| In this work, fulgides A540 and A670 doped polymer films have been studied by means of photochemical and holographic approaches. Polymer host matrices used are polymethylmethacrylate (PMMA), poly(9-vinylcarbazole) (PVK) and copolymer poly-N-epoxypropylcarbazole/polystyrene (PEPC/PS). Two exposure processes characterize Photochromism in fulgides. Upon UV irradiation or colouring process, a photocyclization E → C occurs, leading to the formation of the closed form C. Besides, such irradiation implies the formation of the non-photochromic open isomer Z by E → Z isomerization. Then, the open form is regenerated by visible exposure: the bleaching process. Photochemically, isomerization reaction is favoured upon short UV wavelength exposure, which implies a poor photostationary state in closed form. Contrary to the colouration, the bleaching process is strongly accelerated in A670 doped films. In holographic study, influence of reading wavelength has been studied on the diffraction gratings. For each fulgide, diffraction efficiency and refractive index variation are stronger in PEPC/PS matrix. The fatigue resistance study gives similar photochemical and holographic results. |
