Preparation and characterization of a polyelectrolyte monolayer covalentlyattached to a planar solid surface

A novel concept for the synthesis of molecularly thin polyelectrolyte layer s covalently attached to planar solid surfaces is introduced. The polymer m onolayers are generated directly at the surface by using self-assembled mon olayers of an azo initiator and radical chain polymerization in situ. This "grafting from" approach yields surface-bound polymer molecules with a high molecular weight and with high graft densities of the attached chains ("br ush"-like state). As an example for the preparation of a positively charged polyelectrolyte "brush" at first a monolayer of poly(4-vinylpyridine) (PVP ) was generated at the surface, which was subsequently quarternized to yiel d a poly[4-vinyl-N-n-butylpyridinium] bromide (BuPVP) monolayer. The thickn ess of this resulting cationic monolayer can be controlled in a wide range, starting from 2 nm to more than 1000 nm in the solvent-free state.