Abstract:Natural polymer chitosan (CS) was modified using salicylic acid (SA), then quaternary phosphonium salt (TPPB). Single-factor experiments were then carried out to determine the optimal molar ratios of CS to SA and TPPB and to acquire SA-CS and TPPB-CS polymers. Following this, SA-CS derivatives were adopted as substrates and mixed with TPPB at different molar ratios to obtain the optimal molar ratio based on the water solubility results. Eventually, SA-CS-TPPB polymers were obtained. The three different polymers were subjected to infrared spectroscopy, nuclear magnetic resonance, X-ray diffraction, and thermogravimetric analysis to analyze their structures and properties. Finally, according to the zone of inhibition results, the antibacterial performances of SA-CS, TPPB-CS, and SA-CS-TPPB were examined. The results demonstrate that the optimal molar ratio (CS:TPPB:SA) is 1:1:0.75 and all the CS derivatives exhibit excellent solubility and antibacterial performances. Their solubility can reach up to 100.00%, and they show satisfactory inhibitory effects against Escherichia coli but even more so against Staphylococcus aureus. SA can better enhance the antibacterial performance of CS compared to TPPB, whereas TPPB is more effective at increasing CS solubility than SA. By modifying CS using both SA and TPPB, the solubility and antibacterial activity of CS can be improved synergistically. The CS derivatives acquired also have better film forming characteristics than CS alone. These findings are of theoretical importance for future CS modification and its application as a coating for fruit and vegetable preservation.
