Synthesis of poly(vinyl alcohol)-magnetite ferrogel obtained by freezing-thawing technique

Polymer gels are crosslinked polymer networks swollen by a fluid. If magnetic particles either as powder or dispersed in a magnetic fluid are introduced into the gel then the system becomes sensitive to external magnetic fields and the resulting material is called ferrogel. The polyvinyl alcohol (PVA)-magnetite ferrogels system has properties that are attractive for artificial muscles and drug delivery systems for biomedical applications. This work investigates the synthesis and characterization of a ferrogel obtained by freezing-thawing cycles. PVA (MW 89,000-98,000, degree of hydrolyzation: 99 mol%) and magnetite nanoparticles (similar to 12 nm) obtained by chemical coprecipitation were used as raw materials. The PVA -magnetite ferrogels were prepared by subjecting a PVA/DMSO/magnetite solution (2 g/30 ml/0.2 g) to freeze (+ 25 degrees C)/thaw (+ 25 degrees C) cycles. The resulting ferrogel was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and vibration sample magnetometry (VSM). The magnetic particles inside the PVA matrix formed agglomerates with average size similar to 58 nm. All the ferrogels showed superparamagnetic behavior with maximum magnetization of 0.6 emu/g. (C) 2008 Elsevier B.V. All rights reserved.