Studies On The Regulation,Modification And Functional Application Of Nanocellulose Assembly Structure

Cellulose nanocrystalline(CNC)has attracted much attention because of its wide application,low cost and unique self-assembly.The CNCs suspension after acid hydrolysis can form a balanced and ordered chiral nematic liquid crystal phase,and the solid film after evaporation induced self-assembly(EISA)drying still retains the chiral nematic phase structure,so that the CNC film shows a unique structural color.Recently,various functional materials such as photon response based on CNC film have been applied in various fields of optics,and have broad application prospects in anticounterfeiting,encryption,sensors,optical dyes,information storage and other aspects.Based on the chiral nematic phase structure and self-assembly characteristics of CNC film itself,the following aspects are studied in this thesis:First,pure CNC chiral mesoporous materials with long-range order were prepared.CNC can self-assemble into thin films with chiral nematic phase structure through evaporation induction.On this basis,a simple method was found to prepare CNC mesoporous chiral functional materials with long range order.The ordered cellulose mesoporous photonic paper(CNP)was obtained by freeze-drying the CNC film after swelling with cellulose solvent.It can be seen from UV-Vis and CD spectra that CNP has a certain reflection peak and a consistent CD peak,and with the increase of swelling degree,the peak position occurs red shift,indicating that the chiral nematic phase structure is maintained.From the nitrogen adsorption and desorption curve,it can be seen that the volume and aperture of mesopore increase with the increase of swelling degree.Second,the application of CNP in optical responsive materials is explored.Because CNP has both mesoporous and chiral nematic helical structure,CNP can quickly respond to solvents of different polarity.With the increase of water content of ethanol solution,CNP can show a series of red-shifted colors,namely blue,green,yellow,orange and red.Using this property,CNP was dispersed into its particle suspension to prepare colorchanging inks that could respond to different solvents,such as ethanol,DMF,solution and pure water,showing blue,green and red respectively.In addition,the hydrophilicity of CNP can be adjusted by polyethylene imine(PEI),and the modified CNP shows different colors in the same solvent environment.The CNP material has potential applications in the fields of anti-counterfeiting,decorative materials and sensors.Third,circular polarization luminescence(CPL)materials were further prepared using CNP.CNP chiral materials not only provide the chiral conditions of CPL materials,but also provide space for loading fluorescent substances.Representative fluorescent materials(rhodamine B and carbon quantum dots)were selected to be loaded on CNP.The experimental results show that the composite materials not only maintain the chiral structure,but also have good CPL luminescence performance.