Preparation Of Photonic Crystal Paper Based On Phase Change Matrix And Temperature Controllable Displaying/Hiding Properties

As an important technology extension of magnetical responsive photonic crystals?MRPCs?,photonic crystal papers have been demonstrated functions such as writing/erasing and displaying/hiding,which endow them promising applications in the fields of printing displaying,speed encryption and anti-counterfeiting.The previously developed photonic crystal papers realized the rewriting or reversible displaying/hiding function by form a divese lattice constant or infractive index contrast between the displaying area and background,and then showing different color under external stimuli.However,all the above-mentoned functions are based on the same mechanism,it's hard to integrate them together.In this dissertation,the novel photonic crystal paper with reversible writing/erasing and displaying/hiding multiple functions were preprared by using PEG/CA porous phase change material as matrix and flexible Fe3O4@PVP@PAA photonic nanochains as display units.Meanwhile,by utilizing the liquid/solid transformation material PEG and thermosensitive polymer PNIPAM as the matrix,photonic crystal paper with temperature window properities also was prepared and the tunabilities of temperature window range and optical behaviors were investigated.The main research works of the dissertation are as following:?1?The PEG/CA photonic crystal paper was obtained using the magnetic assisting solvent induced phase separation method by using flexible Fe3O4@PVP@PAA photonic crystal nanochians as basic displaying units.SEM images of the typical photonic crystal paper show porous microstructures,both PEG and Fe₃O₄@PVP@PAA photonic crystal nanochians disperated in PEG are encapsulated in the micropores composed of CA.The sizes of micropores are adjusted conveniently by changing the usage of CA.DSC cooling culves was used to verify the phase change properities of photonic ctyatal paper.?2?The test results of optical performances indicate that applying magnetic field perpendicular or parallel to the surface of photonic crystal paper,the as-prepared photonic crystal paper showed magnetical controllable optical switch“on/off”effect,which offers it the corresponding magnetically rewriting function.The intensity of reflective spectra decays slowly after removing magnetic field and the self-maintain time?reflection intensity decayed to half of the maxmum?is up to 8 minute,resulting an excellent bi-stability and a longer self-displaying time of photonic crystal paper.When temperature declined below the phase change terminated temperature(T_offset),the photonic crystal crystal paper turned opaque and hiding the structural color due to the frozen of PEG.Further increasing temperature above the phase change onseting temperature(T_onset),the photonic crystsal paper displays the hidden color again.As a result,photonic crystal paper shows temperature controllable displaying/hinding performance as well as magnetically rewriting function.?3?The self-display time of photonic crystal paper can be tuned by changing temperature,molecular wight of PEG,or the micropore sizes.The decreasing of temperature,the increasing of PEG molecular weight or reducing of micropore size all lead to an entension of self-display time.Moreover,when the pore size decreased to 1?m,the reflection intensity of photonic crystal paper nearly unattenuated with time and temperatue above T_onset and displays brilliant structure color steadyly.Cycle test indicates that temperature controllable displaying/hiding property of photonic crystal paper has superior cycle reversible stability,which reveals that the“space confinement”has a significant influence on the self-maintain time of photonic crystal paper.Furthermore,compared with rigid photonic crystal nanochians,the adoption of soft photonic crystal nanochains endow photonic crystal longer self-display time and multidiretion displaying properties,which demonstrate that the unique relaxation behavior and deformability of photonic crystal nanochains in micropores is another element ensuring photonic crystal paper functional integration.?4?PEG/PNIPAM matrix-based photonic crystal paper was prepared on the double bond modified glass substrate by using magnetic induced assembly and UV triggered polymerization technology.SEM image indicates that the chain-like photonic structure assembled by Fe3O4@PVP colloidal particles are embedded into PEG/PNIPAM composite matrix where PEG are distributed into the gel network of PNIPAM.Optical performances of the typical photonic crystal paper suggest that photonic crystal paper has unique temperature window property.The critical temperature 31?and 9?originate from the hydrophilic to hydrophobic transformation of PNIPAM at high temperature and liquid to solid transformation of PEG at low temperature respectively both cause the opaque white color of photonic crystal paper.Within temperature window range,photonic crystal paper exhibited thermochromic effect due to thermal sensitive property of PNIPAM.Besiseds,the constration effecst from glass substrate provides photonic crystal paper a significant improvement in response to temperature change with a shape stability.Within the temperature window range,the diffraction wave of photonic crystal paper redshift from 469 nm to 689 nm and span 220 nm with temperature decreasing.?5?Temperature window range of photonic crystal paper can be adjusted by changing mass ratio of NIPAM and PEG,PEG molecular weight,the concentration and type of soluble salt.Either the decreasing of the mass ratio of NIPAM and PEG or the increasing of PEG molecular weight give rise to the raising of low critical temperature and the resultant narrowing temperature window range.The introduction of salt will narrow temperature window of photonic crystal paper by decreasing the high critical temperature.The higher of salt concentration,the narrower of the temperature window.As a comparision,the A₂B type salt had greater influence on temperature window range and optical properties of photonic crystal paper.?6?The as-obtained photonic crystal paper demonstrated outstanding cycle reversible property after 16 times cycles and show broad applications in the fields of smart window and information delivering.