Surface modified solid substrate and a method for its preparation

Abstract

A surface modified substrate, wherein the substrate carries a complex adsorbed thereto, which complex is of a polymeric cationic surfactant that contains primary amino nitrogens as well as secondary and/or tertiary amino nitrogens, and a dialdehyde that has 1-4 carbon atoms between the two aldehyde groups. To said complex there may additionally be bonded an anionic compound and optionally alternatingly additional cationic and anionic compounds. The modification primarily means that positive or negative charges can be imparted to the original substrate. Secondly, however, the point may be to utilize reactive groups in bonded cationic or anionic compounds. The surface modified substrate is prepared by contacting the substrate with the polymeric cationic surfactant and the dialdehyde at such conditions that a complex is formed, which is adsorbed onto the substrate surface, and optionally continuing the ionic bonding with an anionic compound and possibly also alternatingly additional cationic and anionic compounds. The polymeric cationic surfactant and the dialdehyde are preferably utilized, separately or together, dissolved in a polar solvent, preferably water. The formation of the complex takes place at a pH-value above 8, whereupon the charges are preferably created at a pH-value below 7.