Neutral and charged polymer brushes at solid surfaces

Abstract

Neutral and charged polymer brushes covalently attached to planar solid surfaces were generated by using self-assembled monolayers of an azo initiator and radical chain polymerization in situ. The brushes were characterized by FTIR-spectroscopy, optical waveguide-spectroscopy and Ellipsometry. Especially the film thicknesses of surface bound polyelectrolyte (PEL) monolayers were measured by optical waveguide spectroscopy (OWS) as a function of the humidity of the environment. The PEL brushes show strong increases in thickness as well as strong decrease of the refractive index of the surface attached layer due to water incorporation caused by the exposure to the humid environment. Additionally the behavior of neutral as well as charged brushes in contact with solvent was investigated by using multiple-angular-scans of ellipsometry in a total internal reflectance setup. The scaling behavior of the brush height as a function of the graft density of the attached polymer molecules was investigated for the neutral brush as well as for the PEL brush system.