Preparation Of Core-Shell And Hollow Polymer Particles By Dispersion Polymerization

In this paper, monodisperse core (PSt)-shell (cross-linked P(St-DVB)) microspheres were prepared firstly by a two-stage dispersion polymerization in which DVB was charged into reaction system after monomer conversion high up to 80%. The cross-linking mainly took place at the surface of PS particles to form shell layer. Subsequently, hollow particles composed of cross-linked P(St-DVB) were prepared by dealing the core-shell microspheres with a solvent of THF in which the core polymer was dissolved and removed.The morphology of the generated core-shell or hollow structures was observed by SEM and TEM. The influences of some parameters such as the initiator concentration, monomer content and crosslinker amount applied in the dispersion polymerization on the morphology of final hollow particles were investigated. The results indicated that perfect hollow particles could not be readily produced if greater concentration of initiator was used in the first dispersion polymerization, owning to the somewhat difficulty in removing the core polymer with high molecular weight. High monomer content presented in the polymerization could lead to the less rigidity of the final hollow particles, while the low monomer content could bring about densely crosslinked shell, and thus allow some core polymer remained in THF treatment, resulting in the formation of honeycomb particles. Increasing the amount of crosslinker employed in dispersion polymerization, hollow particles with proper thickness and rigidity were fabricated finally.