Preparation and characterization of pH-sensitive semi-interpenetrating network hybrid hydrogels with sodium humate and kaolin

Poly(acrylamide-co-methacrylic acid) semi-interpenetrating network (semi-IPN) hybrid hydrogels including sodium humate and kaolin were successfully synthesized as confirmed with X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. Scanning electron microscopy (SEM) analysis indicated uniform dispersed morphology of the hydrogels. It was specified with thermogravimetric-derivative thermogravimetric analysis (TGA-DTG) that the addition of kaolin provided to increase thermal decomposition temperatures of the hydrogels. The semi-IPN hybrid hydrogel exhibited highest equilibrium swelling percent (ESP) of 28,700% and 3440% in distilled water and 0.1 M NaCl, respectively. The hydrogels had better swelling behavior in basic medium compared to acidic medium. While the ESP value of semi-IPN hybrid hydrogel was about 1590% at pH 2, it was determined as 7046% at pH 9. Each hydrogel showed non-Fickian type diffusion and excellent biocompatibility (> 0.94). The results suggested that the obtained pH-sensitive semi-IPN hydrogels with unique properties can be used as biomaterial, adsorbent, membrane, sensor component and so on.