Copolymers PMDAB-co-AA with excellent antibacterial activity were designed and prepared（MDAB/AA=methacryloxyethyldimethyl dodecyl ammonium bromide with acrylamide）.The chemical structures of the copolymers were characterized by Fourier transform infrared（FTIR）,1 H NMR,13 C NMR and chemical titration.The antimicrobial activities and kinetics of the copolymer against E.coli and S.aureus were examined by viable cell counting method.The compositions of the copolymers could be easily controlled by the feed molar ratio of MDAB to AA.Furthermore,the highest antibacterial activity was achieved when the molar fraction of MDAB was in a range of 5%―20%,and the killing rate reached 100% under the test conditions.In addition,the antibacterial activity of PMDAB-co-AA was maintained and stable without any loss after 15 times of repeated usage.It was proved that the PMDAB-co-AA samples targeted at cell membrane,and caused serious damage to cell integrity and inner membrane permeation.The surrounding conditions,such as pH and inorgainc salts concentrations（CaCl2 or NaCl）,also affected their antibacterial activities.
LU Gui-qianZUO Hua-jiangDONG Wei-minWU Ding-caiFU Ruo-wen
Antibacterial polymers of dimethylaminoethyl methacrylate benzyl ammonium chloride（DMAEMA-BC） with various molecular weights（Mws） were prepared under controlling radical polymerization conditions. The Mws of these polymers were determined by means of static multiangle laser light scattering and viscosity method. A Mark-Houwink equation was established to be [η]=0.154M0.764 for the Mw evaluation of poly（DMAEMA-BC）s. The effects of the Mws of these poly（DMAEMA-BC）s on their antibacterial activities against E. coli and S. aureus were investigated by various methods including viable cell counting, electrical conductivity titration, intracellular constituent leakage tests and electron microscopy. Our results indicate that the antibacterial efficiency of DMAEMA-BC was significantly enhanced after the monomers were polymerized into a polymer and increased obviously with the Mws,as a result of the increase of charge density. Further investigation of the molecular basis underlying the anti-bacterial role of these polymers revealed that poly（DMAEMA-BC） promoted the release of potassium ion from the membrane of bacterial cells and the release increased significantly with the Mws of the polymers used.
LU Gui-qianZUO Hua-jiangDONG Wei-minWU Ding-caiFU Ruo-wen
