The Preparation And Characterization Of Temperature Sensitive Hybrid Nanogels With Fe₃O₄ Nanoparticles

Magnetic nanogel is a kind of hybrid nanogel with magnetic property, which is composed of nanogel and inorganic magnetic particles. They can be classified into two kinds according to their structures. One is composed of magnetic core and nanogel shell; the other is composed of nanogel core and magnetic shell. Up to now, there are two ways to prepare magnetic nanogel. The first method employs nanogel as template for the preparation of magnetic nanogel. The second method employs magnetic nanoparticles as seeds for the preparation of magnetic nanogel. In the present work, these two methods were adopted to prepare magnetic nanogels which are composed of magnetic core and nanogel shell. The magnetic nanogels were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA).â‘ The preparation and characterization of (N-isopropylacrylamide-co-acrylic acid) (PNA) nanogel: A series of (PNA) nanogels with varying amount of the feeding AAc were prepared by precipitation polymerization. With the increasing content of the AAc, the size of nanogels increased from 100nm to 800 nm, characterized by dynamic light scattering (DLS). PNA nanogel is a kind of nanogel with dual sensitivity (temperature and pH-sensitive). The size of nanogels decreased with the increasing temperature. In a certain temperature (the volume phase transition temperature, VPTT), the size of nanogels decreased sharply. With the increasing content of the AAc in the copolymer nanogels, the VPTT of nanogels increased. The pH titration showed that the pKa of nanogels increased with the increasing content of the AAc in the copolymer nanogels. As the pH increased, the size of nanogels increased. This tendency is more obviously as the AAc content in the copolymer nanogels increased. In addition, as the ionic concentration in the nanogel dispersion increased, the size of nanogels decreased sharply at first and then reached equilibrium.â‘¡The preparation and characterization of magnetic nanogels using Fe₃O₄ nanoparticles as seeds: Fe₃O₄ nanoparticles were prepared by coprecipitation method and partial reduction precipitation method. Sodium dodecyl benzene sulfonate and sodium oleate were used to modify the iron oxide nanoparticles in the synthetic process, improved the stability of the Fe₃O₄ nanoparticles. Magnetic nanogels were prepared by using Fe₃O₄ nanoparticles as seeds. The size of magnetic nanogels was 200-300 nm characterized by dynamic light scattering (DLS). The Fe₃O₄ nanoparticles and magnetic nanogels prepared by coprecipitation method exhibited superparamagnetism. The saturation magnetization of magnetic nanogels is lower than Fe₃O₄ nanoparticles probably because of the nanogel shell.â‘¢The preparation and characterization of magnetic nanogels using PNA nanogels as templates: Magnetic nanogel was prepared by coprecipitation method and partial oxidation precipitation method. PNA nanogels was employed as templates. The size of magnetic nanogels was 300-900 nm characterized by dynamic light scattering (DLS). The magnetic nanogels prepared by coprecipitation method exhibited superparamagnetism. A linear correlation was observed between the saturation magnetization of magnetic nanogel and the Fe₃O₄ content in the magnetic nanogel. The Fe₃O₄ content in the magnetic nanogel also influenced the temperature sensitivity of magnetic nanogel. As the Fe₃O₄ content in the magnetic nanogel increased, the VPTT increased, and the temperature sensitivity was blocked if the Fe₃O₄ content in the magnetic nanogel is higher than a critical value.