The properties of ink-jet inks containing a colorant (pigment, macromolecular chromophore, or dye) are improved by adding thereto an additive, specifically, one or more polymers derived from unsaturated surfactants. The unsaturated surfactant(s) has at least one carbon-carbon double bond (C═C). The polymer may be simply an polymer of the unsaturated surfactant. Alternatively, the polymer may be co-polymerized with one or more vinyl monomers or one or more polymers based on the vinyl monomers may be mixed with the unsaturated surfactant polymer. The vinyl monomer(s) or polymer(s) are used to adjust or “tweak” the properties of the resultant polymer. For example, the more hydrophobic the polymer or the higher its molecular weight, then the greater the water-fastness afforded the ink-jet ink. The polymeric additive of the invention improves bleed control, water-fastness, and smear-fastness of ink-jet inks, particularly thermal ink-jet inks.