Preparation Of Structural Color Materials For Solvent-Responsive Double-Inverse Opal Photonic Crystals And Their Properties

By introducing movable microspheres into the inverted opal backbone,the double-inverse opal photonic crystal（DIOPC）formed by the“composite”of opal and inverse opal is affected by the scattering effect of the random distribution of microspheres in the holes,which limits the structural color of DIOPC.Under external stimuli,the transition from disordered distribution to the ordered arrangement of microspheres in the holes of DIOPC may endow DIOPC with responsive structural color.Based on the above analysis,DIOPC and bilayer double-inverse opal photonic crystal（BDIOPC）film materials were constructed in this paper.By infiltrating and filling the gaps of DIOPC with ethanol and water,the microspheres were evenly suspended in the liquid to form an ordered structure,realizing the fast responsive structural color to ethanol and water.At the same time,the BDIOPC film material realized the structural color mixing based on the two-photon band gap in the ethanol response process,and the DIOPC film material could still develop color fast after 500 times of repeated water writing.The specific work is as follows:（1）To construct DIOPC film materials with ethanol-responsive structural color,the silica-coated polystyrene（PS@Si O₂）opal template was filled with ethoxylated trimethylolpropane triacrylate（ETPTA）,poly（ethylene glycol）（200）diacrylate（PEGDA）and acrylic acid（AA）（volume ratio 2:8:1）.DIOPC and BDIOPC film materials with PS microspheres embedded in the pores of the polyacrylate inverted opal backbone were prepared after photopolymerization to form polymer and etching Si O₂ shell.The prepared DIOPC film material has the ability of ethanol to quickly penetrate and fill the gaps in～1 s,so that the randomly distributed PS microspheres in the holes of DIOPC are uniformly distributed by buoyancy,realizing the ethanol-responsive structural color of DIOPC.In BDIOPC film material,the scattering effect of“variable thickness layer”is used to hide the QR code pattern of“fixed thickness layer”,and the anti-counterfeiting of“hiding-display-color”of the QR code pattern is realized by infiltrating and filling the gaps of“variable thickness layer”and“fixed thickness layer”respectively with ethanol.Using ETPTA and PEGDA（volume ratio 1:4）as filling monomers,combined with mask-assisted heat treatment,patterned DIOPC and BDIOPC anti-counterfeiting film materials were constructed.Based on the difference between the pattern and the background structure,the coding pattern has the anti-counterfeiting effect of hiding in the normal environment and responding to structural color in ethanol.（2）To realize the water-responsive structural color of DIOPC,the backbone material of DIOPC was adjusted to have more hydrophilic groups.ETPTA,PEGDA,and AA（volume ratio 1:4:1）were selected as filling monomers to construct the DIOPC film material,and its contact angle with water is～48.5°.The surface of DIOPC was treated with saturated sodium carbonate solution,the carboxyl group in the inverted opal backbone material was changed into sodium carboxylate with stronger hydrophilicity,and its contact angle with water is changed to～28°,which realizes the rapid infiltration and filling of water in the gaps of DIOPC for～2 s.The randomly distributed PS microspheres in the holes before being filled with water were suspended in the water and evenly distributed,realizing the water-responsive structural color of DIOPC.Furthermore,the patterned DIOPC anti-counterfeiting film material was constructed by selectively regulating the surface hydrophilicity of DIOPC with saturated sodium carbonate solution.Based on the difference in hydrophilicity between pattern and background,the coding pattern has the anti-counterfeiting effect of hiding in the normal environment,responding to structural color in water,and further hiding in ethanol.Furthermore,ETPTA,PEGDA,and AA（volume ratio 1:4:2）were used as filling monomers,and the prepared DIOPC was treated with saturated sodium carbonate solution to construct DIOPC ethanol concentration detection film materials.The higher carboxyl anion content in the inverted opal backbone material increases the electrostatic repulsion between the polymer molecular chains,making the inverted opal backbone swell in water.Based on its swelling difference in different concentrations of ethanol solutions（the maximum reflection peak shift exceeds 90 nm）,it can be used to detect the concentration of ethanol-water mixed solutions.（3）To enable the DIOPC film material to quickly develop color by water writing,and can still display color rapidly after repeated use,the DIOPC film materials with a large area（21×17 cm）were constructed by filling the gaps of DIOPC material with ethanol solution of acrylamide to form polyacrylamide（PAM）after photopolymerization.The strong hydrophilic PAM can realize the rapid infiltration and filling of water in the gaps of DIOPC,improve the transformation speed of the ordered rearrangement of PS microspheres in the holes,and realize the fast water-responsive structural color of DIOPC（～0.8 s）.The DIOPC film material filled with PAM has cycle stability of>500“write-erase-write”cycles.Furthermore,the patterned DIOPC anti-counterfeiting film material was constructed by selectively filling the gaps of DIOPC with PAM.Based on the difference in hydrophilicity between pattern and background,the coding pattern has the anti-counterfeiting effect of hiding in the normal environment,responding to structural color in water,and further hiding in ethanol.