Elsevier

European Polymer Journal

Volume 72, November 2015, Pages 202-211
European Polymer Journal

Macromolecular Nanotechnology
Magnetic characterization of chitosan–magnetite nanocomposite films

https://doi.org/10.1016/j.eurpolymj.2015.09.014Get rights and content

Highlights

  • Chitosan films were loaded with nanomagnetite precipitated “in situ“.

  • Morphology and magnetic behavior are greatly affected by nanoparticles content.

  • Composite films containing more than 2 wt.% magnetite exhibit magnetic behavior.

  • Plasticized films present two blocking temperatures due to bimodal particle sizes.

  • TEM and SAXS measurements corroborate the results of magnetic characterization.

Abstract

Magnetic nanocomposites using chitosan as a matrix and magnetite nanoparticles (MNP) generated “in situ” were prepared and magnetically characterized. The content of nanoparticles on the composites was varied from 2 to 10 wt.% and their effects, as well as the addition of 30 wt.% of glycerol as plasticizer in the formulation, were analyzed. The magnetization properties were evaluated using the zero field cooling/field cooling (ZFC/FC) measurements and magnetization loops obtained at different temperatures. The results showed that magnetization at high field (20 KOe) and coercivity increase with magnetite content. Super-paramagnetic behavior was observed for all non-plasticized samples with exception of the film with 2 wt.% of magnetite. Glycerol affected significantly the composite magnetization values and the magnetic interactions between particles, which are reflected in the blocking and irreversibility temperatures of the different systems. Moreover, the size of the precipitated magnetic nanoparticles depends on their concentration as well as on the addition of plasticizer to the formulation, as was corroborated by TEM and SAXS measurements.

Introduction

Magnetic nanocomposites from polymeric matrix have attracted scientific interest due to the potential applications in diverse areas such as biomedicine, biotechnology and materials science among others. If the polymer matrix is a biopolymer, several advantages are incorporated to the obtained material, like biodegradability, biocompatibility and use of renewable resources with the consequent decrease in the environmental impact.

Among a variety of biopolymers, chitosan presents excellent film forming capability, high mechanical strength, biocompatibility, non-toxicity, bactericide effect, high permeability toward water, susceptibility to chemical modifications, cost-effectiveness, etc. [1], [2]. Chitosan is a natural cationic polysaccharide obtained from N-deacetylation of chitin, a major component of crustacean shells and fungal biomass and it is readily available from seafood processing wastes [2], [3]. It is widely used in tissue engineering and magneto hyperthermia applications [4] but also, because of its high amino content, it has been found to possess good sorption capacity for many heavy metal ions through complexation with the amine groups and has been widely used as biosorbent for removing various metal ions from wastewater [3].

On the other hand, colloidal inorganic nanometer-sized particles or nanocrystals have proved to be useful as building blocks for the development of nanomaterials and biomaterials in nanoscience and biotechnology. Their unique physical and optical properties are attributed to nanoscale phenomena [5]. Superparamagnetic iron oxide including magnetite (Fe3O4) and maghemite (γFe2O3) have great potential for various biomedical and biotechnological applications because of their chemical stability, biodegradability and low toxicity [6], [7]. They include magnetic resonance imaging, contrast enhancement, targeted drug delivery, hyperthermia, catalysis, biological separation, biosensors, and diagnostic medical devices [8], [9], [10].

Although magnetic nanoparticles have been synthesized and studied from several years, its incorporation to biopolymers to generate functional nanocomposites is a relatively new area of study. The dispersion of the particles in the polymeric matrix can strongly influence the magnetic properties of the films and thus, the study of the actual magnetic response of final materials is of vital importance to define potential applications. Thereby, considering the previous work about the synthesis and characterization (physical, thermal and mechanical) of chitosan/magnetite nanocomposites [11], the aim of this work is to analyze specifically, the magnetic properties of nanocomposite films made from chitosan (with and without glycerol added as plasticizer) with different content of magnetic nanoparticles.

Section snippets

Materials

Chitosan (CS) (degree of deacetylation 98%, Mv = 1.61 × 105 g/mol), supplied by PARAFARM, Mar del Plata, Argentina was used as received. Glycerol (gly) purchased from SIGMA Aldrich was used as plasticizer. Ferric chloride (FeCl3·6H2O), ferric sulfate (FeSO4·7H2O) and sodium hydroxide were obtained from Aldrich.

Preparation of composite films

The films were prepared by casting, some of them containing glycerol in a wt. ratio glycerol/chitosan = 0.3. Chitosan solutions (2% wt/v) were prepared in aqueous acetic acid (1% v/v), by

Magnetic behavior of non-plasticized films

Typically, the magnetic nanocomposite films of polymeric matrix have at least two different contributions that determine the magnetic properties of the material. One coming from the diamagnetic matrix and the other one from the super-paramagnetic nanoparticles included into it. Under the influence of an external magnetic field, diamagnetic materials generate small currents that oppose to the external field. This is the behavior found in the present work for the neat chitosan film and for the

Conclusions

Complex chitosan-plasticized and non-plasticized films loaded with magnetite nanoparticles precipitated “in situ” were successfully obtained by solvent-casting. Nanocomposite films with nanomagnetite concentrations higher than 2 wt.% exhibit super-paramagnetic behavior, which in turn depends strongly on the magnetic particles content and size and on the presence of plasticizer. In general low concentrated samples present a low blocking temperature, which was related with a small particle or

Acknowledgements

The authors gratefully acknowledge the financial support provided by the National Research Council (CONICET, Grant PIP 0637), the Science and Technology National Promotion Agency (ANPCyT, Grant PICT-2013-1535) and the National University of Mar del Plata (Project # 15/G430) from Argentina. The work at UNICAMP was supported by FAPESP (2011/1234-6) and CNPq (Project # 506394/2013-1) from Brazil. Small-angle X-ray scattering data were acquired at beamline D1B-SAXS1 (17036) at Brazilian Synchrotron

References (29)

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