Preparation And Characterization Of Carboxymethyl Chitosan And Its Magnetic Composite Microspheres

Magnetic polymer microspheres refer to a kind of composite microspheres, whichare made of inorganic magnetic nanoparticles and organic polymer materials. Magneticpolymer microspheres, due to their special properties of polymer microspheres andconcurrently magnetic response, have been widely applied to various aspects inbiotechnology field as novel functional materials. In the paper, well water-solublecarboxymethyl chitosan was prepared by the modification of chitosan, andcarboxymethyl chitosan magnetic composite microspheres were obtained by combinginorganic magnetic nanoparticles with carboxymethyl chitosan.Carboxymethyl chitosan was obtained in the presence of alkali using chloroaceticacid and chitosan as the raw materials. The products were characterized for DS, averagemolecular weight, IR spectroscopy and X-ray diffraction, respectively. The influence ofthe amounts of sodium hydroxide and chloroacetic acid, the volume of isopropylalcohol, reaction temperature, etc., on substitution degree, the yield, and intrinsicviscosity were discussed, respectively. The results showed that the optimal conditions ofproducing carboxymethyl chitosan were aquaired as: the amount of chitosan5g, theamounts of sodium hydroxide and chloroacetic acid were both of13g, and volume ofisopropyl alcohol25mL, reaction temperature30℃, reaction time3h. The IR spectraindicated that the product was N,O-CMC. The X-ray diffraction of samples showed thatthe typical diffraction peaks of chitosan are greatly weakened after carboxymethylation.The MgFe2O4and NiFe2O4particles were synthesised using Fe(NO3)3·9H2O andMg(NO3)2·6H2O/Ni(NO3)2·6H2O as raw materials by the method of sol-gel. NiFe2O4was prepared by hydrothermal method, using Fe(NO3)3·9H2O and Ni(NO3)2·6H2O asraw materials and NH3·H2O to adjust the pH value of the system. The functionalgroups, magnetism, crystal structure, thermal stability, and morphology of the products,were characterized by fourier transform infrared spectrometer, alternating gradientmagnetometer, X-ray diffraction, environmental scanning electron microscope, etc.The results showed that the MgFe2O4and NiFe2O4particles prepared by sol-gelmethod had cubic spinel structure, uniform size, and saturation magnetization of31.52and43.3emu/g, respectively. However, the NiFe2O4particles, prepared byhydrothermal method, exhibited perfect crystal structure, uniform size, smaller particlesize and saturation magnetization being43.1emu/g. Magnetic polymer microspheres have been successfully prepared by emulsioncrosslinking method using carboxymethyl chitosan as matrix material andglutaraldehyde as a crosslinking agent. When O-carboxymethyl chitosan was used asmatrix material, the optimal conditions of producing the microspheres was as follows:the concentration of O-CMC was2%, the dosage of Span80as well as Tween80was1.5g,4mL of glutaraldehyde, the reaction temperature was70℃, and the reaction timewas3h. For N,O-carboxymethyl chitosan, the optimal conditions were that N,O-CMCconcentration was4%, dosage of Span80and Tween80was2.5g,6mL of crosslinkingagent, the reaction temperature was70℃, and the reaction time was3h. The studyshowed that O-carboxymethyl chitosan MgFe2O4microspheres prepared werespherical in shape, had good dispersivity and smooth surface. O-carboxymethylchitosan NiFe2O4microspheres synthesized were spherical, their surface is rough, withgood dispersion, and no adhesion phenomenon. The saturation magnetization ofO-carboxymethyl chitosan MgFe2O4, NiFe2O4(sol-gel method) and NiFe2O4(hydrothermal method) were10.35,17.6and18.6emu/g, respectively.N,O-carboxymethyl chitosan MgFe2O4microspheres prepared had regular sphericalshape, smooth surface and uniform size. N,O-carboxymethyl chitosan NiFe2O4(sol-gelmethod) microspheres had good spherical strcture and smooth surface, but there wereadhesions between the microspheres, and wide diameter distribution.N,O-carboxymethyl chitosan NiFe2O4(hydrothermal method) microspheres showedgood sphericity, larger particle size, not coarse surface. Their saturation magnetizationswere11.9,19.7and14.3emu/g, respectively.