Precipitation and Condensation of Organic Particles

The precipitation and condensation of submicron organic particles are reviewed. The importance of physical state effects is discussed, and the role of compartmentalization in controlling particle size is introduced. The thermodynamic driving forces for precipitation and phase transformation are briefly reviewed. The use of emulsification as a primary step in producing small particle dispersions is described and illustrated with photographic and pharmaceutical applications. Precipitation driven by solvent shifting is illustrated and applications in preparing organic–inorganic composites and protein coacervation are described. Miscible solvent–nonsolvent induced precipitation is outlined, and followed by related applications using supercritical fluid technology. The special case of solvent shifting, pH shifting, is reviewed at length and illustrated to be effective for preparing nanoparticles of organics having weak acid functional groups. The first applications of organic particle precipitation in reverse microemulsion systems are described. The applicability of gas condensation methods is illustrated. Exciting new applications of precipitation in submicron hollow spheres and dye entrapment in submicron polymer gel networks are discussed.