Preparation and properties of thermo- and magneto responsive superabsorbent nanocomposite hydrogel

Abstract

Hydrogels are highly crosslinked polymer materials that are able to swell when immersed in aqueous solutions. Some hydrogels can be designed in such a way that they undergo some conformational changes in responsive to external stimuli such as temperature, pH, ionic strength, light, electrical signal and magnetic field etc. The hydrogels have been exploited in a wide variety of applications including drug delivery and tissue engineering, biosensors and microfluidic devices. Herein, we develop a novel strategy for combining thermo- and magneto-responsiveness into one hydrogel system. Specifically, as thermosensitive part of the hydrogel we used polyacrylamide, which was crosslinked with acrylic-functionalised silica coated magnetic nanoparticles to possess the magnetic responsiveness. Fe3O4 nanoparticles were synthesized and coated with silica, which provides the nanoparticles with a reactive surface for functionalization with −NH2 group through the silanation with 3-aminopropyl triethoxysilane. The −NH2 groups were then further functionalized by reacting with acrylic anhydride to generate magnetic nanoparticles containing acrylic group, which were finally crosslinked with polyacrylamide to give the desired nanocomposite hydrogel. The synthesized nanocomposite was characterized by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), energy dispersive x-ray (EDX), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) analysis. The synthesized nanocomposite hydrogel showed thermo-responsive swelling when dipped in water. Interestingly, we observed that a nanocomposite with a certain composition exhibit greater swelling ratio than that of bisacrylamide crosslinked polyacrylamide hydrogel. This swelling ratio decreased with the increase of magnetic crosslinker in the composite hydrogel. On the other hand, the assynthesized hydrogel showed magnetic behavior owing to the presence magnetite nanoparticles in the form of 3D crosslinker.The prepared nanocomposite hydrogel also exhibited nice self-healing properties due to the presence of Fe3O4 in the system.