On spontaneous and photoinduced orientational mobility of dye molecules in polymers

Abstract A few years ago, a theoretical model has been introduced for the simulation of photoinduced reorientation of dye molecules in amorphous polymers (photoinduced anisotropy, photoassisted electrical poling and all-optical poling). In the present paper, approximations and validity conditions are discussed in details. Simulations of the transient behavior of photoinduced anisotropy and of photoassisted poling, have been computed for different sets of parameters. Here, simulations are compared with new experimental results on photoinduced dichroism and electrooptic properties of azo-dye-containing polymer films. Experiments show an inhomogeneity and a time variation of angular diffusion constants, but also of absorption spectra. These inhomogeneities cannot be introduced in the theoretical model, nevertheless, simulations describe satisfyingly the mechanisms of molecular reorientation induced by trans–cis photoisomerization. The influence of different parameters can be understood, for instance the reverse cis–trans photoisomerization and the anisotropy of the cis state. Some similar results with spiropyran are summarized.

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