Stimuli-responsive cholesteric liquid crystal soft photonic color film

Abstract

In order to realize multiple information encryption or storage of soft photonic crystal patterns，a stimuli-responsive cholesteric liquid crystal（CLC）soft photonic color film is designed and fabricated based on the thiol-acrylate Michael addition and photopolymerization reaction. First，the initial color of the reaction mixture is adjusted by changing the ratio of the doping chiral agent. Then small molecule liquid crystal is added into the mixture to adjust its viscosity. Finally，the temporal programming of the cross-linking density of the CLC soft photonic color film is carried out by ultraviolet （UV）exposure at different stages of the reaction， and the spatial programming is performed cooperatively with the help of photomasks. The experimental results indicate that the Bragg reflection wavelength of the CLC film only moves 19 nm during the reaction process of over 600 min. However，by locally modifying its color response via spatio-temporally dual-programming，the soft photonic film with invisible patterns can be made to gradually take on a colorful appearance from red to green with stretching，and reflected wavelength coverage over 100 nm. This stimuli-responsive soft photonic color film can be employed for the dynamic display of photonic crystal patterns，and is potentially useful for multiple anti-counterfeiting or information storage.