Expanded Core/Shell Poly(vinyl acetate)/Poly(vinyl alcohol) Particles for Embolization

An improvement to a previously published suspension polymerization process for the production of spherical core/shell PVAc/PVA particles is described. To increase the settling time of the beads in the suspension, an expansion stage was introduced. The core/shell structure was obtained through the partial hydrolysis of the PVAc. The particle density was manipulated through addition of a solvent during the suspension polymerization stage and posterior expansion of the polymer beads obtained at the end of the process. This technique allows for effective reduction of the density of the final polymer beads. The expansion stage exerts also a beneficial effect on particle drying, avoiding particle aggregation during post-polymerization processing of the polymer beads.