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.