Preparation of polymer nano- and microspheres by vinyl polymerization techniques

The methodologies and techniques of producing polymer particles (nano- and microspheres) from vinyl monomers are described, with an emphasis on laboratory preparations. Five different techniques are employed in the preparation of polymer micro- and nanoparticles from vinyl monomers. Emulsion polymerization provides particles of about 50-200 nm in diameter, emulsifier free emulsion polymerization produces particles of about 100-1000 nm (0.1-1.0 micron), dispersion polymerization gives particles in the region of 0.3-10 micron, and suspension polymerization leads to the formation of particles of about 20 micron-2 mm. The gap in the 10-20 micron region may be filled by either seeded polymerization or by more elaborately performed suspension polymerization. All of the four techniques mentioned above produce regular, spherical particles. Precipitation polymerization, on the other hand, gives irregularly shaped particles in the range of 0.1-10 micron. An attempt is made to clarify the underlying differences between these techniques and to say how they are practised in the laboratory.