Bactericidal silver ion delivery into hydrophobic coatings with surfactants

A much studied oil-soluble surfactant, bis[2-ethylhexyl]sulfosuccinate, sodium salt, was ion exchanged into the silver ion form and dissolved into microemulsions of immiscible polyurethane step monomers. Coating and curing of these microemulsions produced polyurethane coatings that exhibit bactericidal activity against representative Gram negative bacteria. After 24 h exposure, 0.006-0.012% weight Ag relative to coating weight (0.0013-0.0025 micromol Ag/cm2) results in the three-log reduction in Escherichia coli. A slightly higher level of 0.031% weight Ag relative to coating weight (0.006 micromol Ag/cm2) killed all of the E. coli after 12 h exposure. Similar results were obtained for Pseudomonas aeruginosa. Since the double-tail surfactant anion promotes reverse micelle formation in many different kinds of oils and solvents, it appears an excellent vector for incorporating low and effective amounts of silver ion into many industrial, hospital, and household coating formulations.