This paper presents a comprehensive study of the electromechanical behavior of PAAM hydrogel actuators. In this study, we developed a new method for the characterization of the pH gradient inside the gel actuator. Then we analyzed the volume variation kinetics of the gel responding to various pH stimulations and investigated the electroactivity of PAAM actuators in a fully hydrated gel. Finally we explain the bending mechanism of the hydrogel actuator based on the phenomenon of diffusion of hydroxide and hydronium ions showing the correlation between the electrical, chemical and mechanical properties of such devices.