Preparation Of Crack-free Photonic Crystal

Photonic crystals(PCs)are a kind of 3D dielectric materials which are composed by materials with different refractive index.PC possesses special light manipulation properties owing to its photonic bandgap.As a new type advanced functional polymers,and has been widely used in optical devices,smart display,optical sensor,solar cells,fluorescence enhancement and so on.The traditional fabrication methods of PC include laser etching and holographic lithography,which is arduous,expensive and cannot achieve large-area fabrication.Nowdays,self-assembly method is intensively developed due to its superior characteristics of easy operation,low costs,and safety etc.However,in the process of self-assembly of latex spheres,the increasing adhesion of the substrate and the tensile stress caused by the self-shrinkage of the latex spheres,which resulting in cracks in the PC microstructure.These cracks severely affect the optical quality and greatly restrict its application in optical devices.In this paper,the crack-free photonic crystal was self-assembled by monodispersed latex spheres.The interaction force between latex spheres was enhanced by modifying latex spheres with different contents and different kinds of functional monomers,metallic salt and so on.(1)Monodisperse poly(styrene-acrylamide)(P-(St-AM))latex spheres with regular morphology were prepared with emulsion polymerization by using styrene(St)and acrylamide(AM)as comonomers,sodium dodecyl benzene sulfonate(SDBS)as the emulsifier,and ammonium persulfate(APS)as the initiator.It was continuously stirred at 75? for 8 h.The resulting crack-free PC was obtained by carefully adjusting the AM content of latex spheres solution.(2)Monodisperse poly(styrene-methyl methacrylate-acrylic acid)(P-(St-MMA-AA))latex spheres with regular morphology were prepared with emulsion polymerization by using St,methyl methacrylate(MMA)and acrylic acid(AA)as comonomers,SDBS as the emulsifier,APS as the initiator.It was continuously stirred at 75? for 8 h.The resulting crack-free PC was obtained by carefully adjusting the AA content of latex spheres solution.(3)Monodisperse P-(St-MMA-AA)latex spheres with regular morphology were prepared with emulsion polymerization by using St,MMA and AA as comonomers,SDBS as the emulsifier,APS as the initiator.It was continuously stirred at 75? for 8 h.The resulting crack-free PC was obtained by carefully adjusting the metallic copper and zinc salt content of latex spheres solution.(4)Monodisperse P-(St-MMA-AA)latex spheres with regular morphology were prepared with emulsion polymerization by using St,MMA and AA as comonomers,SDBS as the emulsifier,APS as the initiator.It was continuously stirred at 75? for 8 h.The resulting crack-free PC was obtained by carefully adjusting the p H value of latex spheres solution.