CHARACTERISTICS OF CHARGED NETWORKS UNDER AN ELECTRIC STIMULUS

The electrokinetic phenomena of poly(2-acrylamido-2-methyl-1-propane s ulfonic acid-co-n-butylmethacrylate) were examined to investigate phys ical changes of the gel under an applied electric current. When an ele ctrical stimulus was applied to a piece of the gel, without being in c ontact with an electrode, reversible gel bending was observed. The ben ding degree was directly proportional to the intensity of the applied electric stimulus. This was explained by 'depletion polarization' of i onic species under the stimulus. The swelling of the gel surface facin g the anode increased, due to the decreased ionic strength of the boun dary layer upon electric stimulation, while gel shrinking occurred at the cathode. When the gel is in direct contact with electrodes, deswel ling of the gel was observed at the anode side, while water seepage oc curred at the cathode side. This observation was attributed to the ele ctro-osmosis inside the gel, combined with local pH changes around the electrodes resulting from electrochemical reactions, particularly wat er electrolysis. (C) 1994 John Wiley & Sons, Inc.