Molecular Dynamics Study on Hydrothermal Response of PNIPAM: From Single Chain to Cross-Linked Polymer

Thermosensitive hydrogel can integrate vapor molecular capture, in-situ liquefaction, and thermal-induced water release for freshwater capture. This study aimed to examine the dynamic behavior of poly (N-isopropylacrylamide) (PNIPAM) single chain and cross-linking thermosensitive hydrogel through molecular dynamics simulation. Specifically, the impact of lower critical solution temperature (LCST) on the conformation of polymer chain and the interaction between water and polymer chain were also investigated. The polymer chain conformation underwent a transition from coil to globule when the temperature exceeded the LCST, indicating the temperature responsiveness of PNIPAM. Additionally, thermosensitive hydrogel samples with different cross-linking degrees (DOC) were studied, and relevant parameters such as the number of free water, the diffusion coefficient of water, and the pore size distribution were counted to evaluate the temperature responsiveness and water release characteristics of thermosensitive hydrogel.