Congratulations to Xinyue Liu, Lenan Zhang, Bachir El Fil, Carlos D. Díaz-Marín, Yang Zhong, Xiangyu Li, and their collabtrator Shaoting Lin in the Department of Mechanical Engineering, Michigan State University for their recent work on Unusual Temperature Dependence of Water Sorption in Semicrystalline Hydrogels, which was featured on MIT News.
Water vapor sorption is a widespread phenomenon in nature and has various applications such as humidity regulation, energy storage, thermal management, and water harvesting. However, conventional materials face a thermodynamic limit, making it difficult to capture moisture at elevated temperatures, which restricts their broad applications. In our study, we report an inverse temperature dependence of water sorption in poly(ethylene glycol) (PEG) hydrogels. As the temperature increases from 25 to 50°C, the water uptake in PEG hydrogels can be doubled. Mechanistic modeling of water-polymer interactions reveals that this unusual water sorption is due to the first-order phase transformation of PEG structures. We also identify key parameters for a more generalized strategy in materials development. Our findings open up a new realm of water sorption with an unusual temperature dependence, providing a promising engineering space for harnessing moisture and heat.