Copper phthalocyanine blue was encapsulated with a copolymer of styrene and maleic acid (PSMA) via a phase-separation technique, and a PSMA-encapsulated pigment dispersion was prepared. The effects of the additive on the stability of the dispersion were studied. Scanning electron microscopy photographs revealed that the particles in the PSMA-encapsulated pigment dispersion were more uniform than those in a PSMA-dispersed pigment dispersion. X-ray photoelectron spectroscopy provided evidence that the PSMA-encapsulated pigment acquired abundant carboxylic groups that could improve its wettability to water. Moreover, the results also indicated that the PSMA-encapsulated pigment dispersion had improved color strength, its stability could be greatly influenced by the pH value and ion strength, and its apparent viscosity changed little with an increase in the shear rate. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 211-215, 2010