Abstract
A change of pH inside a polymer hydrogel was induced through electrochemical control of proton production to release the water from inside the gel. The relationship between release rate of water and operating conditions such as applied voltage, electrolytes and solution pH were studied experimentally and the following results were obtained.
The release rate of the water from inside the gel, vt was controlled by both applied voltage and addition of electrolyte. The release rate increases depending on the applied voltage that promotes the production of H+ ion. The additive electrolyte increases the release rate with its concentration because of the increase of electric conductivity of the solution, resulting in an increase of H+ ion production. The addition of alkali, however, decreases the release rate depending on the pH.
The release rate can also be controlled by supplied charge, because there is a stoichiometric relation between the amount of charge and H+ ion production. The release rate based on charge, vq, means the efficiency of charge (proton consumption) in the release of water from inside the gel. The vq depends on the electrolyte and/or the concentration of counter ion inside the gel.
