Superior Antithrombogenic Syndiotactic Poly(Substituted Methylene) with Densely Packed Methoxyethyl Ends of Highly Extended Side Chains at the Solid Film Surface

A syndiotactic poly(substituted methylene) (<i>st</i>-PM) featuring (2-methoxyethoxy)carbonyl side chains (<i>st</i>-PMECM) exhibited considerably superior antithrombogenicity compared to a typical conventional antithrombogenic polyacrylate comprising the same side chain (i.e., poly(2-methoxyethyl acrylate); PMEA). The number of adherent platelets on the surface of the <i>st</i>-PMECM films was 0.8 × 10³ mm^-2, which was one-fourth of that on the PMEA films (3.2 × 10³ mm^-2), and 75% of these platelets were in the lowest activation state. During the platelet adhesion test, the <i>st</i>-PMECM films maintained surface wettability on the substrates, addressing the commonly observed dewetting issue in the practical applications of conventional antithrombogenic polyacrylates. In addition, the <i>st</i>-PMECM films retained their surface structure upon exposure to plasma, as indicated by the unchanged water contact angle over time, unlike in the case of polyacrylates. These characteristics of <i>st</i>-PMECM are attributed to the formation of liquid crystal structure, with the backbone arranged into a two-dimensional lattice and with the side chains stretched at an angle to the backbone axis. Owing to this structure, the methoxy moieties at the ends of the side chains were exposed to the outermost surface and hydrated with water, enabling the <i>st</i>-PMECM films to possess a larger amount of intermediate water on the surface than the PMEA films. The results demonstrate that <i>st</i>-PMs more effectively enhance the functionality of the side chains than polyacrylates featuring the same side chains, enabling <i>st</i>-PMECM to exhibit superior antithrombogenicity attributed to methoxy moieties. To the best of our knowledge, <i>st</i>-PMECM is the first inherently solid-like polymer that simultaneously exhibits outstanding antithrombogenicity.