Polymeric particles

Monodisperse coated hydrogel polymer particles comprising a polymer formed from (a) a hydrophilic vinylic monomer having a log Poct/wat (log P) of less than about 0.6, wherein the hydrophilic vinylic monomer comprises at least one hydrophilic vinylic monomer selected from a monomer comprising —C(O)NH2, —C(O)NHCH3, —C(O)NHCH2CH3, or —C(O)N(CH3)2;

• and (b) a crosslinker comprising at least two vinyl groups;
• and a coating;
• wherein the crosslinker comprises at least one compound of formula (IIa):
• wherein R6 is selected from —C1-C6 alkyl-, —C1-C6 heteroalkyl-, —C1-C6 cycloalkyl-, —C1-C6 hydroxyalkyl-, —C1-C6 ether-, or polyether comprising 2 to 100 C2-C3 ether units, and R7 and R8 are each independently selected from —H, —C1-C6 alkyl, —C1-C6 heteroalkyl, —C3-C6 cycloalkyl, —C1-C6 hydroxyalkyl, or —C1-C6 ether;
• or R7 and R8 are joined together to form-C1-C6 alkyl-, —C1-C6 heteroalkyl-, —C1-C6 cycloalkyl-, —C1-C6 hydroxyalkyl-, —C1-C6 ether-, polyether comprising 2 to 100 C2-C3 ether units;
• and wherein the coating comprises an organic coating formed from at least one epoxide monomer or comprises silica.