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Decreasing the non-specific adsorption of proteins,cells and bacteria onto biomaterial surfaces is of crucial importance for the development of blood-contacting medical devices.For decades the researchers have been searching for the correlations between the biological performance and the surface structures of the materials,especially the in vivo structures in water.To illuminate the insight mechanism of hydrophilicity and antifouling properties,we prepared three series of polyurethanes(PU)with polyethylene glycol(PEG)and phosphorylcholine(PC)in the main chain,the content of PEG or PC,the segmental dynamics in soft/hard phases and the phase separation degree have been investigated with the Fourier transform infrared spectroscopy(FT-IR),the differential scanning calorimetry(DSC),and the dielectric relaxation spectroscopy(DRS).The soft/hard phase dynamics and separation is correlated with the molecular weight of PEG segment,the content of PEG or PC.With the help of DRS measurement in water,the interfacial polarization of PU-water interface has been determined and its frequency-and temperature-dependences have been studied.it is found with increasing PEG or PC,the relaxation of interfacial polarization shift to high frequency with reduced relaxation time and enhanced relaxation increment,the active energy(Ea),enthalpy and entropy changes(ΔH and ΔS)increase,indicating that with the increasing of PEG or PC,there are more water molecules combined at the interface and the interaction between the those water molecules and the polyurethane is stronger.It is such interaction between the material and the water molecules that truly affect the hydrophilicity and antifouling properties of the material.