Two three-component reversible thermochromic materials,with phenyl benzoate and 1-octade-canol as the solvent respectively,were employed to study the photoaging mechanism of electron-transfer-based organic thermochromic materials.Five light sources with different wavelengths were exerted to illu-minate the thermochromic materials.UV light sources have a center wavelength of 254 nm,302 nm,365 nm and 395 nm respectively,and the visible light source is a xenon lamp with a wavelength range of 400-1 000 nm.The aging progress together with the phenomenon of thermochromic materials were showed and the 1H NMR spectra of each irradiated-component were analyzed to investigate their changes by the irradiation of different light sources.The retention content of each component was evaluated to dis-cover the different changes of thermochromic materials with the various wavelength of light sources.Our results suggest that UV-light-induced photoaging of thermochromic materials is mainly caused by the pho-todegradation of components,and visible-light-induced photoaging of thermochromic materials is primarily due to the loss of solvent component.As the wavelength of UV lights reduces,the photodegradation rate of phenyl benzoate and thermosensitive green dye increases,resulting in the accelerated photoaging rate of corresponding thermochromic materials;whereas the negligible degradation effect of 1-octadecanol by UV lights leads to little degradation of corresponding thermochromic material.Under the visible light,the fact that the loss of phenyl benzoate is much greater than that of 1-octadecanol shows the faster photoaging of phenyl benzoate-based thermochromic material in comparison with 1-octadecanol-based thermochromic material.In conclusion,a wavelength-dependent photoaging mechanism has been discovered for three-components thermochromic materials and this sheds a new light on the anti-photoaging strategy of organic reversible thermochromic materials.
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