Photochromic polymer is defined as a series of materials based on photochromic units in polymer chains,which produces reversible color changes under irradiation with a particular wavelength.Currently,as the research progresses,it shows increasing potential applications in various fields,such as anti-counterfeiting,information storage,super-resolution imaging,and logic gates.However,there is a paucity of published reviews on the topic of photochromic polymers.Herein,this review discusses and summarizes the research progress and prospects of such materials,mainly summarizing the basic mechanisms,classification,and applications of azobenzene,spiropyran,and diarylethene photochromic polymers.Moreover,3-dimensional(3D)printable photochromic polymers are worthy to be summarized specifically because of its innovative approach for practical application;meanwhile,the developing 3D printing technology has shown increasing potential opportunities for better applications.Finally,the current challenges and future directions of photochromic polymer materials are summarized.
Time-temperature indicator(TTI)technologies enable real-time quality monitoring of perishable products during transportation-storage.Photochromic material-guided TTI offers significant benefits in terms of nondestructive and convenient visualization.However,photochromic materials with low-temperature-range dependency are rare,limiting the development of cryogenic temperature-responsive TTI methods.This work proposes a novel temperature-gated bicolor photochromic material.Using NaYTiO_(4)as the matrix,which has a native blue color center related to the intrinsic deep trap,Bi^(3+)ions are incorporated to create extremely shallow trap levels(100-230 K)along with an associated longwavelength absorption color center.By combining these two color centers with extended full-spectrum absorption,NaYTiO_(4):Bi^(3+)converts to dark gray upon ultraviolet irradiation below 233 K.With increasing temperature,the trapped electrons in shallow traps are released first,and the color state becomes yellowish until it completely fades back to white above 573 K.The liberation of thermally activated charge carriers is positively correlated with the storage duration and the ambient temperature.For the first time,we realize a TTI method based on photochromic materials at extremely low temperatures,which allows for direct visualization of quality management for cryogenic products without further information extraction and conversion.This work demonstrates the significant ability of photochromic materials as advanced information-recording materials in the next generation of smart TTIs.
Yunwen BaoWei HuYiqing ZhouZhongxian QiuJingxuan ZhangJiaping ZhangJiaren DuShixun Lian
