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Preparation and Characterization of Magnetic Nanocomposite Hydrogels

Author: XiaMengGe
Tutor: ZhuMeiFang
School: Donghua University
Course: Materials Science
Keywords: Nanocomposite hydrogel Magnetic construction In-situ chemical co-precipitation High magnetic content microsphere Photo-initiation
CLC: TB383.1
Type: Master's thesis
Year: 2012
Downloads: 59
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Abstract


In recent years, two different types of hydrogels, conventional chemically cross-linked hydrogels (OR gels) and nanocomposite hydrogels (NC gels) have been widely investigated. NC gels are composed of a unique organic/inorganic (clay) network, the inorganic clay acts as a multifunctional crosslinker in place of an organic cross-linker (MBA) as used in OR gels. Properties of NC gels, such as extraordinary mechanical properties, optical transparency, swelling behavior and biocompatibility are almost proportional to the clay content. NC gels have good comprehensive performance, and exhibit a clear volume phase transition in response to external stimuli such as temperature, pH and solvent composition. However, the reports related to response to external stimuli such as light-sensitive, electric-sensitive and magnetic-sensitive are very rare. This article will resolve the difficult problem for combining high mechanical properties with magnetic designing in the hydrogels, by introducing Fe3O4 nanoparticles into the gel network, and prepared the magnetic hydrogels successfully.(1) To combine high mechanical properties hydrogels with magnetic response, novel magnetic hydrogels (SAM gels) was prepared by embedding magnetic nanoparticles into polyacrylamide (PAAm) based NC gels via in-situ chemical co-precipitation method. Fe3O4 nanoparticles (diameter 60nm) were adsorbed on the PAAm chains, and homodispersed in NC gels network as confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). In addition, the saturation magnetization (Ms) of SAM hydrogels increased with increasing the concentration of iron ions, AAm or decreasing the concentration of inorganic clay. Futhermore, it is revealed that the role of non-covalent bonds of Fe3O4 nanoparticles and the PAAm chains network make the SAM hydrogels exhibit excellent magnetic properties, and their magnetic properties can be regulated and controlled by the concentration of the monomer, the crosslinker or iron ions.(2) In order to overcome single magnetic response of SAM hydrogels, novel magnetic hydrogels (SNM gels) was prepared by embedding magnetic nanoparticles into poly(N-isopropyl acrylamide) (PNIPA, coil-to-globule transition chain) based NC gels via in-situ chemical co-precipitation method. Fe3O4 nanoparticles (diameter 50nm) were adsorbed on the PNIPA hydrogels chain, and homodispersed in NC gels network as confirmed by SEM and TEM. In addition, the Ms of SNM hydrogels increased with increasing the concentration of iron ions, NIPA or decreasing the concentration of inorganic clay. Furthermore, it is revealed that the role of non-covalent bonds of Fe3O4 nanoparticles and the PNIPA chains network make the SNM hydrogels exhibited excellent magnetic properties, and their magnetic properties can be regulated and controlled by the concentration of monomer, crosslinker or iron ions.(3) Normally the designing of magnetic NC gels will take a long time, the Ms and swelling behavior of this kind hydrogel is usually difficult to control precisely. To solve this problem, we have firstly, embedded 15nm Fe3O4 nanoparticles into PS microspheres by miniemulsion polymerization, then grafted photoinitiator HMEM on the surface of PS microspheres, this method successfully produced Fe3O4/PS/HMEM hybrid microspheres with UV irradiation activity, the diameter of hybrid microspheres was about 105nm and can be homodispersed in water. In addition, the Ms of microspheres was 41.89 emu/g, the mass fraction of hybrid microspheres was 50wt% by TGA. This novel Fe3O4/PS/HMEM hybrid microspheres can be used as a multifunctional crosslinker with magnetic response, and photoinitiated activity. Moreover, the Ms of magnetic hydrogel is controllable.(4) In the presence of Fe3O4/PS/HMEM microspheres as a multifunctional crosslinker and AAm as monemer, we prepared homogeneous three dimensional network structure of magnetic nanocomposite hydrogels (MAT gels) by UV irradiation in-situ polymerization. Systematic study was carried on the effect of illumination time, Fe3O4/PS/HMEM concentration, and monomer concentration on the morphology, dynamic mechanical properties, and swelling behavior of MAT hydrogels.Embedding Fe3O4 nanoparticles into the hydrogels network to prepare magnetic nanocomposite hydrogels has advantages of controllable polymerization process, short forming time and low cost. This method provides a new way to prepare magnetic hydrogels, and design the extraordinary mechanical properties hydrogels with magnetic stimuli. Futhermore, it expand the application of magnetic hydrogels in smart magnetic sensing switch, drug targeting release, biomedical and chemical machinery field.

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