| Different from traditional textile coloration,the structural coloration does not require any chemical colorants(dyes and pigments),and it is a visual perception to the selectively re-emitted light by a specific physical structure interacting with incident light through interference,diffraction and scattering.Structural colors usually have the characteristics of vivid,tunable and less discoloration etc.As a kind of typical biomimetic coloration ways,photonic crystals attract much attention from domestic and foreign scholars.In this work,the modispersed nanospheres were used as the structural units to fabricate photonic crystals on rough,porous and flexible textiles to obtain structural colors.By the researches on the related self-assembly methods,mechanisms and control measures it may provide useful theoretical supports and practical experiences for the fabrication of the photonic crystals with structural colors on textiles.This study includes the following five aspects:(1)The P(St-MAA)nanospheres were prepared by emulsifier-free emulsion polymerization.And the particle size,monodispersity,surface morphology,core-shell structure,electronegativity and stability of the resultant nanospheres were systematically studied.(2)Dipping self-assembly methods including gravitational sedimentation and vertical deposition were used to fabricate biomimetic photonic crystals on textile substrates.On the basis of optimizing self-assembly conditions and analyzing the stacking types of the resultant photonic crystals,the self-assembly process and mechanism of the nanospheres on textiles were deeply investigated,and the main differences between the gravitational sedimentation and the vertical deposition were revealed.(3)By digital ink-jet printing self-assembly technology,the patterned photonic crystals with structural colors were successfully fabricated on textile substrates.Specifically,the components of the nanospheres ink were prepared,the effective strategy to inhibit the “coffee ring effect” was provided and the effects of the surface properties of the textile materials on digital ink-jet printing self-assembly were investigated.(4)The optical properties of the photonic crystals with structural colors on textile substrates were studied and the regulation mechanism was revealed.(5)The effective methods to improve binding strength and durability of the photonic crystals on textile substrates were explored.The research results show that:(1)180-350 nm monodispersed P(St-MAA)nanospheres were prepared by emulsifier-free emulsion polymerization via regulating the concentrations of St and MAA as monomers and APS as initiator.The resultant nanospheres are in uniform size,good sphericity and distinct core-shell structure.The Zeta potential values of the nanospheres are less than-30 mV,and the average particle sizes,monodispersity and sphericity change little along with processing time,displaying good stability.(2)By dipping self-assembly technology,three-dimensional face-centered cubic(FCC)P(St-MAA)photonic crystals could be constructed on the textile substrates with gorgeous structural colors and iridescence phenomena.In self-assembly process,firstly nanospheres fill in the gaps of fibers and yarns,then gradually stack to produce a relative smooth fabric surface and finally form a photonic crystal structure with long-range order on polyester fabrics.During this period,along with the evaporation of the dispersion medium,adjacent nanospheres become close to each other and experience disorder-to-order transition during crystallization stage,showing a series of blue-shifted structural colors.Moreover,different from the gravitational sedimentation,the assembled fabrics after vertical deposition have clearer fabric texture and double-sided coloration effect.(3)By regulating the nanospheres concentration,ink pH,surface tension,viscosity,and adding suitable "coffee ring" inhibitors like formamide and ethylene glycol,the prepared nanosphere ink applied to digital ink-jet printing self-assembly.In the evaporation process of ink drops,formamide and ethylene glycol could suppress the “coffee ring” effects owing to guiding capillary flow from outside to inside to effectively controlling the evaporation rates of the ink droplets.In addition,the textile substrates after water repellency treatment or coating treatment to some degree could effectively inhibit the leakage of ink droplets and get better printing effects.By virtue of the digital ink-jet printing self-assembly,the patterned photonic crystals with structural colors could be quickly and accurately positioned on the textile substrates.(4)The structural colors of the photonic crystals could be modulated and changed by the sizes of P(St-MAA)nanospheres and the viewing angles.In the case of other conditions remaining unchanged,the increase in viewing angles or the decrease in diameters of nanospheres could result in the blue-shift of structure color on the polyester fabrics complying with Bragg's law.(5)The polystyrene nanospheres with softer polymer shell and functional groups like carboxyl could facilitate to fabricate photonic crystals with higher binding strength on textile substrates.Within certain limits,the softer nanospheres are,the easier they wind with the textile fibers,the more compact the resultant photonic crystals become,which can make the resultant photonic crystals present higher binding strength on textile substrates.Furthermore,due to the strong polar groups in the molecule,formamide or ethylene glycol of nanosphere inks could enhance the stability of the photonic crystal structures and the adhesion between photonic crystals and textile substrate to effectively improve durability of the resultant structural colors. |
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