Study On The Preparation And Properties Of Antibacterial Materials With Mutiple Strategies

In response to the wide spreading of bacterial disease and the microbial threats on human health caused by microbial contamination,much works have been devoted to prepare antibacterial materials which with high antimicrobial efficiency and broad-spectrum antimicrobial property.Among them,it is a very important method to prepare highly effective antibacterial material by combining different antibacterial agens into asingle system.In this dissertation,the quaternary ammonium salt/N-halamine composites and quaternary ammonium salt/sparingly soluble silver salt composites were synthesized.With increasing occurrences of microbial contamination of environment and bacterial resistance caused by the abscission of antibacterial coating or abuse of antibacterial material,powerful antibacterial material with great stability and recoverability has become necessary.On this basis a series of antibacterial materials have been prepared and multiple test methods were used to characterize their structures and antibacterial properties,and then,analyze the relations among them.The main research cotents and conclusions werer summarized as follows:The grafting copolymerization of suitable monomer onto cellulose is a commonly used flexible technique for cellulose fiber modification.The techniques of graft polymerization and in situ precipitation were used to fabricate the AgCl containing quaternary ammonium salt polymer grafted cellulose fibers?C-g-PVD@AgCl?.The research results showed that the size and content of the immobilized AgCl particles can be influenced by the Ag⁺/Cl^-molar ratio.When the molar ratio of added silver ion to polymer chloride ion were 1:1 and 2:1,the mean size of the AgCl particles on the modified cellulose fibers was 116 nm and 162 nm,and the AgCl content?wt%?was 17.5%and 8.7%,respectively.The two-step graft copolymerization and quaternization method were used to prepare the quaternarized N-halamine grafted cellulose fibers?C-g-PQNH?.Meanwhile,the effects of concentration of monomer,concentration of initiator and reaction temperature on the grafting ratio of monomer were investigated.Moreover,the active chlorine content of C-g-PQNH was determined by iodometric/thiosulfate titration method.The result showed that most of the active chlorine was intensively distributed on the cellulose surface,while the concentration of free chlorine kept low in the solution.A series of antibacterial magnetic nanomaterials were prepared by using the Fe₃O₄ nanoparticles assubstrate.The obtaind antibacterial magnetic nanomaterials could provide larger surface area.Meanwhile,due to their good magnetic recovery capability,magnetic nanoparticles could be easily removed without any contamination.Two kinds of new polymers quaternized N-halamine based cationic polymer and cationic polymer/silver bromide composites were synthesized.And both of them were applied to prepare quaternized N-halamine based cationic polymer modified magnetic nanoparticles?MNPs-CPQN?and cationic polymer/silver bromide composites modified magnetic nanoparticles?MNPs-CP@AgBr?via the simple and mild ligand-exchange reaction,respectively.The layer-by-layer electrostatic self-assembly was a simple,non-toxic,versatile and green method for modification of the nanoparticles,it had been applied to prepare the antibacterial magnetic nanomaterial for the first time in our work.With this method,the sodium citrate anion and quaternized N-halamine cationic polymer multilayer films coated magnetic nanoparticles?MNPs-AQn-Cl?were successfully obtained.The properties of MNPs-AQn-Cl were characterized by series of measurements such as FT-IR,TG,Zeta potential,DLS and TEM.It was proved that,when the nanoparticle concentration and electrolytes concentration were 0.5 mg/mL and the pH value of the solution was 3,the obtained magnetic nanomaterial had good dispersion,strong stability and super paramagnetism.The antibacterial activities of quaternary ammonium salt/sparingly soluble silver salt composite materials?MNPs-CP@AgBr and C-g-PVD@AgCl?were investigated with Kirby-Bauer test and kinetic test,E.coli and S.aureus were selected as experimental strains.The test results showed that both of these two materials had great antibacterial activities,while the antimicrobial activity of MNPs-CP@AgBr was stronger.The mean diameter of the immobilized AgBr nanoparticles was about 27.8 nm,which was smaller than that of the AgCl nanoparticles?116 nm?on the cellulose surface.Therefore,the MNPs-CP@AgBr exerted stronger antibacterial activity,due to their higher specific surface area and Ag⁺ release rate.The antibacterial properties of quaternary ammonium salt/N-halamine composite materials against Gram negative E.coli and Gram positive S.aureus were investigated by the antibacterial kinetic test.After exposure to samples,the bacterias' activities and morphology were investigated by TTC staining method and SEM.Based on the test results,the antibacterial mechanisms of these composites were explored.The results showed that while the negatively charged bacterial cells were captured by the composite materials,the oxidative chlorine could be transferred to the bacteria cell membrane efficiently.Therefore,the quaternarized N-halamine composite materials displayed excellent bactericidal performance.The structures of the magnetic nanocomposites were analyzed which were prepared by ligand-exchange reaction and layer-by-layer electrostatic self-assembly and their antibacterial capabilities were also compared.The stronger antibacterial activity of MNPs-CPQN was due to the greater freedom of movement of the polymer chain on the nanomaterial surface and their larger contact area with bacterial wall.