Nanocomposite hydrogels based on iota - carrageenan and maghemite : morphological, thermal and magnetic properties.

The objective of this work was to prepare and characterize magnetic hydrogels based on iota-carrageenan, a polysaccharide obtained from biomass (Rodophyceae algae), containing maghemite (c-Fe2O3) nanoparticles. The morphological, thermal and magnetic properties of the hydrogels were evaluated, as well as the influence of the crosslinking agent (CaCl2) at different concentrations (0.3 mol L_1 and 0.5 mol L_1) on the hydrogels? properties. The samples were characterized by scanning and transmission electron microscopy, vibrating sample magnetometry, thermogravimetry, Fourier-transform infrared spectroscopy and M?ssbauer spectroscopy. The swelling degree of the hydrogels was also determined. The results showed that the synthesized magnetic material was mostly composed of c-Fe2O3 and presented ferrimagnetic behavior. The hydrogels had spherical morphology and particle size in the range of 710 lm. The TEM images proved the magnetic particles had nanometric size. The hydrogels had good thermal stability and swelling degree in water of around 55%. Both the magnetic nanoparticles and crosslinking agent (Ca2+) were well distributed on the surface of the hydrogels. The samples responded to the stimulus of a magnet