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Effets photomecaniques dans les cristaux organiques photochromes

Abstract : Photochromism is defined as a reversible photoisomerization between two forms having different absorption spectra. The reaction can occur even in the crystalline state when the photoinduced molecular structural changes are not too large. In this report, we study spectroscopic properties of nano- and microcrystals of organic photochromic molecules. For this purpose, we have developed a microspectroscopy setup with a 500nm resolution. During the study of single-crystals of a diarylethene, we have observed a new photomechanical effect. As usual, colorless single crystals turn colored under UV-irradiation. However, when the energy absorbed by crystals reaches about 10µJ, they jump. Moreover, when we prevent crystals from jumping, parallel, equidistant cracks appear due to elastic energy dissipation. These two photomechanical effects correspond to the relaxation of the stresses accumulated in crystals during the photoreaction. We suggest the hypothesis that jumps and cracks are preceded by a periodic surface deformation which could be related to a Grinfeld instability.
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https://tel.archives-ouvertes.fr/tel-00009971
Contributor : Isabelle Colombier <>
Submitted on : Thursday, August 25, 2005 - 9:57:39 AM
Last modification on : Tuesday, September 11, 2018 - 11:00:02 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:56:28 PM

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  • HAL Id : tel-00009971, version 1

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Isabelle Colombier. Effets photomecaniques dans les cristaux organiques photochromes. Physique [physics]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00009971⟩

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