Preparation And Properties Of Responsive Photonic Crystal Films Based On Photonic Nanochains

Thermoresponsive photonic crystals films（TRPCF）can change color under temperature stimulation,their rich and bright structural colors and fast response play an important role in colorimetric sensing,display,camouflage and other fields.The reported thermosensitive photonic crystals are mainly based on the composite of thermosensitive gel and periodic ordered structure,and the photonic crystal structure is embedded in the homogeneous thermosensitive gel.They directly control the lattice spacing through the volume change of the thermosensitive gel under the stimulation of external temperature,thereby realizing the control of structural color.Generally,reducing size and introducing micropores are considered as two effective ways to improve their response speed.However,these two methods usually degrade the mechanical properties of the photonic crystal films,thereby causing instability of the optical properties.In order to solve the above problems,in this paper,based on the composite of non-temperature-sensitive photonic nanochains with high cross-linking degree and a temperature-sensitive matrix,a thermo-responsive photonic crystal film of a heterogeneous gel system was prepared,which was further combined with the PET matrix,and further integrated with the PET matrix to develop a fast-response flexible TRPCF.The main research contents of the paper are as follows:（1）Using superparamagnetic Fe₃O₄@PVP@P（AA-co-HEMA）PNCs with high cross-linking degree as the chromogenic unit,a novel heterogeneous thermoresponsive photonic crystals films（TRPCF-PNC）was prepared by ultraviolet photopolymerization assisted by a magnetic field.Compared with the homogeneous thermoresponsive photonic crystal embedded in the particle chain structure of the same thermosensitive matrix（TRPCF-P）,the typical TRPCF-PNC sample exhibits fast thermochromic properties at a large expansion ratio of the matrix,which can achieve the response to 44°C thermal stimulation within 12 s.The heterogel-based TRPCF-PNCs exhibit a different thermoresponsive mechanism from reported TRPCF,and the high stiffness of PNCs endows TRPCF-PNC with fast response speed and relatively narrow photonic bandgap regulation.In addition,PNCs significantly improved the mechanical properties of TRPCF-PNC,and the elongation at break of TRPCF-PNC along the orientation direction of PNCs was as high as 230%,which was 6 times higher than that of the pure gel matrix,which was 37.5%.The cycle stability test results of TRPCF-PNC between 26℃and 44℃show thatthe surface of the TRPCF-PNC is smooth and intact,and the peak position change amplitude at the same temperature is less than 10 nm,showing excellent optical stability.（2）The surface of the PET film was hydrophilically modified by UV radiation grafting modification method,and the flexible TRPCF-PNC was prepared using the modified PET as the substrate.TRPCF-PNC is firmly anchored to the PET surface and exhibits excellent surface conformality.The optical performance test results show that changing the composition and cross-linking degree of the thermosensitive gel matrix and PNCs can realize the regulation of the photonic band gap,showing a wealth of optical performance regulation methods.（3）The camouflage leaves tailored by typical TRPCF-PNC based on a PET flexible substrate can simulate real leaves of different colors by changing the temperature,and realize the unrecognizable and fast fusion with the real leaf background,showing the important application prospects in the field of camouflage.