Particles with radial variation

A polymeric bead having radius R wherein the polymer comprises 0.3% to 20% by weight, based on the weight of the polymer, of polymerized units of one or more multifunctional vinyl monomer and 80% to 99.7% by weight, based on the weight of the polymer, of polymerized units of one or more monofunctional vinyl monomer,

• (a) wherein the polymerized units of multifunctional vinyl monomer have radial distribution factor MR of 0.9 to 1.1, wherein MR=CMSHELL/CMCORE, wherein CMSHELL is the average concentration of polymerized units of multifunctional vinyl monomer located at a distance from the center of the bead of 0.8*R to R, and wherein CMCORE is the average concentration of polymerized units of multifunctional vinyl monomer located at a distance from the center of the bead of 0 to 0.5*R, and
• (b) wherein some of the vinyl groups in the polymerized units of multivinyl monomer are unreacted, and the unreacted vinyl groups have a radial distribution factor VR of 2.5 or higher, wherein VR is determined by a Raman spectroscopic measurement performed on the bead, wherein
• VR=V1SHELL/V1CORE,
• wherein V1SHELL is the average of ratio V1 for measurements made at a distance from the center of the bead of 0.8*R to R, wherein V1CORE is the average of ratio V1 for measurements made at a distance from the center of the bead of 0 to 0.5*R, wherein V1=PCC/PAR, wherein PCC is the height of the Raman spectroscopic peak due to stretching of carbon-carbon double bonds, and PAR is the height of the Raman spectroscopic reference peak due to stretching of the aromatic ring at 1000 cm−1 .