Polymer brushes are coatings consisting of macromolecules end-grafted to a surface at densities sufficiently high that the chains are forced to stretch away . They can be used in a broad range of applications, from sensors to lubricants and antifouling surfaces , in liquid and in air . There are two general ways of creating polymer brushes: grafting-from , in which polymers are grown from an initiator-functionalized surface, and grafting-to , in which pre-synthesized polymers are immobilized on a surface. Grafting-to is generally easier to perform, and allows better control over the chain length (distribution), but suffers from a drawback: attainable grafting densities are typically low as steric hindrance of already grafted chains precludes the grafting of additional chains.