Photochromism of clay-diarylethene hybrid materials in optically transparent gelatin films

The dispersion of clay-diarylethene hybrid materials into an ionic biopolym er, gelatin, was investigated for the successful preparation of highly func tional photochromic films. A mixture of the gelatin and the clay-diarylethe ne hybrid material dispersed in aqueous N,N-dimethylformamide (DMF) was cas t on a glass plate. The film obtained after drying at 50 degreesC was trans parent 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 th at the diarylethene molecules were able to remain in the clay interlayers w ithout spilling into the bulk gelatin matrix. Moreover, UV-visible polarize d spectroscopic analysis revealed the clay-diarylethene hybrid materials to be oriented essentially parallel to the glass plate, indicating that the d iarylethene molecules are aligned as inclined interdigitated monolayers wit hin the clay interlayers.