To achieve a fast photochromic response in solid matrix, photochromic molecules/segments have been either dispersed into elastomers via physical doping or linked to glassy polymers by soft units through covalent bonding. However, the former is lack of high mechanical strength and the latter owes the drawback of time-consumption of synthesis. Here, we propose a facile strategy of co-solvent evaporation to prepare polymer-dispersed photochromic organogel where both high mechanical strength of the glassy polymer matrix and solution-like fast photochromism of the photochromic molecule within organogel can be retained concurrently. Glassy PVA matrix and dispersed organogel of 1,3:2,4-di- O -benzylidene- d -sorbitol/poly(propylene glycol) (DBS/PPG) provide high mechanical strength and sufficient free volume for intramolecular rotation of photochromic spiropyran (SP), respectively. Interestingly, these thin films behave a solution-like decoloration the decay rate of which is 65–70 fold faster than that in the SP-directly doped PVA film and only slightly slower than those in their corresponding PPG solutions.
Yuedan Wang,Mengjie Li,Yun Lin,Anqi Li,Changhui Li,Mufang Li,Wenwen Wang,Qiongzhen Liu,Dong Wang
In this paper, a high-performance photochromic system with rapid fading was constructed by adjusting the pH of tungstate, introducing dopants, reducing agents and polydimethylsiloxane (PDMS) coatings. In addition, the chromaticity of photochromic materials can be precisely controlled by changing the doping and reducing agent content. Continuous large-scale fabrication of novel photochromic fiber/fabric using dip coating and wet spinning has been proposed. The photochromic fibers/fabric exhibit significant color contrast (ΔE = 40.2), rapid color switching (5 s), fast fading time (10 min), good cycling stability (20 times), as well as long color-retention (7 days) under UV/visible light irradiation. Photochromic fibers after packaging with PDMS have excellent water resistance and maintain good photochromic properties even after washing (20 cycles) when exposed to water, ethanol, and detergent solutions. The photochromic fibers can be used as wristbands or embroidered on various textiles as wearable UV indicators. With the increase of UV dose, it has real-time and sensitive color rendering, which provides early warning for high dose UV radiation. The color-changing mechanism of photochromic fabric has been studied. In addition, photochromic solution has fast UV response and fading ability, which can realize the application of rewritable ink, color-changing film. Notably, its preparation process has the advantages of low cost, environmental friendliness and large-scale production, providing a new solution for smart sensing and anti-counterfeiting application.
Onome Ejeromedoghene,Xiangyu Ma,Olayinka Oderinde,Fang Yao,Sheriff Adewuyi,Guodong Fu
A new quaternary type IV deep eutectic solvent (DES) was prepared for the synthesis of WO3/Nb2O5 complexes via a facile solvothermal route under ambient conditions. PXRD confirmed the formation of orthorhombic niobium tungsten oxide with semi-crystalline crystal phases. The SEM micrograph displayed a well aggregated and clustered particle distribution with irregular shapes, while TEM revealed a flower-shaped morphology of the materials. Furthermore, the UV-Vis measurements indicated electronic absorption in the range of 206–282 nm before irradiation with UV-light. After 5 s of irradiation, there was an instant color change from white to blue, which gradually deepened after 180 s. This color change was accompanied by a broad electronic absorption at 658 nm. Moreover, the intense photochromic material displayed fast fading within 20 min of exposure to the open air and remarkable recyclability. These observed properties could open new avenues for smart windows and color display devices.
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