Nanoporous-template-modulated azopolymers for enhancing reversible photo-transformation

Recyclable utilization of light energy is essential for current information processing. Photochromic films including azopolymers play a key role in capturing photons, in which many optical manipulations can be achieved. Commonly, inorganic nanoparticles are incorporated into organic azopolymers to increase photo-excitation efficiency and reduce the volume shrinkage rate. However, the aggregation of azopolymers and the uneven distribution of nanoparticles can affect both the material transparency and chemical activity. Reversibility of photo-transformation for such a photochromic system is thus inhibited. Here, a new method is proposed that titania porous films with high optical transparency are used as a nano-template for azopolymer deposition. The results showed that inorganic nanoporous structures not only enhance dye adsorption but also inhibit azopolymer aggregation. In a holographic recording, the diffractive signal is increased 3.6 fold and kept constant for a long time with the support of the TiO2 framework. Based on the property, erasable hologram reconstruction is obtained in the nano-hybrid film by the alternated excitation of coherent lights and single light from a blue laser. This work shows a bright way to inhibit molecule aggregation in solid matrices and contributes to exploit updatable photo-transformation devices.