Polymer particles with a gradient composition and methods of production thereof

A non-porous polymer particle comprising a core having a center, a first layer, a second layer, and a particle surface, wherein:

• the core comprises polystyrene, and wherein the core has a diameter greater than 0.1 micron;
• the first layer extends radially from the core to an outer diameter, the first layer comprising a first polymer comprising units derived from styrene and units derived from divinylbenzene (DVB), wherein said first polymer is crosslinked with said units derived from DVB, wherein the first layer comprises a gradient of said units derived from DVB, and wherein an extent of crosslinking increases with radius;
• the second layer extends radially from the outer diameter of the first layer to the particle surface, the second layer comprising a second polymer comprising units derived from glycidyl methacrylate (GMA) and units derived from ethylene glycol dimethacrylate (EDMA), wherein said second layer comprises a gradient of said units derived from GMA and said units derived from EDMA, and wherein a ratio of concentration of said units derived from GMA and said units derived from EDMA in the second layer to units derived from styrene and units derived from DVB in the first layer increases with radius, such that the particle surface consists essentially of polymerized GMA/EDMA.