Interpenetrating polymer networks based on poly(acrylic acid) and gelatin.I: Swelling and thermal behavior

This article describes the synthesis of full and semi-interpenetrating poly mer networks (IPNs) based on poly(acrylic acid) and gelatin as polymers 1 a nd 2, which were crosslinked sequentially using N,N ' -methylene bisacrylam ide (B-Am) and glutaraldehyde, respectively. Various samples were prepared by taking varying amounts of acrylic acid and gelatin in the initial feed. Sequential IPNs were prepared by first polymerizing and crosslinking acryli c acid in the presence of gelatin using redox initiators (ammonium persulph ate and sodium metabisulphite) and B-Am as a crosslinking agent. Gelatin pr esent in the firm gels was then crosslinked using 4% glutaraldehyde. Charac terization of these gels was done by measuring their swelling behavior as a function of pH, temperature, and time. Percent swelling increased with inc reasing amounts of acrylic acid. The swelling ratio was also determined in the pH range of 1 to 12. Acid/alkali or buffers were used for maintaining p H. A significant increase in the percent swelling was observed when pH of d istilled water was above 10. On the other hand, in the case of buffer, the swelling ratio increased with increasing the pH, and a maxima was observed at pH 8.4. A further increase in pH resulted in a decrease in the swelling ratio. Thermal and morphological characterization was done using thermo-gra vimetric analyzer and scanning electron microscopy, respectively. (C) 2001 John Wiley & Sons, Inc.