Construction And Properties Of The Responsive Polymer Photonic Crystal Films

In recent years,with the development of material science,photonic crystal materials with excellent optical properties have attracted extensive attention,and show unique advantages in the fields of visualization,portable analysis and detection,color printing and anti-counterfeiting.As a kind of highly ordered periodic dielectric materials,the periodic modulation of its dielectric constant in space will produce a photonic band gap in the photonic band structure,which will prohibit the passage of light in a specific frequency range and show a unique structural color,The structural color can change its color and light intensity by adjusting its lattice constant or average refractive index through physical or chemical stimulation of the external environment.These responsive photonic crystal materials(RPCs)have important applications in the fields of color display,biological and chemical sensing,ink and photocatalysis.In this dissertation,a series of work is carried out around the preparation of new colloidal particles and the method of further constructing them into responsive photonic crystal materials are mainly studied.On this basis,photonic crystal materials are extended in the fields of sensing,large-area preparation,color writing and color rendering.The specific contents are as follows:In the second Chapter,because the responsive photonic crystal hydrogel can change the structural color under external stimulation,it shows great potential in various applications.However,the traditional polyacrylamide hydrogel has poor mechanical properties and its optical signal is not ideal,so its practical application is greatly restricted.Inspired by the excellent mechanical properties of polyurethane,a new type of Photonic Crystal Hydrogel elastomer was synthesized by combining non-ionic UV curable polyurethane with cross-linked polystyrene poly(N-isopropylacrylamide)(PS-co-PNIPAM)microspheres.The photonic crystal hydrogel has ideal optical properties and narrow reflection half width.When the swelling rate changes,the tensile strength of elastomers varies between 0.1 MPa and 0.43 MPa.As proof of concept,SCN~-was selected as the target analyte.SCN~-can cause the specific swelling behavior of the photonic crystal hydrogel(Hofmeister effect)and its peak wavelength can linear variation in the logarithmic range of 5μm to 500 m M,which enables this material to quantitatively determine the content of SCN~-ions in water within a certain range,get rid of the shackles of large instruments,and realize simple and portable detection.In the third Chapter,the application of stimuli responsive microgels in drug delivery materials has broad prospects,but it is still a great challenge to establish a real-time and simple method to monitor the degree of drug release in situ.In the last chapter,based on the photonic crystal hydrogel,we further developed a thermosensitive microgel nanoparticle and combined it with the polyurethane prepared in the previous chapter to prepare a PAAm-co-PNIPAM-co-PUA composite photonic crystal hydrogel film,which has adjustable structural color and drug delivery capability.As proof of concept,we chose bovine serum albumin(BSA)as the model of protein drugs.The film will show different optical signals during the release of BSA.In addition,we also used the film as a dressing on our hands to verify its practicability.Therefore,the effect of photonic crystal hydrogel on the visualization of drug release process is achieved.In the Chapter 4,photonic crystal films with periodic dielectric structure show great prospects in the development of reusable and environmentally friendly paper substitutes because of their unique dye-free and non-photobleaching properties.The multi-functional hard core/soft shell nanoparticles with controllable size were prepared by semi continuous seeded emulsion polymerization.Compared with conventional colloidal particles,the glass transition temperature(T_g)of the shell of the particles we prepared is relatively low.Therefore,at room temperature,these core/shell nanoparticles can self-assemble to form a large area(more than 10 cm~2)and dense and orderly transparent photonic crystal film.This simple manufacturing route makes the continuous high-throughput production of photonic crystal films possible.The formed film not only has the ability of rewritable solvent(water/ethanol)and multi-color painting,but also can quickly and reversibly change color mechanically.In addition,these photonic films have excellent mechanical properties due to the good compatibility of the core/shell interface.In contrast to the preparation of photonic crystal paper in the previous chapter,in the work of the Chapter 5,we prepared a reactive active colloidal particle and developed an intelligent ink for color writing.Free radical emulsion polymerization was used to copolymerized diacetone acrylamide and styrene to prepare colloidal particles containing active ketones.When the colloidal particles self-assemble to form a structural color coating,the ketone group will covalently crosslink with adipic dihydrazide in the system to form a hydrazone bond make structural color coating firmly combined with the paper.Adding a small amount of carbon black can absorb incoherent scattering and make the structural color brighter.Because the dried coating is long-range ordered on the micro array,its structural color is angle dependent;Moreover,due to the hydrophilicity of the coating,the corresponding structural color will significantly red-shift after wetting the coating with water.All these characteristics make this active photonic crystal ink have great application prospects in the fields of color writing,intelligent anti-counterfeiting and so on.