Structure and dynamics of supercooled water in the hydration layer of poly (ethylene glycol)
作者：Yuqing Li, Zehua Han, Changli Ma, Liang Hong, Yanwei Ding, Ye Chen, Junpeng Zhao, Dong Liu, Guang
關鍵字：hydration water, supercooled, dynamics, qens
論文來源：期刊
具體來源：Structural Dynamics 2022, 9, 054901
發表時間：2022年
The statics and dynamics of supercooled water in the hydration layer of poly(ethylene glycol) (PEG) were studied by a combination of
quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations. Two samples, that is, hydrogenated PEG/deuterated
water (h-PEG/D2O) and fully deuterated PEG/hydrogenated water (d-PEG/H2O) with the same molar ratio of ethylene glycol (EG) monomer
to water, 1:1, are compared. The QENS data of h-PEG/D2O show the dynamics of PEG, and that of d-PEG/H2O reveals the motion of
water. The temperature-dependent elastic scattering intensity of both samples has shown transitions at supercooled temperature, and these
transition temperatures depend on the energy resolution of the instruments. Therefore, neither one is a phase transition, but undergoes
dynamic process. The dynamic of water can be described as an Arrhenius to super-Arrhenius transition, and it reveals the hydrogen bonding
network relaxation of hydration water around PEG at supercooled temperature. Since the PEG-water hydrogen bond structural relaxation
time from MD is in good agreement with the average relaxation time from QENS (d-PEG/H2O), MD may further reveal the atomic pictures
of the supercooled hydration water. It shows that hydration water molecules form a series of pools around the hydrophilic oxygen atom of
PEG. At supercooled temperature, they have a more bond ordered structure than bulk water, proceed a trapping sites diffusion on the PEG
surface, and facilitate the structural relaxation of PEG backbone.