Synthesis And Modification Of Magnetic Nanoparticles Based On Metal-free Photocatalysis ATRP

Magnetic nanoparticles(especially Fe3O4 nanoparticles)are widely used in magnetic resonance imaging,tumor hyperthermia,catalysis and adsorption due to their unique superparamagnetism and high surface activity.However,the high surface activity of the nanoparticles also makes them susceptible to agglomeration and oxidation.For this reason,the combination of polymers and inorganic nanoparticles to prepare the polymer/inorganic hybrid particles can not only protect the nanoparticles,but also achieve multi-functionalization of nanoparticles.Atom transfer radical polymerization(ATRP)is a highly efficient polymerization method for the active and controllable synthesis of well-defined polymers,which can control the composition,molecular weight,molecular weight distribution and topology of polymers excellently.Therefore,it is widely used in the field of preparation and modification of nanoparticles.However,the use of a large amount of transition metal catalysts by conventional ATRP may cause discoloration or contamination of the final product,which is not conducive to further applications.To avoid this problem,this article used the emerging metal-free photocatalysis ATRP to modify the prepared magnetic nanoparticles and to prepare the star-like block copolymers which are used as nanoreactors to synthesize magnetic nanoparticles,thus avoiding the problem of residual transition metal contamination.In this paper,the application of metal-free photocatalysis ATRP in the field of preparation and modification of magnetic nanoparticles was explored.The details are as follows:1.The spherical magnetic nanoparticle clusters with diameters of about 100 nm were prepared by solvothermal method,and the protective SiO2 shell was coated on the surface,then the initiating sites were modified on the surface of the nanoparticles by amidation reactions.Magnetic nanoparticles with surface-modified hydrophobic PtBA were prepared by initiating the polymerization of tBA monomers on the surface of nanoparticles using metal-free photocatalysis ATRP.After hydrolysising,hydrophilic PAA-modified magnetic nanoparticles were obtained.Through various characterizations,it was proved that PtBA/PAA was successfully modified on the surface of nanoparticles by metal-free photocatalysis ATRP,which made magnetic nanoparticles hydrophobic/hydrophilic.The relative amount of surface polymers increased as the reaction time increased.The superparamagnetism properties of the magnetic nanoparticles didn't change before and after modification.2.Spherical magnetic nanoparticles with diameters of 8 nm and surface ligands of oleic acid were prepared by thermal decomposition.Then ATRP initiating sites on the surface of nanoparticles were produced by ligand exchange and amidation reactions.Magnetic nanoparticles modified with PDMAEMA were prepared by metal-free photocatalysis ATRP on the surface of nanoparticles with DMAEMA as monomers.Through various characterizations,it was proved that PDMAEMA was successfully modified on the surface of nanoparticles by metal-free photocatalysis ATRP.The magnetic nanoparticles had superparamagnetism before and after modification,and the magnetic nanoparticles had pH response characteristics after polymer modification,which can change their properties with the changing of environmental pH.3.A series of different molecular weight star-like block copolymers?-CD-PtBA-b-PBA were prepared by metal-free photocatalysis ATRP and further hydrolyzed to obtain the star-like block copolymers ?-CD-PAA-b-PBA.It was confirmed by various characterizations that the molecular weight of each block increased with the increase of the reaction time and the molecular weight distribution was narrow.Three kinds of star-like block copolymers ?-CD-PAA-b-PBA with different molecular weight of PAA were used as nanoreactors to synthesize spherical magnetic nanoparticles with uniform size and superparamagnetic.The diameters were around 4 nm,10 nm and 14 nm,respectively.