Atomically flat films of poly(hydroxymethyl)siloxane (PHMS) were modified at surfaces by oxygen-plasma treatments and characterized by several surface sensitive techniques. The purpose was to develop well-characterized films with SiOx surface properties for various applications. The unmodified and plasma-treated PHMS films were investigated by angular resolved XPS (ARXPS in situ in the plasma equipment), Fourier transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle (CA) measurements. The surface chemical composition and wettability underwent pronounced changes upon plasma treatment, while there was no significant change of the original flatness, and both pristine and plasma-treated surfaces exhibited average roughness values below 0.5 nm. The pristine PHMS surface, having a pronounced hydrophobic character, due to the predominance of methyl groups at the surface-air interface, became progressively more hydrophilic for increasing O-2-plasma treatment times, due to the formation of SiOxCy(x -> 2, y -> 0) phases, resulting in a wetting angle of 20 degrees for the longer plasma-treatment times (60 similar to 600 s). The observed wetting angle character was correlated with the carbon (C) and oxygen (0) content at the polymer surface. Aging of the plasma-treated surfaces was done in air and water, which produced quite different stable wetting angles. After a sufficiently long plasma-treatment time (>= 60 s) a stable wetting angle of 20 degrees-25 degrees was measured, nearly the same as on the freshly plasma-oxidized surfaces. In contrast, storage in pure water, after the same plasma treatment, gave stable contact angles of So or lower. Possible reasons for this difference are discussed. Copyright (C) 2008 John Wiley & Sons, Ltd.
|Titolo:||Oxygen plasma-induced conversion of polysiloxane into hydrophilic and smooth SiOx surfaces|
|Data di pubblicazione:||2008|
|Appare nelle tipologie:||1.1 Articolo in rivista|