Polymer brushes are not always barriers to diffusion

A study was conducted to evaluate the diffusion of free chains through a polymer brush to the underlying surface. The polymer brushes used in the study were composed of monodisperse polystyrene chains grafted to the surface of silicate glass. Polystyrene chains, synthesized by anionic living polymerization and each terminated with a primary amine group, were grafted to the surface of epoxide-derivatized silicate glass by a chemical reaction between primary amine and epoxide groups. The study found that the brush presents no barrier to the diffusion of individual free chains. The speed of grafting showed that the anisotropy of brush environment help the diffusion to the surface, and diffusion was postulated for the transition from mushroom to brush, when free chains make their way to the surface through an denser layer of grafted chains.