Preparation of chitosan-graft-(methyl methacrylate)/Ag nanocomposite with antimicrobial activity

It has been found that composites of chitosan (CS) and Ag nanoparticles can exhibit excellent antibacterial activities. However, the weak mechanical performances of these composite materials limit their wide application. Grafting of vinyl monomers onto CS is one of the most effective methods to improve the performances of CS without sacrificing its properties. A nanocomposite of chitosan-graft-(methyl methacrylate) (CS-g-MMA) containing Ag nanoparticles was prepared by in situ chemical reduction of Ag ions in an aqueous acetic acid solution of CS and graft copolymerization of MMA onto CS. Transmission electron micrographs, X-ray diffraction patterns and UV-visible spectra of the nanocomposite confirmed the formation of Ag nanocrystals. X-ray photoelectron spectroscopy proved that Ag-O bonds exist in the composite. Thermogravimetric analysis/differential scanning calorimetry showed that the decomposition temperature of CS was 319.8 degrees C while that of the CS-g-MMA/Ag composite shifted to a higher temperature of 422.1 degrees C. Antimicrobial experiments showed that the antimicrobial rates of the CS-g-MMA/Ag composite to E. coli, B. subtilis, S. aureus and P. aeruginosa were 93-98%. CS molecules can act as stabilizing agents to prevent the aggregation of Ag nanoparticles in the process of synthesizing CS-g-MMA/Ag nanocomposites. The antimicrobial activity of the as-prepared nanocomposites is higher than that of CS alone. (C) 2009 Society of Chemical Industry