Method for manufacturing porous particles with non-porous shell

A method of manufacturing porous core-shell polymer particles having a nonporous shell comprising:

• providing a first organic solvent containing a dissolved polymer;
• dispersing the organic solvent containing the dissolved polymer in an aqueous phase containing a stabilizer to form an emulsion comprising dispersed droplets of polymer solution;
• adding the emulsion to an excess amount of a second organic solvent relative to the amount of the emulsion wherein the second organic solvent is miscible with water and the first organic solvent, and a non-solvent for the polymer;
• and
• evaporating the first and second organic solvents from the emulsion to form porous core-shell polymer particles having a nonporous shell, wherein the particles have a porosity of from 10 to 70 percent and the nonporous shell has 1 percent or less pore content, and wherein when the emulsion is added to the second organic solvent, the second organic solvent causes phase separation to occur that forms the porosity within the cores.