles with various contents of poly(methacrylic acid ) (PMAA) on the surface by post-addition of methacrylic acid (MAA) via emulsion polymerization. High yields and binding efficiencies (around 90) are achieved by an optimal procedure mainly involving the appropriate addition of MAA and amounts of surfactant and silica. The kinetics investigated indicates that the polymerization follows a mechanism different than that found in some earlier studies. The amount of grafted PMAA was determined by titration and FT-IR, and altered in a wide range (1-40 wt.- to PS). Transmission electron microscopy (TEM) photographs show that the composite nanoparticles are about 60 nm in spherical shape and have a multi-layered core-shell structure with a cluster of primary silica beads as the core and PMAA as the outmost primary silica beads as the core and PMAA as the outmost shell. There are approximately 4 to 21 primary silica beads in one composite nanoparticle, depending on the amount of silica added.