Effect of Different Surface-Charged Lamellar Materials on Swelling Properties of Nanocomposite Hydrogels

This study investigated the effect of different surface-charged lamellar materials on the swelling and diffusion properties of synthesized polyacrylamide-methylcellulose hydrogels (HG). Montmorillonite and thermally activated hydrotalcite (300 degrees C and 550 degrees C) were incorporated during the preparation of nanocomposite (NC) hydrogels. A series of NC hydrogels were prepared by varying the lamellar material content (1:1, 2:1 and 4:1). The results showed that the HG with hydrotalcite (550 degrees C) was strongly dependent on the ionic intensity, and that the swelling degree increased by 50%, 65% and 78% with reducing the hydrotalcite content at (1:1), (2:1) and (4:1), respectively. The water absorption capacity of HG containing montmorillonite or hydrotalcite (300 oC) was slightly affected when the pH was decreased from 7 to 3. However, the pH variation from 7 to 10 increased the water absorption capacity of most HG, except those containing hydrotalcite (550 degrees C) at (2:1) and (4:1). The presence of lamellar nanoparticles in hydrogels made the polymer matrix more rigid, and less likely to absorb water. In contrast, HG with hydrotalcite (550 degrees C) at (2:1) and (4:1) showed anomalous behavior with an increase in their water absorption capacity. The results support that the developed NC-HG can be suitable candidate materials for controlled released applications.