A Fe3O4 nanoparticles-stabilized Pickering emulsion

which is a kind of emulsion stabilized by solid particles instead of traditional surfactants

was used as a cross-linking agent.And a novel composite hydrogel was prepared by initiating monomer acrylamide in the appropriate condition.The structure of nanoparticles and composite hydrogel was characterized through X-ray diffraction (XRD) measurements

and field-emission scanning electron microscope (SEM)

respectively.Moreover

the properties of hydrogels were studied by swelling ability measurements and swelling kinetics analysis

mechanical test and magnetic response test.It can be found from SEM images that the TPM droplet acted as a cross-linking agent in the reactive system and distributed in the hydrogel network orderly.Swelling test indicated that the composite hydrogels had excellent swelling capacity in comparison to conventional hydrogels

and even could swell to about 100 times of their dry weight.And swelling kinetics analysis results showed that the swelling process of the composite hydrogels did not follow the Fickian swelling kinetics model.The mechanical test results showed that the composite hydrogel exhibited outstanding mechanical performance.The composite hydrogels showed a strength of 150 kPa and high elongation at break of 300%.Moreover

the composite hydrogels could return to original state after stretching to several times of its original length quickly and even could make into a knot without damage.Magnetic response test results indicated that the composite hydrogels exhibited a clear magnetic response.