Synthesis And Application Of Curdlan-QAS Bacteriostatic Agent

Curdlan is derived by microorganism.However,the potential application value of Curdlan has not been developed and utilized.Modifications on Curdlan can effecively improve the performances of it to meet different demands.Curdlan-QAS has wide foreground due to its intensification of moisture-absorption and antimicrobial ability.Composites of Curdlan-QAS with PVA and Na⁺MMT should be novel materials of better performances.The Curdlan-QAS was synthesized successfully by two-step.PVA/Curdlan-QAS antimicrobial films were prepared by the method of repeated freezing-thawing emulsifying crosslinked,and nano Na⁺MMT/Curdlan-QAS composite films were prepared by the method of intercalation composite.It is very meaningful and useful to prepare a Curdlan-QAS for the market of natural antiseptic antibacterial agent and it is expected in the field of washing,antibacterial plastics,antibacterial films,antibacterial pad,food preservation and a new type of green biological seed coating and other fields.The main contents are summarized as follow:1.The Curdlan-QAS was synthesized using glycidyl trimethyl ammonium chloride?GTMAC?in NaOH aqueous solution by two-step in homogeneous quaternary ammonium graft modification.The structure,property and morphology of Curdlan and Curdlan-QAS were characterized by ¹H-NMR,¹³C-NMR,FTIR-ATR,XRD,GPC,TG and Ultra-depth three-dimensional microscope.The DS were calculated from the integral area of ¹H-NMR spectroscopy.The results showed that the Curdlan-QAS with different DS had little difference in the molecular weight?Mw?,structure and thermal stability.The TG results showed that the thermal stability of Curdlan-QAS was lower than Curdlan.Turbidity analysis method shows that the aqueous solution of Curdlan-QAS has good stability.The antibacterial activity of Curdlan-QAS was investigated by disc-diffusion methods,which revealed that the Curdlan-QAS with high DS had antibacterial effect against Staphylococcus and Fusarium.However,the inhibitory effect on Escherichia coli is not ideal.The antimicrobial test results showed that the antibacterial activities of Curdlan-QAS against Staphylococcus were much better than Escherichia coli,and the antibacterial activities of Curdlan-QAS against Fusarium were much better than Staphylococcus.2.PVA/Curdlan-QAS antimicrobial films were prepared by the method of repeated freezing-thawing emulsifying crosslinked.The structure and properties were characterized by scanning electron microscopy?SEM?,FTIR-ATR and TG.Casting solution stability and water vapor permeability of the films under different formulations were studied.Results show that after 7 days,the casting solution that the mass fraction of paraffin between 0.4%⁰.8% is still opaque milky white liquid and unstratified,therefore,the casting solution has certain stability.The antimicrobial test results show that the PVA/Curdlan-QAS antimicrobial films had antibacterial effect against Staphylococcus and Fusarium,and the antibacterial activities against Staphylococcus and Fusarium were much better than Escherichia coli.3.Nano Na⁺MMT/Curdlan-QAS composite films were prepared by the method of intercalation composite.The mechanical properties,water vapor permeability,thermal properties,optical properties,water absorption and antibacterial properties were tested,and the fractured surfaces were characterized by scanning electron microscopy?SEM?.The results show that the thermal stability and tensile stress of the films were improved by adding different proportion of nano Na⁺MMT,and the film has the greatest tensile stress?30.3 MPa?,when the nano Na⁺MMT addition is 2.5%,and the elongation at break was the largest?167.4%?,when the addition of nano Na⁺MMT was 1%.The light transmittance and water absorption of the films decreased with different proportion of nano Na⁺MMT,and the film has the lowest water absorption,when the addition of nano Na⁺MMT is 2.5%.The results of SEM showed that nano Na⁺MMT had been successfully dispersed into the PVA and the Curdlan-QAS molecule,and the three of them showed good compatibility and formed the intercalation structure.The antimicrobial test results show that the nano Na⁺MMT/Curdlan-QAS composite film had antibacterial effect against Fusarium and the inhibitory effect did not reduce with increase of nano Na⁺MMT content.