Thermally Responsive Photonic Crystal/Liquid Crystal Composites:Design,Preparation And Application

Photonic crystals are ordered structures that are produced by periodically arranged dielectrics of different dielectric constants.By tuning cyclic refractive index changes of photonic crystals,band gap of a certain wavelength of light can be controlled.In recent years,researchers have combined photonic crystals with liquid crystal materials,ferroelectric materials,ferromagnetic materials,semiconductors and gels,and have obtained functional photonic crystals in response to external light,electric field,magnetic field,temperature,mechanical force and other stimuli.Industrial magnitude massive applications of photonic crystals are also led by large multinational companies such as Apple Inc.In this paper,the photonic crystals(PCs)were combined with liquid crystals(LCs),and PCs/LCs composites were investigated by means of polarizing microscope.The optical properties of PCs/LCs composites were investigated by DSC.The optical properties and thermal deformation mechanism of PCs/LCs composites were observed by optical fiber spectroscopy.Microscopic morphology of PCs/LCs composites were observed by scanning electron microscope.The main research contents are as follows:(1)The silica microspheres with uniform particle size were prepared by modified Stober method.The silica microspheres with uniform particle size are self-assembled by vertical sedimentation to form photonic crystals.The particle size distribution of silica microspheres and the angular dependence and optical properties of photonic crystals were studied.The experimental results showed that the silica microspheres prepared by the improved Stober method are monodispersed systems.By adjusting the ammonia concentration,we prepared a series of silica microspheres with different particle sizes and photonic crystals of different colors were obtained by self-assembly.The obtained photonic crystals are highly reflective,arranged in order and regular.(2)The photonic crystals were combined with liquid crystals to form PCs/LCs composites,and their application as thermally driven actuator was studied.The polymerizable liquid crystal monomers were selected and mixed,and then the liquid crystal monomers were filled into the liquid crystal cell,and after that the PCs/LCs composite film was obtained by light curing.The reversible deformation behavior of PCs/LCs composites under temperature change was studied.When temperature rises,the PCs/LCs composite is bent toward one side;when temperature decreases,the bent PCS/LCS composite material gradually stretches to its original state.(3)An inverse opal photonic crystal/liquid crystal composite was designed and fabricated.Polymerizable monomer was filled in a silica photonic crystal template,and polymer/photonic crystal composite was obtained after curing under UV light.After covered by a mask,the polymer/photonic crystal composite file was selectively etched to obtain a local inverse opal film.The temperature-sensitive liquid crystals were selected and mixed,and filled into the void of inverse opal film.The encapsulating monomer is sprayed on to the inverse opal film and cured to obtain an inverse-opal structured temperature sensing material.In a specific temperature range,when the temperature changes,the material corresponding to show different colors.