Nonaqueous Emulsions - A Versatile Tool for New Types of Functional Nanoparticles

The preparation of functional polymer latex particles is usually carried out in aqueous heterogeneous systems, i.e. for example in emulsion or mini-emulsion polymerization. Due to the presence of water, moisture sensitive reactions like step growth polymerizations or metal catalyzed reactions can not be accomplished without side reactions and / or decomposition. In order to avoid these side reactions, different nonaqueous emulsion systems have been developed. According to the desired polymerization procedure, these systems consist of a nonpolar organic phase surrounded by a perfluorinated solvent or of a polar organic phase which is dispersed in a nonpolar organic solvent. Both emulsions are stabilized by amphipolar block copolymers and result in long time stable particle dispersions. The resulting dispersions yield particles with narrow size distributions and - depending on the reaction conditions - diameters down to tens of nanometers. This technique allows the formation of particles consisting of numerous different classes of polymers, e.g. polyurethanes, polyesters, polyolefins etc. and the formation of more complex morphologies such as core shell structures.