Preparation Of Magnetic Spherical Polyelectrolyte Brush And Immobilized Silver Nanoparticles Research

The nano-effects of metal nanoparticles make them have unique physical and chemical properties,play an important role in the field of catalysis,and show very high catalytic activity and selectivity.Due to the thermodynamic instability of metal nanoparticles,it is extremely prone to migration and agglomeration,which requires a stable carrier for loading.Magnetic spherical polyelectrolyte brushes are suitable for the mounting of metal nanoparticles because of their easy recycling,good dispersion,large surface area,and stable performance.In the synthesis of polyelectrolyte brushes,Atom Transfer Radical Polymerization(ATRP)can produce polyelectrolyte brushes with controlled molecular weight and uniform molecular weight distribution.In addition,the swelling behavior of the polyelectrolyte brush in water directly affects the conformation of the polyelectrolyte brush system.The molecular field theory can be used to analyze the polyelectrolyte brush to obtain the conformation change law.In this paper,superparamagnetic iron tetroxide nanoparticles were synthesized by co-precipitation method,and then the surface of ferroferric oxide was coated with silica by the "St?ber method" to obtain magnetic silica microspheres.The surface of the silica microspheres was amination modified and grafted with initiator,and finally,an inorganic-organic composite magnetic spherical polyelectrolyte brush(PEB)was synthesized by atom transfer radical polymerization(ATRP)using methyl acrylate as the monomer.By controlling the polymerization reaction conditions(reaction temperature,monomer amount,reaction time)to explore the effect of reaction conditions on the degree of polymerization.The optimal reaction temperature was 90 ℃,the monomer addition was 6 m L,and the reaction time was 10 h.At the same time,dynamic light scattering(DLS)was used to characterize the particle size of the polyelectrolyte brush in the water phase under different conditions(temperature,p H)to explore the swelling characteristics of the brush.The results show that the polyelectrolyte brush swells with the increase of temperature and p H.The synthesized polyelectrolyte brush is used as a carrier,and the silver ion is reduced by diethanolamine under heating conditions to support the synthesis of polyelectrolyte brush-nano silver composite material(PEB-Ag).After sodium borohydride reduction of 4-nitrophenol,the classic catalytic reaction,the supported silver nanoparticles have good catalytic activity and stability.The first-order reaction kinetics is used to explore the influence of nano-silver content,graft molecular weight,temperature and PEB-Ag concentration in the brush on the reaction rate of the catalytic reaction.The activation energy of the reaction is 64.03 k J/mol calculated by the Arrhenius equation.In addition,using surface reaction kinetics to investigate the concentration of reactants and simple density functional theory analysis,the results show that the reduction of 4-nitrophenol by sodium borohydride catalyzed by the silver-loaded polyelectrolyte brush proceeds according to the Eley-Rideal mechanism.Finally,the molecular field theory is used to establish a spherical polyelectrolyte brush model,and the probability distribution of the brush conformation is calculated by the statistical thermodynamic method to expand and minimize the Helmholtz free energy simulation.A theoretical model was used to analyze the conformation of the polyelectrolyte brush,and the thickness of the polymer layer was used as the swelling index of the brush to judge the change trend of the swelling property of the brush with temperature,p H and graft density.Numerical calculation results show that the thickness of the polymer layer increases in varying degrees with the increase of temperature,p H and graft density.