Ultrathin antibacterial polyammonium coatings on polymer surfaces
We have developed novel antibacterial coatings from innocuous polyammonium compounds which are chemically coupled to a polymer surface. For immobilization we used two strategies: In the first strategy, the polymer surface is plasma activated to generate radicals. Then antibacterial monomers, such as diallyldimethylammonium chloride (DADMAC) are grafted to the surface by a radical polymerization. In the second strategy, the polymer surface is plasma treated to create oxygen functionalities. Antibacterial copolymers, such as DADMAC copolymers, are coupled to the activated surface. Microbiological data prove that the DADMAC copolymers reduce the settlement of bacteria such as Micrococcus luteus (gram positive) and Escherichia coli (gram negative) by a factor of 10(exp 5)-10(exp 6). The layers were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The extremely thin coatings of only 2-3 nanometers thickness do not change the material properties of the substrate.