| Photonic crystals,a kind of optical materials with periodic arrangement,are composed of two or more materials having different dielectric constants.Generally,the bionic structural colors produced from photonic crystals can be obtained by controlling the position of the photonic band gaps.At present,in order to construct the photonic crystals with conspicuous structural colors,most researchers choose to use the pigment to endow the base colors of substrates,which will inevitably lead to complicated preparation processes and even excessive energy consumption.How to reduce the base color pretreatment process and directly construct the photonic crystals with bright and vivid structural colors on the substrate is a hot topic in recent years.In this paper,a kind of pigment/polymer composite structural units used to construct the biomimetic photonic structures with tunable structural colors were designed and prepared,then the prepared structural units were used to formulate the printinginks and liquid paints,and then the prepared printing inks and liquid pigments were directly applied to construct photonic crystals with structural color patterns on the substrate without pre-color pretreatment by digital printing and hand-painting methods,respectively.The research would provide effective experimental data basis for the construction of photonic crystals with structural colors on substrates without base color pretreatment via colloidal microsphere self-assembly methods.The main research contents of this paper include the following three aspects:(1)Poly(styrene-methacrylate-butyl acrylate)(P(St-MAA-BA))microspheres were prepared by a soap-free emulsion polymerization,and then the P(St-MAA-BA)microspheres were used as seeds to prepare disperse dye and P(St-MAA-BA)composite structural unit(named as disperse dye@P(St-MAA-BA)microspheres)by a swelling adsorption method.The effects of polymerization parameters on the particle size and monodispersity of P(St-MAA-BA)microspheres were investigated.The preparation parameters of the composite structural units were optimized.The surface morphology,glass transition temperature,dye adsorption amount,chargeability and stability of the composite structural units are characterized by the system;(2)The printing inks were formulated using prepared disperse dye@P(St-MAA-BA)microspheres as a main component,and the printing inks were applied to construct photonic crystal patterns with structural colors on white substrates without base color pretreatment by a digital printing method.The effects of the amount of composite structural units,"coffee ring" inhibitors,surface tension modifiers and pH adjusters on the properties of inks were investigated,the effects of self-assembly temperature and time on the coloration of photonic crystals were investigated,the influence of pigment on the coloration of photonic crystals were analyzed,and the optical properties of the resultant photonic crystal patterns were characterized;(3)The liquid photonic crystal paints were prepared by a centrifugal pretreatment,and then the prepared paints were used to construct patterned photonic crystals on white substrates by a hand-drawing method.The effects of centrifugal rate and time on the properties of liquid paints were investigated,the particle fineness,apparent color,rheological properties and light and heat resistance of prepared paints were elaborated,and the structural color effect of photonic crystals constructed by liquid paints was systematically characterized.The results show that:(1)In the soap-free emulsion polymerization,as the amount of St or MAA acid increases,or as the amount of BA or APS decreases,the particle size of P(St-MAA-BA)microspheres gradually increases.For the preparation of disperse dye@P(St-MAA-BA)microspheres,the particle size of the composite microspheres increased slightly with the increase of dye dosage,the dyeing time,the increase in pH or the decrease of seed microsphere dosage.The glass transition temperature of composite microsphereswas 122.3?,the adsorption amount of the dye in the composite microsphere was 0.021-0.026 g/g,and the Zeta potential of the composite microspheres were lower than-30 mV,displaying the composite microsphere had good stability;(2)The inkjet inks consisted of disperse dyes@P(St-MAA-BA)microspheres,"coffee ring" inhibitors,surface tension modifiers and pH adjusters.When the drying temperature was 60? and the drying time was 9 min,the printed inks could form photonic crystals with three-dimensional face-centered cubic structures on the white substrate surface after the self-assembly of disperse dye@P(St-MAA-BA)microspheres.Black disperse dye in composite microspheres plays a role in the absorption of stray light,and the structural color effect of disperse dye@P(St-MAA-BA)photonic crystals is better than pure P(St-MAA-BA)photonic crystals on white substrates;(3)The centrifugal speed and time could directly affect the quality of the paints.The suitable paints could be prepared under 8000 r/min centrifugal speed and 30 min centrifugal time.The prepared paints display bright and iridescent structural colors,which indicates that the disperse dye@P(St-MAA-BA)microspheres of paints had undergone a certain degree of self-assembly under the driving of centrifugal forces.As the particle size of the internal microspheres increases,the fineness of the prepared paints gradually increases,but the overall fineness value was close to that of commercial paints.The viscosity value and the average particle diameters and monodispersity of the internal microspheres of the prepared paints didn't change greatly with the standing time,indicating that the photonic crystal paints presented good stability.The prepared paints could fabricate three-dimensional FCC photonic crystal patterns with bright and iridescent structural colors within 10-20 seconds.Moreover,with the diameters of microspheres decreases or the viewing angle increases,the structural colors would produce blue shift according to Bragg diffraction law. |
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