Process for the preparation of monodisperse polymer particles

A process for the preparation of monodisperse polymer particles comprising:

• 1) preparing monodisperse swellable seed particles by emulsion polymerization, wherein an anionic surfactant is employed as emulsifier under substantially oxygen-free conditions;
• wherein said seed particles are non-oligomeric:
• (a1) contacting said non-oligomeric seed particles with an aqueous dispersion comprising an organic compound with a molecular weight below 5000 Dalton and a water solubility at 25° C. of less than 10−2 g/L;
• the anionic surfactant;
• and optionally an organic solvent in which said organic compound is soluble;
• (b1) allowing said organic compound to diffuse into said non-oligomeric seed particles;
• and
• (c1) contacting the aqueous dispersion of non-oligomeric seed particles with a monomer which is at least ten times more water soluble than said organic compound;
• or
• wherein said seed particles are oligomeric:
• (a2) contacting said oligomeric seed particles with an aqueous dispersion comprising the anionic surfactant;
• and
• (b2) contacting the aqueous dispersion of oligomeric seed particles with a monomer;
• 2) if required adding a water-soluble steric stabilizer, if required adding a porogen, and if required adding a polymerization initiator;
• and
• 3) initiating polymerization of said monomer in an aqueous dispersion containing a steric stabilizer in continuous phase.