Synthesis of O-quaternary Ammonium Salt-oxidized Chitosan and Its Antibacterial Finishing for Cotton Fabric

By utilizing vanillin to form Schiff bases with the C2 amino group of chitosan in order to protect the amino group, and then grafting 2,3-epoxypropyl trimethylammonium chloride(GTA) quaternary ammonium salt on C6 site in chitosan, O -quaternary ammonium chitosan(O-HACC) was synthesized after removing Schiff -base from the solution of dilute HCl and ethanol. Subsequently partial groups at C2 and C3 positions in O-HACC were selectively oxidized into dialdehyde groups with KIO4, so the O -quaternary ammonium salt -oxidized chitosan(O-HAOCC) was finally obtained, which possessed the fiber -reactive and dual antibacterial activities, and then grafted with cotton fabric to obtain O-HAOCC modified cotton fabric. The characterizations of Fourier -transform infrared spectroscopy (FTIR), X-ray diffraction(XRD), proton nuclear magnetic resonance spectroscopy(1H NMR), scanning electron microscopy(SEM) and differential scanning calorimetry(DSC) displayed that, major amino groups were retained while introducing the structure of quaternary ammonium salt and active dialdehyde groups in O-HAOCC molecules, and the crystal morphology was destroyed, as well as thermal stability reduced. Furthermore, the test results showed that the water solubility of O-HAOCC oxidized for 3 h achieved 23.7 g/100 mL, and the 2,2 '-azinobis(3-ethylbenzo- thiazoline-6-sulfonic acid)diamine salt(ABTS) radical scavenging rate after 40 min was 65.58%. The graft ratio O-HAOCC modified cotton fabric arrived at 9.84% when the mass fraction of O-HAOCC was 2%, the reaction time was 2 h and the graft temperature was 80 celcius. The antibacterial rate of modified cotton fabrics against Staphylococcus aureus and Escherichia coli was 98.63% and 93.38%, respectively, furthermore the antibacterial rate maintained above 90.75% after 50 times of washing, manifesting extensive application in antibacterial textile and garment, home textile and medical and sanitary products, etc.