To study the effect of the polymerization conditions on swelling, a copolymer was synthesized from the monomers acrylamide (AA), 2-acrylamido-2-methyl-propanosulfonic acid (AMPS) and N,N-methylenobisacrylamide (BA) as crosslinker by an inverse emulsion technique. The conditions were: concentration of organic solvent, s (an isoparaffinic hydrocarbon, commercially Isopar M), concentration of emulsifier, e (sorbitan trioleate, commercially Tween 85), and reaction temperature, T. These three variables (factors) were explored to achieve highest water absorbency, a 2(3) factorial experimental design having been applied to find the main and two-factor interaction effects of those variables on the swelling capacity. A predictive model including the factors for the swelling is proposed, allowing for the estimation of absorbency capacity in this type of copolymers. The results show that the optimum values of the variables given by the experimental design were s = 8.1, e = 1.0, and T = 49 degrees C, with predicted swelling capacity of 1041 and experimental of 1014. The variables are relevant, with a preponderance of s, and the effect of the square of temperature is also significant. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 520-525, 2010