Construction And Discoloration Property Of Responsive Structure Color Fabrics

Colors are everywhere,decorating nature and our lives.At present,chemical colors such as dyes and pigments are the main colors in fibers and fabrics.Compared with chemical colors,structural colors have wider application prospects due to their diversity of material selection,good color stability and reflection wavelength adjustability.At present,most researches on structural color fibers and fabrics focus on improving basic color properties,such as color saturation and color fastness,etc.,however,researches on their functional application are still insufficient.At present,the research of functional structured color fibers and fabrics mainly focuses on colorimetric sensing,responsive structural color fibers and fabrics have been applied to colorimetric detecting of stress,temperature,solvent and vapor,etc.,especially the detection of solvent and vapor,which has wider application prospects has aroused people’s greater concern.For example,solvent and vapor responsive structural color can be constructed on children’s diapers to realize urine volume detecting,on transdermal patches to realize drug content detecting,and on lab coats or fire suits to realize harmful vapor detecting.However,there are still many problems in solvent and vapor responsive structural color fibers and fabrics:the mechanical stability of the structural color layer is poor,easy to be destroyed,easy to fall off the fabrics;The detection substance is single,the color has no linear relationship with the amount of solvent or vapor;The structural color layers are mainly multi-layer films or three-dimensional opal,which is relatively dense,inevitably hindering the diffusion of solvent and vapor,so slow the response speed;There are no selective response to different kinds of solvents or vapors.To solve the above problems,structural color layers with solvent and vapor response property was constructed on the surface of the fabrics through the selection of materials and the design of structure,which improved its mechanical stability,realized the quantitative detecting of solvent and vapor,and improved the response signal and speed.While solving the above problems,from the perspective of detection substances,the monochromatic response to solvents,multicolor responses to solvents and drug solutions,multicolor responses to volatile organic compound（VOCs）vapor,and selective multicolor responses to benzene,toluene,ethylbenzene and xylene（BTEX）which are more harmful in VOCs were gradually realized,respectively.The specific research contents and main results are as follows:（1）Poly（styrene-n-butyl acrylate-acrylic acid）（P（St-BA-AA））core-shell microspheres were coated on the surface of fabrics by solvent volatilization self-assembly method to construct the structural color fabrics with stable structure and monochromatic solvent response property,its color change property comes from the change of effective refractive index caused by the solvent entering the structural color layer.As a"soft"shell,poly（butyl acrylate）（PBA）（Tg≈-55℃）can effectively improve the binding force between colloidal microspheres themselves,colloidal microspheres and fabrics,while the polystyrene（PS）（Tg≈80-105℃）in the nuclear layer remains spherical,forming an ordered arrangements of photonic crystal structure.Because the outer and inner layers have similar refractive indexes,the obtained structural color coatings were transparent in its original state.When it was wetted with a solvent such as water or ethanol,the corresponding color appeared within2 seconds.The maximum reflection wavelength depends on the particle size of P（St-BA-AA）core-shell microspheres.（2）N-isopropylacrylamide（NIPAM）and acrylic acid（AAc）prepolymers doped with Fe₃O₄@C magnetic microspheres were polymerized on the fabric surface by UV polymerization to construct structure color fabrics with stable structure and multi-color response to solvent,its color change property comes from the change of lattice spacing caused by the swelling of P（NIPAM-AAc）copolymer gel in solvents.Fe₃O₄@C magnetic microspheres were arranged into one-dimensional photonic crystal structures in poly（n-isopropylacrylamide-acrylic acid）（P（NIPAM-AAc））hydrogel.With the absorption and removal of solvent,a reflection peak shift of up to 200 nm can be generated,achieving a multicolor response to the solvent.The visible reflection peak of the structure color fabric has a good linear relationship with the amount of solvent contained inside,so that the solvent content can be quantitatively detected through color changes.In order to expand its application,the solvents were replaced by drug solution to achieve the epidermal temperature-controlled drug release and quantitatively detected of drug contents.（3）Polyurethane（TPU）inverse opal（IOs）structural color coatings were constructed on the fabric surface by template sacrifice method to obtain structural color fabrics with stable structure and volatile organic compounds（VOCs）response property,its color change property mainly comes from the change of lattice spacing caused by the swelling of TPU inverse opal in VOCs vapor.Firstly,SiO₂ photonic crystal templates with appropriate thickness and uniform color were obtained by adjusting the assembly temperature and dispersion concentration on the surface of polyester fabrics.Subsequently,the TPU IOs fabrics were obtained by sacrificing this template.The TPU IOs fabrics can produce a certain shift of reflection peak when in the VOCs vapor,especially in N,N dimethylformamide（DMF）,tetrahydrofuran（THF）,toluene and chloroform vapor,which have a good swelling effect on TPU at room temperature,showed peak shifts of more than 175,128,109,and 88 nm,respectively.The color of TPU IOs fabrics have a good linear relationship with the concentration of VOCs,so quantitative detecting can be achieved.The detection limits of DMF,THF,toluene and chloroform vapor were 1.72,0.89,0.78 and 1.64 g/m³,respectively,and the response times were 105,62,75 and 66 seconds,it is far less than the time required for TPU to reach the swelling equilibrium in it,which is due to the high porosity（≈74%）of the inverse opal structure and the interconnected pore structure,greatly improved the diffusion rate of VOCs in the structural color layer.It showed good signal stability when exposed to VOCs and air alternately as well.（4）PEGDA inverse opal structural color coatings were constructed on the fabric surface by an improved template sacrifice method,and then infiltrated into functional materials to obtain structural color fabrics with stable structure and selectively benzene,toluene,ethylbenzene and xylene（BTEX）response property,its color change property mainly comes from the change of effective refractive index of inverse opal caused by the adsorption of BTEX vapor by functional materials.The functional material poly（4-vinylbenzyl chloride-methyl methacrylate）（P（VBC-co-MMA））was used for selective adsorption of BTEX.NH₂-MIL-88B nanocrystals were used to increase the adsorption capacity and thus increase the signal outputs.There is a good linear relationship between the maximum reflection peak value of the composite PEGDA IOs fabrics and the content of BTEX in the environment,so that the BTEX vapor can be quantitatively detected by color change.The detection limits of BTEX were 2.92,1.85,0.52 and 0.13 g/m³,respectively.In addition,the thickness of PEGDA inverse opal layer is only 5μm and the surface is exposed and porous,which is more conducive to the diffusion of BTEX vapor in it,so the response time and recovery time were only 0.3 and 0.8 seconds.Finally,the structure color coatings were constructed on daily masks to realize real-time colorimetric detecting of BTEX vapor.