**9.4 Particle formation**

The rapid expansion of SCF is a promising new technology for particle formation and distribution of biodegradable polymeric (Debenedetti et al. 1993). Because of the extreme fragility of organic aerogels attempts are made to develop inorganic aerogels. Such microcellular polymers foams can be obtained directly by polymerization in a near critical diluent and SC drying in the same reactor vessel. In polymer industry, polymerization is stopped by adding a termination agent. The polymer solution was contacted with superheated steam to remove unreacted monomer and polymerization solvent (de solvent process). SC-CO2 extraction can be alternative for the de-solvent process of polymer solutions. In fact SC-CO2 can reduce the drying process due to its capability of complete recovery by depressurizing. In addition, SC-CO2 can dissolve the typical polymerization solvents, *n-*hexane or toluene at higher pressures. The design of the de-solvent process requires quantitative information on the distribution of organic solvent between the polymer solution and the SC-CO2 phase (Inomata et al. 1999).
