A polymer brush can be described as polymer chains tethered to a surface or interface with a sufficiently high graft density such that the chains are forced to stretch away from the tethering site. High-density brushes give not only the change in the chemical properties of the substrate surface, but also physicochemical functions based on osmotic pressure in a good solvent. Ionic or zwitterionic polymer brushes afford the super hydrophilic surface leading to the antifouling effect, self-cleaning, inhibition of protein and cells, cell sheet manipulation, and combating marine biofouling in aqueous media. Surface grafting of hydrophilic polymer on the elastomers with low Tg usually suffer from recovery of the hydrophobic surface, due to the surface rearrangement of elastomer after thermal annealing. Introduction of cross-linking into the surface initiator layers are useful to prevent the the surface rearrangement. Polymer grafted nanoparticles with controlled grafting density, molecular weight, and molecular weight distribution have been pursued as building blocks for the fabrication of one-component hybrid materials that are formed via the assembly of brush particles in the absence of an additional matrix polymer.