Write-Read-Erase Molecular-Switching System Trapped in a Polymer Hydrogel Matrix

In this paper we report the encapsulation of the compound 4′,7‐dihydroxyflavylium in a water‐permeable crosslinked poly(2‐hydroxyethyl methacrylate) matrix. The water permeability of the polymer and its transparency allow the use of pH and light stimuli to attain different states on the network defined by the various chemical reactions (multistate/multifunctional system). Unlike in water, in the polymer the compound 4′,7‐dihydroxyflavylium encapsulated exhibits a thermal barrier between the cis‐ and trans‐chalcones, a necessary requirement to define a write–read–erase cycle. An optical memory has come closer to realization with the encapsulation of 4′,7‐dihydroxyflavylium in a water‐permeable crosslinked polymer hydrogel matrix. The water permeability and transparency of the polymer allow the use of pH and light stimuli to attain differently colored states in the flavylium system which can act as a reusable photographic film (see Figure).