PH-RESPONSIVE PERMEABILITY OF POLY(ACRYLIC ACID)-POLY(ETHYLENIMINE) COMPLEX CAPSULE MEMBRANE

Partly crosslinked poly (acrylic acid)-poly(ethylenimine) complex capsules with a diameter of 4.6 mm have been prepared and the permeation behavior of the capsule membrane has been studies. Permeability of phenylethylene glycol from the capsule is low under neutral or weak acidic conditions, but increased remarkably under acidic or alkaline condition. The increase of permeability was considered to be due to swelling of the capsule membrane as determined by measurement of the water content. On the other hand, permeability of p-toluenesulfonate is low under alkaline condition and is increased by lowering pH, probably due to the electrostatic interaction between capsule membrane and the anionic permeant. When the pH of the capsule's environment is changed alternately, there is a reversible change in the permeation rate of these permeants entrapped in the inner aqueous phase. The crosslinking density of the capsule membrane affects the permeability of phenylethylene glycol across the capsule membrane: the permeability decreases with increasing concentration of the condensing agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, during capsule preparation.