Gelatin/PVA composited photochromic film for light printing with fast rewritability and long-term storage ability

Rewritable paper exhibits the potential to replace conventional paper due to its reusable properties. However, compared to conventional paper, rewritable paper can fade, making it impossible to store information stably for a long time in a daily environment, which limits its application. Here, a series of photochromic gelatin/polyvinyl alcohol (PVA) composited films containing polyoxometalate were prepared. The addition of PVA had a significant effect on the mechanical, transparent, photochromic and fading properties of the film. The addition of PVA significantly inhibited the fading process of the film after photochromism. This was due to the increase of crosslink density in the film and the existence of hydrogen bonding between PVA and inorganic photochromic ammonium molybdate. Despite this, the film was able to achieve complete fading in 1.5 days in a humid environment and the fading time could be further accelerated to 2 h by heating. This film could display information stably over a long time while being rewritable. It was expected that this simple and effective design strategy is conducive to the development of a new generation of rewritable paper.