Magnetic and pH-responsive starch-g-poly(acrylic acid-co-acrylamide)/graphene oxide superabsorbent nanocomposites: One-pot synthesis, characterization, and swelling behavior

A series of dual stimuli-responsive starch-based superabsorbent nanocomposites (SANCs) were prepared by a facile one-pot strategy. The SANCs were synthesized via the simultaneous formation of magnetic iron oxide nanoparticles (MIONs) and in situ radical solution polymerization of superabsorbents based on poly(acrylic acid-co-acryl amide) grafted onto starch backbones in the presence of graphene oxide (GO) nano sheets. The chemical structure, morphology, and phase composition of the obtained SANCs were characterized by using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD), UV-Vis spectroscopy, thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The swelling behaviors of the SANCs showed that the incorporation of GO nanoplates in the polymeric network leads to a remarkable improvement in the swelling capacity of the SANCs. These results may be attributed to the sheet-like structure, high surface area, presence of hydrophilic oxygen-containing groups, and multifunctional crosslinking by GO. Furthermore, the SNACs displayed high water absorption capacity under an external magnetic field due to the presence of MIONs in the polymer network. Absorbance of SNACs was also examined in solutions with various pH. The SNACs exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 3 and 9. The results indicate that the synthesized SNACs may be useful for potential applications as smart and superabsorbent nanocomposites for magnetically controlled drug release systems, magnetic-sensitive sensors, and pseudo-muscular actuators.