Near-ambient pressure X-ray photoelectron spectroscopy for a bioinert polymer film at a water interface

A better understanding of the aggregation states of polymers in contact with water is a pivotal issue for the development of highly functional polymer devices that work under water. As a direct experimental method to achieve the above, we used near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) on a poly(methyl methacrylate) (PMMA) film mixed with a small amount of a bottlebrush-type methacrylate polymer with oligo(2-ethyl-2-oxazoline) in its side chain portions, referred to as P[O(Ox)nMA], in a hydrated state. The results showed that P[O(Ox)nMA] was segregated at the surface of the PMMA film and suppressed the adhesion and activation of platelets on the film. Poly[oligo(2-ethyl-2-oxazoline) methacrylate] (P[O(Ox)nMA]) was mixed into a thin film of poly(methyl methacrylate) (PMMA) to construct a bioinert polymer surface in water. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) revealed that P[O(Ox)nMA] having nitrogen atoms in the side chains was segregated at the outermost region of the PMMA film in a water environment. The extent of the segregation was dependent on the architecture of P[O(Ox)nMA] due to the entropic factor, and greater extent was better for the platelet adhesion and activation.