Photochromism of Clay−Diarylethene Hybrid Materials in Optically Transparent Gelatin Films

The dispersion of clay−diarylethene hybrid materials into an ionic biopolymer, gelatin, was investigated for the successful preparation of highly functional photochromic films. A mixture of the gelatin and the clay−diarylethene hybrid material dispersed in aqueous N,N-dimethylformamide (DMF) was cast on a glass plate. The film obtained after drying at 50 °C was transparent in the visible light region and showed highly reversible coloration and decoloration by alternative irradiation with UV light of around 300 nm and visible light of around 600 nm. X-ray diffraction analysis indicated that the diarylethene molecules were able to remain in the clay interlayers without spilling into the bulk gelatin matrix. Moreover, UV−visible polarized spectroscopic analysis revealed the clay−diarylethene hybrid materials to be oriented essentially parallel to the glass plate, indicating that the diarylethene molecules are aligned as inclined interdigitated monolayers within the clay interlayers.