Preparation And Property Of Structural Color Materials Based On Modified Polysaccharide Polymer

The self-assembly of colloidal microspheres and infiltrating polymer into the voids of microsphere-based photonic crystal templates to form composite materials are two important ways to prepare structural color materials of polymer photonic crystals.Polysaccharide-based polymers have the characteristics such as good biocompatibility,low cost,and environmental friendliness.Utilizing them to prepare structural color materials is conducive to the sustainable development of the ecological environment.However,the current polysaccharide-based polymer microspheres can not be used for building photonic crystals due to their broad size distribution.When photonic crystal templates formed from solid spheres are filled with polysaccharide-based polymers to construct structural color materials,a low refractive index contrast causes the problem of low color brightness.In this thesis,two kinds of colloidal microspheres with regular morphology and adjustable size are prepared using modified polysaccharide-based polymer.3D and 2D photonic crystals materials are prepared using the obtained microspheres through self-assembly method.Structural color films with brilliant colors are obtained by infiltrating modified polysaccharide-based polymer into a 3D photonic crystals template composed of hollow microspheres,due to the high refractive index contrast.In the conventional nanoprecipitation method for preparing modified polysaccharide-based polymer microspheres,the size distribution of obtained microspheres is wide due to the simultaneous occurrence of nucleation and nuclei aggregation process.In this thesis,using starch acetate and ethyl cellulose as source materials,microspheres with narrow size distribution in the range of 67～158 nm are obtained by a homogeneous nucleation and solidification method,which seperates the nucleation and aggregation growth process.Based on the Ostwald ripening theory,then a hydrothermal treatment method is applied to adjust the size of microsphere within 1400 nm,and the PDI can reach 0.05.The methods solve the problem that the current method cannot prepare uniform polysaccharide derivative microspheres with controllable size.The methods can also be successfully extended to the preparation of monodisperse synthetic polymer PMMA microspheres within the size in 50～1000 nm.The developed methods provide a new strategy for preparing polymer microspheres through top-down method.Photonic crystals are formed using the modified polysaccharide-based polymer microspheres with regular morphology and adjustable size as building blocks.3D photonic crystals are successfully constructed using starch acetate and ethyl cellulose microspheres with the size of 200～300 nm.Blue,yellow-green,yellow,orange and red structural colors are obtained respectively,which accorded with optical properties of 3D photonic crystals.The structural color of 2D photonic crystals is successfully constructed using starch acetate and ethyl cellulose microspheres with the size of 400～800 nm.The color can be tuned from blue to red,which has typical angle-dependent diffraction characteristics of 2D photonic crystals.The patterned 2D photonic crystals and PDMS composites with typical optical property of 2D photonic crystals light diffraction realizes information encryption.Cellulose acetate and hollow silica 3D photonic crystals with the sizes of 296 nm,257 nm and 227 nm serve as infiltrating materials and template materials,respectively.Photonic crystals films with brilliant red,green and blue color are obtained by the infiltration of cellulose acetate into the voids of the hollow silica 3D photonic crystals,due to the formation of high refractive index contrast.The experimental values of bandgap positions of the photonic crystals film are in agreement with the theoretical values.The film has certain mechanical stability,maintains intact after cyclically bending 1000 times,and the tensile strength of the film can reach 20 MPa.The composite film possesses high transparency(light transmittance>80%),which realizes the switching of color-tranparency just by changing the observing angles.The property makes the films have application potential in the field of banknote anti-counterfeiting.