关键词: 十二烷基二甲基甜菜碱(BS 12), 钼酸铵, 丙烯酰胺, 疏水缔合, 光致变色水凝胶

Abstract:

Hydrogels, composed of crosslinked macromolecules and water, can be formed by chemical or physical interactions and can absorb many times as much water as they contain. The soft and moist properties of the hydrogel are similar to those of biological tissue, and it can respond to a wide range of external stimuli. Due to its extremely high water content and good biocompatibility, the hydrogel has shown broad application prospects in sensors, soft robots, flexible electronics, drug delivery and tissue engineering. Photochromic materials, which can undergo significant and reversible color changes under certain light conditions, have attracted many important studies in the fields of storage, anticounterfeiting, display, and optical switching. Currently, the structurefunction relationship among various photochromic hydrogels has gained a lot of attention. It is still challenging to study the combination of traditional photochromic materials with hydrogels. At the same time, the high cost and complex preparation technology of some photochromic materials are also urgent problems to be solved in the future development of related functional materials. The preparation method of photochromic soft materials with low cost, simple process and good chemical stability is sought to provide new design ideas for a new generation of flexible and intelligent colorchanging materials.

In order to prepare highstrength hydrogels with photochromic properties, acrylamide (AAM) was used as the main monomer of the networks, and dodecyl dimethyl betaine (BS12) was used as a surfactant. The mechanical properties of photochromic hydrogels were enhanced by chemical crosslinking and hydrophobic association through the combination of BS12 rich in positive charges and photochromic ammonium molybdate ［(NH4)6Mo7O24 ·4H2O］. The micelles were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) laser particle size analyzer, and the absorbance, transparency, and mechanical properties of photochromic hydrogels were measured by UVvis and universal testing machine. The results showed that the hydrogel exhibits high transparency and can change color under the irradiation of UV light for only two min, and the fading process can be easily achieved in the air environment. The tensile strength of hydrogels can reach 215 kPa and the fracture elongation can reach 1480%. After five stretching cycles, the lost energy is reduced by about 46%, and the dissipation energy remains unchanged.

The photochromic hydrogel is envisioned as potentially being applied as flexible and stretchable devices for visual display and storage. The photochromic hydrogel has the potential to be a choice for wearable flexible devices, artificial intelligence systems, and erasable optical displays. It might be thought of as a promising candidate for wearable flexible devices, artificial intelligence systems, and erasable optical displays. Therefore, the strategy for designing a soft photochromic material would open the next generation of flexible and stretchable devices.

Key words: hydrogel, photochromic, dodecyl dimethyl betaine, ammonium molybdate tetrahydrate, acrylamide, hydrophobic association, photochromic hydrogels