Visible-Light-Responsive Azopolymers with Inhibited π-π Stacking Enable Fully Reversible Photopatterning

Photoswitchable polymers are promising candidates for information storage. However, two general problems for photoswitchable polymers used in rewritable optical storage are photobleaching and inefficient switching processes in solid state. To overcome both of these obstacles, we demonstrate the synthesis of a new visible-light-switchable azobenzene-containing polymer (azopolymer) with nonstackable azo chromophores for reversible and stable information storage. The new azopolymer (PmAzo) contains ortho-methoxy-substituted azobenzene (mAzo) groups on the polymer side chains and shows reversible trans-to-cis or cis-to-trans isomerization by using distinct wavelengths of visible light. PmAzo is better suited for reversible optical storage than conventional UV-responsive azopolymers because visible light avoids the photodamage caused by UV light. Additionally, mAzo groups do not pi-pi stack in solid state, making photopatterning of PmAzo fully reversible. Moreover, photoinduced patterns on PmAzo can be stored for more than half a year. These properties distinguish PmAzo as a promising candidate for rewritable and stable information storage.