Elastic Deformation Responsive Photonic Crystal Hydrogels With High Strength

Photonic crystal hydrogels,as unique optical materials containing regularly periodically ordered structures,which can regulate the specific wavelength of light,had a wide range of applications in the field of sensors.However,the poor mechanical properties of traditional hydrogel led to that most of the reported photonic crystal hydrogels had poor mechanical properties,which reduced their applications in the field of mechanical sensors.Based on this,elastic deformation responsive photonic crystal hydrogels with high strength were prepared by combining photonic crystals with nano composite hydrogels.The chemical structure,morphology,mechanical properties and optical properties were characterized and analyzed.The main contents and conclusions are as follows:(1)The P(St-MMA-AA)composite microspheres with uniform size and good dispersion were prepared by the emulsion polymerization method,in which the styrene(PS),methyl methacrylate(MMA)and acrylic acid(AA)were main raw materials.The size of microspheres was controlled by changing the amount of emulsifier(SDS)and the speed of agitator by means of orthogonal experiment.The composite microspheres with particle size of 115-207 nm were prepared for the preparation of photonic crystals.(2)Combine P(St-MMA-AA)photonic crystals prepared by the vertical sedimentation self-assembly and alumina nanocomposite hydrogels(AAD gels)via in situ free-radical polymerization,we got tensile stress-responsive photonic crystal hydrogel films.Experimental results showed that hydrogel films prepared by different photonic crystals of including 135 nm,159nm and 185 nm can response to tension.The structure color of photonic crystal gel film had the corresponding blue shift when external tensile stress increased.What’s more,hydrogel films had good fatigue resistance and repeatability during stretching process.As the increasing of AA and aluminium hydroxide content in the initial solution,the cross-linking densities of photonic crystal hydrogels increased,leading to more excellent mechanical properties.When the nanoparticles content was 10 wt % and AA was 30% in the monomer,mechanical strength of the photonic crystal hydrogel films can reach the maximum value up to 1870 k Pa.(3)After mixing high concentration of 50% P(St-MMA-AA)composite microspheres and acrylamide(AM),photonic crystal hydrogel monolayer films were prepared via in situ free-radical polymerization because of repulsion-induced precipitation assembly.Then,the ZAD gels precursor solution was injected into the monolayer films to form bilayer films.The results showed that the gel monolayer films can respond to p H and solvent,and the bilayer films can respond to tensile stress.The structural color of the bilayer films gradually changed from red to yellow,green,and blue when stretched,which covered almost the whole visible-light region.And the films had good fatigue resistance and repeatability during stretching process.