Structural analysis of magnetic nanocomposites based on chitosan

Abstract

This work investigates the structure and magnetic properties of chitosan based films with different contents of magnetic nanoparticles (MNPs) of around 10 nm as well as the effects of the addition of glycerol as plasticizer. Synthesized MNPs were dispersed in the chitosan film forming solution by ultrasonication and then composite films were obtained by casting. From the morphological analysis, a bimodal distribution of clusters was detected; the larger ones seem to be present mostly in the plasticized samples. Regarding the mechanical behavior of the samples, for the non-plasticized samples the outstanding increase in modulus and strength with the increasing content of MNP was explained by a strong interfacial adhesion and very good particles dispersion into the chitosan matrix. This fact was also supported by the model applyed to the strength as a function of the volume fraction of MNP. Regarding magnetic properties, all nanocomposite films evidenced systems with particles of strong dipolar interactions that lead to blocking and irreversibility temperatures close to room temperature (RT). Even though the isothermal magnetization results showed that the particles in the nanocomposite films behave as super-paramagnetic at the highest analyzed temperature (RT). Langevin model as well as FESEM and SAXS analysis supported the hypothesis that the formation of aggregates with different features dominates the magnetic response through collective behavior, mainly in the plasticized films.