Patent ID: 8829081

Claim:
A method of preparing core-shell submicron spheres, comprising: heating an emulsion to a temperature from 10° C. below the emulsion's boiling point to the emulsion's boiling point, the emulsion comprises at least a core monomer being styrene, methyl methacrylate, n-butyl methacrylate, or any combinations thereof; performing a core forming step by adding an aqueous solution of an initiator to the heated emulsion to form a plurality of cores composed of a core polymer polymerized by the core monomer, wherein the weight ratio of the core monomer to the initiator is 20:1 to 1000:1; and performing a shell forming step by adding at least a shell monomer to the emulsion when the conversion rate of the polymerization is 10-95% at a temperature 50° C. below the emulsion's boiling point to the boiling point thereof, and then stirring the emulsion to form a plurality of shells respectively enclosing the cores and composed of a shell polymer polymerized by at least the shell monomer, wherein the compositions of the core polymer and the shell polymer are different, and wherein the shell forming step includes adding a phase transition material to the emulsion, wherein the phase transition material is n-octadecane less than 60 wt % of the unsaturated monomer.