The present invention provides a hollow silica micro- or nanoparticle with a polymer immobilized thereon. The polymer is covalently linked to the silica particle via urethane groups. Provided is also a method of covalently coupling a polymer to a silica surface. The method comprises contacting a silica surface that carries amino functional groups with a polymer with a carbonate group of the general Formula (2). R2 in Formula (2) is the polymer and R3 is one of an aliphatic, an alicyclic an aromatic and an arylaliphatic group or a silyl group with a main chain of about 1 to about 20 carbon atoms and 0 to about 6 heteroatoms selected from the group consisting of N, O, S, Se and Si. The method further comprises allowing the carbonate group of the polymer and an amino functional group on the silica surface to undergo a coupling reaction, thereby covalently coupling the polymer to the silica surface.
