Chitosan　exhibits　good　biocompatibility　and　some　antibacterial　activity,　making　it　a　popular　choice　in　biomedicine,　personal　care　products,　and　food　packaging.　Despite　its　advantages,　the　limited　antibacterial　effectiveness　of　chitosan　hinders　its　widespread　use.　Introducing　a　six-membered　heterocyclic　structure　through　chemical　modification　can　significantly　enhance　its　antimicrobial　properties　and　broaden　its　potential　applications.　In　order　to　explore　the　effect　of　six-membered　heterocyclic　structure　on　the　antibacterial　and　antibiofilm　activities　of　chitosan.　In　this　study,　seven　chitosan　derivatives　containing　six-membered　heterocyclics　were　prepared.　They　were　characterized　using　Fourier　transform　infrared　(FT-IR)　spectroscopy,　nuclear　magnetic　resonance　(NMR)　spectroscopy,　and　elemental　analysis.　Cell　viability　assay　showed　that　they　were　non-toxic.　The　antibacterial　and　antibiofilm　activities　against　Escherichia　coli　(E.　coli)　and　Staphylococcus　aureus　(S.　aureus)　were　evaluated.　Our　research　findings　demonstrate　that　increasing　the　hydrophobicity,　alkalinity　and　charge　density　of　the　substitute　groups　improved　the　antibacterial　and　antibiofilm　activities　of　chitosan.　This　study　also　offers　valuable　insights　into　the　quantitative　structure-activity　relationships　of　chitosan　derivatives　in　terms　of　antibacterial　and　antibiofilm　activities.　©　2024　Elsevier　B.V.