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.
