Multifunctional Hydrogels Fabricated By Nanozyme Initiated Polymerization

Nanozymes are nanomaterials with nanometer size（1-100 nm）and enzymatic catalytic properties.Iron oxide nanoparticles（Fe₃O₄NPs）was demonstrated to have own intrinsic catalytic activity,similar to HRP,without modifying any catalytic groups on their surface.But little attention has been paid to Fe₃O₄NPs-mediated polymerization.Compared with natural enzymes,Fe₃O₄NPs have the advantages of low production cost,stable catalytic properties,strong tolerance to the external environment,adjustable mimic catalytic activity,and magnetic response property.Therefore,it is desirable that Fe₃O₄NPs as enzyme mimics is explored to prepare magnetic hydrogels.The specific research contents of this thesis are as follows:1.Fabrication of multifunctional magnetic hydrogels（MMHs）by radical polymerization with Fe₃O₄NPs/H₂O₂as the initiation system.Enzymatic polymerization is widely used in fabrication of hydrogels due to its high biocompatibility and controllability.However,it usually suffers from the destabilization of enzymes under hard conditions and the requirement of diketones substrates to fulfill radical polymerization.Herein,multifunctional magnetic hydrogels（MMHs）are constructed in the presence of hydrogen peroxide（H₂O₂）by iron oxide nanoparticles（Fe₃O₄NPs）-mediated radical polymerization.In comparison with the natural enzyme initiation systems,Fe₃O₄NPs/H₂O₂system can initiate the polymerization of polyethylene glycol diacrylate instantaneously at ambient temperature without substrate,and can display higher catalytic activity under acidic conditions.The resultant magnetic composites have multifunctionality of the integration of magnetism,superwetting,and photothermal responsiveness,as well as the catalytic activity of a mimic enzyme,achieving effective rapid separation of oil-in-water emulsions and fast degradation of organic dye with good recyclability.2.Fabrication of magnetic hydrogels containing carboxyl groups by radical polymerization with Fe₃O₄@PDA/H₂O₂as the initiation system.In the first part,the inhomogeneous distribution of Fe₃O₄NPs was found in the obtained hydrogels.In this part,we adopted polydopamine（PDA）to improve the dispersity of Fe₃O₄NPs,and fabricated magnetic hydrogels containing carboxyl groups by Fe₃O₄@PDA mediated radical polymerization.First,dopamine,which can self-polymerize into polydopamine（PDA）,was coated on the surface of iron oxide nanoparticles（Fe₃O₄NPs）;Degradation of methylene blue proved that Fe₃O₄@PDA composites had similar HRP mimic property compared to bare Fe₃O₄NPs.Second,magnetic hydrogels containing carboxyl groups were designed by using Fe₃O₄@PDA/H₂O₂as the initiation system,PEGDA as crosslinker,and itaconic acid（IA）as functional monomer.According to scanning electronic microscope（SEM）images,Fe₃O₄@PDA composites were well dispersed in the obtained hydrogels in comparison with bare Fe₃O₄NPs.Third,the obtained hydrogels were used for treatment of complex oil-in-water emulsions in a preliminary study.Only driven by gravity,Fe₃O₄@PDA@poly（PEGDA-IA）magnetic hydrogels exhibited one step rapid and high efficient removal of dye molecules and demulsification of complex oil-in-water emulsions containing methylene blue.