| The structural color materials based on the ordered structure photonic crystal could exhibit bright color with high saturation and never fade,thereby them have been widely concerned and studied.However,the Bragg diffraction caused by the ordered structure makes the structural color materials have an angle-dependence feature,which greatly limits the application of structural color materials in many fields.The main strategy for preparing angle-independent structural color materials currently is to construct photonic crystals with amorphous structure Owing to the isotropic feature of such long-range disordered short-range ordered photonic structure,it could exhibit an angle-independence structural color.However the excessive incoherent scattering caused by its intrinsic structure makes the structural colors pale and faded In order to solve the contradiction between angle-dependence property and vivid color with high brightness in photonic crystal structural color materials,we based on the design of photonic crystal microstructure,and then a novel hierarchical photonic crystal with long surface order and internal amorphous structure was designed.The polystyrene nanospheres coated with polydopamine(PS@PDA),and monodispersed anionic polyurethane dispersed with small particle size were used as self-assembled units.By studying the self-assembly mechanism of colloidal particles,two kinds of dynamic self-assembly processes,thermal assisted and electrophoretic deposition,were designed respectively,and the hierarchical photonic crystal films were successfully fabricated(1)A binary-blended heat-assisted dynamic self-assembly process was designed,and we fabricated an ordered-disordered hierarchical photonic crystal with a surface long-range order and inner amorphous structure based on that.By monitoring the particle morphology during self-assembly,the self-assembly behavior of particles in dynamic self-assembly process is analyzed,and the formation mechanism of ordered-disordered hierarchical structure is revealed The as-prepared hierarchical photonic crystal can exhibit bright structural color with high brightness and also has a low angle-dependence propertyBy investigating the effect of PU addition on the structure and properties of photonic crystals during self-assembly,it was found that the best mass ratio of PU to PS@PDA microspheres was 0.1:1.And at this condition,the as-prepared structural color films exhibit bright color with high color saturation and strong metallic luster When the incident angle of light changes from O°to 60°,the photonic band gap positions only occurred with peak shifts of about 20?30nm which demonstrates that the hierarchical photonic structure films have low angle dependence(2)By studying the self-assembly mechanism of electrophoretic deposition,a variable voltage cathodic electrophoresis self-assembly process was designed to prepare ordered-disordered hierarchical photonic crystals.The cracking problem of photonic crystal film was solved by using Poly dimethyl diallyl ammonium chloride(PDDA)as a charge reversal agent and an adhesive.The effects of pH of colloidal particle dispersion,working voltage and PDDA addition on photonic crystal structure and self-assembly behavior were investigated.A hierarchical photonic crystal coating was successfully fabricated on a curved substrate by using curved conductive substrates(stainless steel spoons)for electrophoresis self-assemblyThrough experimental investigation,it was found that the as-prepared structural color films own an order-disorder hierarchical structure and exhibit bright color when the mass ratio of PDDA to PS@PDA microspheres is 0.09:1;in the first-stage,the electrophoresis working voltage are 40V,and the deposition time is lmin;and in the second-stage the electrophoresis working voltage are 3V,the deposition time are 3 min?... |
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