Synthesis And Synergistic Mechanism Of High Efficiency Antibacterial Waterborne Polyurethane Based On Amino Acids And Quaternary Ammonium Salts

Waterborne polyurethane(WPU)is an environmentally friendly,biocompatible and easily modified polymer,which has been widely used in textiles,leather,food packaging and biomedicine.But WPU is vulnerable to bacterial attack during use,reducing service life and even endangering life and health.This limits its application in high hygiene fields.In this study,based on the biological safety and antibacterial activity of amino acids and quaternary ammonium salts(QAs),hydrophobic amino acids-phenylalanine(L-Phe),positively charged amino acids-lysine(Lys)and arginine(L-Arg)were selected.Their functional groups and QAs were introduced into WPU at the same time by chemical bonding to prepare antibacterial waterborne polyurethane emulsions.(1)Amino acids and QAs were introduced into the WPU molecular skeleton by in-situ emulsion polymerization,and the WPU composite system modified by amino acids and QAs was synthesized.The method is simple,efficient,green and environmentally friendly,and imparts antibacterial properties to the material by covalent bonding,which fundamentally solves the problems of poor compatibility between traditional additive antibacterial materials and matrices,environmental migration pollution,reduced antibacterial persistence and toxicity.(2)The effects of amino acids and QAs on the dispersibility,surface,crystallinity and mechanical properties of WPU were studied.The particle size and Zeta potential tests showed that all emulsions could be uniformly dispersed in water and had excellent stability.By introducing the hydrophobic amino acid L-Phe,the hydrophobicity of WPU films can be effectively improved,and the contact angle can be increased by a maximum of 34.5°.The correlation of XRD,DSC and mechanical data showed that the introduction of Lys and L-Arg significantly increased hydrogen bond strength of WPU and improved mechanical properties of WPU,and increases the tensile strength from 3.9 MPa to 14.7 MPa.(3)The antibacterial activity of the prepared composite system against E.coli and S.aureus was studied by disc diffusion method,and compared with the antibacterial activity of pure WPU and single system.On this basis,the antibacterial mechanism was preliminarily explored by scanning electron microscopy(SEM).Secondly,the effects of different WPU systems on biological properties were investigated by MTT test and CLSM.The antibacterial results showed that composite system of amino acids and QAs had better antibacterial activity than single systems against E.coli and S.aureus.The antibacterial effect of WRPU7 was optimal,from the sum(E.coli: 8.3 mm + 8.3 mm = 16.6 mm and S.aureus:9.8 mm + 9.5 mm = 19.3 mm)of the inhibition circles of L-Arg and QAs to 21.4 mm and 22.6mm,respectively,net efficiency increase of 29% and 17%,fully reflecting the synergistic effect of "1 + 1 > 2 ".The importance of the synergistic effect of amino acids and QAs on the antibacterial activity of WPU is highlighted.The results of SEM images of bacteria proved that due to the synergy of L-Arg and QAs,it was more destructive to the bacterial cell membrane,causing its mechanical damage.These damages made the surface of bacteria unable to repair and accelerated the death of bacteria.In addition,due to the introduction of amino acids and QAs,composite system of WPU showed better biocompatibility.This is beneficial to the application of WPU in biomedicine,food packaging,textile and other fields,and expands its market value.