In　this　work,　single　electron　transfer　living　radical　polymerization　(SET-LRP)　was　used　to　functionalize　chitosan　in　a　well-controlled　manner.　The　chitosan-based　macroinitiator　was　first　synthesized　and　then　initiated　the　SET-LRP　of　methacryloyloxyethyl　trimethylammonium　chloride　(DMC)　in　ionic　liquid　system,　using　Cu0/N,N,N′,N′,N′′-pentamethyldiethylenetriamine　as　a　catalyst.　The　grafting　of　PDMC　brushes　on　chitosan　was　confirmed　and　analyzed　by　Fourier　transform　infrared　spectroscopy　and　1H　nuclear　magnetic　resonance.　Transmission　electron　microscopy　reveals　that　the　chitosan　copolymer　showed　self-assembled　behavior　in　acetone.　Surface　properties　of　the　copolymer　have　been　investigated　by　environment　scanning　electron　microscopy　analysis.　The　linear　relationship　between　the　ln([M]0/[M]t)　and　time,　the　linear　increase　of　number-average　molecular　mass　with　conversion　as　well　as　the　low　polydispersity　index　of　the　polymer　confirmed　the　＇living/controlled＇　features　of　the　polymerization　of　DMC　through　SET-LRP.　Finally,　the　chitosan　copolymer　demonstrates　its　potential　antibacterial　application,　showing　excellent　inhibitive　capability　against　Escherichia　coli.　©　2015　Wiley　Periodicals,　Inc.