Preparation And Antibacterial Property Of The Materials In-situ Grafted With Quaternary Ammonium Salts

Bacteria is easy to adhere to sufaces of materials,which can cause the biological contamination and the biological corrosion of the materials.Therefore,the surface antibacterial modification of materials has been paid more and more attentions.The commonly used methods for antibacterial modification of materials include surface antimicrobial coating,physical incorporation of antimicrobials into the polymers,and surface chemical grafting of antibacterial components through covalent bonding.Although the surface coating and physical blending technique are convienient,the release rate of antimicrobial ingredients will gradually decrease with time and lead to bacterial resistance.However,surface chemical grafting of antibacterial agents might be expected to obtain long-term and stable antibacterial property.Compared with small organic molecules and inorganic antibacterial agents,polymeric antibacterial materials have more active functional groups,good chemical stability without residual toxicity.Therefore,it is of great significance to graft polymeric antibacterial agents onto the surface of the materials by a simple method.In this thesis,the problem of unstable and long-term antimicrobial properties of antimicrobial components after coating and physical addition of antimicrobial components was studied.Polymeric quaternary ammonium salts grafted carbon nanotubes and PP fibers were prepared by different ways such as in situ quaternization and photoinitiating free radical polymerization.The effects of the dose and molecular weight of quaternary ammonium precursors,the addition amount of polymerization monomer and initiator on the surface morphology and structure of composites were discussed.The antibacterial properties of as-prepared materials were also studied.1.The polyethyleneimine was introduced onto the surface of acidified CNTs and then quaternized to obtain polymeric quaternary ammonium salt grafted CNTs(QPEI@CNTs).The QPEI@CNTs/PLA composite films were prepared by solvent evaporation method.The results show that the introduction of quaternary ammonium groups significantly increased the antimicrobial property of CNTs against Gram-negative bacteria and Gram-positive bacteria strains,and improved the dispersibility of CNTs in the PLA matrix.When the molecular weight of PEI is 70,000 with the ratio of 3:1 to carbon nanotubes,the minimum inhibitory concentration(MIC)can reach 20-50 mg/L(Escherichia coli,E.coli)and 50-100 mg/L(Staphylococcus aureus,S.aureus).2.Small molecule quaternary ammonium methacryloyloxyethyl-benzyl-dimethyl ammonium chloride(MBDAC),induced by benzophenone,was introduced onto the surface of PP fibers by free radical polymerization over UV treatment(PMBDAC@PP).The results show that the hydrophilicity of PP fiber was improved since a large number of active functional groups was anchored to the surface of PMBDAC@PP fiber,and the large number of quaternary ammonium salt antibacterial groups also brought it with good antibacterial properties.The antibacterial rates of PMBDAC@PP fiber with 12.68%grafting amount against E.coli and S.aureus were over 99%.3.Polyacrylic acid was grafted onto the surface of PP fiber with the irradiation of UV and then the chitosan was grafted on the surface of the PP fiber by amidation reaction.After that,the PP fiber(QCH@PP-AA)was prepared by grafting quaternization of(2,3-epoxypropyl)trimethylammonium chloride(ETA)through ring-opening reaction to obtain surface grafted chitosan quaternary ammonium salt.It was found that the QCH@PP-AA fiber exhibited even better antibacterial activity against E.coli and S.aureus than PP fiber grafted with chitosan only(CH@PP-AA),and the antibacterial rates of QCH@PP-AA fiber were higher than 98%with 3.51%grafting amount.