Design of sodium alginate/PVA based high-efficiency recycled rewritten film by water-soluble-regeneration

Due to the severe environmental pollution the paper-making process often causes, the rewritten paper has emerged as a key research area to replace traditional paper. However, it is challenging to achieve application control and maximize resource utilization in various occasions when using the recently reported photochromic papers, which have low fading efficiency and poor regeneration effect. In this study, a composite film made of sodium alginate (SA) and polyvinyl alcohol (PVA) with ammonium molybdate serving as the photochromic component was prepared. The film had mechanical properties similar to paper, good resolution, and visible color after 50 days. With a magnification of 20 times, the distinct borders were still discernible. Through water-soluble-regeneration of the damaged film, the photochromic film can be faded, regenerated and reused, which has a lengthy storage time for information. The film quality and resolution do not considerably degrade after ten cycles of the "information writing—dissolution (fading)—regenerative writing" closed-loop process, exhibiting excellent recycling performance and high recovery rate. Hence, the photochromic film presents a refreshing approach to the design of rewriteable paper.