Ester matters? Promoting photoisomerization of donor–acceptor Stenhouse adducts in the solid state and “burn after reading” encryption

Abstract

Striking towards secret leakage is the key challenge in information encryption. In this work, we reported a “burn after reading” secrecy system based on the reversible photoisomerization of donor–acceptor Stenhouse adducts (DASAs) on surface. The isomerization rate and efficiency were demonstrated to be remarkably promoted by the polymers with low Tg and appropriate chemical environment. Furthermore, the isomerization process was unfolded by DFT calculation, where the intramolecular hydrogen bond lengths (OH…O) play a critical role to enhance the isomerization between linear and cyclic DASAs. Polycaprolactone as the invisible inks were stamped onto paper and glass surface to achieve reversible appearance and disappearance of secret messages and fluorescent micropatterns. More importantly, the “burn after reading” was realized using small molecule glyceryl triacetate (GTA) as the invisible inks. Heat triggered cyclic-to-linear isomerization of DASAs and encrypted the information, meanwhile removed the GTA from paper surface and completely “burned” the secret messages.