Preparation And Properties Study Of Chitosan Derivatives And Their Composites

Chitosan is a green,environmental friendly,biocompatibility,biodegradable and renewable resource.It has always been the focus of research for scientists.Chitosan derivatives and its composites are also a research hotspot in the industry.In this paper,chitosan derivatives are used as the main research objects.According to the traditional preparation technology remains to be improved,and some properties of chitosan derivatives in specific applications are insufficient,we have prepared two novel chitosan derivatives and their composite materials,namely,silver?Ag?/titanium dioxide?TiO₂?/chitosan composite antibacterial microspheres?STC?and cross-linked chitosan quaternary ammonium salt film.The structure,morphology and properties of the prepared chitosan derivatives and their composites were characterized by a variety of testing methods.The effects of the preparation parameters on the properties of these materials were discussed.The chitosan derivatives and their composites with excellent antibacterial properties and strong adaptability were obtained by controlling prepared method based on the relationship between process parameters and material properties.The green and safe STC can make up for the defects of the existing water treatment technology?chlorine,ozone and ultraviolet?,which are easy to produce harmful by-products.It is expected to be applied in the field of water treatment.The prepared cross-linked chitosan quaternary ammonium salt film has excellent water stability and repeatability.It can be directly attached to wearable piezoelectric sensor as an antibacterial coating,and inhibit the growth of bacteria on the surface of the sensor.The contents and results of this paper are as follows:?1?Nano TiO₂ with photocatalytic activity was firstly modified by chemical method.Then,glutaraldehyde was used as cross-linking agent and chitosan as precursor.Cross-linked chitosan matrix was prepared by inverse emulsion cross-linking reaction.At the same time,the modified TiO₂ nanoparticles and the reduced silver in situ were doped in the matrix to obtain the STC.The FTIR and SEM characterization showed that the chitosan was successfully cross linked into spheroid,and the successful doping of Ag and TiO₂ was characterized by XPS.The antibacterial activity test showed that the antibacterial activity of STC was enhanced with the decrease of its particle size.When the dosage of glutaraldehyde,reaction time and stirring speed are 2.5%?v/v?,6 h and 450 r/min,respectively,the morphology of STC is the most uniform and the particle size is the smallest?1¹0?m?.The STC?1¹0?m?had excellent antibacterial activity?>99%?against E.coli,S.aureus and P.aeruginosa.Compared with TiO₂/chitosan composites?TC?,it is found that the doping of silver nanoparticles is beneficial to obtain antibacterial agents with high antibacterial activity.In particular,the antibacterial properties of nano TiO₂ can be significantly improved by synergistic photocatalytic activity in visible light;?2?The cross-linked chitosan quaternary ammonium salt?CHACC?film was prepared by chemical cross-linking reaction of epichlorohydrin and HACC.The products were characterized by ATR-FTIR,¹H-NMR,TGA and XRD,indicating the formation of three-dimensional network structure of CHACC.The film is only swelling in water,and the swelling rate is inversely proportional to the dose of crosslinking agent and the reaction time of crosslinking.When the reaction time is 4 h and the amount of crosslinking agent is 4m L,the water stability of the film was the best and the swelling rate is less than 250%.Compared with the HACC film,it was found that the CHACC film with cross-linked structure maintained excellent antibacterial activity.And its antibacterial rate against to E.coli,S.aureus and P.aeruginosa were all greater than 99%,and the minimum inhibitory concentration was 40,320 and 640 g/mL,respectively;?3?Further,the CHACC film was used as an antibacterial layer to directly attach to a self-made polyvinylidene fluoride-trifluoroethylene copolymer?PVDF-TrFE?piezoelectric sensor.The self-made piezoelectric sensors are obtained by spin coating and encapsulation.The sensor was characterized by FESEM,the results showed that the sensor had multilayer structure,the thickness of CHACC layer is 288?m,and the thickness of sensor layer is 240?m.The influence of the attachment of CHACC film on the performance of the sensor is analyzed by the self assembled piezoelectric test device in the laboratory.The results show that the attachment of film has no effect on the piezoelectric output of the sensor.The attachment of CHACC film has no effect on the piezoelectric output of the sensor.Meanwhile,the film with excellent antibacterial activity and reutilization can effectively inhibit the adhesion and breeding of bacteria on the surface of the sensor.