A polymer formed by controlled radical polymerization includes groups that can be modified after controlled radical polymerization to form a radical. The polymer can be the reaction product of a controlled radical polymerization of radically polymerizable monomers, wherein at least one of the radically polymerizable monomers includes at least one group that can be modified after the controlled radical polymerization to form a radical. A compound includes a first group that is stimulated upon application of energy to the molecule to tether the molecule to a surface or to another polymer chain and a second group comprising a controlled radical polymerization initiator functionality. A block copolymer includes at least a first segment to impart a predetermined functionality to a target surface and at least a second segment including functional groups to interact with the targeted surface to attach the block copolymer to the surface. The first segment can free of functional groups that interact with the surface to attach the block copolymer to the surface.