Two-stage dispersion polymerization toward monodisperse, controlled micrometer-sized copolymer particles.

We describe a two-stage dispersion polymerization process to prepare monodisperse micrometer-sized polymer particles in which problematic reagents, such as functional monomers and cross-linkers that commonly disrupt the particle-forming process, were added to the reaction after the nucleation stage was complete. Comonomers added after this point became incorporated into the particles without disturbing the final particle size and size distribution. In this way dye-labeled or functional group-containing micrometer-sized particles with a very narrow size distribution were prepared. By varying the amount of monomer added in the second stage, the final particle diameter could be controlled precisely. Most important of all, this synthetic strategy allowed us to prepare cross-linked particles containing up to 3 mol % cross-linking agent.