Polymer brush refers to a macromolecular assembly which is formed by polymer chains densely attached by one end to a surface or an interface.^1,2  For a brush, the distance between neighboring grafting sites (D) is much smaller than the gyration radius (R_g) of free polymer chains (normally D should be at least smaller than 2R_g) so that the polymer chains stretch away from the interface into the solution.³  Since the report that grafting polymer molecules to colloidal particles was an effective way to prevent flocculation in the 1950s,^4,5  polymer brushes have attracted considerable attention in protein immobilization,⁶  catalysis,⁷  nanoreactors,⁸  environmental engineering,⁹  disease diagnosis^10,11  and other fields.¹²