Preparation of a polyelectrolyte complex gel from chitosan and κ‐carrageenan and its pH‐sensitive swelling

A polyelectrolyte complex gel was prepared by mixing chitosan and k ‐carrageenan solutions in the presence of NaCl. To study the effect of ambient pH on the swelling behavior, the diameter of the cylindrical gel(4 mm x 8 mm) immersed in aqueous NaOH, KOH, or HCl solution was measured. In the range of pH 10–12, the diameter increased with time, and the gel reached swelling equilibrium within 6 days. In an NaOH solution of pH 10.5, the maximum swelling occurred, and the volume of the gel at equilibrium was 10.2 times as large as the initial one. At pH below 9 and at pH 13, no swelling was observed. Thus, the swelling of the complex gel prepared in this study was sensitive to a rather narrow range of pH. The swelling equilibrium in the presence of NaCl was also investigated at various pH. © 1993 John Wiley & Sons, Inc.