Preparation And Characterization Of Magnetic Thermo-sensitive Carbon Sphere

Carbon spheres(CSs), Which have unique structure and excellent physicaland chemical properties, can be applied to many fields，like adsorbent material,catalyst supports, electrode materials and drug delivery and so on. Through thefunction of CSs, introduce some special material, Which has some specialproperties, such as magnetism, electrical and optical, etc., to expand the scope ofapplication of the carbon spheres. This parper introduce magnetic andtemperature-sensitive material into the carbon spheres, making compositeshaving a magnetic and temperature dual response. That expected to havepotential applications in biomedicine, targeting areas such as controlled drugrelease.In this paper, Magnetic carbon spheres (MCSs) were prepared byhydrothermal method using ferrous gluconate, glucose and hexadecyl trimethylammonium bromide (CTAB) as raw materials. MCSs were oxidized by mixtureacids to introduce hydroxyl on the surfure, then though the-OH dehydration condensation with silanol group of silane coupling agent KH-570to introducedouble bonds onto the surface of MCS. On this basis, the temperature-sensitivepolymer poly N-isopropyl acrylamide (PNIPAM) grafted onto the surface ofMCSs to form a coating layer，though the action of initiator and crosslinkingagent.The samples were characterized by field emission scanning electronmicroscopy, fourier transformation infrared spectrometry, thermogravimetric,differential scanning calorimetry, vibrating sample magnetometer and so on. Theresults are as follows:1. Using green resources glucose as the carbon source and ferrousgluconate with similar structure as iron source, at mild conditions hydrothermalsystem to prepare magnetic carbon spheres(MCSs) with uniform particle size,morphology structured, rich surface oxygen functional groups and magnetic.The effect of reactant precursor concentration, reaction temperature and time onthe morphology and structure of MCSs were investigated. The best preparationconditions were: glucose concentration of0.1mol/L, ferrous gluconate of0.1g, CTAB of0.4g, reaction temperature170℃, reaction time12h. At thesame time, the formation mechanism of MCSs has discussed.2. On the basis of oxidation and silylation MCSs，with NIPAM astemperature-sensitive monomer, KPS as initiator, MBA as crosslinking agent tosuccessfully grafted temperature sensitive polymer on MCSs surface. Theeffects of monomer, initiator and crosslinking agent dosage on grafting,morphology and properties were discussed. Best graft polymerization conditions was: each0.2g silanated MCSs was added0.6g NIPAM, initiator KPS1%bymass of the monomer, MBA crosslinker monomer15%by mass of the monomer.Analysis demonstrated that the resulting product have magnetic andtemperature-sensitive.3. Though drug loading and release experiment with aspirin to test theperformance of PNIPAM-MCSs. Sustained-release experiment results showedthat with time delayed release of the drug increases and eventually reachequilibrium. Because when the temperature is higher than the LCST,temperature-sensitive polymer shell shrinking, so the release of the drug at45℃is higher then25℃.