Switching between Solid and Liquid Phases of Spiropyran by Photochromic Reaction

The colorless liquid spiropyran possessing long alkyl chains (SP1822) is transformed to the colored merocyanine state upon UV irradiation. Then, two different solids (J- and H-aggregates) are formed selectively depending on the temperature. These aggregates are converted independently to the initial liquid thermally and photochemically.