Effects of the Structure and Diffusivity of Water on the Antithrombogenicity of Polymers.

The hydration layer at the polymer-water interface has been proposed as a key determinant of the antithrombogenicity of polymer materials in medical devices. To investigate how the structure and diffusivity of water influence antithrombogenicity, molecular dynamics (MD) simulations were performed on two benchmark antithrombogenic polymers: poly(2-methoxyethyl acrylate) (PMEA) and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Although these polymers have markedly different side-chain structures, both are known to exhibit excellent antithrombogenic properties. The results reveal that PMEA-water systems exhibit a significantly higher ratio of intermediate water to bound water than PMPC-water systems. In contrast, the structured water layer in PMPC-water systems shows lower diffusivity and higher activation energy than that in PMEA-water systems. These differences in structure and diffusive properties indicate that the two polymers achieve bioinertness through fundamentally distinct hydration structures and dynamics. The antithrombogenicity of PMEA is governed by a quantitative mechanism, in which the abundance of intermediate water forms a voluminous physical cushion. In contrast, the antithrombogenicity of PMPC is attributed to a qualitative mechanism, forming an energetically robust hydration shield through structural stabilization of the hydration layer. These findings suggest that both the abundance and energetic stability of structured water are critical factors governing the antithrombogenicity of polymer materials, providing a fundamental framework for the rational design of next-generation biomaterials.