Synthesis And Application Of Novel Immobilizing Pyridinium N-chloramine Precursors

In the recent decades,cotton fabrics and polyurethane(PU)has been extensively applied in medical devices and healthcare related field.However,these two substrate materials are good media for microorganism to survive and the consequent surface contamination of pathogenic bacteria have greatly threatened people's health and life.N-chloramines are one of the most promising antibacterial agents due to its high efficacies in inactivating bacteria,broad spectrum of antibacterial and facile rechargeability.To improve the hydrophilicity of N-chloramines,Quaternary ammonium N-chloramines and Pyridinium N-chloramines have recently developed.Satisfactory aqueous solubility was achieved together with the greatly boosted antibacterial efficacy caused by the presence of cationic moieties.It was also found that Pyridinium Nchloramines displayed even higher biocidal activity than the Quaternary ammonium counterpart.In this thesis,analogs of pyridium N-chloramine precursors,which carry siloxane and perfluorophenyl azide(PFPA)units as coupling handles,were designed and chemically synthesized.The resultant precursors were immobilized onto cotton fabrics and PU film respectively,and the antibacterial activity was investigated after chlorination treatment.The main contents were as follows:(1)In chapter 2,two novel siloxane pyridinium N-chloramine precursors(1 and 2)were synthesized using commercially available 5,5-dimethyhydatoin(DMH),hydroxyl-pyridine and 3-chlorapropyltriethoxysilane as starting materials.The structure of the two precursor and all the intermediates were confirmed by using 1H NMR,13 C NMR and HRMS analysis.(2)Cotton fabrics were surface modified by precursors 1 and 2 by the “immersion-drycure” procedure,and the surface modification were confirmed by FTIR,SEM,XPS and titration analysis.The results indicated that precursor 2 was even more readily grafted on cotton fabrics surface,and the antibacterial tests,conducted by “ATCC 100” method,show that cotton fabrics grafted with precursor 2 demonstrated even higher biocidal activity: 100% against E.coli(7.50×106 CFU/m L)and 99.7% reduction against S.aureus(8.30×107 CFU/m L)were achieved respectively within 5 min,whereas,cotton fabrics grafted with precursor 1 inactivated 99.6% and 82.1% bacteria respectively within 5 min.(3)In chapter 3,two novel pyridinium N-chloramine precursors(11 and 12),both of which contain PFPA moiety as the photo-coupling handle,were synthesized using commercially available DMH,hydroxyl-pyridine and pentafluorobenzoic acid as starting materials.The structures of the two precursor were fully confirmed by using 1H NMR,13 C NMR and HRMS analysis.(4)The two precursor were linked covalently onto PU membranes upon 254 nm light irradiation.the surface modification were confirmed by XPS and FT-IR.It could be observed that PU membranes grafted with 12 demonstrated even better hydrophilicity than that of precursor 11.The resulting PU film was rendered biocidal after exposure to dilute household bleach,and their antibacterial activity were tested by “sandwich test” method.antibacterial tests showed that biocidal PU film grafted with precursor 12 demonstrated even higher biocidal efficacy: it caused 53.2% and 75.5% reduction of E.coli(4.31×107 CFU/m L)and S.aureus(1.46×107 CFU/m L)respectively within 15 min.