Synthesis and properties of low‐cost, photochromic transparent hydrogel based on ethaline‐assisted binary tungsten oxide‐molybdenum oxide nanocomposite for optical memory applications

Abstract

AbstractTungsten oxide‐based composites are important smart materials for wider usage in efficient energy windows, rewritable inks and other colored displays. However, the problem of agglomeration has made it challenging to be employed in transparent, photo‐reversible materials especially in functional hydrogels. We herein report the preparation of high transparent hydrogel using water‐soluble tungsten oxide‐molybdenum oxide nanocomposites. The hydrogel was characterized with FTIR, TGA, XPS, SEM, and UV–Vis–NIR, while the mechanical properties were also analyzed. The FTIR confirmed that the metal oxides combined with the polymer units via strong metal‐oxygen bond. For the TGA, the as‐prepared hydrogel was still able to maintain a weight loss of 18.12% at 500°C compared to 10.45% for pristine hydrogel. Also, the EDX mapping revealed microscopic metal oxides particles sizes, without any cluster phenomenon appearance. Additionally, the as‐prepared hydrogel revealed good mechanical properties as it could sustain a high deformation ratio (λ) of 86.3% at a stress of 60.3 MPa due to hydrogen bond crosslinking and ionic bond linkages. Moreover, the hydrogel exhibited high percentage transmittance (T%) of ~83%, as well as remarkable photochromic response, with absorption peaks at ~490, ~630 and ~730 nm appearing as the exposure time of the UV light increases. Furthermore, change in color was observed in 5 s, deepening to deep blue‐black at 300 s exposure to UV, while complete reverse fading was achieved in ~6 h in ambient air without external stimulus, hence making it a good potential for applications in various optical memory, sensors and rewritable devices.