Preparation Of Chitosan-Based Composites By Electric Field Aided Phase Separation

Chitosan?CS?is a natural polymer??-1,4-N-acetylglucosamine?obtained from chitin,owning a rich hydrogen bonding environment?including amino and hydroxyl groups?on the molecule,can be used as mild reducing agent and stabilizer to silver ion and can be used as packaging material because of its biocompatibility and non-toxicity.The CS chain undergoes protonation in an acidic solvent and dissolves,but the dissolved molecular chain still retains a certain degree of aggregation.This is due to the formation of a large number of hydrogen bonds.At the same time,the hydrogen bond structure can control the assembly pathway of chitosan molecular chains.The aggregation of molecular chains due to the hydrogen bonding structure affects the dynamic structure of the molecular chain,such as weakening the interaction with the polymers.In this work,the electric fields was used to influence hydrogen bonding?including intermolecular hydrogen bonds and intramolecular hydrogen bonds?,and a series of problems caused by molecular chain aggregation are solved by adjusting hydrogen bonds,which provides the possibility for more widespread applications of chitosan.The main research content and conclusions are as follows:1.Synthesis of water soluble CS/Silver Nanoparticles?AgNPs?Composites:One-step synthesis of CS/AgNPs composites by phase inversion with electric field.The effect of electric field on the hydrogen bond environment of chitosan was studied by XRD and ATR characterization.The results show that intermolecular and intramolecular hydrogen bonds of CS gradually decrease and weaken as the applied voltage increases.The new condition for hydrogen bonding improves the reduction efficiency of silver,where 100%by weight of silver ions are reduced to Ag⁰ at 1.75 MV/m.This can control the particle size and distribution of the Ag particles to a minimum size of 3.4±0.7 nm.At the same time,during the reduction of silver ions by formic acid,the salt group-NH₃⁺COO^-was formed on the CS chain,which made the CS/Ag nanocomposites obtain water solubility.In the antibacterial test,the synthesized CS/Ag nanocomposites have good antibacterial activity against Staphylococcus aureus.After studying and mastering the control mechanism of nanosilver morphology and structure,the same synthesis method was used to synthesize many kinds of metal particles,including divalent metal?copper ion?,trivalent metal?gold ion?and tetravalent metal?platinum ion?of the reduced body,and found that this research synthesis method has a good applicability.2.Preparation of CS/Nylon 6?PA6?Composite:In the project,CS/PA6 composite was prepared by phase inversion based on the electric field.With polarization attenuated total reflectance infrared spectroscopy and proton longitudinal relaxation time?T₁?distribution characterization analysis,the application of an electric field can orient the polar groups,which will hinder the crystallization of the blend and also increase the interphase interaction between PA6 and CS.The characterization by AFM confirmed that the CS and PA6 reached the tens of nanometers miscible state.Studies have shown that this controlled hydrogen bonding environment caused by the presence of an electric field does indeed greatly impede the deposition of CS without destroying its chemical structure.The miscibility of the blend is improved,the toughness is increased and slightly greater tensile strength is produced.3.Preparation of CS/PA6/ammonium salt composites:CS/PA6/ammonium salt composites were prepared by phase inversion.The effects of salt on the hydrogen bonding environment were discussed by XRD and DSC characterization.The effect of salt inside the system?distinguishing from electric field?on the hydrogen bonding improves the miscibility of the blend.According to the tensile test results,the elongation at break reached 67.7%when the salt weight reached 0.1 g.