Diarylethene-based photochromic polyurethanes for multistate optical memories

Photochromic polyurethanes (PPUs) are synthesised by reaction between a diarylethene end-capped with hydroxyl groups and an aliphatic diisocyanate. In situ polymerisation provides amorphous films with remarkable optical properties. The possibility to vary the amount and the chemical structure of the photochromic monomer without affecting the reactivity of the polymerization allows one to tune in a wide range the optical properties of these films. In addition, different diarylethenes can be mixed together to give copolymers which may find application as photochromic layers for multistate optical memories. A setup for a non-destructive readout based on Raman signal is proposed.