Study On Chain Conformation Of Chitosan Tartrate And Its Application

Chitosan is a widely available and abundant polycationic polysaccharide.The amino functional group of its molecular chain enables it to form complexes with tartaric acid and metal ions.Therefore,chitosan tartrate,chitosan tartrate sodium and chitosan tartrate silver were synthesized in this work.The amino and carboxyl functional groups of the chitosan tartrate sodium molecular chains gave itβ-folded chain,α-helix and random line group conformation.Moreover,the content ofβ-folded chains in chitosan tartrate sodium affects the morphology of self-assembled nanomaterials.Compared with chitosan,chitosan tartrate sodium had more metal ion ligation sites,so that the chitosan tartrate silver gel had the temperature sensitive property,and the chitosan tartrate silver memristor(RRAM)device had the unidirectional storage performance.The relationship between the chain conformation of chitosan tartrate sodium and the morphologies of self-assembled nanomaterials provides a basis and method for the construction of chitosan-based nanomaterials.RRAM devices with both of antibacterial properties of chitosan and silver ions provide the basis for biocompatible electronic storage devices.The innovation points of this work are as follows:(1)Through the coordination of chiral tartaric acid and chitosan,the crosslinked product of chitosan tartaric acid was synthesized by evaporation and crystallization,and the molecular chain of chitosan was regulated.(2)The chain conformation of chitosan tartrate sodium was characterized by circular dichroism spectrum(CD)and Reed’s equation.(3)The chain conformation of chitosan tartrate sodium affected the morphology of self-assembled nanomaterials,which provided a method for the morphology control of chitosan nanomaterials.(4)Chitosan tartrate silver gel was temperature-sensitive,and the memristor constructed by it had the property of unidirectional storage,which provides a basis for storage devices with excellent antibacterial performance.The research contents and conclusions of this work are as follows:The coordination crosslinking reaction between tartaric acid(TA)and chitosan could take place through evaporative crystallization process.The carboxyl group of tartaric acid and the amino group and hydroxyl group on the structural units of chitosan formed a chitosan tartaric acid complex with a cross-linked structure,thereby regulating the conformation of the molecular chain of chitosan.The structure of the chitosan tartaric acid complex was characterized by FTIR,XRD and DSC.The chain conformation was characterized by circular dichroism spectrum(CD).The surface morphologies,particle size distribution and assembly properties of the complex were characterized by TEM,Zeta potentiometer,SEM and POM.The results showed that the particle size of CS-LTA-Na was396±140 nm and the particle size of CS-DTA-Na was 255±155 nm when dispersed in water system,CS-LTA-NA mainly presents helical,folded and random chain conformation,while CS-DTA-NA mainly presentsβ-folded chain.β-folding made the chitosan tartrate sodium easily assemble into nanosheets and helically twisted nanofiber aggregates,and the CS-DTA-Na sample had smaller particle size and more obvious lamellar structure.At low temperature,CS-DTA-Na tended to form a twisted nanosheet structure,and gradually formed a flower-like structure with the increase of temperature,while CS-LTA-Na tends to form an upright lamellar structure.The assembly process of CS-LTA-Na and CS-DTA-Na conforms to the nucleus-growth principle.At room temperature and under mild acidic conditions,silver ions and CS-LTA-Na formed chitosan tartrate silver supramolecular hydrogel,whichhad the temperature sensor.The structure of the chitosan supramolecular hydrogels was characterized by FTIR,XPS and XRD.The morphologies and assembly properties of the supramolecular chitosan hydrogels were characterized by SEM and POM.The results showed that the binding sites of silver ions were the amino and hydroxyl groups on the molecular chain of CS-LTA-Na.Theβ-folding in the system made the gel susceptible to the influence of temperature.When the temperature rised,the thermodynamic motion between molecules was accelerated,and the amino protons of chitosan were partially transferred to the negative ions in the solution,which weakened the binding between the silver ion and the amino group and results in the dissolution of the gel.Chitosan supramolecular hydrogels had good crystal structures.Theβ-folding in CS-LTA-Na allowed it to assemble into nanoscale twisted stacked crystals.The nanocrystalline lamellar structure was formed at low temperature.The diameters of the nanocrystalline lamellar were more than 100μm and showed bright birefringence characteristics under POM.After the addition of silver ions to chitosan tartaric acid solution,the film could be used as the dielectric layer of the resistive memory.The I-V curves was used to explore the influence factors of the device,including setting different rotating speed,TA concentration and heating mode.The results showed that the concentration of TA in the system and the drying method of the film have a great influence on the switching ratio of the RRAM devices.The better RRAM had a switching ratio of 1.07×10~2and a write voltage of 0.4 V,and had the characteristics of one-way storage.The Ag~+complexation and reduction rate in the system are the main factors affecting the performance of RRAM devices.Bio-based RRAM with dual antibacterial properties of chitosan and silver ion and biodegradability has a good application potential in implantable electronic devices.