Adsorption of cationic dendrimers on negatively charged solid substrates

We have good understanding how dendrimers adsorb to oppositely charged substrates. The ad- sorption kinetics is rapid and quickly leads to loose monolayers of low coverage featuring a liquid- like structure. This structure originates from screened Coulomb repulsions between the charge dendrimers, which can be tuned by addition of salt but also through the charge of the substrate. The adsorbed layers are normally irreversibly adsorbed, but desorption may occur for dendrimers of lower generation, especially under acidic and high salt conditions. The desorption is triggered by weakening of attractive electrostatic forces between the dendrimers and the oppositely charged substrate. These forces are also responsible for flattening of the adsorbed dendrimers and their swelling on the surface. Adsorbed dendrimers may swell substantially, especially in acidic and high salt conditions. Adsorbed dendrimers films could have interesting applications in material science. The loose liquid-like structures could be useful for surface patterning. Colloidal lithography used similarly structured particular films as masks [11], but dendrimers do offer the possibility to create pat- terns truly on the nanoscale. Another interesting application might be the swelling response of adsorbed dendrimers. The reversible nature of the swelling process of adsorbed dendrimers could be used as an alternative scheme for drug or gene delivery