Polyacrylamide/sodium alginate photochromic hydrogels with enhanced toughness and fast response for optical display and rewritable information record

Abstract

Photochromic hydrogels have broad prospects in wearable optoelectronic technology, rewritable information storage technology, biological imaging agents and chemical sensors, etc. However, it is still a challenge to develop photochromic hydrogels with high transparency, mechanical properties, fast response, stability and color reversibility. In this study, a novel photochromic hydrogel (PAAm/SA-Mo7) was prepared by loading ammonium molybdate (Mo7) into a double-network hydrogel of polyacrylamide (PAAm) and sodium alginate (SA) through a facile one-step method. The introduction of SA and Mo7 significantly improved the mechanical properties of hydrogels, and the maximum elongation and breaking energy are 27.5 and 86 times higher than those of pure PAAm. Furthermore, the photochromic hydrogels have fast response and stable reversible color change. The coloring process of hydrogels can be precisely controlled by the time and intensity of UV irradiation, and the fading process can also be controlled by temperature. The photochromic hydrogel can be applied to self-erasing rewritable media and information storage. This work provides a new approach for the development of flexible wearable optoelectronic materials.