Optical Properties of Vanadium Oxide/Cellulose Triacetate Photochromic Films

The properties of polymer-based nanocomposites strongly depend on the fillers added and their dispersion on the matrix. Proposing a simple method that can control these variables is essential to obtain nanocomposites with enhanced properties. In this study, cellulose triacetate based nanocomposites modified with sol-gel synthesised vanadium oxide nanoparticles (V2O5) and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO or EPE) triblock copolymer were obtained by two methods: solvent casting (SC, drying at ambient conditions) and solvent vapour annealing (SVA, drying under solvent vapour atmosphere). Nanocomposites were characterised by Fourier-transform infrared spectroscopy (FTIR) and UV-vis spectroscopy. Nanocomposites presented green colour and high transparency, improving the SVA method the surface finish of the films. Moreover, V2O5 nanoparticles provided switchable photochromic properties, changing the film colour from green to pale blue when exposed to UV radiation. Nanocomposites with EPE triblock copolymer presented a more noticeable colour change. As for the speed of the recovery process to the initial state, it increased with the addition of EPE and the sol-gel content. Thus, it was proved that the SVA preparation method was more appropriate that the SC, as well as corroborate that the EPE triblock copolymer and the sol-gel content affected the properties of developed CTA nanocomposites.