Photosensitive polymers undergoing photo-Fries reaction for volume holography: understanding the mechanism of refractive index modulation

Polymers that undergo to photo-Fries reaction show a remarkable modulation of the refractive index that makes them interesting in the field of volume holography. In order to understand the mechanism of the change in the refractive index we performed theoretical calculations (DFT) on model molecules. The results show that the modulation can be ascribed to a change in the polymer density upon photo-reaction whereas the contribution due to a change in molecular polarizability is small. The theoretical conclusions have been supported by experimental results on two polymers: Polyformyloxide styrene (PFS) and polyacetoxystyrene (PAS).

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