Preparation and Post-Functionalization of Hyperbranched Polyurea Coatings

Postfunctionalizable hyperbranched polyurea coatings were prepared by the bulk polycondensation of AB2 monomers on preactivated silicon substrates. As previously shown, AB2 monomers were prepared, comprising a secondary amino group (A) and two blocked isocyanates (B) connected by hexyl spacers, in a single step and in quantitative yields. Covalent anchoring of the coatings on substrates was accomplished by reacting the secondary amino group in the focal point of the polymers with the blocked isocyanates (BIs) of the covalently attached coupling agent. The BIs in the top layer of the coatings were storage-stable under ambient conditions but well-modifiable with amino- or hydroxyl-functional compounds on heating. Attachment of polyethylene glycol or perfluoro-1-decanol afforded hydrophilic or hydrophobic surfaces. Immobilization and quaternization of polyethylenimines yielded highly charged surfaces. The coatings were extensively characterized by a number of techniques, such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, ellipsometry, and contact -angle measurements.