A simple, two-step aqueous polymerization was introduced to synthesize a polyacrylate (PAC)/polypyrrole (PPy) hydrogel. The hydrogel had a semi-interpenetrating network (semi-IPN) structure with a loose, three-dimensional PAC network and a one-dimensional PPy conjugated chain. The presence of PPy led to a higher conductivity (9.1. mS/cm) for the PAC/PPy hydrogel. Because of the acrylate group on PAC and the imine group on PPy, the hydrogel showed typical pH sensitivity with two water absorption peaks at pH 4-6 and pH > 11. The loose semi-IPN structure endowed the hydrogel with good load and release functions. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1376-1383, 2010