polymer films appear uniform, smooth, and free of pinholes. No polymerization takes place on the areas that are covered by methyl-terminated SAMs. The inset in Figure shows a line profile over the 100 nm thick brushes. The ªsquareº profile of the polymer film indicates that the polymers grow as a very dense film. Some broadening of the initial pattern might occur, but this is not visible on the scan sizes that were used to acquire this image. The versatility of various patterned polymer brushes as etch resists was tested by using them as barriers to wet chemical etchants of gold. Figure shows an optical image of a typical polymer brush after 40 s exposure to a solution of gold etchant (4 g KI and 2 g I 2 in 40 mL H 2 O) Only the monolayer protected areas of gold were dissolved leaving the polymer covered areas intact.
Concluding, we have successfully demonstrated the rapid, controlled formation of up to 125 nm thick brushes from SAM bound initiators under mild conditions using aqueous ATRP. Our key observation is that the addition of water to these reactions greatly enhances the rate of brush growth without loosing control over the polymerization. We believe that this method can be exploited for a wide variety of water (or water/methanol soluble) soluble monomers. We did not observe polymerization in solution, which allowed brush formation without bulk polymer sticking to the surfaces. We believe that dense, functional polymer (e.g., PGMA) brushes may provide a suitable cushion that can interact with irregular solid surfaces where monolayers cannot. Such technology may be used as a molecular ªultra-glueº for adhesion to suitable substrates. The possibility of growing brushes in water from a variety of surfaces will potentially be useful in field of polymer electronics, biosensors, or in the fabrication of biocompatible surfaces.