Design Of The "Burn After Reading" Encryption System Based On Photoisomerization Properties Of Donor-Acceptor Stenhouse Adducts

Donor-acceptor Stenhouse adducts(DASAs)are a new generation of photo-sensitive molecules triggered by visible light,thus studying their application in the solid state is the key to expanding their application field.In this thesis,the isomerization behavior of DASAs in solid substrates with different properties is systematically studied,and a high-security encryption system is developed based on the related properties.The main content of this thesis includes the following three aspects:1.The effects of different chemicals on the isomerization of DASAs molecules in the solid state were studied.After physically blending DASA-1 with different polymers,the film was coated by the mixtures on the glass substrate.The absorption spectra of the film were used to compare the isomerization rate and efficiency of DASA-1 in different substrates under different stimulus conditions.Poly(ε-caprolactone)(PCL)has a better effect on the reversible isomerization of DASA-1 among all the polymers.The isomerization rate and efficiency of DASA-1 in PCL increased with the increase of PCL concentration,and the molecules showed good anti-fatigue characteristics.Then,small molecules with different groups were added into the polymer matrix Polyvinyl-pyrrolidone(PVP)which had minimal influence on DASA-1’isomerization process,and were physically blended with DASA-1 and then coated on the glass substrate for testing.The experimental results show that the chemical environment full of ester groups could provide a good isomerization environment for DASA-1 molecules,and the polymers with low T_g could also provide enough space for DASA-1 to isomerize.Finally,the structures of DASA-1’s intermediate in the isomerization process were calculated by DFT calculation,and the bond lengths of hydrogen bond and hydroxyl group in DASA-1 under different chemical environments were compared.The existence of ester groups greatly shortened the length of hydrogen bonds in DASA-1,thus promoting the isomerization process of this molecule.2.The small molecules with ester that promote DASAs isomerization in solid substrates were applied to the design of the encryption system.Firstly,the DASA-1 isomerization process on filter paper surface was promoted by using commercial transparent tape,and it was also applied to different solid surfaces such as glass,wood and aluminum foil.Secondly,the PCL solution is used as invisible ink to realize its encryption on different surfaces,which successively proves the complexity and precision of the encryption system established by using DASA-1.3.In order to further improve the encryption level of the encryption system,the"burn after reading"encryption system is developed,which can make the encrypted message disappear after reading.Firstly,the effect of different small molecules with ester group on DASA-1 isomerization on the paper surface was studied,and the glycerol triacetate was selected to make invisible ink.After the invisible inks with different concentrations were tested by an inkjet printer,a binary image"burn after reading"encryption system was established.Finally,the binary image encryption system was developed to grayscale image encryption system based on the influence of different concentration of ester small molecules on DASA-1 isomerization kinetics.